Re: General tuning question - fuel economy

[romans@starstream.net (Romans, Mark)]

Raise your fuel pressure.  This should bring your bl down a bit.  When it
gets to be interesting is when the bl is high in one part of the map and low
in another.That's when I edited the values in the maf calibration.  (165
ecm).
Mark
----- Original Message -----
From: "Marteney, Steven J." <smarteney@xlvision.com>
To: <gmecm@diy-efi.org>
Sent: Wednesday, June 14, 2000 7:47 AM
Subject: RE: General tuning question - fuel economy


> Unfortunately, the BLM is typically sitting around the maximum.  I've seen
> it at 160, but it's typically around 145-150.  This says to me with the
> bigger cam, it saw it was too lean (more airflow) and therefore it gave it
> more fuel, hence less gas mileage.
>
> Steve
>
> -----Original Message-----
> From: Squash [mailto:realsquash@yahoo.com]
> Sent: Tuesday, June 13, 2000 5:04 PM
> To: gmecm@diy-efi.org
> Subject: Re: General tuning question - fuel economy
>
>
> I'm not sure how that ecm works (165=C3?), but is it possible that the BLM
> is sitting at the
> minimum value?  That would mean it's trying to lean it out, but it stopped
> because of the limit.
>
> Squash
>
> --- "Marteney, Steven J." <smarteney@xlvision.com> wrote:
> > Not having really any engine "tuning" experience I stumble on some of
the
> > basic concepts (such as when to add spark advance).  My rebuilt 350 TPI
> > F-body gets about 20% less highway gas mileage with its bigger cam (GM
> ZZ3)
> > and stock computer.  I figure more air in at X rpm requires more fuel to
> > appease the O2 sensor, hence gas mileage goes down.  How do I
compensate,
> or
> > can I?  I noticed there are some Hiway mode parameters, such as Hiway
> spark
> > add (?), in the 165 ECM that I could take advantage of.  Or, is the only
> way
> > to get better mileage mean changing the target AFR?
> >
> > However, I also thought that this engine cruises at about 2200 rpm on
the
> > highway at 75 mph.  I'm wondering if the different cam (and valve
timing)
> > has defeated the ram tuning effect of the runners and made the engine
less
> > efficient on the highway.  Any thoughts?  I'd appreciate a little basic
> > help.  Since this car is my daily driver (70+ per day) I'd like to keep
> fuel
> > economy in mind when tuning.
> >
> > Thanks,
> > Steve Marteney
> >
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>
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