Who would have thought selecting an engine would be controversial?

This RV-9 will almost certainly have some variation of the Lycomming 0-320 powering it. I know the Subie fans will jeer and poke fun at the Lycosauris, and yes, the Lycomming is an old design. It's noisy, vibrates too much, has poor fuel economy, and is based on 60 year old technology. On the otherhand, it's a proven, reliable design. As the wings go together I'm considering an Aerosport, a mid-time used engine, and a new Lycomming from Van's. Odds are my choice will be for a carburated engine over fuel injection and looking at my budget, I'm guessing a mid time engine will be my choice.

The Eggenfeller Subie looked interesting and I checked it out. It was high on my list of places to visit and explore at Airventure 2001. I'm not here to slam anyone but upon looking into it I became suspicious. This might be more of a reflection on me than on either the engine or the company selling it. There were several things that didn't pass my "sniff test" the biggest one being the indemnification clause in the sales contract. Apparently that's none negotiable and while I understand Eggenfeller's position, it doesn't seem reasonable to me to ask they buyer to indemnify the seller. If it does to you, by all means go for it. I will be interested to see how these engines and the PSRU hold up. At first glance it looked very promising.

I've also considered the Mazda rotary. Water cooled engines seem to me a mixed blessing in an aircraft. On the one hand they offer the ability to regulate temperature far better than an aircooled engine. The results are tighter tolerances, lower oil burn, smoother running, and perhaps better efficiency. The negatives are added weight (not much generally) and one more possible means of catastrophic failure. If a hose bursts you will lose coolant and the engine will likely seize - generally sooner than later. This propensity of water cooled engines creates an immediate problem to deal with (a deadstick landing) and a serious expense assuming you survive the first problem. The Mazda rotary is unusual in this respect in that it can apparently run for some time (10-15 minutes, maybe more) without causing serious damage. That's long enough to find an airport and land. If I build a second plane, the Mazda rotary is going to get a close look, if it's appropriate.

Finally, I've considered a diesel engine...but not very much. The market is very limited and the only advantage seems to be advertised reliability. Actually reliability will have to be proven for each design. The initial investment seems rather high also. I suppose I'm taking a wait and see approach.