2020 Engine Buyer’s Guide

Get your aero motivation here!


Depending on your viewpoint‭ ‬engines are one of those death and taxes things‮—‬a basic unavoidable in the kit-aircraft‭ ‬world or one of the more exciting opportunities to make your airplane exactly‭ ‬the way you want it‭. ‬Unless you’re building a glider‭, ‬it’s inevitable you’ll eventually need to decide which engine to put‭ ‬on your new build‭, ‬or perhaps use to‭ ‬replace an existing powerplant‭. ‬Helping you make that decision is the very point of this guide‭. ‬

Certainly engines are a major investment‭. ‬A new‭, ‬overhauled‭, ‬or custom-built conventional four-cylinder engine is all but guaranteed to cost around‭ $‬25,000‭. ‬Performance modifications or showy presentations can add‭ $‬10,000‭. ‬Traditional‭ ‬six-cylinder aviation engines are more like‭ ‬$35,000‭ ‬to‭ $‬45,000‭. ‬If you’re considering a Rotax then‮—‬in round numbers‮—‬‭ ‬100‭ ‬hp is about‭ $‬19,000‭ ‬carbureted and‭ $‬22,000‭ ‬when fuel injected‭; ‬moving to‭ ‬the turbocharged Rotax powerplants means nearly‭ $‬31,000‭ ‬carbureted and‭ ‬$37,000‭ ‬fuel injected‭. ‬

Reliability and safety are paramount considerations in all but the most specialized racing and record-setting aircraft. That’s smart to keep in mind when engine shopping and something difficult to forget when flying over mountains.

It’s a big chunk of change‭, ‬for sure‭, ‬but powering your airplane is not the place‭ ‬to cut corners‭. ‬Obviously‭, ‬reliability is‭ ‬crucial to safety when talking about‭ ‬aircraft engines‭, ‬so hopefully there’s no need to belabor that point‭. ‬But it’s also important to match the engine to your airframe’s needs and provide you with the performance required to make your overall investment worthwhile‭. ‬This is‭ ‬a critical but often overlooked point‭: ‬No one wants to build a ground-hugging dog‭, ‬even if the goal is gas-sipping cross-country cruising or just a Saturday-morning pancake chaser‭. ‬Therefore‭, ‬even though engines are a considerable‭ ‬investment‭, ‬it’s smart to make all the‭ ‬investment necessary to arrive at the airplane you want‭. ‬

Another reality in the aircraft engine world is that the overwhelming majority‭ ‬of popular kits and plansbuilt aircraft‭ ‬use Rotax‭, ‬Continental‭, ‬or‭, ‬especially‭, ‬Lycoming engines‭. ‬That’s because they‭ ‬are known quantities in the aircraft‭ ‬maintenance and resale worlds‭. ‬They’re also well known to the airframe manufacturers‭, ‬which is why they’re normally the go-to choice on the factory’s ships‭. ‬Sure‭, ‬it’s absolutely possible to build a well-performing airplane around other engines‮—‬such as those in this guide‮—‬but that’s best a job for the seasoned‭ ‬builder with a solid foundation in engine fundamentals‭. ‬For most builders‭, ‬replicating‭ (‬not necessarily duplicating‭) ‬what the airframe creator has done is the fastest‭, ‬lowest-stress way to a flying airplane‭. ‬

Where to Buy an Engine

There are a surprising number of ways‭ ‬to purchase an engine‭. ‬Most direct is to order the engine through your airplane’s‭ ‬kit manufacturer‭, ‬assuming they offer‭ ‬that service‭. ‬Kit makers such as Van’s and‭ ‬Zenith often make arrangements with‭ ‬engine manufacturers to offer the suggested engines through the kit maker‭. ‬You simply check the‭ $‬29,000‭ ‬box on the kit maker’s website and wait for motor freight to arrive‮…‬‭ ‬That approach greatly simplifies sourcing such things as inlet ducts‭, ‬exhaust systems‭, ‬baffling and so on‭.  ‬

Next up in convenience is likely ordering an engine directly from an engine manufacturer‭. ‬Be aware that even with Lycoming and Continental‭, ‬the engine‭ ‬makers keep few of their engines in‭ ‬stock‭. ‬In fact‭, ‬volumes are so low they list the individual engines they have on the shelf on their websites‭. ‬Obviously‭, ‬the farther you get from the mainstream engine choices the greater the chance you’ll have to wait for the engine to be built‭. ‬This can be a meaningful amount of time with some of the overseas makers‭, ‬so if you’re considering something such as a Jabiru or Rotec radial‭, ‬definitely call ahead well in advance‭. ‬A year ahead is not too soon to make an inquiry‭. ‬The exception is Rotax‭; ‬it sells in such volume and is well-enough funded that its engines seem to be in ready supply‭. ‬It’s always smart to double check‭, ‬though‭.‬

Because the market for Experimental aircraft has grown to be such a significant portion of the new-airplane world‭, ‬Lycoming and‭ ‬Continental have established their own in-house boutiques‭ ‬to provide non-certified‭, ‬often custom‭ ‬engines to the Experimental market‭. ‬Lycoming’s solution is a separate assembly shop in the corner of their factory offering all sorts of custom services and aftermarket parts‭; ‬the resulting engines‭ ‬are sold under the Thunderbolt name‭ ‬and compete directly with the better‭ ‬aftermarket overhaul houses such as‭ ‬Aero Sport Power‭, ‬Barrett Precision Engines‭, ‬and Ly-Con Aircraft Engines‭. ‬

Continental simply builds a line of engines under the Titan brand name‭; ‬these‭, ‬too‭, ‬may include aftermarket parts and specialized machining‭ ‬steps‮—‬porting‭, ‬for example‭. ‬Continental‮—‬at least under the Continental name‮—‬is not in the Experimental market and offers only certified versions of its engines wearing Continental data‭ ‬plates‭. ‬At the other extreme‭, ‬Rotax‭ ‬is firmly in the Experimental aircraft market and therefore has no need for an in-house boutique or separately named engines‭. ‬A‭ ‬Rotax is a Rotax‭. ‬

Once past factory-new engines‭, ‬the purchasing process becomes less straightforward‭. ‬But if the considerations go‭ ‬up‭, ‬so do the optional possibilities‭, ‬and the price could go down‮—‬though that assumes you’re wiling to consider a used or overhauled engine‭. ‬Remember that with some engines what can be thought of as a new engine is actually a combination of mainly new and a few used‭, ‬rebuilt parts‭. ‬No one is building new‭ ‬Corvair engine cases‭, ‬for example‭, ‬so such engines are bound to have a‭ ‬“seasoned”‭ ‬case‭, ‬as the machinists like to say‭. ‬This is not a reliability or safety issue‭, ‬but some builders are only comfortable with a 100%‭, ‬brand-new engine‭. ‬

Topping the roll-your-own method‭ ‬is to work with an overhaul shop‭. ‬Some of these are relatively large‭, ‬well-known outfits such as the aforementioned Aero‭ ‬Sport‭, ‬Barrett‭, ‬and Ly-Con‭. ‬They are‭ ‬accustomed to working nationally and internationally‭, ‬so crating up their wares to Kuala Lumpur or the like is not an issue‭. ‬All‭ ‬of these shops overhaul certified engines as their bread and butter business‭, ‬but they have their own line of special parts and‭ ‬hot-rod knowledge even the factories likely don’t possess‮—‬ideal if you’re looking for something special‭, ‬racy‭, ‬or show-worthy‭.‬

Other shops are far more local‭, ‬ranging all the way down to one-man-in‭-‬a-hangar operations‭. ‬The quality and capabilities of such outfits runs the‭ ‬gamut from‭ ‬superb‭ ‬to‭ ‬no way‭; ‬which is which falls to the buyer to determine‭. ‬It’s worth noting the small operations have very limited‭, ‬if any‭, ‬machining capabilities and must work with specialist firms for things such as connecting-rod reconditioning‭, ‬balancing‭, ‬crankshaft grinding‭, ‬or engine case machine work‭. ‬

When dealing with an engine shop‮—‬large or small‮—‬you can either walk in the door empty handed or start with a core engine or even‭ ‬a partial pile of engine parts‭. ‬Even if the core engine you have isn’t the engine you need for your current build‭, ‬it’s trading fodder‭. ‬Alternately‭, ‬the larger shops keep surprisingly large inventories of core engines and parts on hand‭, ‬so if you‭ ‬are starting from scratch‭, ‬the shop can often supply a core to start from‭, ‬for a price‭, ‬of course‭. ‬This can be a cost effective‭ ‬way to arrive at a fresh engine‭, ‬so it’s worth exploring‭. ‬

Until a couple of years ago‭, ‬it was not unusual for the engine shops to buy a new engine kit from Superior‭, ‬Lycoming‭, ‬or other parts manufacturers‭. ‬Such kits are simply the parts needed to assemble an engine‭, ‬delivered to the engine shop as unassembled parts‭. ‬The kit pricing used to make this a viable way for a buyer with no core engine to arrive at an essentially new‭, ‬assembled engine‭. ‬But wanting that business for themselves‭, ‬the parts makers have raised their kit prices such that simply buying one of their experimental engines makes as much financial sense‭. ‬The engine kits are still available‭, ‬and if a hot-rod engine is desired from a custom shop‭, ‬they still are a viable starting point‭. ‬

In the VW and Corvair engine market‭, ‬kit engines are still the norm‭. ‬These‭ ‬engines are aimed at the hands-on‭ ‬enthusiast who’s happy to assemble his‭ ‬engine and keep the cash that would‭ ‬have been spent paying the shop to do the same‭. ‬If you’re not that guy‭, ‬almost all such shops will assemble the engine for you for a fee‭, ‬so keep that in mind when comparing prices‭. ‬

Our Guidelines

A few engines may seem to be missing‭ ‬from this guide‭. ‬We’re not going to‭ ‬cover Pratt‭ ‬&‭ ‬Whitney’s latest turbofan‭, ‬nor are we delving into the ultralight engines‮—‬less than 50‭ ‬hp‭. ‬The large-bore Continentals‭, ‬such as the IO-550‭, ‬aren’t here‭, ‬either‭; ‬Continental does not want to sell them direct to the Experimental market‮—‬so we haven’t listed them here‭. ‬If you have a kit that needs one of these‭, ‬chances are the kit manufacturer will help you source one‭.‬

We’ve continued our tradition of‭ ‬grouping engines by general design feature‭. ‬Thus‭, ‬the flat‭ (‬horizontally opposed‭) ‬four-stroke engines are flocked together‭, ‬followed by the inline and vee configurations‭, ‬followed by the round-motor radials and‭ ‬rotaries‭, ‬Wankels‭, ‬Diesels‭ (‬Jet A‭), ‬and‭, ‬because they are something unto‭ ‬themselves‭, ‬Volkswagen derivatives‭. ‬We‭ ‬close with turbines‭, ‬Corvairs‭, ‬and the few two-strokes that fit our criteria‭.‬

Horizontally Opposed Four-Stroke Gasoline

AC Corporation

This display engine shows AC Corporation’s AX50 cylinders on the left and cutaway Lycoming cylinders on the right. Furthermore, AC’s enlarged and smoothed composite cold air intake and runners are also seen here.

Andy Higgs is the personality powering‭ ‬AC Corporation‭, ‬where performance‭ ‬is the word and clean-sheet designs are the order of the day‭. ‬Best known for his AX50‭ ‬cylinder based on Lycoming‭ ‬360/540‭ ‬parallel-valve architecture‭, ‬Higgs has combined that cylinder with his own Lycoming-based crankcase and‭ ‬intake designs to arrive at some very modern-looking flat engines that will‭ ‬fit under common kit-aircraft cowlings‭. ‬Both four‭- ‬and six-cylinder engines are possible‭, ‬and all are not to be confused‭ ‬with other‭ ‬“clone”‭ ‬type replacement‭ ‬Lycoming engines‭. ‬Instead‭, ‬these use much more optimized intake airflow‭ ‬paths with rather obvious visual changes in manifold design‭. ‬Inside‭, ‬they feature multiple AC Corporation parts such as valves‭, ‬valve springs‭, ‬pistons‭, ‬connecting rods and even crankshafts‭. ‬

A quick glance at the AX50‭ ‬cylinder shows just how different these designs are‭. ‬Most obviously the cooling fins are‭ ‬more robust‭, ‬the machined surfaces‭ ‬typically more organic in the way they flow from surface to surface‭, ‬rather than the blocky functionality offered by stock Lycoming parts‭. ‬A closer look shows the AX50‭ ‬cylinder is a single aluminum casting‭, ‬rather than a separate head and barrel joined together‭, ‬and a removable sleeve is provided for the‭ ‬cylinder bore‭. ‬The sleeve can be field‭-‬replaced at overhaul time‭. ‬

Currently AC Corporation is listing‭ ‬its Lycoming-based engines under the‭ ‬“RS”‭ ‬banner‭, ‬that standing for Race Spec‭ ‬powerplants‭. ‬These engines are built to‭ ‬order in the United Kingdom‭ (‬Higgs is based in Japan‭, ‬but is originally from England‭), ‬then shipped to the customer‭. ‬

A new initiative is water-cooled cylinders for Lycoming engines‭. ‬The idea is to replace the excess cooling fuel used during take‭ ‬off with water‭; ‬Higgs says he’ll‭ ‬be at the Reno races September 2020‭ ‬with a water-cooled 540‭ ‬derivative‭. ‬

BRP Rotax

For all-around performance and utility, it’s tough to beat the 912 series of Rotax engines. Customers are more willing to pay for the electronically fuel injected models lately say Rotax dealers.

