iat relocate works
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iat relocate works
i mounted it so that it went through the core support. im getting better gas mileage.no bog down when motor gets completely warmed up. and best of all no code 32. i cant remember who wrote up article on it but thank you. update 32 came back this morning however still no bog down though.
Last edited by bbsr72; Jul 31, 2012 at 09:37 AM. Reason: update
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Re: iat relocate works
lol man, that sucks. You really saw a difference though? Theres a lot of people that argue about this working or not. Ill give it a try. How do you remount it? Do you have to drill a new hole in the plenum or what?
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Re: iat relocate works
i just unplugged it from under the plenum, cut wires then spliced in two new pieces of wire. i already had an xtra sensor laying around. put sensor through pre existing hole then used a piece of rubber hose to hold it in place. unhooked battery for a few. then drove it. now its reading actualoutside temp.
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Re: iat relocate works
This may or may not work out OK. The EGR system uses the MAT temperature as the activate threshold. So a cooler sensor reading will have the EGR inactive.
Dependent upon the EGR activation temperature, which is calibration dependent, if hot enough the EGR will be activated. When not activated the EGR malfunction test isn't run either.
RBob.
Dependent upon the EGR activation temperature, which is calibration dependent, if hot enough the EGR will be activated. When not activated the EGR malfunction test isn't run either.
RBob.
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Re: iat relocate works
I did the reloaction over 5 years ago & no driving problems nor emissions problems, so I think RBob might be reading too much into the whole system than is really there.
But your pulling in stale, barely moving outside air that this time of year will still be fairly warm.
Do the IAT relocation into the incoming airstream & your be telling the ECM what the engine is really getting, plus moving air is cooler to start with..
http://www.austinthirdgen.org/index.php?pid=24
If it is a Firebird then just put a hole in the intake tubing behind the filter. If it is a TBI then put the IAT in the snorkel or anywhere near the incoming air stream, although the stock location for TBIs is not that bad.
But your pulling in stale, barely moving outside air that this time of year will still be fairly warm.
Do the IAT relocation into the incoming airstream & your be telling the ECM what the engine is really getting, plus moving air is cooler to start with..
http://www.austinthirdgen.org/index.php?pid=24
If it is a Firebird then just put a hole in the intake tubing behind the filter. If it is a TBI then put the IAT in the snorkel or anywhere near the incoming air stream, although the stock location for TBIs is not that bad.
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Re: iat relocate works
yea was going to put it in intake pipe but if it didnt work, id of put hole in it for nothing. but i like the fact it dont lose horsepower when its real warmed up.
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Re: iat relocate works
When relocating the MAT, it can also disable the EGR system. Fact.
As I posted, it all depends upon the calibration as to when the EGR is enabled. Dependent upon the MAT threshold to enable the EGR system. And the reported MAT temperature.
Dig into the code, it is there for all to see. No mystery here...
RBob.
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Re: iat relocate works
There is also code for the mat vs air enable as well. Not every article on the internet has 100% truth.
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Re: iat relocate works
Oh, but I am not reading too much into this. It is fact that the '86-89 MAF TPI systems and '90 - 92 SD TPI systems use the MAT temperature to enable the EGR system.
When relocating the MAT, it can also disable the EGR system. Fact.
As I posted, it all depends upon the calibration as to when the EGR is enabled. Dependent upon the MAT threshold to enable the EGR system. And the reported MAT temperature.
Dig into the code, it is there for all to see. No mystery here...
RBob.
When relocating the MAT, it can also disable the EGR system. Fact.
As I posted, it all depends upon the calibration as to when the EGR is enabled. Dependent upon the MAT threshold to enable the EGR system. And the reported MAT temperature.
Dig into the code, it is there for all to see. No mystery here...
RBob.
Just saying that IAT is not nearly as "crucial" as you made it sound like. Of all the IAT relocation that I've heard of, not one has caused any problems on the car. So yeah....On that FACT? You are reading too much into it. My mpg increased & my emissions tests still passed WAY below requirements. Those are facts too. Personal facts, not something based on internet reading.
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Re: iat relocate works
What is the purpose of relocating the mat sensor ? It seems like it was engineered to go in the plenum?
