EGT Rise Question

[Jaybird180]

Why does the EGT rise when turning off one magneto? Why does the temps normalize when running both again?

 

[Bill]

Why does the EGT rise when turning off one magneto? Why does the temps normalize when running both again?

My guess: Less complete combustion in the combustion chamber leads to more of the charge burning off in the header causing the EGT rise.

 

[Geico266]

My guess: Less complete combustion in the combustion chamber leads to more of the charge burning off in the header causing the EGT rise.

We have a winner!

 

[Ted]

My guess: Less complete combustion in the combustion chamber leads to more of the charge burning off in the header causing the EGT rise.

You are correct. It's similar to retarding ignition timing, because the mixture on the far side of the cylinder burns later - it doesn't have that spark on the other side to get it going. And they then return to normal because you've returned the engine to its normal operating condition.

 

[Sac Arrow]

My guess: Less complete combustion in the combustion chamber leads to more of the charge burning off in the header causing the EGT rise.

That exactly. I've forgotten to turn my mags to "both" before a couple times in the past. Symptoms were a loss in power, and EGT's went through the roof.

 

[Clark1961]

That exactly. I've forgotten to turn my mags to "both" before a couple times in the past. Symptoms were a loss in power, and EGT's went through the roof.

The EGT/TIT just went bonkers when I lost a mag while in cruise in the 'kota. Reducing power to about 20" got things sorta stable. I'm pretty sure the wastegate (Merlyn) was totally open at that point.

Anyway, not much fun from an engine operation point of view and a real eye-opener in terms of thinking about losing a mag on departure. Basically I think you'd have to cook the turbo or stop the climb.

 

[Ted]

The EGT/TIT just went bonkers when I lost a mag while in cruise in the 'kota. Reducing power to about 20" got things sorta stable. I'm pretty sure the wastegate (Merlyn) was totally open at that point.

Anyway, not much fun from an engine operation point of view and a real eye-opener in terms of thinking about losing a mag on departure. Basically I think you'd have to cook the turbo or stop the climb.

Yep. I've noticed that Continentals especially don't like running on one mag, although I'm not sure why. I've run Lycomings for hours on end on one mag without as much of an impact.