Thanks to you all for the congratulatory comments … attached is a picture of expansion tank and preflight roll-out … the orange line is fuel return; the brass is pressure gauge pickup and snifter valve installation.

After reading Eds’ email I now know why the water temperature was so high.  I installed a thermostat with the onset of cold weather, but I couldn’t use the original Mazda thermostat because my temperature bulb protrudes across the bypass hole.  Originally the bypass hole was plugged and there was no thermostat; however, I removed the bypass plug and used a non-Mazda thermostat !! … so that’s why the underside of the Mazda thermostat is so long! Thanks Ed for setting me straight and based on your comment about 20% loss of efficiency, I could possibly see 230F x 0.8 or as low as 184F on next flight … that would be great! For now the thermostat is gone and bypass is re-plugged.

Closer examination of the belt and rubber deposits on underside of top cowling suggests the belt got jammed in the pulley and cut by friction.

I tried again last night to remove the alternator pulley nut … what’s the secret? Left-hand thread? Loctite or what? It’s so tight I’m afraid of damaging something trying to get it off.

Jeff

 

 

 

Congratulations, Jeff!!  Safe first flight and that’s what really counts, the rest of the stuff you’ll get it solved.

 

On my first flight 13B (No Thermostat – plug the ½” hole in the bottom of the thermostat housing if you have a 13B – not certain about the Renesis) I had oil temps up to 240F (high as the gauge went).  I don’t recall the exact temps on the coolant but I do know they were over my 220F red line.

 

But, with an outside temp of 32F, I am surprised that the coolant got that high and did not come back much when you throttle back.  However, I would say that the fact that your pressure gauge was that high was a further indication that the coolant temp problem was real rather than just a gauge or sensor problem.  As other’s have suggested, calibrate your sensor and gauges  if you have not  already done so.

 

Another problem may well have been the missing belt.  It is possible that particular if the two belts were not of the same exact length and then you lost one – that the water pump load may have been causing the belt slip and your water pump rpm may not have been where it should have been.  Any signs of belt slippage (shiny, hard glaze on the running surface of the belt??).  I fly with the dual belt racing beat/MazdaTrix pulley and really like it. 

 

I personally fly without a thermostat – however, it seldom gets and stays that cold at my airport for any length of time.  Another thing is that if you are using the 13B (can’t speak for the Renesis) with a thermostat – it MUST be a Mazda RX-7  Thermostat OR you MUST plug the ½” hole in the bottom of the thermostat housing.  If it is not plugged, approx 20% of your coolant flow effectiveness is compromised.  IF you have an RX-7 thermostat then it has a feature that plugs the hole when the temps comes up but other thermostats do not.

 

Lets seem some photos of your cooling ducts and system if you have any available.

 

Again, congratulations on the first flight.

 

 

 

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