dkallen
Well-Known Member
- Joined
- Apr 21, 2010
- Messages
- 366
- Reaction score
- 27
There is a rubber flap that is at the air intake that I was unaware of. This air intake seal had never been replaced on my plane because it had the original rivets still in place; however, the seal had deteriorated and was gone. In the 3 years I had the plane, I had never questioned the air intake because I didn't know how it was made until one day when I was doing a pre-flight, I thought it was strange that I could look in that port and see out the rear of the lower cowl. It finally struck me that it just didn't seem right.
I have been questioning the CHT and EGT temps I had been seeing since I installed the engine analyzer, but couldn't put my finger on the problem. We have spent hours looking for induction leaks, valve seat issues, plug issues and anything else we could think of that would cause the 250F EGT spreads and the >100F CHT spread between #2 and #4 cylinders. Also the trends indicated a weird looking temp shift when I transitioned from climb to cruise.
I told my mechanic to humor me and see what that air inlet design was supposed to be and make it as Piper intended. Bingo, it looks like the problem was resolved. The CHT spread is now 40F and that is between #2 and 4 cylinders and the EGT spread is now 140F, again #2 is hottest and #4 is coldest. I have a few other things I will be checking out over the next few flights such as partial carb heat which seemed to somewhat help the combustion mixture distribution when I had tried it before and maintain a carb inlet temp of approx. 38-40F when in cruise. I believe what was happening is that the missing seal increased the pressure under the cowl, resulting in poor air flow across the cylinders. Any confirmation to my conclusion? JimC? Magman?
I have been questioning the CHT and EGT temps I had been seeing since I installed the engine analyzer, but couldn't put my finger on the problem. We have spent hours looking for induction leaks, valve seat issues, plug issues and anything else we could think of that would cause the 250F EGT spreads and the >100F CHT spread between #2 and #4 cylinders. Also the trends indicated a weird looking temp shift when I transitioned from climb to cruise.
I told my mechanic to humor me and see what that air inlet design was supposed to be and make it as Piper intended. Bingo, it looks like the problem was resolved. The CHT spread is now 40F and that is between #2 and 4 cylinders and the EGT spread is now 140F, again #2 is hottest and #4 is coldest. I have a few other things I will be checking out over the next few flights such as partial carb heat which seemed to somewhat help the combustion mixture distribution when I had tried it before and maintain a carb inlet temp of approx. 38-40F when in cruise. I believe what was happening is that the missing seal increased the pressure under the cowl, resulting in poor air flow across the cylinders. Any confirmation to my conclusion? JimC? Magman?