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Re: iat relocate works
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Re: iat relocate works
This link explains it pretty well.
http://www.austinthirdgen.org/index.php?pid=24
http://www.austinthirdgen.org/index.php?pid=24
So are you saying to do this because gm engineers were stupid on tpi from 85-92 with the mat It this why they went to iat on other vehicles. Seems like a wasted effort to get false reading to the ecm for the thermistor. Supreme Member
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Re: iat relocate works
My answer was not vague at all. It was a link to a complete explanation. If you had gone to the link (apparently you didn't) you would have understood.
3 reasons to do the relocation.....
#1.....The IAT sensor that GM used for TPI was stuck in the metal plenum so it would get heat soaked therefore the temp for the incoming air that it told the ECM was false.
#2.....The IAT sensor that GM used for TPI was nothing more than a Water Temp Sensor so again it could not provide a true reading.
#3.....By relocating it into the incoming air stream, it will tell the ECM of the true & accurate reading of the incoming air.
Copied directly from the link "
With the stock TPI IAT (heatsoaked CTS part), the computer saw 132 degrees in the intake on a 95 degree night. That measurement was performed on the highway, i.e. with lots of air flowing through the engine compartment. Stopped at idle, the temperature reading was even higher.
With the relocated TBI IAT sensor, the computer saw 97 degrees on the SAME night, with 95 degrees outside. Again, this measurement was performed on the highway but the reading did not increase much at lower speeds or at idle.". Please read the bold letters. Do you want the ECM thinking it is consuming 132 degree air & adding the "correct" amount of fuel for 1321 degree air, on a 95 degree night?
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Re: iat relocate works
So if your just wanting to give the ECM false data why dont you just install a 1800 ohm resistance on the mat sensor circuit. This modification does not make sense .does the mat reading affect injector pw ?
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Re: iat relocate works
How is it not making sense or giving a false reading? It is giving the ECM a TRUE reading or the AIR & not being influenced by heat soaking in a hot underhood metal part.
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Re: iat relocate works
I think the true temperature of the air , is what the air is in the plenum. Relocating the IAT sensor to the airbox area will reduce fuel mileage not increase it.
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Re: iat relocate works
It was engineered to go into the plenum. You have to think ,we have what is called a plenum on our cars. The air gathers in there and sits, so by the time that incoming cool air gets through our throttle bodies and into our plenum and sits , it is going to be hotter than that air near the airbox. So, by the time it gets into the engine through the plenum it IS hotter than the airbox temp air. So, the true reading of the air is in the plenum of after. Sure the temp in the plenum is going to get hotter on hot days or sitting in traffic ,but it is still a more accurate measurement of the air temp that is entering the engine and thus how much fuel should be injected to match. I think GM engineers did this for economy and effeciency's sake. You will be burning lots more fuel with the IAT sensor in the airbox.
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Re: iat relocate works
The MAT compensation tables for the PW calculation in the $8D mask has misleading titles. The purpose of the two 'MAT' tables is to provide an inverse temperature term for the PW calculation.
Colder air has a greater density. This needs to be accounted for in the PW calculation. The inverse temperature term provided by the 'MAT Compensation' routines is based on both CTS and MAT.
The amount of CTS vs. MAT that is used can be varied. One table is a model of the intake tract heating of the incoming air. IOW, how hot does the air become just from its travels through the intake. The engine coolant temperature affects this.
When the MAT is relocated and becomes an IAT sensor the table calibration is no longer correct.
When the intake design is changed (say to a LT1 or single plane manifold) the table calibration is no longer correct.
There is also an option bit involved. At location $018, b4 is used to select either the intake tract heating model table, or to just use the MAT/IAT as is. If this bit is set to a 1, then the intake tract model table is used. Else, if set to a 0, then the MAT/IAT is used as is.
Using a MAT as is would probably work OK. Using an IAT as is would not. There is going to be some heating of the air from the intake tract. For a decent tune this needs to be accounted for.
Here is the Intake Tract Heating Model table (with the original title):
Note the table is based on airflow. The less time the air is within the manifold the less heat it will absorb from the intake tract.
