MAP Impact on Peak EGT

[lr172]

I have a FP and my initial climb is around 90%+ power (2500/27 or 28). I would like to figure out my peak EGT in this configuration, but I prefer not to lean it to peak with that much power to figure it out.

I have noticed that my PEAK EGT temp is higher at 2700 than 2500 and that makes sense. I am wondering if the MAP also affects peak EGT temp.

If I find my peak EGT at 2500 and 75% power, can I safely assume that my peak EGT at 2500 and 90% power is the same? Or do I need to lean to peak in that configuration to truly determine the Peak EGT temp?

Thanks,

Larry

[DanH]

Originally Posted by lr172

I am wondering if the MAP also affects peak EGT temp.

If I find my peak EGT at 2500 and 75% power, can I safely assume that my peak EGT at 2500 and 90% power is the same? Or do I need to lean to peak in that configuration to truly determine the Peak EGT temp?

You may safely assume it is the same.

From the FAA dyno; IO-540K, variables are manifold pressure and mixture. Note that peak EGT is pretty much the same (1525~1530) for all MP settings from full throttle down to 22". I've removed the Swift fuel curves for clarity.

[lr172]

Thanks Dan.

[BobTurner]

I'd say 'it depends'. Some carbs have an 'auto enrich' feature which makes the mixture richer at full throttle.

[rzbill]

While I have never done it on a carb like that, I would think that the enriching circuit efffect would be negated by leaning the mixture to peak.

[BobTurner]

Originally Posted by rzbill

While I have never done it on a carb like that, I would think that the enriching circuit efffect would be negated by leaning the mixture to peak.

Bill, read the OP post again. He is reluctant - wisely, I think - to lean to peak at full power. He wants to know where he's sitting with regard to mixture, without leaning.

[rzbill]

Originally Posted by BobTurner

Bill, read the OP post again. He is reluctant - wisely, I think - to lean to peak at full power. He wants to know where he's sitting with regard to mixture, without leaning.

Sorry Bob but I don't read it the same way you are. I still say that the carb richening circuit would be overridden by the mixture control at a peak EGT condition and therefore irrelevant to the OPS post.

I guess that is an example of how two people can see the same thing and comprehend it differently.

[lr172]

for clarity, Bob was correct. I was hoping to gain an understanding of peak EGT at or near full power without the need to go there to find it. Going that lean at very high MAP levels is a dangerous game, based upon my experience tuning auto engines. You're just asking for detonation.

Also, I have Fuel Injection, but for some reason, my signature stating that didn't show up. Sorry about that.

While some carbs do have a WOT enrichment circuit, the mixture valve sits upstream of all circuits in the carb, setting a maximum flow. As long as the main jet is flowing all of the fuel available through the mixture valve, additional enrichment through other circuits is not possible.

Larry