MAF vs MAP

[Shannen Durphey]

xxalexx at ix.netcom.com wrote:

> > Date:          Wed, 25 Feb 1998 01:51:42 -0700
> > From:          Shannen Durphey <shannen at mcn.net>
> > To:            diy_efi at efi332.eng.ohio-state.edu
> > Subject:       Re: MAF vs MAP
> > Reply-to:      diy_efi at efi332.eng.ohio-state.edu
>
> >
> >
> > xxalexx at ix.netcom.com wrote:
> >
> > > > Priority:      Normal
> > > > To:            diy_efi at efi332.eng.ohio-state.edu
> > > > From:          "bruce plecan" <nacelp at bright.net>
> > > > Subject:       Re: MAF vs MAP
> > > > Date:          Mon, 23 Feb 98 13:43:45 PST
> > > > Reply-to:      diy_efi at efi332.eng.ohio-state.edu
> > >
> > > > ref KV:
> > > > GM (OEM) specific
> > > >   IMHO it's as much about application as anything.  Both use
> > > > feedback from the O2 sensor for the final trimming of injector timing,
> > > > so at less than WOT, there is about 0 difference.  Now at WOT,
> > > > and for off-highway use racing the MAP is the winner since there
> > > > is no MAF restriction.  As I understand things now, on the newest
> > > > GMs some use both a MAF, and MAP.  Does anyone know if they
> > > > do this for averaging, or backup, or what conditions they use each
> > > > for??..
> > > I would say atmospheric correction, most flow meters are calibrated
> > > at STP(std temp press 29.92"Hg  68F) you need intake air and
> > > atmospheric pressure to get actual corrected flow.
> > > alex
> >
> >   And backup.  Unhooked MAF of running 96 Corsica 3100 V6, engine never even
> > hiccupped.  smooooth and snappy.
> >
> > Shannen
> >
> Yes, I accidentally did the same thing, must say a liitle surprised
> and alot of comments like throw it away, who needs it.
> Rather busy with other problems at time so did not look in to it
> further.  How does it run under load?
> alex

  I was in the middle of a service job, so I didn't have time to check.  Wild
thing about these OBDII cars, they don't always set a code when there's a
problem.  It sets a counter and if the problem occurs again within X ignition
cycles, the light goes on.  Anyway, I'll get another one in to try out.
Technician across the shop was working on government fire truck today with a 96
Vortech 454.  The truck was driven 50 miles to get to the shop, and the problem
turned out to be a blown fuse to the MAF.  These new vehicles can't run too badly
without it.

Shannen