Proof: IA temp sensor needs relocated on 92-93 vettes
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Racer
Joined: Aug 2000
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From: Houston, Texas
Proof: IA temp sensor needs relocated on 92-93 vettes
Here is a datamaster log from last nights run at Houston Raceway Park.
I pointed out some interesting things of the graph with arrows. One think to look at is the indicated air inlet temp. The IA temp sensor was indicating 130F inlet temp at the start of the run and it got down to 108 at the 1/4 mile mark. The temp outside was 78 degrees at the time. As the airflow across the AI temp sensor increased it started to cool it down closer to the true air temp. (the sensor is getting heat soaked by the radiator).
In a MAF car it's not that big of a deal because the PCM doesn't use IA temps to determine air flow (it uses the MAF). But for you speed density guys, your ECM uses (cylinder volume, RPM, V.E. tables, MAP, and air inlet temps) to guess how much air your engine is using.
So how much error will that give you? Well 108-130 degrees when it's really 78 is 5% - 9% error (remember to convert to absolute values)
[Modified by Red94Vette, 1:44 PM 6/1/2002]
I pointed out some interesting things of the graph with arrows. One think to look at is the indicated air inlet temp. The IA temp sensor was indicating 130F inlet temp at the start of the run and it got down to 108 at the 1/4 mile mark. The temp outside was 78 degrees at the time. As the airflow across the AI temp sensor increased it started to cool it down closer to the true air temp. (the sensor is getting heat soaked by the radiator).
In a MAF car it's not that big of a deal because the PCM doesn't use IA temps to determine air flow (it uses the MAF). But for you speed density guys, your ECM uses (cylinder volume, RPM, V.E. tables, MAP, and air inlet temps) to guess how much air your engine is using.
So how much error will that give you? Well 108-130 degrees when it's really 78 is 5% - 9% error (remember to convert to absolute values)
[Modified by Red94Vette, 1:44 PM 6/1/2002]
Safety Car
Joined: Dec 1999
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From: Framingham MA
Re: Proof: IA temp sensor needs relocated on 92-93 vettes (Red94Vette)
I don't know where the IAT sensors on the LT1, but your air intake temps are not the outside temperature. The air is heated by the intake manifold track. If the sensor is getting heated so is the air inside your intake. The reason people use MAT reloators is to fool the PCM (ECM in 93 and earlier) into think the air is cooler.
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Racer
Joined: Aug 2000
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From: Houston, Texas
Re: Proof: IA temp sensor needs relocated on 92-93 vettes (dgoodhue)
The IA Sensor is right after the MAF which is about 2 feet from the air cleaner.
My friend in a 94 vette has his moved to the air box and it reads perfect with his A/C outside temp readout, both were at 84F when I read his PCM.
My friend in a 94 vette has his moved to the air box and it reads perfect with his A/C outside temp readout, both were at 84F when I read his PCM.
Team Owner
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St. Jude Donor '03-'04
Cruise-In 1-2-3-4-5 Veteran
Re: Proof: IA temp sensor needs relocated on 92-93 vettes (Red94Vette)
On MAP-sensor LT1s, the stock IAT sensor is in the snorkel just 3" in front of the TB. It's not close to the manifold, or the radiator. It's in the air above and in front of the water pump.
Moving it a foot or so forward, just behind the air filter, has never appeared, logically, to make a big difference...
Moving it a foot or so forward, just behind the air filter, has never appeared, logically, to make a big difference...
Drifting
Joined: Mar 2001
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From: Lafayette IN
Re: Proof: IA temp sensor needs relocated on 92-93 vettes (Matt Black)
My only question is this, and I am just kinda brainstorming here.
GM engineers were pretty smart. They also tried to cut costs on all sorts of things. First off, I think it would be easier/cheaper for them to locate the sensor in the air intake tract. By placing it in the manifold, you up the machining costs. So I actually think that they would have taken heat soak into account when they did the calibrations. IOW, they had a fudge factor in equation somewhere calculating the actual amount of air entering.
I just don't have a WB O2 to check this out yet.
Don't get me wrong, everyone who does relocate it says that they get good gains/more accurate readings--but why would they put it in the manifold considering it would actually cost them more to put it in there in the first place? Just looking for an answer, because once I find out for sure, I will decide to do it or not. :cheers: -Matt-
PS, your proggie rocks. I thought I had made just about all the Excel macros I could until I have seen some of the stuff you have 'shown off'. Given me some good graphing ideas to go with the ones I already have!
EDIT-Doh! I ws thinking L98's where the sensor is on the bottom of the manifold.
[Modified by HighHopes85, 8:35 PM 6/1/2002]
GM engineers were pretty smart. They also tried to cut costs on all sorts of things. First off, I think it would be easier/cheaper for them to locate the sensor in the air intake tract. By placing it in the manifold, you up the machining costs. So I actually think that they would have taken heat soak into account when they did the calibrations. IOW, they had a fudge factor in equation somewhere calculating the actual amount of air entering.
I just don't have a WB O2 to check this out yet.
Don't get me wrong, everyone who does relocate it says that they get good gains/more accurate readings--but why would they put it in the manifold considering it would actually cost them more to put it in there in the first place? Just looking for an answer, because once I find out for sure, I will decide to do it or not. :cheers: -Matt-
PS, your proggie rocks. I thought I had made just about all the Excel macros I could until I have seen some of the stuff you have 'shown off'. Given me some good graphing ideas to go with the ones I already have!
EDIT-Doh! I ws thinking L98's where the sensor is on the bottom of the manifold.
[Modified by HighHopes85, 8:35 PM 6/1/2002]
Thread Starter
Racer
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From: Houston, Texas
Re: Proof: IA temp sensor needs relocated on 92-93 vettes (HighHopes85)
No macros here, I use Visual Basic along with Excel all on one spread sheet. It works great.
Here is some screen shots of my ever changing/improving spread sheets.
Here is some screen shots of my ever changing/improving spread sheets.
