Maf/iat?
Thread Starter
Advanced
Joined: Aug 2007
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From: Cambridge Ohio
Maf/iat?
I have the heads off my 87 for gasket replacement. I was going to relocate my IAT, but I'm seeing conflicting info on whether to do this to a MAF equipped car or not. If the IAT inputs to the EGR on a MAF engine, it won't do me any good to relocate it as I have the EGR deleted on my current chip.
Race Director
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From: Overland Park Kansas
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You must mean the MAT sensor (not IAT). MAT measures manifold air temps which helps control the EGR function. Without the EGR, MAT is useless.
IAT is a stepper motor that controls how much air bypasses the TB blades. It is quite beneficial/necessary for proper operation of a TPI car. Don't delete or move this. (Not sure you could even move it).
IAT is a stepper motor that controls how much air bypasses the TB blades. It is quite beneficial/necessary for proper operation of a TPI car. Don't delete or move this. (Not sure you could even move it).
Pro
Joined: Jul 2002
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From: Yukon OK
IAT is not directly related to the EGR. IAT measures the air temp to calculate the density of the air and together with the MAF / ECM to calculate the required amount of fuel to hit the target AFR.
The EGR is run by the ECM based on RPM / Load conditions for emissions control. I would think that the air temp would go up when the EGR is open so you would want to measure inside the plenum with the EGR functioning to account for that.
But even without the EGR I can't see any good reason to move the sensor since its purpose in life is to give the ECM accurate information about the temperature about the temperature of the incoming air supply.
The EGR is run by the ECM based on RPM / Load conditions for emissions control. I would think that the air temp would go up when the EGR is open so you would want to measure inside the plenum with the EGR functioning to account for that.
But even without the EGR I can't see any good reason to move the sensor since its purpose in life is to give the ECM accurate information about the temperature about the temperature of the incoming air supply.
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From: Cambridge Ohio
I thought the IAC controlled the bypass air on the TB? I've read several threads stating that the IAT being located on the bottom of the plenum gets heat soaked from the engine, and relocating it ahead of the TB gives it a truer reading of ambient temp. If the 87 only uses the IAT for EGR functions due to this being a MAF equipped engine, then moving it does me no good. I'm not sure if 87's have a intake air sensor, a manifold sensor, or both?
Race Director
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From: San Jose CA
The IAT is in the bottom of the plenum, and people do relocate it for a truer temperature as it's a bit warmer inside the plenum than it is in the air bridge.
There is also a temperature switch for EGR located on the back of the intake manifold near the passenger side valve cover.
And you're right, the IAC introduces a "vacuum leak" to adjust the idle speed of the motor.
There is also a temperature switch for EGR located on the back of the intake manifold near the passenger side valve cover.
And you're right, the IAC introduces a "vacuum leak" to adjust the idle speed of the motor.
Team Owner
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From: Summerland B.C. Canada
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Pro
Joined: Jul 2002
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From: Yukon OK
Not a debate or even a challenge to this statement. Just a clarification. I went back and read every reference to intake temp (MAT or IAT) in Probst's book on Corvette fuel injection. He makes one reference on page 75 that says it is indeed an input to EGR operation. He says in other sections on open loop that the IAT / MAT is used in conjunction with the MAP or MAF in controlling the engine. He does not exclude the L98 in these sections.
On page 176 he says that the IAT and ECT are both used to influence idle speed via the IAC and includes the L98 in the list.
Granted his book covers muliple engines and sometimes his statements are somewhat broad. I just did not find a definitive statement that says the IAT is EGR only on the early L98.
Anyone have a better or other source?
On page 176 he says that the IAT and ECT are both used to influence idle speed via the IAC and includes the L98 in the list.
Granted his book covers muliple engines and sometimes his statements are somewhat broad. I just did not find a definitive statement that says the IAT is EGR only on the early L98.
Anyone have a better or other source?
