A few years back I decided my aircraft was due a tidy up on the engine baffles, nothing bad just a few cracks here and there, stiff baffle rubbers the odd gap, you know they story. This is an updraft cooled pusher.
So in I went, it took about 3 times longer than I thought but I wanted it the best it could be.
Previously it was not unusual to see the coldest sitting on 310F and the hottest at 375F
I was more than a little pleased to see on the first flight that with mixture and throttle butterfly positioning I could achieve all 4 cylinders within 2F of each other and sitting around the 330 mark.
What really surprised me was the effect it had on the EGT spread, the O-200 is about as crude as they come and the EGT's were generally random but could be manipulated with throttle position, carb heat and mixture setting. Whilst there was a pattern it was complex and fluky to replicate.
Now with tidied up cooling a distinct repeatable pattern emerged, at WOT the front pair carried significantly higher CHT's than the back pair due to the front pair running much leaner. Cock the throttle butterfly a few degrees by coming off WOT and everything starts to even up. So much so it is nearly smooth enough to go over the hump to LOP. Makes me think this might be one engine that could actually see significant benefits from an internal induction flow straightener or at the other end of the spectrum a swirl plate eg. Hyclone device.
All from attention to detail on a engine baffles.
Last edited by Obidiah; 30th Mar 2015 at 23:30.