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Old 04-28-2008, 09:52 AM   #16 (permalink)
jpgmtech
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Location: Drayton Valley, Alberta, Canada
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duramax - '05 Chevrolet Silverado LT
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Quote:
Originally Posted by Duffman View Post
I know BMW was experimenting with a throttleless gasoline engine a few years ago that used EGR to extensively reduce O2 to the cylinders. Not sure what ever happened to it, I am not up on new BMW stuff.

Personally I think EGR is one of the worst technologies we have put on gas or diesel engines and that targeting NOx emissions are counter productive. Traditionally we have countered NOx with the following methods:

Richen A/F mixture up to 14.7:1 for a 3-way Cat (lowers FE, raises CO & HC emissions)
Retard ignition timing (lowers FE, raises CO & HC emissions)
Lower Compression ratio (lowers FE, raises CO & HC emissions)
Add EGR, facilitates pinging so CR & timing are further reduced and while neither leaning or richening the mixture (gas engine), it does dilute the quality of burn. In a diesel it does displace O2 which hurts FE.

The only good thing that EGR does is promote faster engine warmup and reduce pumping losses in a gasoline engine but cylinder deactivation, VVT and using small turbocharged engines are a better ways to do this.

As pointed out in the TDIs it also soots up the engine which increases maintenance requirements and soot in the oil increases wear. I can verify that EGR has not been good for the powerstroke diesels either.

What we need is Urea injection or NOx reduction catalysts to come online so engineers can start building efficient engines again instead of clean ones.
X2!

BTW, NOx reduction catalysts are already in use in most GM products, including the D-max.
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