Fuel Econ and Hiway Mode

[Bruce Plecan]

> 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.

I'd be alot more predesposed to think the #3 gasket problems are a problem
with the exhuast porting to the intake face rather then the EGR itself.
There are 3 exhuast ports leading from the center exhuast valve pocket.  By
allowing the EGR to work then that passageway gets alot more thermal
loading, so it's just the way the design is executed rather then the
principal that is wrong.  IMHO.
  I really think the problem with EGR is cheap poorly designed executions
rather then the design.
Bruce



> 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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