Initial experience
With only 46 hours of novice test pilot experience I can hardly be considered an authority on the Aero Sport Power IO-375. Nonetheless, I will share those observations I have made so far. (My prior experience includes around 900 hours in a Cessna Cardinal behind an angle valve IO-360.)
My IO-375 was built using the parallel valve Lycoming case and cylinders giving me roller tappets with low compression pistons installed. The stroker crank is from ECI and a Superior sump and cold air induction round out the bottom. It is equipped with dual P-mags, the Silver Hawk fuel injection and turns a Whirlwind RV200. It starts and runs smoothly at low idle although I do not generally idle with a closed throttle.
I have used the standard Vans cowling, tightly fitted with the SW (now Meggitt Troy) 8406R oil cooler mounted on the baffle aft of #4. Cooling is more than adequate on standard days with CHT?s even on climb out not exceeding 360 and oil temps struggling to get up to 178 with 1/3 of the cooler blanked off. I am not concerned about the coming Texas heat.
The higher displacement is accompanied by a slightly higher fuel burn than experienced with the Cardinal. Max speed recorded so far is 184 KTAS at 7500? WOT and 125 ROP. That run was during phase one testing and may not be optimized. I am going to repeat max performance runs soon now that I have become better acquainted with the plane and the engine is reaching break-in.
Recent cruise at 7500?, WOT 68% pwr and 30-50 degrees LOP produced 173 KTAS burning 9 gph. Leaning to 8.8 gph was well tolerated and resulted in slight reduction in power and speed as expected. I have also tried leaning at lower altitudes with 60% power and 8.6 gph producing 160 KTAS at 3500?. CHT?s run 300-320 when LOP and only modestly more at cruise ROP. OATs have been in the range of 55-75 degrees F.
So far I have been very happy with my choices and Aero Sport Power has been a pleasure to deal with. As I become more familiar with the plane and am hopefully able to better define performance figures, I will be happy to share them with the group.