This table is used to combine the MAT/IAT sensor value with the CTS value. Here is the math:
T = ((CTS - MAT/IAT) * MULT) / 128 + MAT/IAT
What is being done is a portion of the CTS value is being added to the MAT/IAT value. This provides a new temperature term (T). In simpler words: take the difference between the air temperature and the coolant temperature, take a percentage of this difference and add it back to the air temperature.
The table value for 0 gms/sec airflow is 128 (MULT), in affect the T term is going to be the same as the coolant temperature (CTS).
As the airflow increases less of the coolant value (CTS) is added to the air value (MAT/IAT).
Here is an example at 64 gms/sec, 10°c MAT/IAT and 85°C CTS. From the table the MULT term is 27 at 64 gms/sec:
T = ((85 - 10) * 27) / 128 + 10 = 26°c
The same temperatures at 128 gms/sec gives this:
T = ((85 - 10) * 16) / 128 + 10 = 19°c
The MULT term is changed to 16 (from the table) and the final temperature term (T) is lower at 19°c.
What is interesting about the above examples is that a MAT sensor with a engine at 85°c is probably not going to be at 10°c. Well, maybe if the ambient air is at -50°c. That is where the stock calibration falls apart with a relocated MAT to an IAT.
A MAT would be about (SWAG here) 50°c when the engine is up to temperature. Lets run the first example with that:
T = ((85 - 50) * 27) / 128 + 50 = 57°c
Quite a difference from the T = 26°c of the first example. In this case relocating the MAT will cause the engine to run richer and the BLMs to drop. The table will need to be recalibrated.
The last table is easy. The values in this table shouldn't really need to be changed. Here it is:
Easy enough, use the temperature term from the previous calculation and look up the inverse temperature term (~T) to be used in the PW calculation.
The column labled 'MAT Deg c' is really the T term. Which can and should be a combination of the MAT/IAT and CTS values.
In closing, as others have stated the Intake Tract Heating Model table is the key to recalibration. With a better understanding of how the table works it should be easier to do a better tune.
My thoughts on the stock calibration shows that at low air flows the stock long tube TPI setup adds a lot of heat. This can be seen by the full CTS temperature term at 0 gms/sec
Even at higher air flows with a heat soaked MAT, the Intake Tract Heating Model will move the T term to a high value.
An intake with shorter runners will heat the air less then a TPI. There is simply less surface area and less time for the air to pick up heat as it travels through the manifold.
RBob.
Colder air has a greater density. This needs to be accounted for in the PW calculation. The inverse temperature term provided by the 'MAT Compensation' routines is based on both CTS and MAT.
The amount of CTS vs. MAT that is used can be varied. One table is a model of the intake tract heating of the incoming air. IOW, how hot does the air become just from its travels through the intake. The engine coolant temperature affects this.
When the MAT is relocated and becomes an IAT sensor the table calibration is no longer correct.
When the intake design is changed (say to a LT1 or single plane manifold) the table calibration is no longer correct.
There is also an option bit involved. At location $018, b4 is used to select either the intake tract heating model table, or to just use the MAT/IAT as is. If this bit is set to a 1, then the intake tract model table is used. Else, if set to a 0, then the MAT/IAT is used as is.
Using a MAT as is would probably work OK. Using an IAT as is would not. There is going to be some heating of the air from the intake tract. For a decent tune this needs to be accounted for.
Here is the Intake Tract Heating Model table (with the original title):
Code:
;======================================= ; (COOLANT - MAT) DELTA MULT ; FOR INV TERM L.U. vs AIR FLOW ; ; TBL = MULT * 128 ;======================================= ;-------------------------------------- ; MULT ; GMS/SEC AIR FLOW ;-------------------------------------- L880E: FCB 128 ; 1.000 0 FCB 96 ; 0.750 16 FCB 64 ; 0.500 32 FCB 36 ; 0.281 48 FCB 27 ; 0.210 64 FCB 20 ; 0.156 80 FCB 16 ; 0.125 96 FCB 16 ; 0.125 112 FCB 16 ; 0.125 128 FCB 16 ; 0.125 144 FCB 16 ; 0.125 160 FCB 16 ; 0.125 176 FCB 16 ; 0.125 192 FCB 16 ; 0.125 208 FCB 16 ; 0.125 224 FCB 16 ; 0.125 240 FCB 16 ; 0.125 256
This table is used to combine the MAT/IAT sensor value with the CTS value. Here is the math:
T = ((CTS - MAT/IAT) * MULT) / 128 + MAT/IAT
What is being done is a portion of the CTS value is being added to the MAT/IAT value. This provides a new temperature term (T). In simpler words: take the difference between the air temperature and the coolant temperature, take a percentage of this difference and add it back to the air temperature.
