REFLECTOR: Engine choice

[c.harbert at comcast.net]

Ben, I would not recommend that you use a heavy engine (IO-540, V8, Mazda 20B, etc) in a Std, short wing V because of the W&B problems it causes. I had a turbo 20B in my std V  (450 lbs) and it weighed 1,600 lbs with an aft CG problem. I ended up with 2 batteries in the nose, plus lead weights. Al Geitzen has done a masterful job with his non-turbo 20B, but he also is at near 1,600 lbs (he has the big wing). When I switched to the IO360, my finished weeight was 1,350 lbs. I have built a turbo system (not installed yet) for the plane that will add about 50 lbs, but it will only be turbo normalized (below 210 hp). Turbo's work well if properly designed and installed, but that's not easy to accomplish. Richard Vanderstein has a beautifully designed TIO-540 that really works (200+kts at 12.5 gph at 16K') in a XL, but he's a genius and had lots of experience with racing turboed engines.

After my experiences, I'm now a believer that lighter is better, especially if cost of fuel is important. As I'm sure you know, there is no free lunch in airplane performance. The faster you want to go, the more fuel you burn. The closest thing to a free lunch is to make hp at higher altitudes where the air is thinner and drag reduced which means turbocharging a light engine. A heavier airplane burns more fuel, so adding 250-300 lbs is generally not efficient, plus it significantly reduces your load carrying capacity.   

An IO 360 is a good engine, but it has serious issues because of the 180 degree power pulses, particularly with constant speed props. I'm still hoping someone will perfect a CS prop that will hold together that doesn't cost $10+K. If you go fixed pitch, you have to choose between T/O or speed. I have a Catto that will get my V to 185kts, but my T/O rpm is only 2,200 rpm which is too little. The turbo can be used to help this, but again a CS prop would really help for both T/O and high speed cruise at altitude. 

When I first started my project I was going to have 350 hp and easily cruise at 200 kts. I had the 350 hp, but my fuel burn was over 20 gph. If you run the numbers, 200 actual  hp is 18-20 gph at reasonable BSFC numbers. A diesel would cut this by 20-25%, but there are no proven diesels (other than Thielart?) available. Since you're in Germany you might want to check them out. I saw a experimental prototype water cooled Lyco 6 cyl diesel at the Reno air races, but who knows when, or if, that will ever be available.

I'm still praying that eventually we'll get a 200 hp lightweight, smooth running, turbo diesel that will be reliable and cost less than $30K, but I'm not holding my breath. That's what I think I know. Good luck on your build.

Chuck H



 
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