[Diy_efi] Intake manifold flow testing

[Grant Beaty]

>From the things I've seen with my own car and read about others, 35C is
about 1 entire a/f point (ie 11:1 to 12:1) if everything else is equal. Of
course, everything else is rarely equal (especially timing w/ active knock
control), so YMMV.

Grant

----- Original Message -----
From: "Geddes, Brian J" <brian.j.geddes at intel.com>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Sent: Tuesday, February 11, 2003 6:17 PM
Subject: RE: [Diy_efi] Intake manifold flow testing


How different would the A/F ratio in the cylinders need to be in order to
create a 100F difference in EGTs?  Are we talking about a tenth of a point,
or a point, or a couple points?  My concern is the EGT may be too coarse a
measurement.

- Brian

>
> I would never use it for any kind of absolute numbers as it
> is as much timing
> related as anything else. With that said you are only looking for a
> differential.. If the timing is the same in all cylinders and
> the fuel is the
> same then the egt ought to be as well if you allow a little
> 'windage' for
> cooling system issues. If they are different then I would bet
> the only thing
> that is different is the airflow.. It might be worth a little
> fuel tweaking to
> even them up if they are a lot different.. Over 100 deg F
> would be my threshold
> to play a little.
> Dave
> "Geddes, Brian J" wrote:
> >
> > Is there a close enough correlation between EGT and A/F to
> use EGT to estimate the relative airflow differences?  I
> thought that the EGT-A/F connection wasn't very exact...but
> I'm certainly no expert.
> >
> > - Brian
> >
> > > -----Original Message-----
> > > From: Dave Dahlgren [mailto:ddahlgren at snet.net]
> > > Sent: Tuesday, February 11, 2003 12:15 PM
> > > To: List for general do-it-yourself EFI talk
> > > Subject: Re: [Diy_efi] Intake manifold flow testing
> > >
> > >
> > > The sad part about this problem is that it most likely
> > > changes with rpm as well
> > > that is to say they can move around. a rich one at 4500 might
> > > be a lean one at
> > > 6000.  You could probably verify they stay the same by using
> > > some egt probes and
> > > data logging them along with rpm map and tps..Above all i
> > > think i would only
> > > want to add fuel.. Best idea is get a better intake manifold.
> > > Dave
> >
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