Fuel Econ and Hiway Mode

[Mark S. Riley]

Like Jim Testa, I also "mess" with a bunch of GN TType Buicks and simply
raise the enable on the EGR to never, never land so that it keeps the #3
cylinder the same temperature as the other 5 and consequently doesn't blow
the #3 head gasket into orbit or wrap the fire ring backwards around the
head bolts. I've seen more head gaskets blown on Buick v6's at light
throttle in 5:00 pm traffic than at wide open anywhere else. Deleting the
EGR usually causes a mpg loss which careful driving doesn't quite get back.
My understanding was that it lessened the octane requirement allowing light
throttle spark advance to be much higher. Leaner, lessened fuel mixture
cause you don't have a cylinder of clean fresh air to have to feed to 14.7:1
or there abouts. And in more recent years, probably most important is the
NOX reduction by maintaining lower cylinder temps. I believe Bruce is quite
correct in thinking that some MPG is hidden in the EGR function and
adjustments.

Mark Riley

----- Original Message -----
From: "Bruce Plecan" <nacelp at bright.net>
To: <gmecm at diy-efi.org>
Sent: Tuesday, October 10, 2000 2:50 PM
Subject: Re: Fuel Econ and Hiway Mode


>
> > >So.....  If a person had a choice  EGR or not EGR - and didn't have to
> worry
> > >about emissions, which would it be?  What factors would influence one's
> > >decision
> > >to go either way?
> >
> > If you don't have to worry about emissions, why add to the mess by
adding
> > EGR???
> > It's a pain to tune.
>
> It would almost me fun to see what you could do with it for MPG.  I lost
MPH
> when using it with hot rods, but for a stocker might be lots of tinkering,
> and interesting
> Bruce


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