[s-cars] 3071 turbo & Pastore RS2 code question

[Jim Green]

On 3/21/06, djdawson2 at aol.com <djdawson2 at aol.com> wrote:
>
> That statement would be true if there were no means to correct
> mixture.  However, those means do exist.
>
> 1) The MAF measures the mass of air... thin or dense, mass remains
> constant... and that's one way the ECU determines the fuel requirement.
> 2) The ECU incorporates a barometer... which identifies changes in
> altitude, and modifies A/F R.
> 3) The ECU takes input from the O2 sensor... and also changes A/F R based
> on those readings.
>
> Now, if we had an 034EFI system, installed and programmed it in a car at
> high altitude... trailered it to sea level and hit the dragstrip... THEN
> we'd have a meltdown.  Only one map (fuel,ignition,boost)... no compensation
> ability for altitude... no means to deal with denser air (not even a MAF).
>
> This is why I have stayed away from standalone engine management.  Hap's
> car will be an interesting "test mule" to see how the AEM system can deal
> with it.  Regardless, I would still expect him to have problems when he goes
> to sea level... and substantial additional programming will be required to
> make it work right down low.
>
>
>
Hey Dave, I thought I'd chime in with my findings.  I've had the laptop and
WB O2 up at the top of Eisenhower 11,xxx ft twice now and have found that
only a few % difference in fuel is required.  I had made a rough map in the
altitude compensation cells that pulled about 7% of the fuel out from Denver
to the top of the pass.  This was way to much and the car was running lean.
I changed it to the minimum values which is about 2% between the two
extremes and it ran great.  Bottom line is you could get away with not even
changing anything.  By nature the MAP sensor is constantly correcting for
the pressure outside so having a second sensor on board for this seems to be
a moot point.  What you do have to program is the temperature compensation.
This is the biggest thing that has an effect on air density for MAP based
systems.


--
Jim Green
'89 90 GT35R quattro
'89 80q
http://www.mswanson.com/~jgreen/car_home.html