Ken The problem I see with the use of the new Saturn engine is having the knowledge to modify the existing electronics to aircraft use without losing any of the output or reliability. Also, your engine choice should be one that has as flat of a torque band and as long of a horsepower band as possible. What I mean is that when you look at a graph of the horsepower and torque numbers, the graph shows them to be over as much of the hp and torque band of operation as possible. Example: your operating range is say 0 to 5000 rpms for (a liquid cooled conversion). Your ideal example would be a torque band that stretched from say 1500 to 4500 rpms at nearly the same average amount, and hp that stretched from say 2000 to 5000 rpms, with nearly the same average, and peak prior to your redline. You want a nice buffer between your redline and your peak hp so that you do not have to worry about something getting broken if you accidentally over rev. Example: Small block Chevy has stock redline of 6000 rpms, so I would always shift at 5000 rpms giving me a 1000 rpm buffer against over rev. By having the curve as long as possible, you will get the best chance of having a good combination prop matched to your engine that can give a good climb rate and a good cruise, at a reasonable rpm for long engine life.
If using a PSRU, plan on a final weight add-on of approximately 65 pounds (Northwest Aero belt drive weighs this, as does Belted Airpower's version). The reduction needs to match the engine where the planned max redline of MAX ENGINE life is being used, is the max REDUCED rpm for the prop. This SHOULD yield the best overall operation for the engine and prop. If too much reduction is used the engine revs too high for max life and gets peaky in its performance, ie: prop can't produce significant thrust below 3000 rpms. Too little reduction and the engine gets loaded down, so overall performance suffers. Remember the engine still needs a thermostat to operate properly, or all the computer sensors will go nuts. Also the computer needs to be insulated from as much heat as possible, and weather, and it is best if you use a straight shift donor car for the least amount of computer to transmission interaction. Keep the straight shift flywheel as the added weight helps to eliminate some of the harmful harmonics according to Robert Finch. I too am going liquid cooled in the future, but not for this plane or model. Too hard to make the weight limitations... Colin Rainey brokerpilot9...@earthlink.net EarthLink Revolves Around You.
