MAT Sensor - Funny Stuff!
Thread Starter
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
MAT Sensor - Funny Stuff!
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.
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.
Le Mans Master
Joined: Feb 2005
Posts: 6,473
Likes: 564
From: Clearwater Florida
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.
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.
Instructor
Joined: May 2001
Posts: 186
Likes: 0
From: Midwest
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.
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.
Thread Starter
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
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:
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:
Code:
LDEF0: LDAA L0060 ; Manifold Air Temperature (inverted ADC voltage)
CMPA LC23A ; disable EGR if MAT < (30 = -17.5°C = 0.5°F)
BCS LDF45 ; BR if < -17.5°C = 0.5°F (disable EGR)
; ... else
LDD LC238 ; Enable EGR if TPS > (A = 5 = 1.95%, B = 8 = 3.13%)
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
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:
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:
Code:
LDEF0: LDAA L0060 ; Manifold Air Temperature (inverted ADC voltage)
CMPA LC23A ; disable EGR if MAT < (30 = -17.5°C = 0.5°F)
BCS LDF45 ; BR if < -17.5°C = 0.5°F (disable EGR)
; ... else
LDD LC238 ; Enable EGR if TPS > (A = 5 = 1.95%, B = 8 = 3.13%)
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
Last edited by Pwnage1337; Sep 4, 2011 at 04:20 AM.
Team Owner
Joined: Jan 2003
Posts: 20,254
Likes: 221
From: Summerland B.C. Canada
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.
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.
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.
Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
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Of course, O2 data (on the backside) constantly monitors and correct what the ECM thinks it needs to do.
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Le Mans Master
Joined: Feb 2005
Posts: 6,473
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From: Clearwater Florida
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 ..........
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
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. 
Race Director
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From: Overland Park Kansas
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Melting Slicks
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Light years ahead of most others yet today.
Many secrets yet to be cracked open & explanation in full unfolded.
Safety Car
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From: Houston TX
Thread Starter
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
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.
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.
Race Director
Joined: Nov 2003
Posts: 12,220
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
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!
Instructor
Joined: May 2001
Posts: 186
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From: Midwest
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.
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.
Le Mans Master
Joined: Aug 2007
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From: WV
.......Then post....
...WW
Last edited by WW7; Sep 5, 2011 at 11:16 AM.
Melting Slicks
Joined: Aug 2003
Posts: 3,377
Likes: 387
From: Lakeville MI
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
Start up enrichment
crank fueling pw
idle speed time out IAC steps vs coolant or MAT