Air-Cooled Volkswagen

The air-cooled Volkswagen aero conversion community shares an unusually large number of characteristics. Obviously they are all built from the same core engine, even if some of them have been upgraded with improved aftermarket cases and other hardware to the point where there are no original VW parts in them.

This means all VW conversions offer compellingly light weight, impressively low costs due to overwhelmingly favorable economies of scale from a car that sold 22 million copies, an upper limit of about 100 hp and a customer base interested in maximizing these characteristics. These are also well-sorted, mature engines as the conversions have been in development and on sale for decades. It’s also something of a world unto itself, including common sources of VW parts. When those sources hiccup, the effects reach every corner of the VW world, including the aviation engines. In 2022 and going into 2023 the issue was a lack of new engine cases. These come out of Brazil from a single supplier, and they hadn’t built a new case in half a year as we went to press due to a contractual dispute with Volkswagen. This will be resolved and new cases made, but exactly when no one knows. In the meantime engine kit prices have gone up as case prices—along with many others—keep going up.

Another shared characteristic is almost all VW aero engine conversions are sold as kits. This saves both the engine manufacturer and the customer money. The one outlier is the original VW aero converter and elder statesman of hot-rodded air-cooled VW’s, Revmaster. They assemble their engines and ship them as ready to run powerplants, something to keep in mind when comparing prices.

For 2023 all four VW engine shops have not made any meaningful technical changes to their engines, but unlike last year, pricing is moving up, sometimes rapidly. Best to check the manufacturer’s website as our printed prices may have been superseded.

AeroVee

AeroConversions, maker of the AeroVee engine, is the piston engine division of Sonex aircraft. A busy, pocket-size aircraft manufacturer producing everything from gliders to single-seat jet sportsters and government UAVs, Sonex’s original core is a series of airframes designed for air-cooled Volkswagen power. Now mature designs, there are no technical changes to the resulting AeroVee engines for 2023.

There are two AeroVee engine kits, the 80-hp 2.1-liter naturally aspirated engine along with a turbo version rated at 100 hp. A turbocharger water cooling system was introduced four years ago and is a near-universal option on the 100-hp engine thanks to its transparent-to-the-pilot electronic control. AeroVee’s laser-cut baffle system and AeroInjector carburetor are also popular.

Spotty parts supply across aviation has been an issue since COVID, but actual engine delivery delays have been few as AeroVee is motivated to keep inventory up to meet their own in-house demand for Sonex airframes. Furthermore, AeroVee suppliers are diversified with Motoravia in Brazil supplying the cases, Empi the cylinder heads, etc. This seems to have spread the risk in AeroVee’s case. Incidentally, AeroVee does not offer two-cylinder VW variants; their line is four-banger only.

Great Plains Aviation Supply

It’s pretty much business as usual at Great Plains. Demand is good, and while there have been issues obtaining enough magnesium cases, the parts supply situation is generally excellent.

Great Plains notes there are aftermarket aluminum Type 1 cases available, but they are not suitable for aviation because “they’re twice the weight of a magnesium case and not as near strong.” Furthermore, the aluminum cases are prone to leak. “I try to talk people out of them.”

Great Plains offers both four- and two-cylinder VW variants, with a choice of driving from the pulley or flywheel end of the engine. They’ll also happily sell short- or long-block engine kits. Many accessories are offered, including a belt-drive propeller speed reduction unit. Pricing is up slightly, just about 2%–5%, which is expected as there was no price increase last year.

Hummel Engines

Supplying Hummel Aircraft with engines is clearly the main business here, but Hummel Engines also does plenty of business supplying four- and mainly two-cylinder VW-based engines to the rest of the hobby. For the third year they’ve been “absolutely swamped” filling the need for Legal Eagle, Fisher 202, Ultra, Thatchers, Mini-Maxes and others in addition to Hummel.

Hummel’s offerings favor the lower power end of the VW spectrum and begin with a bare-bones 35-hp, 85-pound, two-cylinder bereft of starter or second magneto and tops out with a fully optioned 85-hp four-cylinder with starter, dual ignition and alternator.

Prices are up $300 for four-cylinder engines due to higher case prices, plus delivery times are extended so order early. One thing hasn’t changed: Hummel Engines guesstimates they’ve sold close to 1000 engines in the last 26 years, so they have plenty of experience.

Revmaster Aviation

Easily the most experienced VW engine house—they’re approaching serial number 4000—Revmaster is standing pat with their well-developed offerings for 2022.

Their bread-and-butter powerplant is the R-2300 (2331cc, 142.2 cubic inches) at 82 hp using 3350 takeoff rpm; the continuous rating is 2950 rpm. Clearly now a well-sorted combination backed by all sorts of aviation and super high output automotive testing, the naturally aspirated R-2300 uses Revmaster’s own cylinder head and bristles with internal upgrades. These include a four-bearing crankshaft, the unique ability in the VW market 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.

A turbocharged version of the 2300 is finished and can be purchased but still hasn’t flown. It’s rated at 102 hp at 3200 rpm up to 12,000 feet. Call if you’re interested in taking this one airborne.