Old hands think of Continental or‭ ‬Lycoming as the world’s number one‭ ‬light aircraft engine makers‭, ‬but by a large margin it’s actually been Rotax for a long while‭. ‬A division of BRP‭, ‬Rotax is based in central Austria‭, ‬where it is tasked with‭ ‬building engines for the greater BRP‭ ‬empire which includes all sorts of light recreational vehicles such as side-by-side utilities‭, ‬boats‭, ‬personal watercraft‭, ‬snowmobiles‭, ‬motorcycles‭, ‬and light aircraft‭. ‬Therefore‭, ‬Rotax is a larger engine maker than it might seem at first‭, ‬with first-rate production facilities and engineering‭. ‬

For 2020‭ ‬Rotax is continuing with its existing 912‭, ‬914‭ ‬and 915‭ ‬series engines‭ ‬which combine air-cooled cylinders‭ ‬with water-cooled cylinder heads‭. ‬These‭ ‬relatively lightweight and compact‭ ‬engines are designed for higher rpm‭, ‬therefore they all include a built-in spur‭ ‬gear propeller speed reduction unit‭ ‬‭(‬gearbox‭) ‬to optimize propeller rpm‭. ‬All are dry sumped and employ hydraulic valve lifters‭; ‬carburetor or electronic‭ ‬fuel injection are offered depending‭ ‬on the model‭. ‬Warranty periods are‭ ‬relatively short for Rotax engines in‭ ‬experimental applications‮—‬just 18‭ ‬months or 200‭ ‬hours‮—‬but in certified aircraft that grows to two years or 400‭ ‬hours for essentially the same hardware‭. ‬Also lengthening over the years has‭ ‬been Time Between Overhauls for the four-stroke Rotaxes‭; ‬the 912‭ ‬is now at 2000‭ ‬hours TBO‭. ‬Rotax offers several distributors and‭ ‬maintenance facilities in North America‭, ‬with some of those‭, ‬such as California Power Systems and‭ ‬Lockwood Aviation‭, ‬offering various schools for interested homebuilders‭ ‬or maintenance pros‭. ‬The engines are dependable and rebuildable‭. ‬

Still the best selling Rotax is the‭ ‬carbureted 912‭ ‬series‭, ‬available in 80‭ ‬hp‭ ‬carbureted form as the 912‭ ‬UL or with 100‭ ‬hp as the 912‭ ‬ULS‭. ‬The 80‭ ‬hp is most popular in Europe where higher octane gasoline is difficult to find while the 100‭ ‬hp variant is number one in‭ ‬the United States‭. ‬It’s worth noting‭, ‬however‭, ‬that Rotax engines do best on unleaded‭ ‬mogas because the lead in 100LL eventually accumulates as sludge‭ ‬in the gearbox‭. ‬Furthermore‭, ‬Rotax‭ ‬says the‭ ‬912’s market share is starting to transfer quickly to the 912‭ ‬IS and turbocharged 915‭ ‬IS engines‭, ‬both of which feature electronic fuel injection‭. ‬

Rotax offers two turbocharged engines‭, ‬the carbureted 914‭ ‬and its newest‭ ‬powerplant‭, ‬the 915‭ ‬IS‭, ‬which is entering its second year of full production‭. ‬The latter is definitely spendy at over‭ $‬38,000‭, ‬but offers the best power-to-weight ratio in its class‭, ‬along with a meaty 141‭ ‬hp up to 15,000‭ ‬feet for excellent mid-altitude performance‭. ‬By comparison‭, ‬the 914‭ ‬will save you about‭ $‬7,000‭ ‬in trade for carburetion and a maximum of 115‭ ‬hp‭; ‬the 914‭ ‬has a TBO‭ ‬of 2000‭ ‬hours compared to the 915’s 1200‭ ‬hours‭, ‬as well‭.‬

If the all-singing‭, ‬all-dancing 915‭ ‬Rotax‭ ‬does offer some interesting performance capabilities to anyone interested in zipping along just a bit shy of the flight‭ ‬levels‭, ‬it’s worth remembering even the‭ ‬entry-level 80-hp Rotax offers aviating‭ ‬for notably less than half the money and in a definitely less-stressed‭, ‬should-last‭-‬forever package‭. ‬

Rotax releases pricing at the first and mid-year‭, ‬so the prices given here are for late 2019‭. ‬Like other European engines‭, ‬pricing in 2019‭ ‬has been stable or even slightly lower thanks to a strong dollar‭, ‬but pricing will change with the euro‭/‬dollar relationship‭.‬

Continental‭ / ‬Titan

Big-bore Continentals such as this IO-550 are popular performance engines in fast-plastic airplanes, but not available to experimental builders factory-direct. Best to source these via a performance engine shop.

Last year we reported The Big C had started construction of a new headquarters‭ ‬and manufacturing facility‭ ‬in Alabama‭, ‬very close to its heritage site in Mobile‭. ‬We can now report all‭ ‬administrative and engineering staff‭ ‬have moved into the new building‭, ‬but at our press time manufacturing was continuing in the old factory as the new machine tools‭ ‬were arriving and being‭ ‬installed‭. ‬It’s proving to be a large‭, ‬lengthy process‭, ‬but generally speaking the new manufacturing line should be operational in late 2020‭. ‬

The new plant should also be worth the wait as not only is the building new‭, ‬but the manufacturing machinery inside will also jump forward a generation or‭ ‬more‭. ‬A good example is crankshaft‭ ‬manufacturing‭. ‬Currently it takes eight machines plus heat treating to bring a crankshaft to life‭; ‬that will change to‭ ‬one machine in the new plant‭. ‬That‭ ‬means seven fewer set-ups to save both costs and increase machining accuracy‭. ‬

Continental continues to offer a huge selection of engines if you consider the various legacy certified gasoline Continentals‭, ‬the newer certified diesel‭ ‬engines‭, ‬plus its Titan line of experimental derivatives of Lycoming parallel-valve architecture engines‭ (‬320‭, ‬340‭, ‬370‭ ‬four-cylinders and a 540‭ ‬six-cylinder‭). ‬They now even have a certified version of the 370‭ ‬parallel-valve engine‭, ‬sort of like Ford building its version of a Chevy LS‭.‬

Now‭, ‬before getting carried away‭ ‬on Continental‮—‬we should say Titan‭, ‬because that is the brand they are being sold under‮—‬building Lycoming clones‭, ‬Continental/Titan is quick to point‭ ‬out its improvements of the breed‭. ‬For‭ ‬sumps/intake manifolds Titan’s standard offering is a magnesium version of‭ ‬the traditional‭ ‬“hot sump”‭ ‬casting‭; ‬it‭ ‬saves a meaningful seven pounds over the original aluminum casting‭. ‬Optional sumps are either Titan’s vertical or the Superior Air Parts cold air intake with a forward-facing throttle body inlet‭. ‬There is no forward facing hot sump‭, ‬or rear-facing sump of any kind‭. ‬

Titan engines also boast steel insert thrust washers for the crankshaft‭. ‬The original design has thrust loads taken by the parent aluminum of the case‭, ‬which can gall if run hard before fully wetted during break-in or under very‭ ‬hard loads or extreme time in service‭. ‬Titan simply machines its cases to accept the steel thrust washers first seen in Continental 470/520‭ ‬engines to essentially eliminate this issue‭. ‬

All Titan engines now fit roller valve lifters as standard‭, ‬although if you really‭ ‬want flat tappets they are optional‭. ‬Titans allow front or rear propeller‭ ‬governors as the customer specifies‭, ‬too‭. ‬Also stock is Continental’s nickel-carbide cylinder treatment‭ (‬NiC3‭) ‬for better durability and corrosion resistance‭. ‬They’re happy enough with it to offer a five-year warranty against cylinder rusting on all Titan engines along‭ ‬with its normal two-year or TBO warranty on the rest of the engine assembly‭. ‬Warranties begin when the engine is put in service‭, ‬not to exceed one year after purchase‭. ‬

Another help is now that the 370‭ ‬engine has been certified under‭ ‬the Continental Prime banner‭, ‬the required Operator’s plus the Maintenance and Overhaul manuals are‭ ‬now available‭; ‬they should be a help to all Titan engine owners‭. ‬And for RV builders‭, ‬Titan is offering the base version of several of its engines‮—‬these are engines configured for specific RV models‮—‬at‭ ‬“very competitive”‭ ‬prices on the Titan website‭. ‬This gives simple‭, ‬check-the-box shopping for RV engines‭, ‬albeit just in the configuration suggested by Van’s‭. ‬If modifications from those standards are desired‭, ‬it’s back to the regular Titan line-up‭. ‬

Speaking of modifications‭, ‬while‭ ‬Titan does not offer a‭ ‬“custom shop”‭ ‬storefront‭, ‬Titan offers an extensive‭ ‬line of optional gear buyer’s can choose from‭. ‬The aforementioned Superior cold air intake is one example‭, ‬another is the newest EFII System 32‭ ‬electronic engine management system‭, ‬added in the fall of 2019‭. ‬All Titans have electronic ignition of some sort‭. ‬

As for 540s‭, ‬Titan is the only source‭ ‬other than Lycoming for these powerful‭, ‬lightweight six-cylinders‭. ‬Titan has‭ ‬one helicopter customer taking a slow‭, ‬steady supply of these‭, ‬along with the occasional RV-10‭ ‬builder‭. ‬


Extreme compactness and light weight are what D-Motor gained by reverting to a flathead valvetrain. North American-bound D-Motor engines are to be assembled in Canada soon.

Another engine from Belgium is the technically curious D-Motor‭. ‬We say‭ ‬curious because it combines the very dated flathead combustion chamber layout‮—‬shades of your‭ ‬’32‭ ‬Highboy‮—‬with such advanced features as dual electronic engine management‭. ‬Actually‭, ‬the flat-head design is not quite as technologically antiquated as it might seem‭. ‬With‭ ‬rpm limited to just 3000‭ ‬revolutions‭, ‬engine breathing is less demanding than in higher speed engines‭, ‬so the flathead‭ ‬layout‮—‬where the valves are sequestered in the engine block‭ (‬case‭)‬‮—‬doesn’t pose as much breathing restriction as we might first think‭. ‬Let’s also note the flathead combustion chamber is hardly the last word in efficiency and certainly would never pass emissions testing as an automotive engine‭, ‬but for the moderate compression ratios run in aircraft engines and without emission limits to contend with the D-Motor proves its contrarian point‭. ‬

The flathead advantages are a very‭ ‬much more compact engine‭, ‬especially‭ ‬in width‭, ‬along with a lesser parts‭ ‬count‭, ‬reduced weight and cost‭. ‬It’s‭ ‬simple‭, ‬in other words‭, ‬and that’s rarely‭ ‬a bad thing in aircraft where simple‭ ‬typically means reliable‭. ‬

More to the high-tech side‭, ‬D-Motor used Nikisil coated cylinders for corrosion resistance‭. ‬This is a high-nickel‭ ‬treatment favored by Porsche‭, ‬among‭ ‬others‭. ‬There are the dual computers‭, ‬electronic fuel injection and ignition‭, ‬and it’s worth noting the fuel injection is returnless‭, ‬meaning there is no need to plumb a fuel line from the engine back to the fuel‭ ‬tank‭. ‬Also convenient are the engine mounting points‭; ‬they are identical to Jabiru and ULPower engines‭, ‬which aids finding a workable mount‭. ‬

Given its bent for simplicity‭, ‬the‭ ‬D-Motor is understandably not a real‭ ‬fire-breather‭. ‬The four-cylinder version‭ ‬is rated at 92‭ ‬hp‭; ‬the six-cylinder variant yields 125‭ ‬hp/121‭ ‬hp continuous‭, ‬also‭ ‬at 3000‭ ‬rpm for maximum power‭, ‬so‭ ‬smaller diameter propellers are a must on these direct-drive engines‭. ‬But for an LSA where reduced weight and simplicity are key‭, ‬the D-Motor seems better suited‭. ‬

Let’s also note that after a rocky start several years ago‭, ‬D-Motor has replaced its original North American distributor‭. ‬Furthermore‭, ‬North America has been overshadowed by European demand for D-Motors‭, ‬but recognizing the market here D-Motor is setting up an‭ ‬assembly facility in Canada to service the Americas‭. ‬It will assemble engines using parts‭ ‬manufactured in Belgium‭. ‬A deposit‭ ‬system‭ ($‬1000‭ ‬into an escrow account‭) ‬is now in place‭; ‬expect Canadian engine‭ ‬assembly for North America and thus‭ ‬engine deliveries here to commence in early‭- ‬to mid-2020‭. ‬

Franklin Aerospace

A mainstream certified engine during‭ ‬WW-II and for quite a while later‭, ‬the Franklin lives on thanks to the amazing parts inventory produced‮—‬mainly‭ ‬for military consumption‮—‬during the‭ ‬engine’s heyday‭. ‬Used extensively in‭ ‬Stinsons‭, ‬the Franklin still has a following in the certified ranks‭, ‬but with its type certificate now the property of‭ ‬a Polish company‭, ‬Franklin Aerospace engines assembled in the U.S‭. ‬today‭, ‬mainly from new old stock‭, ‬are experimental-only powerplants‭. ‬

And that’s what the U.S‭. ‬based Franklin Aerospace offers with its 4A-235‭ ‬four-cylinder and 6A-350‭ ‬six-cylinder engines‭. ‬The four-banger is kept in stock for ready‭ ‬delivery‭; ‬the six-cylinder is built‮—‬or‭ ‬perhaps we should say rebuilt‮—‬to order‭. ‬Both boast Electroair electronic ignition‭ ‬and a Rotec throttle body along with‭ ‬lightweight starters‭, ‬but modifications‭ ‬to customer order are also possible if you have something specific in mind‭. ‬

One thing Franklin Aerospace has done is reduce the compression ratio‭ ‬for mogas compatibility‭. ‬The originals‭ ‬were pretty high compression engines‭ ‬to begin with‭, ‬so the current six cylinder is good‭ ‬“for about 210‭ ‬hp‭.‬”‭ ‬There is no shortage of parts‮—‬at least most of them‮—‬according to Franklin Aerospace‭. ‬Private owners have been gathering surprisingly large stashes for years‭, ‬and Franklin is still buying major collections‭, ‬often by the semi-truck load‭. ‬Combined with machining new examples of the few non-plentiful parts the Franklin remains viable today‭.‬


Jabiru’s fourth-generation engines can be identified by the head and cylinder cooling fins that are relatively even in height. Earlier Jabirus featured cylinder head fins notably taller than the cylinder fins.

