[Diy_efi] Intake manifold flow testing

[John Stricker]

I can't specifically answer your question but in aircraft, at first it takes
large movements of the mixture control to affect EGT.  As we get close to
proper leaning, very slight movements can make a great deal of difference in
EGT.  As to tuning by EGT, there is a company called GAMI that balances
fixed orifice injectors in aircraft mechanical fuel injection systems by
doing just that.  You fly the airplane and record EGT's and they can vary
fuel with injector sizes.  On some engines (large, turbo-charged
Continentals) it makes a VAST difference in how well they run and their fuel
efficiency.  On others (smaller Lycoming, for instance) there isn't enough
difference to even come close to warranting the change.  The difference
between the engines is how well balanced their intake piping is to begin
with.

John Stricker

----- 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 5:17 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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