DIY_EFI Digest V5 #27

Scott Croughwell scott at
Tue Jan 18 19:57:04 GMT 2000

> How does the hot exhaust gas cool the fresh charge.... Or have I got this
> wrong and you mean that the exhaust gas isn't heating the cool intake
> charge and the cold intake charge is causing the detonation????

Believe it or not... the gasses coming from the EGR have had enough time to
cool enough so that the portion of exhaust temp re-entering the intake port
is cooler than the intake manifold.  (Thus, EGR valve only opens when the
engine is at "operating temperature".)  But if engine knock is only apparent
at something other than high engine loads and/or speeds... I'd be willing to
bet dimes to dollars it's due to the EGR being disconnected or inoperable.


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