Guys,

I recently rerouted my air intake and MAT sensor to get colder air from under the car. How can I modify my MAT tables to take advantage of this? Or is it even necessary?

Thanks.

what application are you talking about here?

historically on this board most people seem to recommend against relocating the mat, and that if you do relocate it, you have to recalibrate it and then you are back to where you started from, no gain.

my personal suggestion and what i'd do with my own car, is put the MAT back in the stock location. you'll still gain the advantage of the cold air box/intake, and the MAT will more correctly report intake air temp to the ECM in the way the stock ECm calibration expects to see it.

Screw that. I am definitely a supporter of relocating the MAT. What's the point of having a MAT if it is not reporting the correct temperature of the incoming air? The underneath of the TPI plenum is totally heat soaked. Anybody programming their own PROMs should move the MAT and recalibrate the MAT tables. It's a PITA but worth it if you want to record data and have a true reading of the incoming air temps.

There is absolutely no need to move the MAT if you are looking for a performance gain. I just recommend doing it for the hardcore guys who have a 'need to know' the true incoming air temps. I definitely have that 'need to know'.

Tim

Yikes! I guess I need to hang around here more often. It's been several months since i've been on here too much, and back then i remember everyone saying that there was no gains to be had and recommended leaving it in the stock location because it wasn't gaining you anything.

you mention there's no need to move the MAT if you are looking for a performance gain. What's the reasons then? Just curious. I can see it mattering in a forced induction situation, or maybe testing of different air intake paths?

Just curious!

I'm a fan of the relocated MAT too. To me it definitely made the car 'feel' better after a heat soaked start, and my track times also got dead nuts consistent after i relocated as well (which i attribute to correct air temp readings rather than varying degrees of heat soak depending on how long in staging, etc)

As for recalibrating the MAT tables i am using values copied from an ancient glenn91l98gta post. I had also used the anht vette values as well but my BLMs varied a bit more with those than i've seen with glenn's. Now that i have my own scan tool maybe i'll tweak it for myself, but so far i see no point.

The air temp is at the bottom of the air duct in the picture. It's picking up air from under the car- not quite ram-air, but cooler air.

Ed, where can I get these tables you were talking about?

Before anyone asks, here's the Inverse MAT Delta Multiplier Table that I use with my relocated MAT. I found that with these settings and a relocated MAT, that I had more consistent BLM/INTs than with the stock setup. Now, that I have a Miniram, I must run a relocated MAT.

You may find that you will need to tweak/adjust your injector constant and possibly your VE tables, but once you get yourself running 128/128, you should find your BLM/INT is much more consistent in a wider range of ambient air temps.

Here's a question:

Does the MAT get used for ANYTHING on a MAF car other than setting codes? Just curious...

Because if not, that would be an easy input...

I've gotten quite deep into the $6E code and I have yet to find the MAT do anything besides controling the EGR enable temp (and set codes as you point out).

Changes in ambient air temp (and elevation) are recognized in the voltage reading given by the MAF wire for air/fuel. Installing a relocated MAT does nothing for a MAF car except alter when the EGR comes on (later with a relocated MAT because of the lower temp reading).

Good deal, I'll go ahead and take a stab at using the MAT connection as an input for a WBO2 reading.

Of course, I'll have to 'disable' MAT codes with a couple well-placed values, but that's easy.

Yes, I'll be modifying my ALDL software to handle the changes. It will display WBO2 AFR on the summary page, and let you log it just like any other variable.

If the MAT doesn't pan out, I'll use some other input. Have to do something different for the 730 users...

Just need to take into account the 1k PU to 5 volts on that input. It depends upon which WB you are using whether this makes a difference.

On the '730 the TPS2 input is the best choice.

RBob.

edit: on the '165 the MAP inputs are low pass filtered with a 19 Hz @ 3db cutoff.

If you relocate the MAT I recommend using a better sensor that give a true incoming air temperature reading like the LT1 temp sensor or a 1985-88 FIERO v6 MAT. For more info check out my old post:

https://www.thirdgen.org/techbb2/sho...hreadid=136007

I've never seen that first sender used for MAT,
The second sensor is a true MAT/IAT sensor. It has to be *open* for air flow.

In short, the IAT/MAT sensor works fine as such, and is fast responding, and DOES NOT read the surface heat of what it's mounted on/in.

There are a few sensors that have faster responses, listed in the Packard book, but so far they aren't available.

With the right corrections, you can **crutch** the timing fuel corrections to make up for the SLIGHT error when you actually measure MAT.

Please don't think that IAT and MAT are interchangeble. There is a huge difference. And MAT means mounted in the plenum. Actually the best place is just behind the T/B so as to have some air flow directly past it.

I'm not sure in a N/A how much HP you'll really see, TBI have gotten by without them for years, but have slight glitches from not using them, but that is mostly in drivibility. At WOT the MATs are a fairly well given. Turbo S/C cars are an entirely different issue.