Cliff Harris

While looking at the 1227165 BUA code that's in my car, I discovered that the MAT sensor is ONLY used to turn on the EGR.

So all you guys who relocated your MAT sensors in the hope of getting more performance have changed the EGR enable characteristics a tiny amount. EGR gets enabled if the MAT temperature is higher than -17.5 deg C, which is 0.5 deg F.

C409

Sorry to bust your bubble , but MAT is used along with MAP or MAF , ECT , O2S , and TPS to determine the correct fuel injector pulse width to maintain proper engine operation under varying conditions ... it plays a minor role however , and any performance benefit derived from its relocation would be miniscule at best ..........

dynocar

You could be right but I suspect that MAT does control fuel and spark but is not accessible to us tuners. It would be interesting to put a potentiometer in place of the sensor and watch the timing and O2 as the pot is changed. I would hate to run a boost application without MAT.

Cliff Harris

Fuel, spark and everything else is controlled by the CTS - Coolant Temperature Sensor.

I'm looking at the CODE. No guesses. No rumors. No "I read somewhere...". No "Somebody told me...".

If you want to check it out, look here:

http://home.earthlink.net/~cliff_har...5/BUA/BUA.html

The EGR code in question is at LDEF0, using the MAT at L0060. L0060 is not used ANYWHERE else:

Pwnage1337

That being said, can the MAT sensor be totally eliminated if you aren't running EGR?
Possible to remove the SES light also? I'm assuming it would flash if the MAT were disconnected.

Doesn't the engine need to have some idea of how hot/cold the air charge is? 40 degree air is more dense than 100 degree air, and requires more fuel to achieve the correct AFR. The engine can't determine the outside air temperature by how hot/cold the coolant is.

Not saying what you have found is wrong/incorrect, but I am interested in how the engine would operate without knowing the temp of the air. I know when my MAT failed, it always read -40C when datalogging

LTxDave

I wonder why the LT4 gets a MAT sensor if it doesn't use it.

AGENT 86

Later years, the intake temp was used for more than EGR. I get a laugh when people move the MAT on the early C4's.

GREGGPENN

Consider that MAF cars use a heated single wire to detect incoming air. I gotta think the temperature of the air also has an affect on the MAF reading....making it look like more air is coming in the motor.

Of course, O2 data (on the backside) constantly monitors and correct what the ECM thinks it needs to do.

C409

..... I stand corrected ... the MAT has no other function on MAF cars other than to enable EGR ... it does however , contribute to fuel calcs on SD cars .................

coupeguy2001

Yea, but it is in an inacessible place that is very hot. I was nice enough to put it in a place that was much cooler. Now I can see it every time I open the hood.

AKS Racing

I relocated mine on my '87 and the computer uses it to calculate enrichment fueling. The MAT sensor is critical to how mine runs.

GREGGPENN

Since the code Cliff linked is for a 1986. It seems we can't conclude what later MAF ECMs do with MAT readings.

87 vette 81 big girl

All the engineers & computer programmers behind these C4 Corvettes never cease to amaze me.

Light years ahead of most others yet today.

Many secrets yet to be cracked open & explanation in full unfolded.

AKS Racing

Mine is SD, so therefore the MAT is used in the fuel enrichment circuit.

Cliff Harris

Keep in mind that I'm looking at the '86 code, specifically BUA 1728, which is automatic trans with 3.07 rear gear. My car is an early '86 (I got it 12-24-85) and it actually has BUA 9340 code in it. One of these days I'll do a .bin compare and find out what the differences are between the 9340 & 1728.

I don't know if the MAT reading was used for more things in later years (or when the changes were made).

The 1227165 ECM was used from '86 through '89, but obviously there were code changes along the way, especially for '89, where there were major changes.

GREGGPENN

Yep, that's when they tried to stop CSI. Instead, we started to see all it's spin-offs....CSI NY, CSI Miami, etc.....

Never could stop those things though. They've got a life of their own now!

Pretty funny, eh?


I'm sorry!


Not that funny?


I'll shut up now!

dynocar

Personal opinion. I don't think that any of our tuning programs have every tuning table or parameter displayed for us. Before we had such programs, we used to do a prom bit and hex dump, then look for anything that looked like it could be a tuning table, make changes to it, burn a new chip, re-install it in the vehicle to see what changed. If GM ever used many single hex tables, I doubt if all were ever found. Even the early 32K proms seemed overwhelming in those days. Thus, I've never felt that just because I could not find a way to make a change, that it did not exist. If this controversial opinion is true, could it explain some of the controversies that we have?

WW7

Gregg, It is Labor Day, so I guess your allowed to Drink.............Then post.......WW

frenchyoliver

on my L98, locating the MAT in front of the car helped A LOT in having a very nice idle.
It s not a question of power.

tequilaboy

The $6E code does make more use of the MAT sensor than either $32 or $32B. It is used optionally in a few places instead of coolant temperature FWIW.

Start up enrichment
crank fueling pw
idle speed time out IAC steps vs coolant or MAT