re. factory instrumentation accuracy & mpg

ben swann benswann at
Mon Jan 27 11:25:33 EST 2003

I have not had a chance to verify the on-board computer with the actual
fillup on the '91, but Dan said it is accurate.

I know he said it would give me the 20MPG, but I was surprized that
there would be such a difference between my '87 QLCC chipped wagon,
which got 28MPG (hell if I didn't leadfoot, I'd get well over 30, or
could make it drop to 20 too) on the highway - as verified by pump
fillups - and fully loaded.  I usually got at least low 20's around
town, though admittedly it was lower when colder and on short trips.

I will check the thermostat, but I find it hard to believe this would
be effecting the fuel mileage on the car after it had been thouroughly
warmed up.  The weather was cold(low 20s), so time will tell.

More later.



----- Original Message -----
From: Phil Rose <pjrose at>
Date: Sunday, January 26, 2003 4:51 pm
Subject: Re: re. factory instrumentation accuracy & mpg

> At 1:10 PM -0500 1/26/03, Brett Dikeman wrote:
> >At 12:24 PM -0500 1/26/03, ben swann wrote:
> >>Yes - peeve # 2 on the new aquisition of the '91 200 20v tq
> avant.  Has
> >>SJM chip with 2.5 bar pressure transducer AFAIK.  Gas mileage
> abysmal>>on the way home - 20MPG and no I was not easy on the gas
> and probably
> >>averageing over 70.  My '87 5000 tq would get an easy 28 mpg
> under the
> >>same conditions.  I thought Motronic was supposed to be superior at
> >>engine management, including economy, over CIS (CIS/motronic).
> >>
> >>What's up with that?
> >
> Ben, were you referring to mileage from the on-board computer--or
> actualfill-ups? If the former, don't forget the error in computed
> MPG may be
> pretty large (mine was at least 10% low) unless the fuel-
> consumption factor
> is corrected (this is done by an IC adjustment, and I believe my
> write-up
> about this can be found on Chris Miller's web site.) If you
> measured by
> odometer and pumped amount, then I dunno.
> I agree that 20 MPG sounds rather low--unless your foot was really
> into it
> a lot. In my '91 200q, good gas mileage requires an extremely steady
> throttle (irrespective of speed it seems). With very steady
> cruising I'll
> routinely get 28 MPG even at 80 MPH; however with a lot of
> passing, hills,
> etc., could easily drop to low 20s.
> Phil
> Phil Rose
> '91 200q lago blue                        	Rochester, NY USA
> '91 200q tornado red                        	pjrose at

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