Seemingly having found its stretch in its fourth generation‭, ‬the Australian Jabiru‭ ‬engines make a simple-is-better appeal‭ ‬to LSA and smaller E/A-B aircraft‭. ‬Their combination of lower cost and simplicity‭ ‬via air cooling‭, ‬direct-drive and simple‭ ‬slide-carburetion have made them popular at the populist end of the light aviation market‭, ‬including the Arion Lightning‭, ‬which‭ ‬is appropriate as Arion is the Jabiru distributor for North America‭. ‬

The fourth generation Jabiru relies heavily on aluminum construction of‭ ‬the crankcase and cylinders‮—‬silicon carbide and nickel coated‮—‬for low‭ ‬weight and rapid heat transfer‭. ‬Jabiru in Australia has the parts mainly constructed by specialist machine shops‭ ‬in South Queensland‭, ‬Australia‭, ‬then assembles them in its own nearby facility before shipping them to Arion in‭ ‬

Shelbyville‭, ‬Tennessee‭. ‬Although sales are good and the supply chain between Australia and the U.S‭. ‬is always moving‭, ‬so it’s smart to plan ahead when ordering‭, ‬which is done through Arion‭. ‬

Two engines are offered‭, ‬a four‭-‬cylinder 2200‭ ‬rated at 80‭ ‬hp and a‭ ‬six-cylinder 3300‭ ‬good for 120‭ ‬hp‭. ‬Both are popular‭, ‬the just 132-pound 2200‭ ‬in the smaller Zenith and Sonex airframes‭; ‬the bigger 3300‭ ‬typically being seen in the‭ ‬Arion‭, ‬larger Zenith‭, ‬RANS and Van’s models‭. ‬Again‭, ‬simplicity‭, ‬light weight and affordable‭ ‬cost are Jabiru goals‭, ‬so both engines use a single Bing slide-type carburetor‭, ‬mechanical fuel pump‭, ‬and inductive ignitions built into the flywheel‭. ‬There are distributors‭, ‬but they have no timing component‭ ‬as timing is fixed‭. ‬Both the alternator and ignition are integral to the engine‭, ‬and both should be working as long as the engine is rotating‭. ‬

Perhaps unique in general aviation‭, ‬Jabirus are fitted with RAMAIR air‭ ‬ducts at the factory‭. ‬These fit under the cowling and simplify engine installation as the air baffling is already fitted to the‭ ‬engine‭. ‬There are no technical or price changes to the Jabiru line for 2020‭. ‬


Lycoming’s Thunderbolt line continues to grow in popularity. Performance mods are a given, as are dress-up items. Besides the red paint, this one sports carbon weave pushrod tubes and oil filler, along with some chrome bling.

In the traditional big-bore‭, ‬direct-drive aviation piston world‭, ‬Lycoming continues it dominance of the Experimental/Amateur-Built market‭. ‬Embracing‭ ‬the experimental airframers years ago‭ ‬has been a big part of why its engines‮—‬or clones thereof‮—‬are seen more often‭ ‬than any other in the burgeoning‭ ‬build-it-yourself airplane neighborhood‭. ‬Also‭, ‬with Continental now‭ ‬owned by the Chinese‭, ‬Lycoming is the last large U.S‭.-‬owned aircraft engine manufacturer and thus has a leg-up in the drone/UAV‭ ‬market where military‭ ‬contracts lean toward U.S‭. ‬content‭. ‬Today Lycoming continues to extend‭ ‬its reach by offering anything from dead stock grocery-getting certified‭ ‬mills to extreme performance thumpers for aerobatic and racing fans‭. ‬

For 2020‭ ‬Lycoming reports more of the same in the engine hardware department‭, ‬with no price increase‭, ‬but there is an increasing‭ ‬range of optional gear on its hot rod engines‭. ‬The latter includes a new electronic ignition system developed as a Lycoming part in partnership‭ ‬with SureFly‭. ‬A drop-in replacement‭, ‬magneto-like‭, ‬electrically self-generating unit‭, ‬its big potential is adjustable ignition timing for better fuel economy‭, ‬along with no maintenance or overhaul requirement for the life of the engine‭. ‬Experimentals can run the system now‭; ‬CubCrafters‭ ‬is one of the first of the certifieds to offer it stock‭. ‬

Before talking options on the Thunderbolt engines‭, ‬we should note a balanced crankshaft and reciprocating assembly is standard‭, ‬as are ported‭ ‬cylinders and limited number of paint colors‭ (‬more colors are optional‭, ‬as is‭ ‬chrome detailing‭). ‬Airflow Performance‭ ‬or Avstar constant-flow‭, ‬mechanical‭ ‬fuel injection is also standard‭, ‬along‭ ‬with magneto ignition‭. ‬Not to be overlooked‭, ‬all Thunderbolt engines are broken in on one of Lycoming’s dynos for between 1.5‭ ‬and 3‭ ‬hours‭, ‬eliminating any worries about the engine’s viability during the first flight‭, ‬plus relieving the harried‮—‬and often‭ ‬apprehensive‮—‬pilot from following‭ ‬restrictive engine break-in protocols‭.‬

Typical modifications in the Thunderbolt line are increased compression to 10:1‭, ‬with the caveat that 100LL fuel is then required‭ (‬no mogas‭), ‬along with‭ ‬any number of electronic ignitions‭. ‬P-MAG and LightSpeed Engineering‭ ‬Plasma series are popular‭. ‬

It’s a measure of how custom-oriented the engine market is getting to hear‭ ‬Lycoming say its Thunderbolt engines‭ ‬are best-sellers and constitute approximately 35‭ ‬percent of its production‭. ‬The biggest issue they’ve reported recently‭ ‬is keeping up with demand‭. ‬All Thunderbolts are assembled in the Advanced Technology Center‭, ‬a dedicated shop inside Lycoming’s Williamsport‭, ‬Pennsylvania facility where two-man teams concentrate on building one engine at a time‭. ‬Lycoming says they have‭ ‬three such build teams working and need to add more‭, ‬always a good sign‭. ‬

And where are all the engines going‭? ‬On Van’s RVs‭, ‬of course‭, ‬followed by‭ ‬the back country airplanes according‭ ‬to Lycoming‭. ‬The remainder of Thunderbolt and mainstream Lycoming production is spread over the entire range‭ ‬of experimental and general aviation‭, ‬including some direct sales overseas‭. ‬

As for the engines themselves‭, ‬Lycoming lists its familiar‭, ‬O-235‭, ‬320‭, ‬360‭, ‬390‭, ‬540‭ ‬and 580‭ ‬cubic inch‭ ‬designs in its Thunderbolt line-up‭. ‬That’s pretty much the entire line of current Lycoming production save the eight-cylinder 720‭, ‬which can still be had as a certified‭ ‬engine if you really need that much oomph‭. ‬Of the engines offered‭, ‬all use parallel valve cylinders except the 390‭ ‬and 580‭, ‬which employ angle-valve cylinder heads‭. ‬That makes them more efficient and powerful‭, ‬but also heavier‭. ‬

Finally‭, ‬to put things in perspective‭, ‬Lycoming holds one major trump card in the time-tested nature of its‭ ‬powerplants‭. ‬There are so many Lycs‭ ‬flying that the company estimates the Lycoming brand accrues 1‭ ‬million fleet hours monthly‭. ‬

MW Fly Aero Power

While in basic terms MW Fly groups its engines as either BT22‭ ‬or BT25‭ ‬units‭, ‬when combinations of displacement‭, ‬power ratings‭, ‬drive type and gearbox ratio are considered‭, ‬MW Fly offers no less than 12‭ ‬engine combinations ranging from 100‭ ‬to 155‭ ‬hp‭. ‬These modern‭, ‬designed for aviation engines use a flat‭ ‬cylinder layout to better integrate into‭ ‬existing cowlings and mounts‭, ‬but are water-cooled for tighter internal tolerances and quieter operation‭. ‬The result is commendable fuel economy on mogas‭, ‬immunity to shock cooling and potentially better engine life and power‭. ‬They seem to offer somewhat better power or performance depending on the application due to either higher engine output or the propeller gearing‭. ‬

MW Fly is dedicated to electronic FADEC controls‭. ‬A plug-and-play philosophy is supported by the CAN bus electrical architecture‭, ‬so integrating the engines into an EFIS or custom tailoring the engine electronic mapping is said to be relatively easy‭. ‬Engine installation is also aided by the direct mounting of coolers and the accessories‭. ‬

Gearbox-equipped models turn higher‭ ‬engine rpm‮—‬as much as 4550‭ ‬rpm‮—‬for‭ ‬increased power and slower prop rpm‭ ‬to support longer propellers‭. ‬There are two gearbox ratios available‭; ‬some can‭ ‬accommodate hydraulically-controlled‭ ‬constant-speed propellers along with‭ ‬either left‭- ‬or right-hand rotation‭. ‬

In June of 2019‭ ‬MW Fly released a‭ ‬mandatory service letter counseling‭ ‬against low-octane or old gasoline‭. ‬It‭ ‬requires a fuel system draining and system flow check if the aircraft has not been operated in more than two months‭, ‬so the issues surrounding rapidly degrading mogas would appear universal‭. ‬

MW Fly is an Italian company‭; ‬distribution in North America is through MW Fly Sales and Service North America Ltd in Carp‭, ‬Ontario‭, ‬Canada‭, ‬but separate dealers are being sought for Canada‭, ‬the U.S‭. ‬and Mexico‭. ‬A pending project is the turbocharged B25T‭ ‬variant‭. ‬MW Fly sees it as a‭ ‬“green”‭ ‬engine for use in UAV‭, ‬urban mobility platforms and general aviation‭. ‬Three versions of the B25T are being considered‭, ‬a 170-hp‭ ‬turbo-normalized‭, ‬plus two 240-hp options‭, ‬one turbo-supercharged and one turbo-hybrid‭. ‬


Pegasus’ half-an-O-200 is taking a little longer than hoped to reach production, but 2020 really should be the year this new engine comes to market.

Patience is a virtue around new engines‭; ‬witness the O-100‭ ‬Pegasus DP-1‭, ‬a twin-cylinder derivative of the mega-popular O-200‭ ‬Continental‭. ‬It’s designed to use all-new Pegasus parts where needed and existing Continental O-200‭ ‬parts as possible‭. ‬LSA fans have been patiently waiting for the engine for several years since the first-article DP-1‭ ‬was first shown running on an engine stand‭, ‬and while‭ ‬this should have been the year the new 58-hp engine went into production‭, ‬we’re going to need a little more patience says Pegasus majordomo Pete Plumb‭.‬

Two changes have slowed the DP-1’s debut‭. ‬To provide slimmer packaging‭, ‬Plumb has spent the last two years redesigning the oil sump and case to accommodate the intake runners‭. ‬Not only does this allow tucking the intake runners more tightly under the engine‭, ‬but allows mounting the carburetor‭ ‬directly to the aft end of the plenum at the back of accessory case‭, ‬either horizontally or vertically‭. ‬To save weight‭ ‬Plumb favors simple slide-type carburetors‭. ‬Achieving the new carburetor mounting meant extending the engine case a half inch deeper than a stock O-200‭. ‬Therefore a stock Continental accessory case would still work‮—‬if a moon-shaped shim was inserted in the‭ ‬gap‮—‬but Plumb wanted the better‭ ‬solution of modifying the case to fit‭. ‬

The other change was from the originally intended Austempered Ductile‭ ‬Iron‭ (‬ADI‭) ‬crankshaft to a traditional forging‭. ‬The ADI process has strength-to-weight and prototyping advantages‭, ‬but apparently all such manufacturing‭ ‬capability has been outsourced from‭ ‬Detroit to Mexico‭, ‬complicating things impossibly for the DP-1’s small production runs‭. ‬Plumb has therefore reverted to the tried-and-true forging process‭, ‬and was awaiting proof samples at our deadline‭. ‬Once the forged crankshaft is proven via testing by Pegasus the remainder of the engine has been finalized and is production-ready‭; ‬a prototype DP-1‭ ‬has already completed 50‭ ‬hours of trouble-free flight testing‭. ‬

Furthermore‭, ‬along with the costly‭ ‬investment in forging dies‭, ‬Pegasus is ready‭ ‬with relatively high volume parts runs‭ ‬by aviation standards‮—‬100‭ ‬engines‮—‬to hopefully satisfy start-up demand‭. ‬Plumb also pointed out there is no price increase due to‭ ‬the crankshaft change‭. ‬


Parts maker turned engine manufacturer Superior has a huge line of upgraded Lycoming-architecture parts to draw on. Their cold air intake/sump is the industry standard for experimental Lycomings and their derivatives.

Superior Air Parts comes to engine‭ ‬building from decades of building‭ ‬aftermarket replacement parts for‭ ‬popular engines‭, ‬especially Lycomings‭. ‬As its inventory of part numbers grew‭, ‬it became logical for them to begin selling‭ ‬complete engine kits‭, ‬and eventually‭ ‬assembling its parts into replacement‭ ‬engines‭. ‬Superior is quick to point‭ ‬out‭ ‬that they’ve upgraded materials and‭ ‬manufacturing processes to provide‭ ‬better parts at competitive prices‭. ‬They’ve also provided important competition to help keep costs in line across the engine marketplace‭. ‬

While Superior offers some certified engines‭, ‬it is its XP line of experimental‭ ‬engines based on Lycoming architecture that are of interest to experimental‭ ‬builders‭. ‬Several options are available‭, ‬including your choice of flat or roller tappets‭, ‬or intake manifolds based on the original Lycoming model of combined oil sump/intake manifold or‭ ‬Superior’s cold air style intake‭. ‬

The Superior cold air intake is its more popular offering‭, ‬not only due to the efficiency of the cold air design‭, ‬but also because it is available in traditional updraft or horizontal layouts‭. ‬The horizontal cold air allows a slimmer cowling and eases packaging a ram style air inlet‭, ‬while the updraft version accommodates existing standard-depth cowls‭. ‬Superior offers a choice of Bendix-style mechanical fuel injection from Precision Airflow or traditional carburetion on all its engines‭.‬

Superior was offering 382‭ ‬and 400‭ ‬cubic inch stroker versions‭ (‬longer‭ ‬crankshaft throw‭) ‬of its engine‭, ‬but‭ ‬after some issues Superior recalled those engines in a buy-back program and is no longer offering strokers‭. ‬

Another initiative of Superior’s is the Gemini opposed-piston Jet A fuel engine‭. ‬While the project was announced several years ago‭, ‬it is still in development‭ ‬and is not for sale at this time‭. ‬Superior is based‭ ‬in Texas and is Chinese-owned‭. ‬


ULPower engines are where the legacy horizontally-opposed, air-cooled layout meets electronic fuel injection and ignition. A single computer is standard; dual ECUs are optional, as are dual electric fuel pumps and alternators.

