Subaru Sonerai

Fresh in from Casa Grande, Arizona, Joe William’s Sonerai II cools on the French Valley ramp. The plane was originally built with an O-200 Continental by Kelly Dunn in 1978; not happy with the performance he switched to the Subaru.
Fresh in from Casa Grande, Arizona, Joe William’s Sonerai II cools on the French Valley ramp. The plane was originally built with an O-200 Continental by Kelly Dunn in 1978; not happy with the performance he switched to the Subaru.

If there was an Iron Butt award at the Alternative Engine Conference held at French Valley Airport in Temecula, California, Joe Williams would have been in the running  last Saturday. True, he flew his Sonerai II just somewhat over two hours from Casa Grande, Arizona, but in such a diminutive speedster that’s sure to be a major cross country.

Williams bought his Sonerai II as a flying airplane, complete with a ’93 Subaru Legacy 4-cylinder, double over-head cam, water-cooled EJ22 engine in it. But he’s worked and flown the combination enough (it has 500 hours on it) to log his own adventures and he seems eager for more.

Heavier and thirstier than the VW engines the Sonerai was designed for, the Subaru EJ22 Legacy water-cooled 4-banger does fit well and adds over half again the horsepower. Actual power is untested; stock Legacy engines are rated at 135 hp at 5500 rpm, Williams runs his at 4500 rpm for something over 100 hp.
Heavier and thirstier than the VW engines the Sonerai was designed for, the Subaru EJ22 Legacy water-cooled 4-banger does fit well and adds over half again the horsepower. Actual power is untested; stock Legacy engines are rated at 135 hp at 5500 rpm, Williams runs his at 4500 rpm for something over 100 hp.

Performance is good. Williams figures on 140-150 kt IAS at 5 gph, or a bit over 9 gph at WOT. He also quoted 172 mph TAS at 5.5 gph, so in the real world he’s putting right along on not much fuel. Earlier he tried a set of Delta 230 grind racing cams in the EJ22, and they made noticeably more power (+25 hp and +25 ft lb of torque) that worked great in climb and cruise. However, their lumpy idle was sufficient to fail the right upper engine mount, so he repaired the mount and removed the cams until he can figure out a stouter engine/mount interface.

Perfectly trouble-free speed reduction is provided by a now vintage Don Parham RFI Power Systems re-drive turning 1.82:1. The belt is 85mm wide and rides on a 2-bearing shaft.
Perfectly trouble-free speed reduction is provided by a now vintage Don Parham RFI Power Systems re-drive turning 1.82:1. The belt is 85mm wide and rides on a 2-bearing shaft.

An engine mod that’s worked great is a shallow oil pan from Outfront Motorsports. The stock Subaru pan is especially deep; the Outfront pan hangs through the lower cowling and is literally out in front, so it provides much needed aero streamlining.

One thing the Subaru installation is is heavy, if you can call an empty weight of 752 lb. portly. But between the Subie and the full-framed Williams he figures his Sonerai is 300 lb. heavier than a stocker. But he’s got the power to pull it, and with a 1,150 lb gross he’s got the breathing space for fuel and what luggage will fit. He did, however, replace the two 11-lb lead acid batteries with a pair of 1.5-lb Shorai LFX14L2-BS12 lithium Ion units and rates them as “fantastic.” “They weigh nothing and each one has 210 CCA.”

Cooling comes via an ’83-‘86 VW GTI racing radiator measuring 300 x 500 x 40 mm and laying about 30 degrees from horizontal in the an SC-266 under-cowl scoop (that’s an aftermarket automotive hood scoop from up22.com cut-to-fit by Williams). An auxiliary 11-in. Perma-Cool fan on the backside of the radiator comes on automatically at high temps, which so far has only been during ground testing without the prop in place. The scoop opening is 26 sq. in. and the exit over 60 sq. in., plus auxiliary louvers for plenty of draw. It works great says Williams, noting coolant temps run consistently right at the stock thermostat setting of 197 degrees F.
Cooling comes via an ’83-‘86 VW GTI racing radiator measuring 300 x 500 x 40 mm and laying about 30 degrees from horizontal in the an SC-266 under-cowl scoop (that’s an aftermarket automotive hood scoop from up22.com cut-to-fit by Williams). An auxiliary 11-in. Perma-Cool fan on the backside of the radiator comes on automatically at high temps, which so far has only been during ground testing without the prop in place. The scoop opening is 26 sq. in. and the exit over 60 sq. in., plus auxiliary louvers for plenty of draw. It works great says Williams, noting coolant temps run consistently right at the stock thermostat setting of 197 degrees F.

And Williams flies his Sonerai. After his first 11 hour jaunt to Oshkosh from Casa Grande he said he “couldn’t feel my butt for two days,” a situation cured by memory foam cushioning.

While the stock Subaru engine management and injectors have run well for Williams, to gain a conventional aviation mixture control function he’s added an E-Tune from Perfect Power.com. Designed for ethanol, it’s worked fine on the Subie. It offers a 384 point map (16 loads and 24 rpm points) allowing +/- 50 percent fuel control. Williams has it set for a basic 0 to -15 percent manual fuel flow reduction at all rpm. As the stock Subaru ECU runs the stock map, so the E-Tune allows extra leaning during cruise. A pair of fuel pumps—one main, one back-up—supplies the all-important fuel pressure.
While the stock Subaru engine management and injectors have run well for Williams, to gain a conventional aviation mixture control function he’s added an E-Tune from Perfect Power.com. Designed for ethanol, it’s worked fine on the Subie. It offers a 384 point map (16 loads and 24 rpm points) allowing +/- 50 percent fuel control. Williams has it set for a basic 0 to -15 percent manual fuel flow reduction at all rpm. As the stock Subaru ECU runs the stock map, so the E-Tune allows extra leaning during cruise. A pair of fuel pumps—one main, one back-up—supplies the all-important fuel pressure.

 

A Warp Drive 3-blade ground adjustable prop converts the Subaru power into thrust. Williams says he’d like to change to the extended version of the RFI re-drive to jutt the prop and cowling forward for more aerodynamic streamlining.
A Warp Drive 3-blade ground adjustable prop converts the Subaru power into thrust. Williams says he’d like to change to the extended version of the RFI re-drive to jut the prop and cowling forward for more aerodynamic streamlining.

 

Originally a two-seater, Williams has added a second 14-gallon fuel tank to what was a cramped front cockpit anyway. His now single seat Sonerai II thus has good room for his over six-foot tall frame, plus the original 10-gallon header tank for a bladder-busting 4-hour range.
Originally a two-seater, Williams has added a second 14-gallon fuel tank to what was a cramped front cockpit anyway. His now single seat Sonerai II thus has good room for his over six-foot tall frame, plus the original 10-gallon header tank for a bladder-busting 4-hour range.

Tom Wilson

Tom Wilson is a professional magazine writer and nurtures an ongoing affair with all things internal combustion. His writing is most often found in automotive magazines, but aviation is his first love. Working as a line boy, he learned to fly while in high school, but still hasn't mastered the art of keeping a paper chart in an open cockpit.

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