Mike,

Don didn’t report speed.  I took his pitch and rpm and figured it.  That speed at cruise is what he would get with no slippage or “lift” from the prop.  Most of the folks with the Catto are actually getting higher speeds than would be calculated which indicates that the prop is producing “lift”, not slippage. 

But his engine rpm with that big prop are higher than any I have seen.  With the rotary, rpm = horsepower.  If you aint making the rpm, you aint making the horsepower.  It doesn’t seem to matter what you have done to the engine…ported, PP, turbo, supercharger.  If you look at the dyno charts that are all over the web, you will see that torque is pretty flat after about 4K, about 150 ft lbs.  The horsepower is around 150 at 6K, maybe 180 at 7K, and 200 at 7.5K.  You can get more horsepower than that, but only if you scream it up to 8K  or 8.5K.  All the charts I have seen are within 10 horsepower of each other at all rpms.  The difference in total horsepower is always a higher max rpm.

We all talk about wanting to cruise at 5800 and make 200 horsepower…it aint happening!  Not with the rotary.

Bill B

Bill,

I went back and looked at Don's previous post. Saw reference to climb performance, RPMs, and temps, but no speed numbers. Has he previously reported cruise speeds over 200? Last post from him that I saw with any speed numbers reported 174MPH IAS at 8000. If he's over 200 now, wow those are good numbers!

Mike Wills

Those are the best numbers I have seen with anyone with a Renesis so far.  In fact, I have not heard of numbers that good on any 13B.  Don is getting over 200 MPH with a cruise prop and climbing at over 1400 fpm with it.  The only way he is going to do better is either with an electric CS prop and/or turbo.  If he shaves the prop off to say, 74”, he will get a couple hundred more rpm, but will probably lose in total thrust.  Diameter is a big determiner in thrust. 

I would like more pictures of Dons intake and exhaust!

Bill B