I was in the right seat (flight engineer) when my homebuilt 2+2 made its first flight yesterday with the 13B Mazda engine, but not without problems. The coolant temperature reached 230F by circuit altitude; after throttle back and approach it had only dropped to about 225F; the oil temperature was indicating only 160F (this could be a mounting-point issue or real I’m not sure … oil temp measure point is from a small manifold bolted to the PSRU mounting plate, with oil flowing from engine to PSRU) outside air temperature was about 32-33F. The coolant pressure pegged the gauge beyond 20 psi, which was a surprise as the pressure cap is rated for 20 psi … I expected the engine to burp itself out and maintain 20 psi.

 

I tightened up the cowling around the radiator and removed the thermostat in an attempt to make a second flight but while removing the thermostat I noticed one of the alternator V-belts was broken … got another belt only to find it didn’t match the other … these belts really need to be a matched-pair. Prior to flight, I noticed the outside belt (which broke) did not have the same tension as the inside belt; it must have climbed out of the pulley groove and got sliced by the pulley. Previously I bought a double alternator pulley from Racing Beat but never installed it, due to difficulty with removing the nut … thought it best to leave well enough alone … I will now put on that new pulley.

 

Hope to make another flight next weekend if the test pilot is in agreement.

Any comments/experience on thermostat Vs no thermostat?

Why would the pressure cap hold beyond its rating?

Jeff Whaley

C-FJWW