EGR questions...

jzurlo at thales.math.uwm.edu jzurlo at thales.math.uwm.edu
Fri May 26 02:05:52 GMT 1995


> 
> What would be the effect of lots of EGR under part throttle conditions?  I was 
> thinking that might be a way to improve mileage say under highway driving 
> conditions.  My reasoning is this:  Adding exhaust gas to the intake would 
> dilute the A/F mixture, without changing the actual A/F ratio, since exhaust 
> doesn't contain oxygen or fuel.  Thus reducing the amount of fuel sent to the 
> engine, without the problems associated with a lean mixture.  comments anyone?

Actually small amounts of EGR (~5-10%) improves mileage at part load. 
What happens, as someone else pointed out, is that power output decreases,
so that you open the throttle more.  Opening the throttle reduces pumping
losses and improves mileage.  Large amounts of EGR ~20% decreases mileage
because flame speed is reduced enough to offset the reduced pumping losses.

Jim
jzurlo at thales.math.uwm.edu




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