The table value for 0 gms/sec airflow is 128 (MULT), in affect the T term is going to be the same as the coolant temperature (CTS).
As the airflow increases less of the coolant value (CTS) is added to the air value (MAT/IAT).
Here is an example at 64 gms/sec, 10°c MAT/IAT and 85°C CTS. From the table the MULT term is 27 at 64 gms/sec:
T = ((85 - 10) * 27) / 128 + 10 = 26°c
The same temperatures at 128 gms/sec gives this:
T = ((85 - 10) * 16) / 128 + 10 = 19°c
The MULT term is changed to 16 (from the table) and the final temperature term (T) is lower at 19°c.
What is interesting about the above examples is that a MAT sensor with a engine at 85°c is probably not going to be at 10°c. Well, maybe if the ambient air is at -50°c. That is where the stock calibration falls apart with a relocated MAT to an IAT.
A MAT would be about (SWAG here) 50°c when the engine is up to temperature. Lets run the first example with that:
T = ((85 - 50) * 27) / 128 + 50 = 57°c
Quite a difference from the T = 26°c of the first example. In this case relocating the MAT will cause the engine to run richer and the BLMs to drop. The table will need to be recalibrated.
The last table is easy. The values in this table shouldn't really need to be changed. Here it is:
Code:
;======================================= ; Temperature Compensation vs. CTS - MAT ; ; TABLE is Temperature COMP COUNTS ;======================================= ;-------------------------------------- ; BIN ; MAT Deg c ;-------------------------------------- L87FD: FCB 0 ; -40 FCB 12 ; -28 FCB 24 ; -16 FCB 36 ; -4 FCB 48 ; 8 FCB 60 ; 20 FCB 72 ; 32 FCB 84 ; 44 FCB 96 ; 56 FCB 108 ; 68 FCB 120 ; 80 FCB 128 ; 92 FCB 128 ; 104 FCB 128 ; 116 FCB 128 ; 128 FCB 128 ; 140 FCB 128 ; 152
The column labled 'MAT Deg c' is really the T term. Which can and should be a combination of the MAT/IAT and CTS values.
In closing, as others have stated the Intake Tract Heating Model table is the key to recalibration. With a better understanding of how the table works it should be easier to do a better tune.
My thoughts on the stock calibration shows that at low air flows the stock long tube TPI setup adds a lot of heat. This can be seen by the full CTS temperature term at 0 gms/sec
Even at higher air flows with a heat soaked MAT, the Intake Tract Heating Model will move the T term to a high value.
An intake with shorter runners will heat the air less then a TPI. There is simply less surface area and less time for the air to pick up heat as it travels through the manifold.
RBob.
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Re: iat relocate works
This mat to iat relocation really seems like a gimmick like the kit tpis and street and performance use to sell. Just some packard connections and a lt1 iat for a stupid price.
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Re: iat relocate works
Everyone....When you come back with experience rather than theories? Hou are welcome to join the discussion.
I see what people are saying but my PERSONAL EXPERIENCE contradicts their theories & thoughts on the matter.
I'm actually sick of repeating this over & over so I'm unsubscribing. Do whatever you want to. I'm not changing my IAT relocation based on any of you guys THEORIES. I'm gonna stick with my PERSONAL FIRSTHAND EXPERIENCE WITH THE ACTUAL MOD.
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Re: iat relocate works
And you are wrong, based on my FIRST HAND PERSONAL EXPERIENCE.
Everyone....When you come back with experience rather than theories? Hou are welcome to join the discussion.
