I knew there was going to be a learning curve with this project. But I had no idea how much debate there was conscerning engines in aircraft.

When I started considering building a plane, I figured I would use the standard engine recommended by and distributed by Van's aircraft. For the RV-7 this is the Lycoming IO-360. A 360 cubic inch four cylinder, opposed, air cooled, aircraft engine with fuel injection, rated at 200HP. Boy, is ignorance bliss. All seemed well until I started reading about engines in aircraft. The Lycoming is a 40 year old design that has problems from head to toe. The pistons are too big, the stroke is too long, the mixture requires continuous tuning, it can be shock cooled if you bring back the power, the mags are fixed timing, you can't spin the engine over 2700 rpm, the plugs foul, it leaks and burns oil and did I mention it's 40 freakin years old. I almost forgot - it costs $32,000.

Last time I checked, a late model engine is water cooled, has electronic fuel injection, electronic ignition, doesn't burn oil, doesn't foul plugs, starts instantly (always), adjusts the mixture automatically at all altitudes, weighs less, makes more power and burns less fuel than earlier engines, etc.

It didn't take long to stumble across information about the NASA GAP program. GAP is an acronym for General Aviation Powerplant. Apparently NASA is more concerned than I about the status of aircraft engines. So much so that a couple of years ago they made many millions of dollars available to companies who were willing to design new technology engines for small aircraft. Apparently on its own, the industry had failed and general aviation was suffering with outdated engine designs with no hope of resolution in sight. There are now five different turbo diesel engine designs underway as part of the GAP program. When one or two of these new engines become commercially available and get a couple of years of teething pains out of the way, this should be a great engine solution for home builders. But that is the future - not the present.

I quickly became very confused (and dissapointed in Lycoming) about what to do for an engine. After doing a lot of internet searching and reading, I found a number of people and companies using converted auto engines in small aircraft. They all had one common result - they loved their engines. I found Mazda rotaries, Chevy and Ford V6s, and Subarus. What I didn't find much of were fully engineered "firewall forward" engine packages

Looking at all options available, all companies available, all commentary available, specs, weights, reliability predictions, installation complexity, engine mount availability, and on and on and on, the correct choice for me seemed to be a late model Subaru EJ25 motor. This is a 2.5 liter four cylinder, opposed, water cooled, EFI, overhead cam, four valve per cylinder, extremely reliable, modern engine. The Subaru is also lighter, quieter, and has much less vibration than the IO-360. It's probably not far from the motor that Lycoming would have come up with if they had an engine design department. The EJ25 makes 165HP in stock form and is well suited to the addition of a magic little device called a turbocharger.

The good 'ol $32k Lycoming puts out 200HP at sea level. According to the Lycoming data sheet you get 150HP at 8,000 ft. and 130HP at 12,000 ft. The power derating with altitude is of course because there is less oxygen the higher you go and hence less power can be made. So 130HP at 12,000 ft., for $32k - that just didn't inspire me to grab the check book.

The Subaru EJ25 with 3 lbs of boost from the turbo (that's nothing in terms of added engine stress) will put out 200HP from sea level to 12,000 ft. And even if you only run it to 75% power, that's still 150HP at high altitude. Not to mention that the EFI motor is always spot on with the mixture and is far more fuel efficient than the Lyc. (and less than half the price)

Subaru EJ25 Horsepower and Torque Curves

To make a long story end sooner, I installed an Eggenfellner H4 motor, and later added a supercharger. After a couple hundred hours flying, I installed an Eggenfellner STI high performance 4 cylinder supercharged motor. After another hundred and fifty hours, I installed an Eggenfellner H6 motor. The H6 is a very nice smooth motor to fly behind. The Eggenfellner factory has since had it's ups and downs with engineering and delivery issues.

So, the big question is "after experiencing it all, what would I do if I were to start a new project today?" I would have to say I would use a high performance Lyc clone motor with electronic engine management. These motors can be had new for a little over $20k these days.

The Subaru motors were fun to play with, but the parts supply and engineering of the engine packages have both been persistent problems. So make your best decision. Talk to lots of people on both sides of the fence before writing big checks.