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

If you haven't calibrated the EM2 fuel flow yet, the GPH reading does not mean anything.  Don't make any decisions based on that reading.   Calibrating the fuel flow is the most difficult and time consuming parts of EM2 setup.   That's the down side of doing it with such an inexpensive flow sensor ($0.00) since it has none.   The other option is to use a Floscan flow sensor with the EM2  but they are pricy.

  At 30" of manifold pressure and best power mixture setting and 6400 RPM you should get a fuel burn somewhere around 15 - 18 GPH.  The exact amount will depend on other factors like exact mixture setting, your intake manifold, exhaust system, air temp, etc.

Tracy Crook