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. In fact, one of the most successful VW strategies has been cutting the engine in half for use in minimalist flying machines.

These are also well-sorted, mature engines as the conversions have been in development and on sale for decades.

Another shared characteristic is almost all VW aero engine conversions are sold as kits. That is, the customer receives a complete set of engine parts and assembles it himself. 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 VWs, Revmaster. They assemble their engines and ship them as ready-to-run powerplants—something to keep in mind when comparing prices.

For 2022 all four VW engine shops have not made any technical changes to their engines and have mainly bucked the trend toward higher pricing.

AeroVee

AeroConversions, maker of the AeroVee engine, is the piston-engine division of Sonex Aircraft. A busy, pocket-size aircraft manufacturer producing everything from motorgliders to single-seat jet sportsters and government UAVs, Sonex’s original core is a series of airframes designed for air-cooled Volkswagen power.

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 three 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 has been an issue in 2021 and going into 2022, notably for pistons. 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. AeroVee does not offer two-cylinder variants.

Great Plains Aviation Supply

“Staying busy” meeting demand and “trying to hold the line on prices” are the main activities at Great Plains these days. “Shipping to New Zealand and the UK has been an issue lately,” was the other report, not unexpected as the world’s logistics scene tried to untangle itself going into 2022.

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.

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 two years they’ve been “absolutely swamped” filling the need for Legal Eagle, Fisher 202, Ultra, Thatcher, Mini Max 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 top out with a fully optioned 85-hp four-cylinder with starter, dual ignition and alternator.

Combining brisk sales with supply issues means there was a 10-month wait between ordering and shipping a new Hummel engine, so patience is a virtue. This is after adding CNC mills to speed production. And speaking of production, Hummel Engines guestimates they’ve sold close to 1000 engines in the last 25 years.

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 cu. in.) 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.