[Diy_efi] Intake manifold flow testing

Grant Beaty gbeaty at ufl.edu
Wed Feb 12 17:22:14 GMT 2003


> A lot of tribal knowledge is just that chicken bones and voodoo....
> Dave

I know, thats why I said YMMV (Your Milage May Vary) :) Certainly didn't
mean to present it as fact.

FWIW, FJO did some tests (I think on a V8) with their WB and found the EGTs
increased by about 35C per a/f point.

Grant

----- Original Message -----
From: "Dave Dahlgren" <ddahlgren at snet.net>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Sent: Wednesday, February 12, 2003 6:28 AM
Subject: Re: [Diy_efi] Intake manifold flow testing


> The whole point about logging it is to see if the problem is real or
imagined..
> A lot of tribal knowledge is just that chicken bones and voodoo....
> Dave
>
> Grant Beaty wrote:
> >
> > >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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