It is curious that pereivers performance RPM numbers are so far below what we are getting.

The date/update on his page dates back to June of 2001. There may have been a lot of design/re-design work done by the factory on the motor since then that would make the newer ones perform that much better. I have no performance experience with the older Ryobi motors but just from looking at the piston/ring design it is clear that there is a great improvement from the old single ring piston to the newer two ring piston. BTW pereivers mentions nothing about pistons or rings on his page.

We know nothing about the ambient conditions prevailing during his tests but even if they were vastly different than the conditions of our tests it would only be several hundred RPM and not a 1000 RPM difference.

pereivers mentions exhaust back pressure as being a detriment to the motor's performance and mentions that he's using tuned pipes, but other than that doesn't say much about it. In his photo there is the header of what looks like a tuned pipe. I wonder if his pipe design is what has made his motor perform so poorly. Jennings accounts clearly that if you mess up the design of the pipe you'll cause the motor to perform worse than with a properly configured one, and by inference maybe worse than a modified stock muffler!

Maybe his tach was not working correctly. There is only prop speed data and no thrust data to cross check the RPM data.

diceco