Pierre wrote: >> It feels as if I've hit a brick wall. I had a 48(pitch) X 52 prop on my KR2S> (haven't flown yet). The max revs I got was 2,760rpm static.<<
Depending on the displacement of the VW engine, you likely need less pitch (as others were quick to point out). The way the prop maker measures pitch is important also. Having had about 20 different props on my KR2S and KR2, I can tell you that the pitch numbers vary wildly, with respect to RPM. Sterba, for example is almost always has higher pitch numbers for a prop that would turn the same RPM from somebody else. Tennessee props tends to be nearer to Sterba than others. If you haven't seen it already, take a look at the prop vs engine numbers listed for fifty different KRs at http://www.krnet.org/kr-info.html . That may help you narrow it down. Another issue is are you sure the ignition timing is correct? It's worth double checking everything involved in making that right (TDC mark, for example). Ignition timing is everything. Checked at 2700 rpm or above for full advance to 30 degrees? That eliminates advance issues. I know it's a real pain to check timing with a a propeller installed, and very dangerous, so I've started doing it before the prop is even installed. Given that I do have a flywheel on the back of the engine for the starter and alternator, it's not going to hurt the engine for a few minutes, and it allows precise setting of the timing without the adventure of a prop being there. What a huge difference in pucker factor! And you know for a fact that the cam timing is dead on? Have you considered having the 48x52 repitched to something a little less? At least that way you have two data points. As a data point, I can turn 3200 rpm static and turn it up to 2450 or so wide open with a 2180cc engine with 8.6:1 compression ratio and 30 degrees of advance at wide open throttle. I would be reluctant to take off with only 3000 rpm with my short runway. Mark Langford ML at N56ML.com http://www.n56ml.com