Product of a consortium of Belgium companies‭, ‬the ULPower line of engines has been one of the more popular‭ ‬“alternative”‭ ‬‭(‬non-Lycoming‭) ‬engines on the experimental market‭. ‬Its distributorships have been growing in the U.S‭., ‬and there are now firewall-forward kits for the popular‭ ‬RV and RANS airframes from Kaolin‭ ‬Aviation if that’s your need‭. ‬There’s up to 200‭ ‬hp available‭, ‬if you can handle 3300‭ ‬rpm‭, ‬so ULPower engines are not just for evening flight flivvers‭. ‬The same six‭-‬cylinder is rated at 182‭ ‬hp at 2800‭ ‬rpm should you be using a long prop‭. ‬

ULPower engines are an interesting‭ ‬combination of traditional horizontally‭ ‬opposed‭, ‬overhead valve‭, ‬air-cooled‭, ‬direct-drive layout and contemporary electronic engine management‭. ‬All ULPower engines‮—‬both the four‭- ‬and six-cylinder units‮—‬are‭ ‬electronically fuel injected and sparked‭. ‬A single computer is stock‭, ‬but dual ECUs are optional‭. ‬Dual electronic ignition is standard‭. ‬Just make sure you‭ ‬have a steady and voluminous number‭ ‬of electrons as these engines demand 21‭ ‬amps running and 50‭ ‬amps of charging‭. ‬

We also recommend spending some‭ ‬time with the company’s good online‭ ‬technical information as the fuel system is entirely reliant on electrical pumps‮—‬there is no mechanical fuel pump‮—‬so that is something to consider‭. ‬

Pricing of the ULPower line is dependent on the euro to dollar exchange rate‭. ‬At press time that was just 1.1:1‭, ‬so the dollar is buying many euros‭, ‬making the ULPower engines price competitive‭. ‬Robert Helms‭, ‬the main ULPower spokesman in North America says the engine remains technically unchanged‭ ‬for 2020‭; ‬market acceptance of the‭ ‬brand appears to be growing‭.‬

Manufacturer/ModelDrive TypeHorsepower/ConfigWeightPrice
AC Corporation
AC-379RSdirect230 hp 4-cyl248 lbs wo/ fuel system, ignition, or starter$34,562
AC-568RSdirect350 hp 6-cyl370 lbs wo/ fuel system, ignition, or starter$53,000
AC-758RSdirect475 hp 8-cylSpecial orderTBD
AC-335RS Gladiatordirect210 hp 4-cyl, liquid cooled226 lbs wo/ fuel system, ignition, or starter$28,895
AC-379RS Gladiatordirect240 hp 4-cyl, liquid cooled236 lbs wo/ fuel system, ignition, or starter$34,562
AC-568RS Centuriondirect360 hp 6-cyl, liquid cooled354 lbs wo/ fuel system, ignition, or starter$53,000
BRP Rotax
912 ULgeared80 hp @ 5800 rpm carbureted130 lbs w/ exhaust, internal alternator$16,503
912 ULSgeared100 hp @ 5800 rpm carbureted137 lbs w/ exhaust, internal alternator$19,701
912 iSgeared100 hp @ 5800 rpm EFI155 lbs w/ exhaust, internal alternator$23,284
914 ULgeared115 hp @ 5800 rpm carbureted, turbo155 lbs w/ exhaust, internal alternator$31,539
915 iSgeared135 hp @ 5800 rpm EFI, turbo, intercooled185 lbs bare, approx 245 installed$38,667
Continental Motors / Titan Brand
OX-320direct160-167 hp carbureted240 lbs w/ mags, fuel system, starter$26,775
IOX-320direct160-167 hp injected240 lbs w/ mags, fuel system, starter$28,245
OX-340direct166-180 hp carbureted244 lbs w/ mags, fuel system, starter$28,455
IOX-340direct166-180 hp injected244 lbs w/ mags, fuel system, starter$29,925
OX-360direct180-185 hp carbureted277 lbs w/ mags, fuel system, starter$28,350
IOX-360direct180-185 hp injected277 lbs w/ mags, fuel system, starter$29,820
OX-370direct185-187 hp carbureted278 lbs w/ mags, fuel system, starter$29,505
IOX-370direct185-187 hp injected278  lbs w/ mags, fuel system, starter$30,975
OX-370direct195 hp carbureted, counterweighted crank283 lbs w/ mags, fuel system, starter$29,925
IOX-370direct195  hp  injected, counterweighted crank283 lbs w/ mags, fuel system, starter$30,345
OX-540direct260 hp carbureted, counterweighted crank401 lbs w/ mags, fuel system, starter$45,045
IOX-540direct260 hp injected, counterweighted crank401  lbs w/ mags, fuel system, starter$45,236
LF26 2690cc 4-cyldirect92 hp @ 3000 rpm137 lbs w/ alternator, starter, dual ECU, exhaust, fluids$17,640
LF39 3993cc 6-cyldirect125 hp @ 3000 rpm184 lbs w/ alternator, starter, dual ECU, exhaust, fluids$30,429
Franklin Aerospace
4A-235 4-cyldirect125 hp @ 2800207 lbs w/ starter, alternator, Rotec TBI, Electroair EI$15,900
6A-350direct220 hp @ 2800344 lbs w/ starter, alternator, fuel injection, ignition$28,900
HKS Co. Ltd
700E Twingeared60 hp @ 6200 rpm (3 min) 56 hp @ 5800 continuous121 lbs w/ carburetors, fuel pump, dual CDI$10,990
Jabiru AU
Generation 4 2200 (4-cyl)direct85 hp @ 3300 rpm136 lbs w/ exhaust, carb, starter, alternator, ignition$14,900
Generation 4 3300 (6-cyl)direct120 hp @ 3300 rpm184 lbs w/ exhaust, carb, starter, alternator, ignition$18,900
O-235-EXPdirect118 hp @ 2800 rpm carbureted parallel valve250 lbs w/ mags, fuel system, starter$26,100 S, $29,700 T
O-320-D1Adirect160 hp @ 2700 rpm carbureted parallel valve255 lbs w/ mags, fuel system, starter$26,900 S, $30,500 T
IO-320-DIAdirect160 hp @ 2700 rpm injected parallel valve270 lbs w/ mags, fuel system, starter$28,500 S, $32,100 T
O-320-D2Gdirect160 hp @ 2700 rpm carbureted parallel valve250 lbs w/ mags, fuel system, starter$26,400 S, $30,000 T
O-360-A1Adirect180 hp @ 2700 rpm carbureted parallel valve285 lbs w/ mags, fuel system, starter$27,500 S, $31,100 T
O-360-A4Mdirect180 hp @ 2700 rpm carbureted parallel valve285 lbs w/ mags, fuel system, starter$27,400 S, $31,000 T
IO-360-M1Bdirect180 hp @ 2700 rpm injected parallel valve290 lbs w/ mags, fuel system, starter$28,700 S, $32,300 T
IO-360-A1B6direct200 hp @ 2700 rpm injected angle valve325 lbs w/ mags, fuel system, starter$33,100 S, $36,700 T
IO-390-A3B6direct210 hp @ 2700 rpm injected angle valve315 lbs w/ mags, fuel system, starter$33,800 S, $37,400 T
IO-390-EXPdirect220 hp @ 2700 rpm injected angle valve315 lbs w/ mags, fuel system, starterNA, $38,000 T
IO-540-D4A5direct260 hp @ 2700 rpm injected parallel valve400 lbs w/ mags, fuel system, starter$47,700 S, $51,300 T
IO-580-B1Adirect315 hp @ 2700 rpm injected angle valve440 lbs w/ mags, fuel system, starter$65,000 S, $68,600 T
IO-580-B1Adirect320 hp @ 2700 rpm injected angle valve440 lbs w/ mags, fuel system, starterNA, $69,500 T
MW Fly
B22D-L-100direct100 hp @ 3300 rpm176 lbs w/ alt, starter, FADEC ECU, oil & water tanks$20,290
B25D-L-115direct115 hp @ 3300 rpm176 lbs w/ alt, starter, FADEC ECU, oil & water tanks$22,750
B22D-R-100direct100 hp @ 3300 rpm176 lbs w/ alt, starter, FADEC ECU, oil & water tanks$19,550
B25D-R-115direct115 hp @ 3300 rpm176 lbs w/ alt, starter, FADEC ECU, oil & water tanks$22,010
B22G-L-122-Ageared (1.730)122 hp @ 3950 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$22,620
B22G-L-135-Bgeared (1.958)135 hp @ 4550 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$23,850
B25G-L-140-Ageared (1.730)140 hp @ 3950 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$30,000
B25G-L-155-Bgeared (1.958)155 hp @ 4550 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$32,460
B22G-R-122-Ageared (1.730)122 hp @ 3950 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$23,240
B22G-R-135-Bgeared (1.958)135 hp @ 4550 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$24,470
B25G-R-140-Ageared (1.730)140 hp @ 3950 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$30,620
B25G-R 155-Bgeared (1.958)155 hp @ 4550 rpm (2400 prop)185 lbs w/ alt, starter, FADEC ECU, oil & water tanks$33,070
Pegasus Motor Corp.
DP-1 100ci Twindirect58 hp @ 2900 rpm110 lbs w/ Slick mags, carb, no starter$4,495
Superior Air Parts
XP-O-320-A1AC2direct160 hp carbureted, fixed pitch285 – 290 lbs w/ mags, fuel system, starter$26,300
XP-IO-320-A1AC2direct165 hp injected, fixed pitch285 – 290 lbs w/ mags, fuel system, starter$27,100
XP-O-360-A1AC2direct180 hp carbureted, fixed pitch288 – 297 lbs w/ mags, fuel system, starter$26,300
XP-IO-360-A1AC2direct185 hp injected, fixed pitch288 – 297 lbs w/ mags, fuel system, starter$27,100
XP-O-320-B1AC2direct160 hp carbureted, constant speed285 – 290 lbs w/ mags, fuel system, starter$26,600
XP-IO-320-B1AC2direct165 hp injected, constant speed285 – 290 lbs w/ mags, fuel system, starter$27,400
XP-O-360-B1AC2direct180 hp injected, constant speed288 – 297 lbs w/ mags, fuel system, starter$26,600
XP-IO-360-B1AC2direct185 hp injected, constant speed288 – 297 lbs w/ mags, fuel system, starter$27,400
UL260i 4-cyldirect97 hp @ 3300 rpm / 82 hp @ 2800 rpm159 lbs w/ accessories, oil, and exhaust$20,000
UL260is 4-cyldirect107 hp @ 3300 rpm159 lbs w/ accessories, oil, and exhaust$21,000
UL350i 4-cyldirect118 hp @ 3300 rpm173 lbs w/ accessories, oil, and exhaust$23,000
UL350iS 4-cyldirect130 hp  @ 3300 rpm173 lbs w/ accessories, oil, and exhaust$24,000
UL390i 6-cyldirect140 hp @ 3200 rpm / 130 hp @ 2800 rpm220 lbs w/ accessories, oil, and exhaust$29,000
UL390iS 6-cyldirect160 hp @ 3200 rpm / 140 hp @ 2800 rpm220 lbs w/ accessories, oil, and exhaust$30,000
UL520i 6-cyldirect180 hp @ 3200 rpm / 169 hp @ 2800 rpm238 lbs w/ accessories, oil, and exhaust$31,500
UL520iS 6-cyldirect200 hp @ 3200 rpm / 182 hp @ 2800 rpm238 lbs w/ accessories, oil, and exhaust$32,500

Inline and Vee Four-Stroke


AeroMomentum’s line of auto conversion engines is well-supported by in-house electronic expertise. This includes a new-this-year Aero-Graph instrument that allows the pilot to closely monitor ECU performance using one or more displays.

It’s not everyday an engine maker says its biggest challenge is finding enough of the right employees to keep up with demand‭, ‬but that’s the current challenge at the compact‭, ‬privately-owned Aero-Momentum where work mainly consists of converting various non-V-8‭ ‬automotive engines into aero powerplants‭. ‬

For 2020‭, ‬the AeroMomentum eight‭-‬strong engine line-up is unchanged‭, ‬meaning a 1000cc three-cylinder‭, ‬1300‭ ‬and 1500‭ ‬four-cylinders and a turbocharged 2.0-liter four-cylinder‭. ‬Power ranges from 75‭ ‬to 260‭ ‬hp via a series of standard and high-performance variants of most of these different displacements‭. ‬Suzuki is the source of the 1300‭ ‬and 1500‭ ‬engines‭; ‬the others are non-Suzuki and cannot be revealed as part of the sourcing agreement‭. ‬All engines are‭ ‬built from all-new parts‭; ‬no salvage or used engines are ever used‭.‬

What is new is the‭ $‬585‭ ‬Aero-Graph‭, ‬an engine monitor AeroMomentum‭ ‬builds in-house‭. ‬A plug-and-and-play‭ ‬unit‭, ‬the Aero-Graph displays what’s‭ ‬going on inside the AeroMomentum‭ ‬FADEC computer‭, ‬plus oil pressure‭, ‬temperature and fuel pressure‭. ‬Because it is CAN bus compatible‭, ‬multiple Aero-Graphs can be daisy chained together or used with‭ ‬an EFIS‭ (‬AeroMomentum offers one of those‭, ‬too‭) ‬in any combination‭. ‬Aero-Graph is sold with the round display that fits into a‭ ‬2-inch panel cutout‭, ‬harness and the three oil and fuel sending units‭. ‬It offers a series of pre-set out-of-limit alarms‭ (‬programmable via cell phone if desired‭) ‬and is calibrated to the supplied sensors‭. ‬

A more minor change is AeroMomentum is now CNC-porting rather than hand-porting its cylinder heads‭. ‬

Core to AeroMomentum’s conversions is a helical‭, ‬spur-gear prop reduction gearbox‭. ‬It features custom 8620‭ ‬alloy gears‭ (‬these aren’t quick change‭ ‬auto racing gears‭), ‬and like many of‭ ‬AeroMomentum’s other parts‭, ‬is‭ ‬designed in-house‭; ‬forged‭, ‬machined‭, ‬heat-treat and otherwise produced by out-of-house vendors‭; ‬then assembled in-house at AeroMomentum‭. ‬The highest time gearbox so far logged 5500‭ ‬hours in an airboat with no issues‭. ‬

Adept Airmotive

Based in South Africa‭, ‬Adept Airmotive has been working up a small group of auto conversion engine combinations for several years now‭. ‬Aiming for the higher performance end of the conversion market‭, ‬Adept is using a DOHC V-6‭ ‬with a propeller gearbox and has announced 280N plus 320T and 360T versions‭, ‬the 280‭ ‬hp version being naturally aspirated and the 320‭ ‬and 360‭ ‬hp variants turbocharged‭. ‬Adept has displayed at AirVenture in‭ ‬conjunction with Evolution aircraft‭, ‬but the latest information has been difficult to come by from the company‭. ‬

Auto PSRU’s

If this 360-hp LS-3 package from AutoPSRU’s is a little too powerful, they are still offering their 2.5- and 3.0-liter Subaru packages.

