Thread: EGT's

Originally Posted by uninformed

ok guru's

will engine compression braking cool EGT's quicker than Idle?

the reason I ask is I have noticed on more than one occassion that when driving for more than min of say 20mins with load, so the Egts would settle at say a min of 200-250c after turbo that if engine braking it seems to bring them down alot quicker than idle......????

if so, why?

cheers,
Serg

When you are compression braking your engine is injecting the amount of fuel for idle, however more air is being sucked through, so EGTs are reduced because A:F ratio is increased.

FWIW - I find that mine also come down quicker at RPM slightly above idle.
At say 270deg pre-turbo, if I increase the RPM above idle (by a few hundred RPM) the EGT will drop more quickly than just letting it idle.

Guess the temperature from combustion is less than the turbo/manifold so more airflow cools it down quicker. Basically the same effect as increased airflow due to engine braking.

Steve.

As the others said, it's pulling more air through which is why it cools faster.

At idle up a skifield my EGT guage will at least register something, but on the way down the hill using engine braking it stays pinned on the bottom stop. No heat.