165 $6E cold idle

[rr]

I can understand your confusion with the mat temperature. I haven't
quite figured it all out yet either. I do know that when the sensor is
in the air cleaner it is an IAT (intake air temp), as opposed to mat.
The code that I have seen handles it differently.

Apparently the mat picks up heat from the surrounding manifold. How
much is from radiated or transferred through the sensor body is a
good question. I know that as the air moves through the manifold it
picks up heat. Slow air more, faster air less. Then the faster air starts
heating up due to friction. Maybe the sensor is located in a 'dead'
area, not much air flow past it. On TPI's I think it is mounted in the
back of the manifold.

Additional heating is done by the throttle body coolant passage
along with the egr.

To see how an IAT is handled check the azty hac of mask $88. This
engine uses a sensor mounted in the aircleaner housing. The canister
type as the Firebird you have.

Here is the math I did for temp change vs AFR change (well only the
answers):

Going from 14.7:1 afr at 102F to 0F makes the afr 17.9:1

Going from 14.7:1 afr at 0F to 102F makes the afr 12.0:1

So, the change is significant.

I've added an IAT sensor & support code to the ecm I'm currently
using. It will be interesting to see how it works out. I suspect that BLM
changes will be less.

BobR.

p.s. on the $8D mask, '730, the egr is enabled by the mat temp.


Bob Wooten wrote:

> 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

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