Auto PSRU’s offers a few complete‭ ‬automobile conversion engines‭, ‬but‭ ‬really they are fully involved in everything firewall forward for its customers‭ ‬as necessary‭. ‬Their main attraction is‭ ‬a time-tested spur gear prop reduction unit with centrifugal clutch‭. ‬Available in several sizes‭, ‬it works with smaller four-cylinder engines up to V-8s‭. ‬As Stuart Davis of Auto PSRU’s put it‭, ‬“we handle from about 150‭ ‬to 550‭ ‬horsepower‭.‬”‭ ‬Its complete engine offerings center on the Chevy LS series and Subaru engines‭. ‬

For 2020‭, ‬Auto PSRU’s is phasing out the VW350‭ ‬gearbox for an updated version‭, ‬the SD400‭ (‬the numerals indicate the unit’s horsepower capacity‭). ‬The changes making the SD400‭ ‬are mainly packaging items designed to accommodate the more common 11-inch‭ ‬Chevrolet flywheel and matching aftermarket starter motors‭. ‬This eliminates the previous need for spacers and adapters‭; ‬the fundamentals of the gearbox and clutch are unchanged‭.‬

An aerobatic qualified gearbox has been added‭, ‬the SD550‭. ‬It is the SD400‭ ‬box beefed up with an external brace‭, ‬much stronger prop shaft‭, ‬larger bearings‭, ‬different splines on the top gear drive‭, ‬all to better withstand gyroscopic loads‭. ‬The main market for it is the replica P-51‭ ‬crowd as not too many RV-10‭ ‬fan boys are aerobating their rides‭. ‬

The existing 200Z gearbox is the basis of the new 300Z unit which can now handle V-6‭ ‬and even small V-8‭ ‬power and is oriented for vertical engine installations in helicopters‭. ‬These smaller Auto PSRU’s are also good for inline six-cylinders for narrow-nosed aircraft‭, ‬WW-I‭ ‬replicas and so on‭. ‬They allow slow‭, ‬1800‭ ‬rpm propeller rpm perfect for the wooden props popular on such aircraft‭. ‬

Davis points out he can customize‭ ‬gear ratios to any need‭, ‬plus easily fit his gearboxes to almost any engine with a custom adapter plate or housing‭. ‬That‭ ‬means all the major features such as‭ ‬self-contained lubrication‭, ‬pressurized‭ ‬bearing lubrication and the ability to accommodate constant-speed propellers remains with all his gearboxes‭. ‬

Currently‭, ‬Auto PSRU’s have off-the-shelf fitments for the Chevy LS series‭, ‬popular Subaru‭, ‬and Mazda 13B engines‭. ‬It is typically involved in everything‭ ‬firewall forward as its customers work‭ ‬through its auto-conversion installations‭, ‬including helping with engine mount weldments and other major pieces‭. ‬They caution against wanting to hot rod the‭ ‬Chevy V-8‭ ‬applications‮—‬a common‭ ‬customer desire‮—‬as the engines are well-engineered in stock form‭, ‬lose reliability when modified and most airframes can’t‭ ‬use more power anyway‭. ‬

Firewall Forward Aero Engines

Perhaps the first thing to get squared away is to not confuse Firewall Forward Aero Engines with The New Firewall Forward‭ ‬Engines‭. ‬They are separate outfits‭; ‬the‭ ‬first being the Canadian engine maker we’re covering here‭; ‬the latter is a rebuild shop in Loveland‭, ‬Colorado‭.‬

Firewall Forward Aero Engines has‭ ‬two Honda-based four-cylinders on‭ ‬offer‭, ‬the CAM 100‭ ‬and the CAM 125‭. ‬These are legacy auto conversions based on the Honda Civic engine and apparently proven enough to earn a 2500-hour TBO and a five-year warranty‭. ‬The CAM 100‭ ‬displaces 1488cc and makes 100‭ ‬hp‭; ‬the CAM125‭ ‬is a little larger at 1590cc and makes 125‭ ‬hp‭. ‬Both engines are offered with or without a 100mm‭ ‬wide belt-drive prop speed reduction‭ ‬unit‭; ‬we’re listing them with its reduction drive in our chart‭. ‬

Firewall Forward’s other mainstay is a husky Camdrive 500‭ ‬PSRU for V-8‭ ‬engines at‭ $‬19,995‭. ‬It packs a three‭-‬gear helical arrangement to mate with GM crate engines‭. ‬These drives have‭ ‬been updated since their debut in the late 1990s and‭, ‬while retaining the same outer physical form‭, ‬have been machined internally for now-larger GM flywheels‭. ‬Other features are a cast aluminum construction‭, ‬two mounting pads machined on the sides plus two‭, ‬optional‭, ‬power‭ ‬take offs for a propeller governor‭, ‬vacuum pump or standby alternator‭. ‬Additionally‭, ‬the propeller flanges are‭ ‬separate to more easily accommodate‭ ‬different propellers‭.‬

Changes for 2020‭ ‬include the addition of Ray Watson‭, ‬president and‭ ‬owner of Moose Mods‭, ‬as the U.S‭. ‬sales outlet‭. ‬Moose Mods specializes in compete firewall-forward kits using the Camdrive 500‭ ‬PSRU for the Murphy Moose‭, ‬with up to 530‭ ‬hp available at‭ $‬45,000‭ ‬plus prop and governor‭. ‬Canada sales are through Archie Dobbins‭,‬‭ ‬operations manager of Firewall Forward Aero Engines‭. ‬

Robinson V8‭ ‬Power

Re-powering Seabee amphibians is‭ ‬where Robinson got its start converting‭ ‬Chevy LS engines‭, ‬and having developed a successful combination‭, ‬they’re sticking with it‭. ‬Besides complete Seabee‭ ‬conversions‭, ‬Robinson offers its converted LS engines in a pleasantly complete base package designed to give the LS fan a head start in fitting the popular Chevy to‭ ‬almost any airframe‭. ‬Rated power of the conversions ranges from 300‭ ‬to 425‭ ‬hp‭.‬

The base kit starts with a new Chevy‭ ‬long block‮—‬Robinson works with a‭ ‬variety of LS engines‭, ‬both naturally aspirated and supercharged by GM‮—‬to offer a wide range of performance‭. ‬Highlights of the base package are‭ ‬exhaust manifolds‭, ‬alternator‭, ‬starter‭, ‬flywheel‭, ‬ignition harness‭, ‬an engine‭ ‬control module‭ (‬computer‭), ‬engine wiring harness‭, ‬throttle body‭, ‬and a propeller gearbox‭. ‬The latter is available in three lengths‭, ‬two gear ratios and uses a Morse chain drive allowing variable pitch‭, ‬constant-speed or reversing propellers‭, ‬those being popular with seaplane pilots‭. ‬The base kit is delivered assembled as far as practical‭, ‬too‭. ‬

Robinson uses the stock General‭ ‬Motors computer‭, ‬but removes the‭ ‬unneeded code regarding oxygen sensors‭ (‬which are deleted‭) ‬and other emissions components‭. ‬Mogas‭ (‬91‭ ‬octane‭) ‬or 100LL are allowed‭; ‬Robinson reports a 12‭ ‬gph fuel burn with the 425‭ ‬hp LS-3‭ ‬engine at cruise power settings of 23‭ ‬inches and 3300‭ ‬rpm‭.‬

Optional accessories are a custom engine mount‭, ‬the remainder of the‭ ‬exhaust system and an entire cooling system based around the Chevy Corvette radiator‭. ‬Robinson asks for 30‭ ‬percent down when ordering‭, ‬another 30‭ ‬percent a month later‭, ‬another 30‭ ‬percent‭ ‬at the second month and the final 10‭ ‬percent prior to shipment‭.  ‬There is no refundable deposit‭. ‬

Air conditioning is something of a surprise and delight feature of the Robinson conversions‭, ‬which retain their‭ ‬automotive air conditioning hardware‭. ‬Cockpit heat is also fast acting‭. ‬

Viking Aircraft Engines

Honda Fit and Civic engines are the starting points for Viking’s two largest offerings. Thus, they are one of the few modern aircraft engines using direct fuel injection for better fuel economy.

Specializing in Japanese auto conversions‭, ‬Viking has an affordable‭ ‬three-engine line-up based on current‭, ‬multi-valve‭, ‬computer-controlled engines from Honda and Mitsubishi‭. ‬Viking prides themselves in keeping a large enough inventory to claim next‭-‬day shipping of its several firewall-forward kits‭.‬

Viking’s entry-level offering is a 90-‭ ‬hp version of a three-cylinder Mitsubishi engine‭. ‬Fitted with Viking’s own gearbox‭ (‬climb or cruise gear ratios can be ordered‭; ‬it can also work in pusher applications‭) ‬the combination weighs but 159‭ ‬pounds and posts a particularly muscular low-end torque curve‭ ‬when augmented with the lower of the two gear sets‭. ‬

For its popular 130-hp engine‭, ‬Viking starts with the Honda Fit four-cylinder power plant‭. ‬Also geared with a fairly steep 2.33:1‭ ‬ratio‭, ‬and also with good low‭- ‬and mid-range thrust‭, ‬the combination weighs 220‭ ‬pounds‭. ‬Because the Fit engine has its exhaust manifold integral with the cylinder head‭, ‬the engine is not a good candidate for turbocharging‭, ‬but it does boast gasoline direct fuel injection‭ ‬‭(‬fuel is shot directly into the cylinders‭). ‬This gives an in-cylinder cooling that allows a higher compression ratio for increased efficiency‭. ‬By venting crankcase blow-by to the atmosphere instead of back into the engine‭, ‬Viking escapes the valve deposit‭ ‬issues found in some automotive GDI applications‭. ‬

Viking’s top offering is the 170-hp version of the Honda Civic engine‭. ‬Naturally this gives a fat low-end torque curve‭, ‬also augmented‭ ‬by the gearbox and Honda’s gasoline direct injection‭. ‬Weight‭ ‬naturally rises to 260‭ ‬pounds‭, ‬but either 100LL or mogas can still be run‭.‬

Multiple firewall-forward kits are‭ ‬available from Viking to support these engines in Zenith‭, ‬RANS‭, ‬Van’s‭, ‬Kitfox‭, ‬Glastar and other airframes‭. ‬Viking says they have engines in the field with over‭ ‬1000‭ ‬total hours and that its product‭ ‬development program has a 100-hp version of the three-cylinder engine in the‭ ‬works for release at a later date‭. ‬

Manufacturer/ModelDrive TypeHorsepower/ConfigWeightPrice
Aero Momentum
AM10geared85 hp @ 6000 rpm-upright139 lbs w/ PSRU, starter, alternator, ECU$8,495
AM13ugeared100 hp @ 5800 rpm-upright170 lbs w/ PSRU, starter, alternator, ECU$8,995
AM13hgeared100 hp @ 5800 rpm-low profile170 lbs w/ PSRU, starter, alternator, ECU$10,995
AM13hpgeared126 hp @ 6500 rpm-low profile174 lbs w/ PSRU, starter, alternator, ECU$15,495
AM15ugeared117 hp @ 5800 rpm-upright185 lbs w/ PSRU, starter, alternator, ECU$10,495
AM15hgeared117 hp @ 5800 rpm-low profile185 lbs w/ PSRU, starter, alternator, ECU$12,495
AM15hpgeared147 hp @ 6500 rpm-low profile189 lbs w/ PSRU, starter, alternator, ECU$16,495
AM20Tgeared260 hp @ 6000 rpm-low profile310 lbs w/ PSRU, starter, alternator, ECU, turbo$19,995
Adept Airmotive
260N V-6geared260 hp @ 5500 rpm normally aspirated306 lbs w/ radiator, alt, EFI, starter, dry sump system$60,000
280N V-6geared280 hp @ 5500 rpm normally aspirated306 lbs w/ radiator, alt, EFI, starter, dry sump system$65,000
300N V-6geared300 hp @ 5500 rpm normally aspirated306 lbs w/ radiator, alt, EFI, starter, dry sump system$75,000
320T V-6geared320 hp @ 5500 rpm turbocharged340 lbs w/ radiator, alt, EFI, starter, dry sump system$85,000
360T V-6geared360 hp @ 5500 rpm turbocharged340 lbs w/ radiator, alt, EFI, starter, dry sump system$95,000
Auto PSRU’s
LS-3 Chevroletgeared360 hp @ 4500 (centrifugal clutch) 1.666:1 ratio580 lbs installed, typical, complete$39,200 FF
2.5L Subarugeared150 hp @ 5000 (centrifugal clutch) 1.859:1 ratio355 lbs installed, typical, complete$27,400 FF
3.0L Subarugeared230 hp @ 5000 (centrifugal clutch) 1.859:1 ratio375 lbs installed, typical, complete$27,600 FF
Firewall Forward Aero Engines (CAM engines)
CAM100 Honda100 mm belt100 hp @ 5500 rpm226 lbs w/ PSRU, injection, no starter or alternator$16,790
CAM125 Honda100 mm belt130 hp @ 5500 rpm247 lbs w/ PSRU, injection, no starter or alternator$18,645
Robinson V-8 Power
LS-3 Chevrolet  (LS-376/480)geared450 hp @ 5000 rpm 1.98:1 ratio525 lbs installed, typical, ready to run$39,500 base
Viking Aircraft Engines
V-90 Mitsubishigeared90 hp @ 5800 rpm160 lbs w/ exhaust, alternator$9,995
V-130 Honda Fitgeared130 hp @ 5400 rpm215 lbs w/ exhaust, alternator$10,995
V-170 Honda Civicgeared170 hp @ 5400 rpm260 lbs w/ exhaust, alternator$16,995

Radial and Rotary

Classic Aero Machining

Whether you’re in the market for an honest-to-gosh rotary engine or not, you have to admit Classic Aero Machining’s take on the venerable Gnome Monosoupape is a thing of beauty.

