165 $6E cold idle

[Bruce Plecan]

I'd really look at the code/hac before relocating the MAT.
In some cals., it's used for figuring the air density entering the motor.
Might even allow for some heating of the fuel.  In some applications is used
for EGR stuff.   The Fuel has a number of different temps for when the
various light **aromatics** boil off so you can maybe generate a richer
condition in one operating set of conditions and then really fubar things
for when things turn suddenly cool.  I'd strongly suggest doing programing
changes for calibration fixes rather then mechanical patches for software
fixes.

Relocating the MAT, for something like this is taking an instant step back 3
years to when the hacs weren't available, IMO.

Some cals., do not make timing corrections for MAT, which is a much more
important issue in my opinion.   If your seeing an inprovement in
performance you much isolate if in fact it's fuel or timing.

Just by example:

On a hot day you lose performance,
fuel is hotter, and the octane will vary, higher temps., faster boil off of
the lighter stuff in the fuel which is what generates the Octane
(primarily).  So in that respect you need to richen the mixture a lil, and
retard the timing, BUT in order to recover the differences in pumping
changes, you'd want to increase the timing (the above at WOT).  Then if your
running EGR, is another whole barrel of snakes.

Are you really up to the challenges of the above to get it right?.

For the time diddling with the above, you probably could spend the time to
figure out the best answer.
HTH
Bruce




> I would think that in regards to the MAT that the location is not as
> important as the change in output for a change in temp.  assuming that the
> motor was tuned to where it ran well (w/an air temp of X), if the temp
went
> down by 5% you would expect that the MAT would report the 5% change.  now
> the ECM could compensate by the 5% (or some reduced/enlarged percent) for
> that change.  the only down side that i could see to having the MAT on the

> bottom of the manifold is that it is hot all the time & it makes me wonder
> if it is seeing the air temp change.
>
> the reason for interest here is that i just put a fresh air package on my
> car.  previously i had a K&N connected to the TB & was sucking in nice
warm
> air right from the radiator.  in a black car, in traffic, in S. California
> the MAT temps were very high (sorry don't have #'s right now).  when i
went
> to the fresh air package i thought that the MAT temps were going to drop
40
> - 60 Deg or so but that did not happen.  I am truly taking the air from in
> front of the car.  this leads me to think that the sensor connected to the
> manifold dampens the response, maybe saturation from the plenum into the
> sensor.
>
> the air filter canister that i have is from a  Firebird & it does have the
> hole for the MAT, but is it that important?  The temp of the air certainly
> affects the density of it.  & most cars tend to run faster when the sun
> starts to go down & the air temp drops.  so this leads me to think that
> this does have a fairly sizable impact on the hp the motor is making but
it
> just does not seem to pan out.  what am i missing?  maybe i will start
> another thread on this subject.  this leads me to thinking about density &
> speed density systems & PE mode.
>
> I am headed back to the track in a few weeks.  maybe i will take the old
> filter with me & do a back to back run with the fresh air & W/O & see if i
> can time (& record with data master) a difference.
>
> Thoughts?
> BW
>
>
> > [Original Message]
> > From: Marteney, Steven J. <smarteney at xlvision.com>
> > To: <gmecm at diy-efi.org>
> > Date: 2/12/01 7:22:45 AM
> > Subject: 165 $6E cold idle
> >
> > Found my idle problem this weekend... cold weather.  The weather here
> (East
> > Coast FL) went cold for the first time since I started playing around
with
> > closed loop disabled.  Both my lean and rich chips ran like crap.  This
> > weekend, both chips ran great.  The lean one's idle was a little rough,
> but
> > not that bad with the low end of the MAF Scalar table turned up a bit.
> > Looks like I've got some cold weather idle tuning to do.  Any thoughts?
> >
> > Here's my thinking.  With the MAT sensor located under the plenum, it's
> > coupling all the heat from the motor.  The MAT readings from a cold to a
> > warm day only differ by about 6-10 degF, even though outside air temp is
> 30+
> > degrees below normal.  Would relocating the sensor away from the motor
> help?
> > (Thought about mounting it to the air filter can, right fender well in
TPI
> > Firebird.)  Or, can the air really warm-up that quick when it enters the
> > plenum?  In that case, is the problem the MAF sensor is giving an
> erroneous
> > reading from the cold air?
> >
> > Any suggestions are definitely welcomed!!!
> > Steve
> >
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>
>
> --- Bob Wooten
> --- r71chevy at earthlink.net
> --- www.r71camaro.homestead.com
>
>
>
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