Hi Josh

Thanks for the flattery!! Always susceptible to a bit of flattery.

On the overpropping, its a very interesting subject.

Firstly I am sure you are not doing the engine any harm at all, if anything you are probably subjecting it to little less stress than the more normal rev range of 5000+. If you think about it you are running at a more conventional crank RPM (i.e. 8800, which would be absolutely typical for a normal ungeared 4 stroke).

By revving the SP engine higher as we normally do you do get an increase in power (as power = torque x RPM). However as the engine breathes less efficiently at higher speed the torque drops of somewhat so the net increase in power is not that significant. So as long as its enough to fly the plane then you are probably doing the right thing.

Probably the main limiting factor would be the pitch. As the RPM goes down the effective maximum forward speed (4400 * 10 inches per minute = 40mph) gets a bit low. However the engine will unload in the air, the RPM will increase and prob give you enough in hand.

To be honest we have always traditionally run the engines in the 5000-6000RPM range, but aside from the pitch question its probably more efficient to run in the 4000-5000RPM range, but then you do start to run into forward speed v pitch problems on some model. Also the prop sizes required to load the SP engines down to this speed become a bit impractical.

So to sum up, it works well and it isn't going to do any harm so keep going!

Regards

Keith