With its barking exhaust‭, ‬intermittent‭ ‬cylinder cut-out‭ ‬“idle”‭ ‬and memorable‭ ‬gyroscopic personality‭, ‬there’s nothing in aviation that begins to replicate the experience brought by a rotary engine‭. ‬And for those seeking the ultimate authentic WW-I experience‭, ‬New Zealand based Classic Aero Machining has been developing a brand new Gnome monosoupape engine for several of years‭. ‬It is a faithful rendition of the Gnome used in many French‭, ‬English and German aircraft just‭ ‬prior to and during the first war‭. ‬

This year CAM has improved the‭ ‬induction ports and developed a fuel pump for the engine‭ (‬the originals relied strictly on gravity‭). ‬Purists may decry it‭, ‬but CAM also has an electric starter for its rotary‮—‬it must be the first non hand-propped rotary ever‮—‬and lists output at a muscular‭ ‬120‭ ‬hp and 580‭ ‬pound-feet of torque while whirling at just 1120‭ ‬rpm‭. ‬

CAM wants to emphasize these‭ ‬engines are viable‭, ‬reliable‭, ‬real-world‭ ‬choices for WW-I replicas and that they’re in rotary business for the long term‭. ‬They certainly are the only new engine capable of delivering the true‭ ‬early-bird rotary experience‭, ‬which‭ ‬might be a little more performance oriented‭ ‬than first imagined‭. ‬CAM reports its‭ ‬rotary has a Sopwith Pup replica going 110‭ ‬mph straight and level‭, ‬plus 1000‭ ‬fpm vertically‭. ‬They expect several more of its engines to fly by next spring‭.‬

CAM is part of the burgeoning replica and restoration scene in New Zealand and has a well-established business replicating various warbird parts‭, ‬especially P-40‭ ‬items‭. ‬

Warner Engine Company‭ (‬Monocoupe Aeroplane Corporation‭)‬

Last year we reported on the Monocoupe organization’s effort to put the 185-hp Warner engine back in production as the experimental-only 185X‭. ‬That effort has‭, ‬unfortunately‭, ‬failed and has been closed down‭. ‬It’s unlikely‭, ‬but there may be a handful of parts loose on the market with 185X numbers on them as the licensing agreement required all new parts to be identified as 185X pieces‭, ‬and a very few parts were made‭ (‬no complete engines were built‭).‬

The Warner type certificate holder is John Duncan who does business as The‭ ‬Warner Engine Company‭. ‬John has some certified Warner parts for sale‭, ‬but no complete engines‭. ‬It’s too bad the 185-hp Warner hasn’t made it back to production as it’s a perfect fit for many experimental aircraft‭, ‬especially replicas‭. ‬A big-bore version of the much more common 165‭ ‬Warner‭, ‬these radials were good engines in their day‭, ‬and according to John‭, ‬given modern manufacturing‭ ‬capabilities should prove bulletproof‭ ‬reliable‭, ‬with good power-to-weight‭ ‬ratios packaged in an attractive size for personal aircraft use‭. ‬

Motorstar NA

Designed in Russia by Vendeneyev and last in full production in Romania, the M-14P radial is powerful, robust and popular for those needing a healthy dose of round power but not quite ready for a Pratt & Whitney 985. New engines are still available; rebuilds are more practical.

There aren’t too many homebuilts that‭ ‬take all the muscle a 621‭ ‬cubic inch M-14P radial can dish out‭, ‬but if you‭ ‬want a new‭ $‬50,000+‭ ‬one from builder Motorstar Romania then Coy Aircraft Sales is also Motorstar NA‭, ‬and they can make it happen‭. ‬More practically Coy can also source a factory overhaul‮—‬now a fixed‭ $‬21,500‭ ‬if you have a core‭. ‬That gets you the‭ ‬three‭-‬ring piston upgrade and Savarese ignition‭, ‬along with overhauled air compressor‭, ‬carburetor and‭ ‬oil pump‭, ‬test stand run-in‭, ‬all work‭ ‬being done in Romania‭. ‬The turnaround is 60‭ ‬days and shipping‭ $‬3300‭. ‬

As usual‭, ‬when an M-14P goes in for‭ ‬overhaul‭, ‬more often than not it goes‭ ‬from the base 360‭ ‬hp to the 400‭ ‬hp M-14PF upgrade as the price isn’t that‭ ‬much greater‭. ‬Other sources for these‭ ‬robust Russian-designed radials are Jill Gemerzke’s M-14P Inc‭. ‬in Kingman‭, ‬Arizona‭, ‬and Barrett Performance Engines in Tulsa‭, ‬Oklahoma‭, ‬which specializes in hot rod versions with‭ ‬electronic ignition‭ ‬and Airflow Performance fuel injection‭.‬

Rotec Aerosport

Thanks to being just the right size, Rotec’s R-2800 and R-3600 radials have spurred a resurgence in smaller round-engine sport aircraft. Both engines turn a frisky 3600 rpm but are geared for slower prop speeds.

In the not-too-big‭, ‬not-too-small radial‭ ‬category is Australian engine maker‭ ‬Rotec‭, ‬which continues to supply the‭ ‬most round motors to the experimental market‭. ‬The naturally slow-turning and‭ ‬geared Rotecs provide the sound and‭ ‬long-prop looks so popular with amateur builders looking for either a vintage appearance or who simply want something a little different than the ubiquitous flat-engine norm‭. ‬The engines‭ ‬remain unchanged for 2020‭.

Rotec offers two engines‭, ‬the seven-cylinder R2800‭ ‬good for 110‭ ‬hp‭, ‬and its big brother R3600‭ ‬which sports nine of the same cylinders for a 150-hp rating‭. ‬Both are un-supercharged‭. ‬The smaller engine is most often paired with a fixed-pitch 76-inch-diameter‭ ‬prop while the R3600‭, ‬which was later to market but‭ ‬seems to have picked up sales steam‭ ‬lately‭, ‬can swing 90-inch blades‭. ‬

Standard Rotec induction is a simple‭ ‬Bing slide carburetor‭, ‬but Rotec’s own‮—‬and still quite simple‮—‬TBI Mk 2‭ ‬throttle-body fuel injection is optional‭. ‬Its‭ ‬main attraction is staying on the job during aerobatics‭, ‬and besides fitments for its radials‭, ‬Rotec offers versions of its carburetor for everything from VW conversions to Rotax‭, ‬Jabiru and even Lycomings‭. ‬

Rotec sells direct‭, ‬so planning ahead‭ ‬for engine construction and freighting‭ ‬from Australia will help avoid frustration‭. ‬

Verner Motor‭

Interest is definitely building in the Verner line of radials, which range from a rather compact three-cylinder to a 158-hp nine-cylinder. In fact, the Verner line was so populous they cut back to one each of their larger five-, seven- and nine-cylinder Scarlett models this year.

A bit under our lower power limit is the little 42-hp three-cylinder engines put out by Verner Motor‭, ‬but if you have‭ ‬raging dreams of a Demoiselle reproduction‭, ‬the pocket-sized Verner radial bears a look‭. ‬Otherwise‭, ‬one of Verner’s larger five‭, ‬seven‭, ‬or nine-cylinder radials has the compact dimensions to fit a number of fun-flying personal planes and give‭ ‬them the unmistakable round motor look‭, ‬feel and sound‭. ‬So far that’s been Hatz biplanes‭, ‬older Kitfoxes and a slew of WW-I replicas‭, ‬both scale and full-size‭, ‬as Verner continues to make in-roads‭ ‬on the U.S‭. ‬market‭. ‬

Built in the Czech Republic by a‭ ‬small company that’s been in the airplane engine business since 1993‭, ‬the Verner radials we’re detailing here use the same two-valve‭, ‬3.62‭ ‬x 4.02-inch cylinder‭, ‬but fit five‭, ‬seven‭, ‬or nine of them as power needs rise‭. (‬Let’s note‭ ‬the little 28-inch diameter three‭-‬banger shares its smaller cylinders‮—‬now aluminum with steel liners‮—‬with a five-cylinder version as well‭). ‬All of the larger engines‭, ‬which Verner groups under the Scarlett name‭, ‬are relatively‭ ‬low-rpm‭, ‬direct-drive designs using‭ ‬no supercharging but employing carburetor and optional fuel injection‭. ‬Designed to run on 93-octane U.S‭. ‬or 95-octane European premium mogas‭, ‬the Scarlett series‭ ‬has a 32-inch diameter and a TBO of 1000‭ ‬hours‭. ‬Experience shows some lead fouling on a steady diet of 100LL fuel‭, ‬but this‭ ‬responds favorably to lead-scavenging‭ ‬additives or simply by running mogas‭.‬

Power ranges from 83‭ ‬hp in the Scarlett 5Si to 158‭ ‬hp in the largest Scarlett‭, ‬the 9S‭. ‬A recent change is a rationalization of parts and engine models to improve Verner’s production efficiency‭. ‬That’s eliminated the 7Si and 7H models which were fairly redundant to the remaining 7U‭, ‬plus all crankcases are‭ ‬now magnesium‭. ‬Three U.S‭. ‬dealers‭ ‬are available‭, ‬and seem to be enjoying‭ ‬a growing interest in these engines for various retro-themed airframes‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
Classic Aero Machining Service
Gnome Monosoupaperotary120 hp @ 1125 rpm260 lbs with oil pump, air pump, ignition$62,000
Motorstar NA 
M14-Pgeared360 hp @ 2900515 lbs w/ air or electric start, B&C alternator$52,000
M14-PFgeared400 hp @ 2900515 lbs w/ air or electric start, B&C alternator55000 ($28K-32K reman)
Rotec Aerosport Pty Ltd
R-2800geared110 hp @ 3600 rpm224 w/ starter, alternator, carb, ignition, stub exhaust$22,500
R-3600geared150 hp @ 3600 rpm275 w/ starter, alternator, carb, ignition, stub exhaust$27,500
Verner Motor
Scarlett Radial 3V, 100cidirect42 hp @ 2500 rpm86 lbs w/  starter, alternator, carb, ignition$7,250
Scarlett Radial 5V, 166cidirect60 hp @2300 rpm119 lbs w/ starter, alternator, carb, ignition$9,315
Scarlett Radial 5S, 207cidirect83 hp @ 2200 rpm152 lbs w/ starter, alternator, EFI, ignition$14,670
Scarlett Radial 7U, 290cidirect124 hp @ 2300 rpm183 lbs w/ starter, alternator, EFI, ignition$19,262
Scarlett Radial 9S, 372cidirect158 hp @ 2400 rpm238 lbs w/ starter, alternator, EFI, ignition$25,710

Rotary (Wankel)

American Rotary Engine

American Rotary Engine is the aviation sidebar to Atkins Rotary‭, ‬which makes hop-up parts and adapters for Wankel‭ ‬engines for just about anything that‭ ‬moves‭. ‬So‭, ‬while the parent company stays busy with automotive and other‭ ‬outlets‭, ‬American is keeping a low‭ ‬flame under the aviation engine part of the business‭. ‬

American has some of its earlier‭ ‬engines flying and continues to slowly develop its Mazda 13B-based airplane‭ ‬engine‭. ‬They have a new rotor housing cast and are now machining it‭, ‬but truth is they are getting more calls on‭ ‬its marine Wankel applications than‭ ‬aviation units so progress is limited‭. ‬As‭ ‬always‭, ‬American is ready to build its Wankel to order‭, ‬which uses a Power‭-‬sport PSRU gearbox‭.‬

Auto PSRU’s

While Auto PSRU’s continues to offer full support for the Mazda 13B engine as a kit‭, ‬they say interest in Wankel engines has significantly fallen off across the full breadth of the alternative engine community‭. ‬They don’t know why‭, ‬as the Wankel‭ ‬remains available and still a power-to‭-‬weight champion‭, ‬but they’ve seen little interest in the rotary lately‭. ‬Because the Auto PSRU’s 13B kit was finalized some years ago‭, ‬it’s no problem for Auto PSRU’s to continue to keep the option in its catalog‭; ‬all that’s needed are customers‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
American Rotary Engine
2 rotor 13Bgeared180 hp @ 6000 rpm320 lbs wet w/ alternator, starter, ECU, EFI and EI$20,000
Auto PSRU’s
Mazda 13Bgeared180 hp @ 7600 (centrifugal clutch) 2.778:1 ratio385 lbs installed, typical, complete$28,400 FF
Mazda 13B Turbo Normalizedgeared200 hp @ 7600 (centrifugal clutch) 2.778:1 ratio410 lbs installed, typical, complete$36,900 FF

Compression Ignition (Diesel & Jet A)


Continental’s diesel offerings are diverse, with water-cooled auto-based engines and more traditional air-cooled flat engines such as this CD-230 in the lineup. Expense and Continental’s policy of not selling direct to homebuilders keeps these engines mainly
in certified airframes.

Diesels or‭ (‬Jet A engines‭) ‬are by nature premium devices full of expensive parts‭, ‬so their penetration into the amateur‭-‬built world by any manufacturer has‭ ‬been more promise than actuality‭. ‬Several‭ ‬very‭ ‬interesting engines have been under development for some time‭, ‬but they’re so complex and expensive they’re‭ ‬just now breaking into the defense‭ ‬department budget as possible drone‭ ‬engines‭. ‬Whether we’ll ever get an‭ ‬affordable‭, ‬well-developed Jet A burner remains a wide open question‭. ‬

In the meantime‭, ‬Continental has a surprising well-populated line of certified diesels as it seems to enjoy buying up diesel programs started by Thielert‭, ‬Austro‭, ‬and other European outfits‭. ‬At least in their technical specifications‭, ‬these engines are suited to larger‭ ‬homebuilt aircraft‭. ‬But since they’re‭ ‬certified engines‭, ‬Continental has no interest in selling them to homebuilders‭, ‬though they can be purchased indirectly through‭ ‬non-factory outlets‭.  ‬

To this group we can now add‭ ‬Continental’s 3.0-liter CD-300‭, ‬a‭ ‬powerful‮—‬300‭ ‬hp at a quiet 2300‭ ‬rpm‮—‬V-6‭. ‬Its specifications read like an aircraft engine wish list with four-valves per cylinder‭, ‬common rail injection‭, ‬twin-turbos‭, ‬water cooling‭, ‬dual‭ ‬FADEC electronics with single lever control‭, ‬gearbox‭, ‬and prop governor‭. ‬Already announced as going into Diamond Aircraft’s DA50‭ ‬single-engine‭ ‬luxury‭ ‬cruiser‭, ‬the CD-300‭ ‬is EASA certified with FAA certification pending‭. ‬The combination weighs 548‭ ‬pounds‭, ‬which can be offset by carrying less fuel because it is rated at just 9.2‭ ‬gph at cruise power‭. ‬If that all sounds irresistible‭, ‬remember if you need to ask how much it costs you can’t afford it‭ (‬pricing is not announced‭, ‬but it’s not likely to be package-competitive with gasoline engines of the same power‭). ‬And the current time‭ ‬between replacement‭ (‬not overhaul‭) ‬is‭ ‬just 1200‭ ‬hours‭ (‬2000‭ ‬hours is the projected eventual TBR‭). ‬

AC Corporation‭ / ‬Higgs Diesel

The same Andy Higgs we met in the‭ ‬horizontally-opposed section of this guide is active in the diesel world as well under the Higgs Diesel banner‭. ‬Andy‭ ‬has been showing a series of interesting compression ignition engines on his website‭, ‬without question the flashiest one being the E-1000‭ ‬V-12‭ ‬which carries a cool 1000‭ ‬to 1600‭ ‬hp rating‭. ‬He also displays upright and inverted V-4s on his website‭. ‬

