Bathman wrote:
But how about running on UL91 wouldn’t that make these problems go away?
I can say that before my club changed from 100LL to 91/96UL (another unleaded fuel, very common in Sweden) we experienced the common problem with rough running on one magneto during the engine runup. After changing to unleaded fuel the problem disappeared completely.
Almost 3 years later, #2 cylinder has done something funny again.
The EGT dipped a long way down and the engine started running rough. I immediately cycled the mixture all the way down, then all the way up, then leaned back to norma and by the time I finished that, everything was fine. This is the EDM700 log. It is sampled around every 5 secs which is too slow.
It doesn’t look like a sticky valve this time. More like a bit of dirt blocking the #2 injector.
The only notable thing is that #2 cylinder has a lower CHT than the others and at the time this happened (a long descent) it was 280F. In normal cruise it is around 300-340F. However, a later flight also at 280F failed to produce any problem. This shows the CHT:
The #2 exhaust valve, borescoped today a few flights later, looks ok
Any views?
