89FormulaL98

where exactly are these located and what does it do for me to move them.. and what does it involve?

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89' Firebird Formula WS6 L98, MSD 6AL MSD Blaster, Hypertech chip, K/N filter cone,flowmaster 80 series, hypertech air foil, koni shocks, edelbrock trailing arms

more to come soon.....

89FormulaL98

opps... i meant IAT (what is that anyways?)

Rob P

iTrader: (1)

Mat (manifold air temp) IAT (inlet air temp).
Mounted under the plenum on a TPI. Moving it to the air box fools the computer into dumping more fuel (in a nutshell).

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Rob P
89RSconvtZZ4TPI
Edelbrock Hi-Flow Intake
SLP Dual Cold Air Intake
1 5/8" Headers
Semi-Siamesed Runners
MSD6AL/relocated MAT/ AdjFPR/IROC frnt@rear swaybar/wonderbar/steeringbox/alum drvshaft/ Alston SFC/3:23posi disc rear/MAC LCA/H.Adams Panhard Rod/KYB struts/ shocks/
92Z28convt5spd
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

Grim Reaper

I have been reading the hac for the MAF system and I do not see ANYWHERE in the hac where there is ANY correction of the incoming temperature for the MAT. The only thing I can find regarding the MAT for MAF cars appears to control the operation of the EGR.

SD cars definitely have a correction table for the MAT, which makes total sense at SD cars need to calcuate the amount of incoming air. But I cannot find an equivalent table for MAF cars. I am not sure, but possibly the fact that MAF measure the air over a heated wire, the MAF system already accounts for air temperature just by the way it measures the incoming air.

I have been chatting with Greg Westphal (MAF owner) and he too has noticed that there is NOTHING that he's been able to find to indicate that the MAF system uses the MAT for anything other than the EGR.

If this is all true, for MAF cars, a relocated MAT may only be a "fancy thermometer" for people using a scan tool while they are driving.

SD cars DO use the MAT however to calcuate air flow.

AaronIROCZ

iTrader: (5)

Maybe it is just me but I relocated my IAT sensor and to me it felt like it had helped out a bit, especially when it is at normal oprating temp, 180-220. I felt better throttle response since I did it. I have a 1989 Iroc with a 305 tpi. soon to be a 350 can't wait. Thats my .02 worth

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89 Iroc 350 TPI,
Forged pistions
Comp Cam .510 lift 230dur
Flowmaster exhaust
Aluminum Heads SOON!!!
MINI RAM SOON!!!!!
stock TPI for now 24# inj

Vader

Glenn,

I think you might be right (like THAT's a big surprise!). I cannot find the MAT sensor offsets for fuel trim on MAF cars, either.

LDEF0 shows a MAT low cut-off for EGR, and there are a couple of error code lines for the MAT, but that's about all. The '88-'89 cars without the cold start valve use it for comparison to the CTS to determine a cold start condition and enrichment, but that's about all there is on the MAF cars. It appears that most of the temperature-related fuel trim is based on the CTS sensor alone.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

Grim Reaper

Thanks Jeff, I forgot about the "start up" routines. I will dig a little more and see if possibly the MAT value is stored somewhere and then used later as a factor in calculating the fuel trim.

The more I think about the MAF itself, the more I can see how the MAT may not be necessary as is the baro is not necessary. I can see how colder air and different density of air will alter the way the MAF reads the incoming air flow. The question is, does the MAF account for these changes (temperature and elevation) correctly. And if not, should the eprom for MAF be recalibrated for people living at higher elevations or during cooler climates for optimal performance.

I suspect that the MAF does account for all these and does it adequately for "day to day" driving. During closed loop operation, this is all irrelevant as the O2 sensor is the ultimate "umpire". But, if you are "fanatical" about peak WOT performance, you may benefit from a little "tweaking" of the MAF Scalar tables during colder weather or if you relocate to a higher elevation.

Matt87GTA

Just FYI, GM has officially named that sensor the IAT (Intake Air Temperature) sensor not the MAT sensor.

Grim Reaper

Matt, not as of 1991. Even the SES error codes call it the MAT.

Matt87GTA

What the name of the sensor is, is really not that important but I truly thought that they all are called the IAT sensor. I took the time to look over some GM service manuals and came to these conclusions:

The sensor is called a MAT sensor if it is on a MAF system because it merely measures the manifold air temperature to control the cut-off of the EGR valve. In this system it does not have anything to do with the rest of the engine controls - only the EGR (I found all of this information in a service manual for a 1987 Firebird with the MAF system).

The sensor is called an IAT if it is on any system that does not use a MAF sensor to measure the incoming air's temperature (Speed Density Systems). ( I found that on Speed Density engines such as the vortec V6 CPI engine, the sensor is called an IAT.)

Therefore, in a MAF system on a TPI, the sensor is called the MAT sensor and on a Speed Density system on a TPI, it should be called the IAT sensor. I think this theory makes sense and I will consult some other GM engine control system gurus to make sure.

I guess it really doesn't matter what it is called but I thought that GM had settled on one name for that sensor but I guess not. It depends on the system. Anywho............

Laterzzzzzzzzzzzzzzz

F22Raptor

The name issue is pretty interesting! (that must have been a slider, it completely threw the subject off "the subject")

Anyway, can we PLEASE get back to the not so interesting technical aspect of this thread, that is the function of the whatchamacallit?!? IAT-MAT

crack-head-iat/MAf_riCk

Matt87GTA

It is just like Vader and Glenn were saying:

On MAF systems, the MAT sensor only controls the EGR valve and has nothing to do with the fuel and timing data (except on 88-89 cars where it is used to determine cold start conditions, which it can do just as well in the stock location). Relocating the MAT on a MAF system would most likely be a bad idea since the sensor is located strategically in the plenum behind where the EGR gases mix with the incoming air. I think that the purpose of the MAT sensor is to cut off the EGR valve if the temperature gets too hot due to the hot exhaust gases being recirculated into the engine crossing some predetermined threshold. Having the sensor located in the stock position should tell the ECM when it needs to stop EGR pulse width modulation. What do you guys think???

I have very little experience with Speed Density systems on L98's but I would guess that moving the sensor on a SD system would be benificial since the ECM relies on the IAT (MAT....or whatever ) to tell it what the air temperature is and the fresher the air charge is that flows across the sensor, the better the power, throttle response, and overall driveability will be since the ECM is provided with the best data possible.

These are my thoughts on this.

Laterzzzzzzzzzzzzzzzzzzzzzz

Grim Reaper

Relocating the MAT on a SD car is only beneficial if you correct the MAT Inverse Look-Up table to ensure you have the proper correction factors for the cooler readings.

The MAT was designed by GM to work at the stock location with a heated Throttle Body. Hence, they GM gave it a "richer" factor than it should have if the MAT was measuring the actual incoming air temperature.

Without correcting the MAT table in the eprom, a relocated MAT will cause your car to run far too rich, especially in cooler temperatures. All the factors are "off".