I see what people are saying but my PERSONAL EXPERIENCE contradicts their theories & thoughts on the matter.
I'm actually sick of repeating this over & over so I'm unsubscribing. Do whatever you want to. I'm not changing my IAT relocation based on any of you guys THEORIES. I'm gonna stick with my PERSONAL FIRSTHAND EXPERIENCE WITH THE ACTUAL MOD.
Everyone....When you come back with experience rather than theories? Hou are welcome to join the discussion.
I see what people are saying but my PERSONAL EXPERIENCE contradicts their theories & thoughts on the matter.
I'm actually sick of repeating this over & over so I'm unsubscribing. Do whatever you want to. I'm not changing my IAT relocation based on any of you guys THEORIES. I'm gonna stick with my PERSONAL FIRSTHAND EXPERIENCE WITH THE ACTUAL MOD.
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Re: iat relocate works
And you are wrong, based on my FIRST HAND PERSONAL EXPERIENCE.
Everyone....When you come back with experience rather than theories? Hou are welcome to join the discussion.
I see what people are saying but my PERSONAL EXPERIENCE contradicts their theories & thoughts on the matter.
I'm actually sick of repeating this over & over so I'm unsubscribing. Do whatever you want to. I'm not changing my IAT relocation based on any of you guys THEORIES. I'm gonna stick with my PERSONAL FIRSTHAND EXPERIENCE WITH THE ACTUAL MOD.
Everyone....When you come back with experience rather than theories? Hou are welcome to join the discussion.
I see what people are saying but my PERSONAL EXPERIENCE contradicts their theories & thoughts on the matter.
I'm actually sick of repeating this over & over so I'm unsubscribing. Do whatever you want to. I'm not changing my IAT relocation based on any of you guys THEORIES. I'm gonna stick with my PERSONAL FIRSTHAND EXPERIENCE WITH THE ACTUAL MOD.
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Re: iat relocate works
I WAS speaking from my first hand experience. I didn't say that there was no difference in the way the car performed,but it will be at the expense of gas mileage. It may have richened up the mixture a little and the car felt stronger. It did run more consistent and a little smoother ,especially on hot days,but I was going through so much gas that it is not worth it unless you tune your chip around this mod. There is a table in Tunerpro that needs to be adjusted. Your BLM's will have to already be close enough to 128 though. So, you would need to tune first.
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Re: iat relocate works
So if one extreme is using the stock brass type sensor inside the plenum to measure incoming air temperature, and the other extreme is using a newer "cage" style sensor in the air-box....
Would the best "middle ground" solution be to use the cage style sensor and keep it in the original location inside the plenum??
Reason I ask is because according to what I've read the cage style sensor is much more accurate at reading correct temperature...
I'm really curious now since this discussion has come up with some new info i didn't know before. I had done this mod in the past without having any real data to back it up, it just seemed like a good idea at the time
Would the best "middle ground" solution be to use the cage style sensor and keep it in the original location inside the plenum??
Reason I ask is because according to what I've read the cage style sensor is much more accurate at reading correct temperature...
I'm really curious now since this discussion has come up with some new info i didn't know before. I had done this mod in the past without having any real data to back it up, it just seemed like a good idea at the time
Last edited by quisterio; Aug 3, 2012 at 01:11 PM.
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Re: iat relocate works
that thing may melt in the plenum,need to use stock IAT sensor in the plenum
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Re: iat relocate works
Instead of the brass covering the thermistor it has a nylon cage. I believe it was nyon. Or that's how I found my 85 camaro. Some one could have jacked it up though. I replaced it with a cts.
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Re: iat relocate works
I have also seen the same thing
just in 85 camaros and corvettes acdelco 213-190
just in 85 camaros and corvettes acdelco 213-190
Last edited by Tuned Performance; Aug 5, 2012 at 12:48 AM. Reason: more info
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Re: iat relocate works
So the nylon/plastic cage sensor should be ok in the plenum? Surely to god it don't get hot enough in there to melt plastic??
Or better yet, will the better sensor in the plenum still throw the computer off? As in was the computer originally calibrated to read from the "hunk o' brass" sensor that was originally there?
