Quote:
Originally Posted by Leadfoot
I controlled the EGR flow by changing the ECU tune with a programmer which I custom tune from my laptop. I first doubled the EGR flow with no problems, just a loss of power and mileage. When I tripled the EGR flow some missing was noticeable. Scangauge does not work with this truck so the gas mileage was recorded over a few tanks of 93 octane. I record the mileage onto index cards but I never marked the info for this test so I cannot give you an actual figure, I just remember that doubling or tripling the EGR flow resulted in less gas mileage. The stock EGR flow values seem to be optimal. With no EGR flow I did not notice any change in mileage or power but I set the EGR flow back to stock for the chance that id did improve fuel mileage 1%.
My theory to this matter is that it robbed too much power. I think trying to move a 4000lb vehicle that is 20% down on power actually eats up more fuel. Like how some trucks with modular V8's get better gas mileage in the city than modular V6's. That or some of the fuel is not being burned.
One thing to watch out for is the EGR gumming up your intake, after 80,000miles it will rob power and fuel economy if not cleaned. The throttle body getting gummed up is the biggest thing to worry about.
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Extra EGR flow should only affect low rpm/part throttle conditions, it should not affect WOT (EGR should be closed)
If your able to tweek ECU , I would try raising spark timing in part throttle/cruising area (when EGR is on). The stock ECU probably does this also so some testing would be needed .
For sure adding extra EGR will make the car less responsive and need more throttle (thats what you want, and if all goes right some extra MPG might happen) .
2x increase sounds a little extreme , I would start lower % and test, work your way up .