Patriot under construction
Nice plane, Razor
I got into the OPS engines many years ago. This is the last one I bought, I think in 94. They are picky picky to set up with a carb, at least the pylon engines. I've tried them with and without the Perry Pump on the carbs, and I've found for this installation I've got the best runs without the pump and running crankcase pressure, not muffler. I put a check valve in the case line so I can fuel it up without flooding. These engines are made to really rev, so I'm fighting cooling problems with the large prop. I've lowered the compression to where I can run an OS A5 plug, and haven't burned it after 5 full tanks on the bench, so I think I've got it. RPM's are now a steady 18200 running rich enough to see a good exhaust trail. I may stick it on my old airmadillo to check it out good. I've done a lot of work in the cowl to redirect the air and raise the pressure. I should have made the intake much smaller but I've blocked off a lot of the flow to help cool it. Most of the air bypasses the engine. Around the back of the engine I did work to keep the air pressure up. Maybe I'll do the whole plenum chamber thing over the winter.