Lean of Peak

[jlunseth]

You should be able to make full rated power to critical altitude. I have seen definitions of CA where it is the ability to maintain a 100 fpm climb, but I can make 36” at 22,500 in my Merlyn equipped 231 before the MP knob can’t go any further and the MP starts to fall with further altitude, so I don’t know why you would not be able to make 36 in the 252. (Actually, the CA varies depending on day temps somewhat.)

 

[Will.iam]

5 minutes ago, jlunseth said:

You should be able to make full rated power to critical altitude. I have seen definitions of CA where it is the ability to maintain a 100 fpm climb, but I can make 36” at 22,500 in my Merlyn equipped 231 before the MP knob can’t go any further and the MP starts to fall with further altitude, so I don’t know why you would not be able to make 36 in the 252. (Actually, the CA varies depending on day temps somewhat.)

 

Thanks for the confirmation. That’s what i thought too. I’m guessing i have a leak somewhere. Hopefuly find it at annual time. 

[kortopates]

6 hours ago, Will.iam said:

Thanks to both of you for your insight and suggestions. If i understand Paul’s method correctly going from the rich side to lop has the turbo already fully accelerated instead of me going from a lop setting and trying to increase the turbo output. I’m still concerned though when i went to full throttle full mixture and full rpm, basically everything firewalled like for takeoff, the highest mp pressure was only 35” instead of 36”. Seems to me i have an airleak or exhaust leak somewhere considering my critical altitude is 22k, i should be able to develop full boost at 10k. The fuel flow was higher than at takeoff but considering OAT was -5C i assumed that was matching the denser air going through the engine. In other words if i climbed to 20k as a test i should still see 36” especially on a standard temp day. Is there an adjustment my A&P make to increase the boost so the wastegate controller can achieve 36” at altitudes above 10k or is that only a sign of an air leak or worn turbo blades? It was overhauled only a hundred hours before i got the plane. 
 

will download the data later today and look more closely at it. Unfortunately i only have the jpi 711 so I don’t have MP or RPM recorded. But i forget what the fuelflow went to at 10k. 

Probably no leak, perhaps just oil temp above 175F. The controller is completely adjustable but set up to deliver redline MAP at normal operating temp of 165-175F. Below that with cold oil, such as first takeoff of the day, it will naturally over boost if set up properly and above 180F+ with warmer oil it will under boost - which is likely what you experienced. This is also why they specify multi-weight oil for Turbo's. 

Its kind of a problem though that you don't have oil temp data in your data to determine if your controller is out of adjustment or not. But we're only talking about fine tuning it since one inch isn't a big deal.

Edited October 24, 2022 by kortopates