On Feb 6, 8:03 am, Charles Vincent wrote:

Isn't it more aptly a modern Continental C-85? I think the "modern VW"
as far as homebuilts go is one of the subaru's.

Charles

They're not the big solution, either. I installed a Subaru 2.2
litre on a Glastar, using an RAF redrive. The problems I encountered:
-Some vibration at around 1400 engine RPM. Caused by the very light
RAF aluminum flywheel, which doesn't absorb all that much pulsation,
and this interacts with the prop's mass, which has a different
resonance. We had initially used an Ivoprop, and could not balance it
chordwise because the blades would shift a little on the hub bolts.
The subsequent Warp Drive prop was better, but had much narrower chord
and did not pull as well as the Ivo. Further, the Ivo's blades would
flutter if there was too little tension on the torque rods. Scary.

-Burned valves. The engine had a converted Holley two-barrel, with
mixture control that was way too sensitive, to the point that it
either ran or didn't. I modified the valve to get some range. On a
short-field takeoff, usual SOP with an aircraft engine is to lean to
max RPM with the brakes locked and throttle wide open; do that with
the Soob and the valves will burn real quick. The engine has four
valves per cylinder and they're about the size of the valves in a
Briggs and Stratton lawnmower engine. Tiny, with little skinny stems.
Compare them to a Lyc's valves. The 16-valve Soob was designed for
computerized fuel injection, for good reason.

-Couldn't install a mechanical fuel pump in it. No place for one. So,
since you can't rely on gravity feed (the Holley has a small float
valve designed for a 4 to 7 psi fuel pressure) you need an electric
pump. Two of them, just in case. And the ignition is run off the
aircraft's fuel system. So, since (as anyone with car or airplane
mechanical experience knows) 90% of all engine problems are
electrical, it's asking for trouble. Real quiet trouble. Avoiding that
requires another battery and a big diode to protect it, more weight
and complexity and cost and room that isn't there.

-The engine was rated at 130 hp at 5600 RPM. The Glastar was designed
for engines from 125 to 180 hp. Should be good enough, right? It was
OK for takeoff and climb, but for cruise it was lousy. A Lycoming,
redlined at 2700 RPM, is easily cruised at 2500 or even 2600. The
engine is rated for 2700 continuous, if you want that. The Subaru, if
you try to cruise it at an equivalent RPM of, say, 5300 or 5400, will
wear out in no time flat and will burn phenomenal amounts of fuel,
too. And makes the most awesome cabin noise. So you end up cruising at
4700 max, which gives an anemic cruise of 110 mph instead of the 135
that the Lyc 125 would give you. Both engines will give the claimed
143 mph at full RPM, so it's not a propeller pitch issue.

-The exhaust system was two tiny mufflers that did little to contain
the noise. There's no room under the heads, inside the cowl, since the
engine sits low to get the thrust line up where it belongs. I could
hear this airplane 7 miles away. When I flew it, I stayed away from
town.

-The engine compartment was very tight, once the radiator and its
associated baffling was put in. The cooling system was the one thing I
built that worked really well. The cabin heater was the Subaru's
heater core.

-The ultimate cost, in terms of the stupidly complicated engine mount
I had to build and have professionally tigged (17 pieces of tubing and
four special engine brackets), the time I spent, the constant
tinkering, the cowling modifications necessary to make it fit, and the
ultimately much lower resale value it had (half or less than a Lyc-
powered Glastar), it just wasn't worth it.

Dan