As an example, in my Twin Beech, when the OAT is 92dF, the temperature
AFTER the venturi in the carburetor is 35dF.  That temperature drop
across the venturi is not there in an injected engine.  Now add another
100dF so that the IAT is 192 and the carb temp is 135.  That is not a
good thing.  At high powers, with higher CHTs, the detonation margin is
quite a bit narrower.  This isn't too much of a problem in the lower
compression engines but can quickly cross the threshold in the higher
compression engines.

If you draw a higher (by 100dF) IAT when the OAT is very cold, it's not
a big deal--the engine just thinks it's summer time!  If you do that
during the summer, when the OAT is already high, it could quickly
become an issue in the higher compression engines.  By the time one
adds 9 or 10:1 pistons, it can get ugly quickly.

This effect is why we think intercoolers are so important.

Walter,

 

OK, I will continue to suck unfiltered air as long as it is only diesel-greasy Chicago air - I would have to do something else if I was in windy-gritty West Texas.  Bugs I burn as pure protein.

 

Inter-coolers, for me, just introduce more cooling drag.  Of course, if the cooled induction air power pick-up cubed the drag loss, I might reconsider.  Also, the inter-cooler would have to be inconviently introduced before the throttle body - otherwise, the fuel computer would be confused.

 

Have you measured the cooling effect of atomization at the cylinder head?  If not, why would it be different than that occurring in the carb?

 

Hmmmm.... every answer gives rise to more questions.