Or better yet, will the better sensor in the plenum still throw the computer off? As in was the computer originally calibrated to read from the "hunk o' brass" sensor that was originally there?
Last edited by quisterio; Aug 6, 2012 at 10:15 AM.
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Re: iat relocate works
Wow! What a discussion/argument.
From my personal experience with these things which began back when these cars were new, relocating the MAT (not IAT) sensor out of the plenum and into the air filter box or somewhere it reads actual intake air temp produced little difference in performance BUT it was more consistent hot vs. cold. Didn't drop off as much when it got hot. Talking half a tenth difference in ET on a hot engine, if that.
Better or worse fuel mileage vs. temperature? Not that I observed. Nor is it likely with a functioning O2 sensor.
Frankly, I don't really know how "smart" the programming was back then in terms of it's sophistication altering tuning based on MAT input. I read the above posts with the fields that can be modified and that's certainly something (but again, a very modest something). Moreover, I wonder if the factory even did a good job using those tables to help performance, or if they made it worse.
One thing I will add from my own experience and those of generations of hotrodders before me is that intake manifold temps have little effect on the temperature of the air going into the cylinder. The air is just not in the intake long enough to make much difference. For example, the performance between the Performer RPM and the Performer RPM Air Gap intakes is known to be very very small, despite the fact one has isolated runners and the other has an exhaust crossover underneath it that gets hot enough to fry an egg on. Air is past the throttle plates and arrives at the intake valve in literally the blink of an eye at WOT. And if that's true, trying to tune based on an artificially high MAT reading that spikes really bad on a hot soak (and is very slow to cool down again when you go to WOT) is likely to do very little to CONSISTENTLY make the tuning better, no matter what numbers you put in the table.
You'll notice that many later EFI vehicles switched to an IAT sensor in the intake ducting and, finally, they eventually built the IAT right into the MAF sensor itself (with absolutely nothing to keep track of manifold temps). I suspect the engineers learned that intake air temps were a more reliable variable to base their tuning trims on as opposed to the slow-reacting and heat-soak-prone MAT sensor readings.
Anywho..... it's a really really small difference on these cars anyway. Probably not worth the increase in blood pressure.
From my personal experience with these things which began back when these cars were new, relocating the MAT (not IAT) sensor out of the plenum and into the air filter box or somewhere it reads actual intake air temp produced little difference in performance BUT it was more consistent hot vs. cold. Didn't drop off as much when it got hot. Talking half a tenth difference in ET on a hot engine, if that.
Better or worse fuel mileage vs. temperature? Not that I observed. Nor is it likely with a functioning O2 sensor.
Frankly, I don't really know how "smart" the programming was back then in terms of it's sophistication altering tuning based on MAT input. I read the above posts with the fields that can be modified and that's certainly something (but again, a very modest something). Moreover, I wonder if the factory even did a good job using those tables to help performance, or if they made it worse.
One thing I will add from my own experience and those of generations of hotrodders before me is that intake manifold temps have little effect on the temperature of the air going into the cylinder. The air is just not in the intake long enough to make much difference. For example, the performance between the Performer RPM and the Performer RPM Air Gap intakes is known to be very very small, despite the fact one has isolated runners and the other has an exhaust crossover underneath it that gets hot enough to fry an egg on. Air is past the throttle plates and arrives at the intake valve in literally the blink of an eye at WOT. And if that's true, trying to tune based on an artificially high MAT reading that spikes really bad on a hot soak (and is very slow to cool down again when you go to WOT) is likely to do very little to CONSISTENTLY make the tuning better, no matter what numbers you put in the table.
You'll notice that many later EFI vehicles switched to an IAT sensor in the intake ducting and, finally, they eventually built the IAT right into the MAF sensor itself (with absolutely nothing to keep track of manifold temps). I suspect the engineers learned that intake air temps were a more reliable variable to base their tuning trims on as opposed to the slow-reacting and heat-soak-prone MAT sensor readings.
Anywho..... it's a really really small difference on these cars anyway. Probably not worth the increase in blood pressure.
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eightsixseven
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Dec 16, 2024 01:50 PM