All of these AC Corporation diesels use a two-stroke engine cycle‭, ‬but Andy says he has a way of stratifying the exhaust charge inside the combustion chamber resulting in many benefits‭. ‬The main idea is by more carefully controlling the charge distribution inside the cylinder Andy is able to optimize the traditional two-stroke port’s flow and‭ ‬scavenging characteristics‭, ‬sufficiently that the intake charge is admitted‭ ‬straight into the cylinder without passing through the crankcase‭. ‬A cascade of advantages follow‭, ‬including cleaner oil‭, ‬increased piston cooling‭, ‬better fuel economy and so on‭. ‬

Like anything in the 1000-hp class‭, ‬if you’re interested in the E-1000‭ ‬V-12‭ ‬Condor engine you best talk directly to Andy about pricing and availability‭. ‬The‭ ‬E330J/G Hawk V-4‭ ‬seems a little further out developmentally‭, ‬and is listed‭ ‬as 300‭ ‬‮–‬‭ ‬500‭ ‬hp and costing‭ $‬54,000‭ ‬‮–‬‭ $‬74,000‭ (‬the latter with turbocharging‭). ‬

Finally‭, ‬there is the FL1500‭ ‬inverted-V-4‭. ‬Designed to weigh just 148‭ ‬pounds and offer between 120‭ ‬and 200‭ ‬hp‭, ‬the little guy is‭ ‬touted as a Rotax replacement‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
AC Corporation
AC E-1000J/Ggeared1600 hp liquid cooled JET A679 lbs w/ starter, ECU and alternators$260,000
AC E-660J/Ggeared800 hp liquid cooled JET A499 lbs w/ starter, ECU and alternators$150,000
AC E-330J/Ggeared350 hp liquid cooled JET A286 lbs w/ starter, ECU and alternators$58,000
AC FL-2000geared150-230 hp liquid cooled JET A154 lbs w/ starter, ECU and alternators$39,000
Continental Motors
CD-135geared135 hp @ 3890 rpm295 lbs with accessories, dual FADECKit program only
CD-155geared155 hp @ 3890 rpm295 lbs with accessories, dual FADECKit program only
CD-230direct235 hp @ 2200 rpm450 lbs with accessoriesBeta Program


AeroConversions‭   ‬

Sonex’s test mule AeroVee engine sits on their in-house dyno across the runway from AirVenture in Oshkosh, Wisconsin. Like many VW-based engines, the AeroVee is sold as a kit so that buyers can save some money by assembling it by themselves.

As its website says‭, ‬AeroConversions‭ ‬is a product line of Sonex aircraft‭. ‬This makes perfect sense‭, ‬as Sonex has been‭ ‬selling aircraft kits designed for air‭-‬cooled Volkswagen power for ages‭, ‬and‭ ‬has been offering its own converted‭ ‬VW engine‮—‬the AeroVee‮—‬to match for just as long‭. ‬

There are two AeroVee engine kits‭, ‬the 80-hp‭, ‬2.1-liter naturally aspirated engine along with a turbo version rated at 100‭ ‬hp‭. ‬Notice we said kits‭, ‬as all AeroVees‭ ‬arrive at the customer’s door‭ ‬as disassembled engines‭. ‬The idea is‭ ‬you don’t pay AeroConversions a lot of money to assemble your engine‭, ‬but rely instead on a thorough instruction manual‭, ‬other AeroConversion support and‭ ‬your own initiative to keep that money‭ ‬in your pocket‭. ‬

For 2020‭, ‬there are no hardware‭ ‬changes to the two well-developed‭ ‬AeroVee engines‭, ‬but we can say the‭ ‬turbocharger water cooling system‭ ‬introduced last year has proven popular and is a near-universal option on the 100-hp engine‭. ‬It uses a bare pint of water in a self-contained system to cool the turbocharger’s center bearing‭, ‬but only after the engine has shut down and the running supply of engine oil isn’t flowing‭. ‬A timer starts and stops the electrically-motivated system‭, ‬making it transparent to the pilot‭. ‬The system runs anywhere from 20‭ ‬minutes to an hour after engine shut down and is independent of the master switch‭. ‬

Great Plains Aviation Supply

Another outfit offering you-assemble‭ ‬engine kits is Great Plains‭. ‬Again‭, ‬this‭ ‬keeps costs low and also helps Great‭ ‬Plains market a surprisingly wide variety of VW engine variants‭. ‬To start‭, ‬Great Plains has‭ ‬“full”‭ ‬or four-cylinder VWs‭, ‬or two-cylinder half-VW engines‭. ‬In four-cylinder engines you can choose among driving the propeller from‭ ‬the flywheel end‭, ‬or the pulley end of the‭ ‬engine‭, ‬the former with an accessory‭ ‬isolation kit‭, ‬and with or without a‭ ‬belt-driven propeller speed reduction‭ ‬unit‭. ‬Kits are available as short‭- ‬or long-blocks‭. ‬In fact‭, ‬the entire Great Plains offerings are available in just about any‭ ‬combination of parts and kits imaginable‭, ‬and they offer a wide range of accessory items‭.  ‬

Hummel Engines

Certainly the Volkswagen-based engine world is a price-conscious market‭, ‬but even so Hummel Engines stands out as the minimalist’s choice‭. ‬By leaving off all the frills‭, ‬Hummel offers assembled VW-based engines ready to fly for about the price of a good porting job at most engine shops‭. ‬These are also extremely light engines‭.‬

Of course‭, ‬this means you’ll get good‭ ‬at hand propping and won’t feel bad about flying on one magneto because‭ ‬there is but one magneto‭, ‬no starter or alternator at the entry-level price points‭. ‬But those dual-mag and starter motor luxuries are available optionally‭, ‬and the price‮—‬and weight‮—‬are still low‭. ‬Hummel even has a full line of two-cylinder‭ ‬half-VW engines if less is more your‭ ‬style‭. ‬Hummel reports activity is brisk‭, ‬with the lead time for a new engine running around eight months‭. ‬Interestingly‭, ‬they say the majority of its activity is in two-cylinder engines these days‭, ‬so the super light market is apparently robust‭. ‬


It may look like a VW‭, ‬but it’s really the‭ ‬VW engine completely re-engineered‭ ‬as an aviation engine‮—‬the Cadillac of VWs if you will‭. ‬Motorav’s parent company is Rima‭, ‬a very large Brazilian mining and industrial outfit that bought out VW’s Brazilian die casting plant and also has its own supply of magnesium and other metals‭. ‬Starting with the Type 1‭ ‬VW architecture‭, ‬Motorav has addressed every‭ ‬aspect of the design to strengthen it for aviation as a 175‭ ‬cubic inches‭ (‬2868cc‭), ‬air-cooled‭, ‬flat-four yielding 100‭ ‬hp at 2900‭ ‬rpm with a 1200-hour TBO‭. ‬

Notable improvements are a reinforced magnesium case‭, ‬one-piece‭ ‬crankshaft with integral propeller flange‭ ‬‭(‬like Lycoming‭, ‬Continental‭, ‬et al‭.), ‬unique cylinder heads with down-facing exhaust ports and dual spark plugs‭,  ‬fittings for standard aviation CHT sensors‭, ‬hydraulic lifters‭, ‬built-in alternator‭, ‬and increased oil capacity‭. ‬Electronic‭ ‬ignition and a single-point fuel injection systems are standard‭. ‬

Motorav was listing Polymet Alloys as its U.S‭. ‬distributor‭, ‬but that arrangement seems to have ended as Motorav searches for another sales path in the U.S‭., ‬so contact Motorav directly‭.‬

Revmaster Aviation

Not quite in full production is this turbocharged version of Revmaster’s best-seller, the R-2300D. Revmaster says getting the architecture over 100 hp is the big push in air-cooled aviation VWs today.

Elder statesman of the air-cooled VW is Joe Horvath of Hesperia‭, ‬California‭. ‬He’s been hot rodding VWs for terrestrial vehicles since 1959‭(!), ‬just about when VWs were first being seen in any number in the U‭.‬S‭. ‬Later teaming with aeronautical engineer Ralph Maloof‭, ‬they optimized the air-cooled VW for aviation as much as possible short of completely redesigning it‭. ‬

Its bread-and-butter power plant is‭ ‬the R-2300‭ (‬2331cc‭, ‬142.2‭ ‬cubic inches‭) ‬at 82‭ ‬hp using 3350‭ ‬take-off rpm‭; ‬the continuous rating is 2950‭ ‬rpm‭. ‬A well-sorted combination by now‭, ‬the R-2300‭ ‬uses Revmaster’s own cylinder head and‭ ‬bristles with internal upgrades‭. ‬These‭ ‬include a new four-bearing crankshaft‭, ‬the unique ability in this market segment to support hydraulically controlled propellers‭, ‬an eight-coil/eight-spark plug‭ ‬dual CDI ignition‭, ‬dual 20-amp alternators and a simple‭, ‬slide-type‭, ‬floatless Rev-Flo carburetor‭. ‬

The latest development of the R-2300‭ ‬is a turbo version that has been in development for over 100‭ ‬hours of run time‭. ‬It gives 102‭ ‬hp at 3200‭ ‬rpm up to 12,000‭ ‬ft‭. ‬The R-2300DT Turbo has been on‭ ‬the front burner at Revmaster for several years now and continues to be the center of the development attention‭. ‬

Not so much on the front burner has‭ ‬been a re-drive‭ (‬PSRU‭) ‬version of the‭ ‬R-2300‭. ‬This belt-drive development‭ ‬came from apparent demand of the long-prop and WW-I replica aviation crowd‭, ‬but demand seems to have dropped off‭, ‬so Revmaster is holding off the expensive tooling commitment until demand warrants the attention‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
AeroConversions (Sonex)
AeroVee 2.1direct80 hp @ 3400 rpm160 lbs w/ alternator, starter, carb, ignition$7600 kit
AeroVee 2.1 Turbodirect100 hp @ 3400 rpm185 lbs w/ alternator, starter, carb, ignition$11,995 kit
Great Plains Aircraft Supply
1835cc front drivedirect65 hp @ 3600 rpm, 60 @ 3400 continuous163 lbs w/ alternator, starter, carb, Slick 4220$6239 kit
1835cc flywheel drivedirect65 hp @ 3600 rpm, 60 @ 3400 continuous156.5 lbs w/ alternator, starter, carb, distributor$5898 kit
1835cc reductionbelt85 hp @ 4200 rpm, 65 @ 3400 continuous176.8 lbs w/ alternator, starter, carb, Slick 4220$6766 kit
1915cc front drivedirect69 hp @ 3600 rpm, 65 @ 3400 continuous163.2 lbs w/ alternator, starter, carb, Slick 4220$6239 kit
1915cc flywheel drivedirect69 hp @ 3600 rpm, 65 @ 3400 continuous156.7 lbs w/ alternator, starter, carb, distributor$5898 kit
1915cc reductionbelt85 hp @ 4200 rpm, 65 @ 3400 continuous177 lbs w/ alternator, starter, carb, Slick 4220$6766 kit
2180cc front drivedirect76 hp @ 3600 rpm, 70 @ 3400 continuous164.5 lbs w/ alternator, starter, carb, Slick 4220$7070 kit
2180cc flywheel drivedirect76 hp @ 3600 rpm, 70 @ 3400 continuous158 lbs w/ alternator, starter, carb, distributor$6228 kit
2180cc reductionbelt103 hp @ 4200 rpm, 70 @ 3400 continuous180 lbs w/ alternator, starter, carb, Slick 4220$7205 kit
2276cc front drivedirect80 hp @ 3600 rpm, 76 @ 3400 continuous165 lbs w/ alternator, starter, carb, Slick 4220$7070 kit
2276cc flywheel drivedirect80 hp @ 3600 rpm, 76 @ 3400 continuous158.5 lbs w/ alternator, starter, carb, distributor$6228 kit
2276cc reductionbelt105 hp @ 4200 rpm, 72 @ 3400 continuous180.5 lbs w/ alternator, starter, carb, Slick 4220$7205 kit
Hummel Engines
1600ccdirect50 hp @ 3600 rpm140 lbs w/ carb, Slick mag, wo/ starter or alt$4,150
1835ccdirect60 hp @ 3600 rpm145 lbs w/ carb, Slick mag, wo/ starter or alt$4,350
1915ccdirect65 hp @ 3600 rpm145 lbs w/ carb, Slick mag, wo/ starter or alt$4,375
2180ccdirect76 hp @ 3600 rpm147 lbs w/ carb, Slick mag, wo/ starter or alt$5,625
2400ccdirect85 hp @ 3600 rpm147 lbs w/ carb, Slick mag, wo/ starter or alt$5,925
Motorav Aircraft Engines
Series 100HPdirect100 hp @ 2900 rpm185 lbs w/ EFI, electronic ignition, oil cooler$12,900
Revmaster Aviation LLC
R-2300Ddirect85 hp @ 3200 rpm170 lbs w/ alternator, starter, carb, dual CDI$9,400
R-2300DT Turbodirect102 hp @ 3200 rpm, to 12,000 feet190 lbs w/ alternator, starter, carb, dual CDI$11,850
R-2300 with Redrivebelt90 hp @ 3650 rpmTBD lbs w/ alternator, starter, carb, dual CDI$11,600 (est)

Jets & Turboprops

PBS Aerospace

PBS has the small but highly visible amateur-airplane jet market to itself. So far the TJ100 is racking up a very low maintenance and trouble-free reputation, but overhaul costs are still an open question as no one has reached that many hours yet.

