DIY_EFI Digest V4 #575

[Laura & Neil]

> Date: Mon, 11 Oct 1999 19:21:01 -0400
> From: "crash70" <crash70 at epix.net>
> Subject: MAP Sensors & Pushrods
>
> With all this talk of MAP sensors, I have to ask the question: What is the
> best way of measuring incoming air on an engine? Flap doors are obviously a
> huge restriction. Hot wire and film sensors seem like a good method, but
> MAPs are TOTALLY unobtrusive on the intake system.
>
> I've noticed that the majority of American cars use MAP sensors, as well as
> newer Hondas. European manufacturers seem to favor the film or wire sensor.
> Is it an economic issue, like the American resistance to ditch pushrods?
>
>

I think it is a matter of cost.
Yesterday I daignosed a 91 Plymouth Laser with a 2.0 turbo motor as having a bad MAF
sensor. (Real errratic idle untill the MAF was disconnected forcing the computer to
use the default setting, ran perfectly at idle with the MAF disconnected).
The MAF is a dealer item only at $670!!. The average MAP is about $50 retail.

> > Date: Mon, 11 Oct 1999 00:50:01 +1000
> > From: Phil Lamovie
> > Subject: Re:Up Up and Away
> >
> > <snip>
> >
> > There is absolutely no need to calculate the mass of the atmosphere on
> > Earth and then divide that by the ratio of volume of inlet manifold.
> > Though it would work.
> >
> > Please note the total lack of Patents for Altitude correction of
> > aircraft fuel injection computers. Also total lack of altitude sensors
> > on all Ford and GM vehicles. I suppose they don't have mountains in
> > the
> > USA.
> >

Surely engine vacuum is relative to the ambient atmospheric pressure. And as the MAP
sensor is vented to atmosphere it will have a fair degree of self correction for
altitude.