does the EGR help or hurt fuel economy?

[Matt Timion]

I recently read somewhere that someone suspected that EGR valves may actually hurt fuel economy.

more on EGR Valves

I personally think that by their very design an EGR valve will help with fuel economy.

What say you?

[MetroMPG]

i suspect a properly operating EGR's effect on f/e is negligible.

depending on the volume of EG inhaled, it could reduce the proportion of 02 in the intake charge relative to ambient air. is that where you're going?

[diamondlarry]

I've heard people say that it depends on the car. Some cars get better mileage without it and some are better off with the EGR.

[SVOboy]

I've heard people say that it depends on the car. Some cars get better mileage without it and some are better off with the EGR.

I agree. On h-t this was a topic because someone asked about taking it off and one of the responses was that it helped fuel economy on their buick but hurt it on the honda. The general Honda consensus is to leave it on, Honda builds their stuff well.

[MetroMPG]

...buick vs honda...

but really, how accurately did they test this? i suspect the difference would be very small in any case, and unless they ran a really controlled experiment... etc. etc.

[SVOboy]

Well, the difference for honda was vouched many times, but anyway, he claimed the difference to by like 3-5 mpg on a 25 mpg car (with egr).

[SVOboy]

http://honda-tech.com/zerothread?id=1426570

One case, not the one I mentioned though.