Ah‭, ‬the whine of jet power‭. ‬In the‭ ‬homebuilt world today that only means one thing‭, ‬the SubSonex jet kit powered by the PBS TJ100‭ ‬turbojet engine‭. ‬Another product‭ ‬of the Czech Republic’s aviation industry‭, ‬currently the‭ ‬PBS engine alone has the correct combination of thrust‭, ‬man-rated safety‭, ‬size‭, ‬and availability to make it a viable powerplant for Experimental/Amateur-Built aircraft use‭. ‬

Our own‭ ‬Turbofueher‭ ‬Paul Dye has‭ ‬been regaling us with tales of turbine‭ ‬derring-do so we’ll leave the many details‭ ‬of TJ100‭ ‬ownership and operation to his many-part series on building and flying his own SubSonex jet‭, ‬but suffice to say here the little whistle is no doubt the most bulletproof‭, ‬reliable engine in this guide‮—‬and likely the most fuel thirsty as well‭. ‬Actually‭, ‬to that last statement‭, ‬we must add the SubSonex has demonstrated sufficient fuel economy to make it a thrilling local flyer‭, ‬and with generous prior planning can make the hajji to Air Venture from the west coast‭, ‬too‭. ‬

If considering a PBS jet it’s good to know the company is a large‭, ‬well-established firm with many products in diversified fields‭. ‬It is hardly dependent on the‭ ‬530‭ ‬sales of TJ100s to date for drones‭, ‬UAV’s‭, ‬experimental aircraft and the‭ ‬like‭; ‬it has the resources necessary to field a proper jet turbine‭. ‬Furthermore‭, ‬in addition to the TJ100‭ ‬it also builds‭ ‬both smaller and slightly larger turbojets‭, ‬the TP100‭ ‬turboprop and the TS100‭ ‬turboshaft engine for rotorcraft‭. ‬

Sales of the TJ100‭ ‬are through Sonex‭ ‬for the SubSonex or direct with PBS‭. ‬Furthermore‭, ‬Turbine Solutions Group‭, ‬while no longer a PBS dealer‭, ‬has experience with a TP100-powered RV-10‭, ‬Velocity and Lancair airframes if you’re headed in that direction‭. ‬

Manufacturer/ModelDrive TypeThrustWeightPrice
PBS Velká Bíteš
TJ 100 turbojetNA247 lbs maximum, 173 lbs continuous43 lbs w/ accessoriesNot provided


Azalea Aviation‭

Sport Performance Aviation has teamed with Corvair guru William Wynne to build 105-, 115- and 119-hp versions of the venerable GM flat-six. SPA uses them in their Panther kit but supports all Corvair applications.

Corvair aviation engines are just part of the very busy operation involving Saberwing aircraft and Spyder Corvair conversion engines‭. ‬Proprietor Bill Clapp‭ ‬is dedicated to expanding sport aviation and safety as much as possible‭, ‬and his Spyder Corvairs fill the power bay in his Saberwing experimental airplane‭. ‬

The naturally-aspirated 100-hp has been on sale and is built from reconditioned GM parts reinforced by a steel front hub on the‭ ‬crankshaft‭, ‬added front main bearing‭, ‬nitriding‭, ‬a 30-amp rear-mounted alternator and plenty of new service parts‭. ‬

The newer 125-hp version gets its‭ ‬oomph from a brand-new‭, ‬counterweighted‭, ‬1/4‭-‬inch stroker crankshaft that takes it out to 3.1-liters displacement‭. ‬This is without having to cut the case for overly large cylinders‭, ‬thus preserving case integrity‭. ‬All Spyder Corvair‭ ‬engines are built to order‭. ‬

In the works is a turbo package which will add‭ $‬3500‭ ‬to the price and plenty‭ ‬of altitude performance‭. ‬Bill reports‭ ‬about two years and 300‭ ‬hours of turbo‭ ‬prototype engine run time so far with‭ ‬no issues‭, ‬and more beta engine testing to come‭. ‬In the meantime he’s gotten all the Corvair teardown‭, ‬operation and other manuals online for everyone’s free use‭. ‬His operation also includes firewall forward parts such as cowlings‭, ‬spinners‭, ‬props and so on for a number of applications‭ (‬Zenith and Sonex among others‭), ‬plus he’s always running some sort of‭ ‬builder assist or tutorial programs at his Cook County‭, ‬Georgia headquarters‭. ‬

Sport Performance Aviation

Another Corvair engine and airframe‭ ‬combination is Sport Performance‭ ‬Aviation‮—‬SPA‮—‬that combines their‭ ‬take on the Corvair with their Panther single-seat sport plane and it’s coming soon two-place Cougar big brother‭. ‬The secret weapon behind SPA’s Corvairs is‭ ‬their association with William Wynne‭, ‬the universally acclaimed guru of flying Corvair engines‭. ‬William does business at Fly Corvair where there is a wealth of information‭, ‬but his expertise is mainly made material at SPA‭. ‬

For 2020‭, ‬SPA has added a stroker‭ ‬crankshaft option to their line-up‭, ‬giving them the stock 2.8-liter displacement‭, ‬plus the big-bore 3.0-liter and now the 3.3-liter option‭. ‬By working with William they claim their combinations are built from 90%‭ ‬new parts and are sufficiently inclusive to be true one stop shopping solutions to a running Corvair‭. ‬The‭ ‬base price is for kit engines‮—‬unassembled parts in a box‮—‬with bottom-end‭ ‬assembly a‭ $‬600‭ ‬option and full engine assembly and test run‭ $‬2000‭ ‬extra‭. ‬

The 3.3-liter is arrived at by combining the enlarged bore of the 3.0-liter with‭ ‬a new‭, ‬made in the USA stroker crankshaft hewn from billet‭. ‬It’s the same size outside‭, ‬and thanks mainly to the lighter crankshaft‭, ‬is weighs less than a standard Corvair‭. ‬SPA offers the engine as a Jump Start Kit for the 3.0-liter‭; ‬add the Jump Start Kit to the 3.0‭ ‬and you get the 3.3‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
Azalea Aviation
Spyder 100direct100 hp210-215 lbs wet with alternator$10,500
Spyder 125direct120 hp210-215 lbs wet with alternator$12,900
Sport Performance Aviation LLC
2775cc (169ci) 6-cyldirect105 hp @ 3150 rpm225 lbs w/ starter, ignition, and alternator$12,495 kit
3000cc (183ci) 6-cyldirect115 hp @ 3300 rpm225 lbs w/ starter, ignition, and alternator$13,495 kit
Fly Corvair
3300cc (201ci) 6-cyldirect119 hp @ 2800/125 hp @ 3300 rpm225 lbs w/ starter, ignition, and alternator$16,395 kit

Two Stroke


Hirth’s well-respected line of dedicated two-stroke aviation engines is topped by its 100-hp three-cylinder. Like all Hirths, it can be optioned into a wide range of configurations. Carburetion is standard, for example, but fuel injection is optional, as shown here.

The very name Hirth is deeply associated with two-stroke engines‭, ‬which‭ ‬the German company has specialized in‭ ‬for decades‭. ‬Furthermore‭, ‬Hirth two‭-‬strokes in our guide are designed strictly for aviation‭, ‬meaning they are tuned for lower rpm and greater durability than typical ground-based engines‭. ‬Notable features are Al-Nikasil coated cylinders and 4130‭ ‬chrome moly crankshafts‭. ‬

Hirth engines are distributed in‭ ‬the North America by Recreational‭ ‬Power Engineering in Ohio‭, ‬and while their selection of engines starts at just 15-hp‭, ‬we’re showing the 50-hp and up‭ ‬powerplants here‭. ‬Keep in mind each‭ ‬Hirth engine model is typically offered‭ ‬with or without a gearbox‭ (‬with many‭ ‬gear ratios to choose from‭), ‬and could have‭ ‬other important ordering options such as adding a centrifugal clutch to the drive‭, ‬an electric starter or oil injection or electronic fuel injection‭. ‬For this guide we’re displaying the base engine for each model‭ ‬in our charts‭. ‬Furthermore‭, ‬there can‭ ‬be tuning differences within an engine‭ ‬model line‭, ‬meaning power and torque‭ ‬peaks can be selected between‭ ‬“high”‭ ‬and‭ ‬“low”‭ ‬options depending on if maximum‭ ‬peak power or maximum cruise fuel‭ ‬efficiency is more valued‭. ‬Lower power Hirth engines are air-cooled‭; ‬the larger engines are water cooled‭. ‬

Because Hirth engines are manufactured in limited‭, ‬non-continuous runs‭ ‬there can be a 4‭ ‬to 6‭ ‬week lead time when‭ ‬ordering‭, ‬so planning ahead is smart‭. ‬Warranty terms are good‭, ‬up to including pre-paid shipping when returning an engine for service‭. ‬


Today Rotax is known for their four-stroke engines for‭ ‬“big”‭ ‬Experimental/Amateur-Built aircraft‭, ‬but their start was with two-stroke ultralight‭ ‬engines‭. ‬Just one of those engines‭ ‬remains in the Rotax line up today‭, ‬the 582UL‭. ‬It’s rated at 65‭ ‬hp and with the light weight and friendly pricing good for the most basic Experimental/Amateur-Built aircraft‭. ‬

The 582‭ ‬is available in direct-drive‭ ‬form‭, ‬and with one of two gear-boxes‭. ‬The B gearbox‭ (‬“drive”‭ ‬in Rotax speak‭) ‬is suitable for smaller diameter‭, ‬lighter three-blade propellers while the E gearbox is larger and includes an‭ ‬electric starter at its bottom‭. ‬The other 582‭ ‬engines place the starter at the rear‭, ‬or other end‭, ‬of the‭ ‬engine‭. ‬The E box can handle roughly‭ ‬twice the inertial mass at the propeller as the B drive‭. ‬For 2020‭ ‬Rotax has not made‭ ‬any technical changes to the 582‭ ‬line‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
BRP Rotax
582UL inline WC twingeared65 hp @ 6500 rpm carbureted104 lbs wo/ radiator, w/ E gearbox and exhaust$7,607
F-23 opposed twinbelt drive50 hp @ 6150 rpm71 lbs free air w/ starter, exhaust$6,312
3202 inline twingearbox55 hp @ 5500 rpm79 lbs fan cooled w/starter, exhaust; opt. gearbox adds 19 lbs$6,218
3203 inline twingearbox65 hp @ 6300 rpm79 lbs fan cooled w/starter, exhaust; opt. gearbox adds 19 lbs$7,045
3502 inline WC twingearbox60 hp @ 5000 rpm79 lbs fan cooled w/starter, exhaust; opt. gearbox adds 19 lbs$7,147
3503 inline WC twingearbox70 hp @ 6500 rpm79 lbs fan cooled w/starter, exhaust; opt. gearbox adds 19 lbs$7,876
3702 inline triplegearbox84 hp @ 4950 rpm108 lbs wo/radiator, w/ starter, exhaust; 127 lbs w/gearbox$10,970
3703 inline triplegearbox100 hp @ 6000 rpm108 lbs wo/radiator, w/ starter, exhaust; 127 lbs w/gearbox$11,847



While Pipistrel is mainly dealing with‭ ‬airframe manufacturers and is not‭ ‬actively engaged with the amateur-built hobby‭, ‬we’re listing four of their electric‭ ‬power systems for the more intrepid‭ ‬experimental builders who may be looking for a completely new challenge‭. ‬

And make no mistake‭, ‬electric propulsion is completely different from our usual 100LL and Jet A engines‭. ‬It’s best to have a thorough understanding of which‭ ‬wire typically goes where in electrical‭ ‬systems before attempting to install such e-motivation in your home-built‭. ‬That’s‭ ‬because these are high-amperage‭, ‬high‭-‬voltage electrics that demand the upmost‭ ‬in respect‭. ‬That said‭, ‬the potential for‭ ‬petroleum-free aviating is strong for aircraft that stay relatively close to the airport‮—‬training is where electric airplanes‭ ‬are gaining their toe-hold in the market‮—‬and a fun little electrically-powered flyer for those sunset flights‭, ‬pattern work or relatively close-by pancake chasing has‭ ‬considerable appeal‭. ‬

Pipistrel’s offerings are electric propulsion kits designed for air framers‭. ‬They include the motor and batteries‭, ‬along with the battery charger‭, ‬battery‭ ‬management system‭, ‬motor controller‭ ‬and even a propeller if necessary‭. ‬Pipistrel also has the trapeze and controls‭ ‬for a retractable arm should you be‭ ‬designing a motor glider‭. ‬

Manufacturer/ModelDrive TypeHorsepowerWeightPrice
Pipistrel Aircraft
20 Ah 4.75 kWh Electric Propulsion Systemdirect40 kW takeoff, 30 kW climb130 lbs w/ batteries, motor, and controlsTBD
30 Ah 7.10 kWh Electric Propulsion Systemdirect40 kW takeoff, 30 kW climb165 lbs w/ batteries, motor, and controls$25,000
40 Ah 9.70 kWh Electric Propulsion Systemdirect40 kW takeoff, 30 kW climb200 lbs w/ batteries, motor, and controls$29,200
80 Ah 24.25 kWh Electric Propulsion Systemdirect60 kW takeoff, 50 kW continuous441 lbs w/ batteries, motor, and controls$66,500

We hope this guide has been of help‭ ‬in understanding the engine market or selecting an engine for your project‭. ‬While we take considerable effort to insure accuracy and completeness‭, ‬we appreciate‭ ‬any‭ ‬help in increasing the quality of our‭ ‬work‭. ‬Send all comments to [email protected]‭, ‬and in the meantime‭, ‬enjoy this age of powered flight‭.


  1. For the record, the engine manufactured by Adept engineering in South Africa is a complete new design, not a converted auto engine.

    Last I heard they were trying to get approval in the USA and Europe, which as you are well aware is a timely process .

  2. So I just came across this pretty comprehensive list – thanks for that, especially the pricing information! – but i’d like to add a few engines from across the pond. It’s an old article by now, but maybe someone will read the comments. I realize importing from Europe wouldn’t make much sense in most cases, but, for completion’s sake:

    Germany’s Sauer Flugmotoren (http://www.sauer-flugmotorenbau.de) are offering VW conversions from 60hp up to 110hp in certified as well as uncertified versions. Limbach (http://www.limflug.de) has a lineup of EASA-certified VW-based engines up to 160hp.

    Parma Technik in the Czech Republic (https://www.parmatechnik.cz/nove-motory/) are still building the old Walter Mikron III direct-drive, hanging four cylinder inline engines with 82hp. Their english website is pretty basic at the moment and those engines are not exactly state-of-the-art anyway, but could be interesting for builders who want a low-profile inline engine that was actually developed for aeroplanes in the first place.

    I should also name LOM Praha (http://www.pistovemotory.cz/en/), who are still offering a range of EASA-certified inline six- and four-cylinder engines from 120hp to 250hp. I’m not aware whether they are still selling to homebuilders, but there have been some experimentals powered by LOM engines in the past.

    And then there is/was(?) Germany’s Take-Off GmbH (http://www.takeoff-ul.de/), offering a PSRU to use with BMW’s horizontally-opposed 2-cylinder motorcycle engines, resulting in relatively modern 90-115hp engines that have been used in trikes, but also Zodiacs, Cherrys and some other homebuilts. I’m not sure they are still in business, their website does look pretty dated.

  3. Now that COVID and inflation has ruined pricing to levels we wouldn’t have thought about five years ago, is there a way to get an updated pricing list? Trying to do research with articles that are even a couple years old can be wildly inaccurate now.


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