[KingLT1]

^ This is facts.

[EDFHOBBIES]

Originally Posted by JANNETTYRACING

I am going to politely disagree with you here.

On the ZL-1

IAT1 is in the MAF
IAT2 is in the TMAP
MAT is a calculation as I mentioned above.

MAT refers to IAT table for timing adder or subtractor.

On the SS,

You only have IAT1, even if you move it to the blower.

MAT is a calculation taking in to account all the things I mentioned above.

MAT refers to IAT table for timing adder or subtractor.

Ted.

Thanks Ted,

In simplest terms on my SS with the harness what do I set the gauge to monitor if I want to see the temp of the air going into the intake runners after it's been cooled by the bricks.

[LiqTenExp]

Originally Posted by JANNETTYRACING

I am going to politely disagree with you here.

On the ZL-1

IAT1 is in the MAF
IAT2 is in the TMAP
MAT is a calculation as I mentioned above.

MAT refers to IAT table for timing adder or subtractor.

On the SS,

You only have IAT1, even if you move it to the blower.

MAT is a calculation taking in to account all the things I mentioned above.

MAT refers to IAT table for timing adder or subtractor.

Ted.

Ted,

I am willing to learn something here, and would like to figure out why all my evidence below is incorrect.

I just went down to my car and pulled the MAF connector. Both IAT1 and IAT2 report -40°F, MAT was 80°F something. I ran the car for a little to bring up MAT over ambient. I shut off the car and brought it back to the run position (not started). When I reconnected the MAF (while logging) IAT1 and IAT2 jumped to near ambient at the same time and MAT didn't flinch.

This was the basis of my believing IAT2 doesn't exist as a physical sensor. This is also a heat soaked engine so I would have expected IAT2 to be hotter than IAT1... see attached log. I don't see how IAT2 could be within 1° of IAT1 if it was sitting in drivers side bank of the heat soaked blower.

Everything is on a +200° to -50°F scale below

[LiqTenExp]

Here is a log of when my IC circuit ran out of coolant due to a leak in drivers side brick. I had no coolant left and if IAT2 really represents TMAP (aka post IC bricks) it should have gone sky high, it did not. MAT crept up the entire run, IAT2 reduced...

Hopefully this is enough evidence as to why I believe my prior post is correct.

[asthmamax11]

So alternatives to E85 and Methanol (for cooler IATs and more consistency):

1. Octane enhancer like Boostane for every tank ?

2. Killer chiller type charge cooling system ?

[asthmamax11]

Btw
I appreciate all the responses and info guys.
I knew there would be alot of first hand experience in here.

Laynlo still has his teeth too
Lol

[Joshinator99]

Originally Posted by asthmamax11

So alternatives to E85 and Methanol (for cooler IATs and more consistency):

1. Octane enhancer like Boostane for every tank ?

2. Killer chiller type charge cooling system ?

Boostane can help with the octane number, which helps prevent detonation. But zero impact on IATs.

Killer chiller can definitely help with IATs.

[JANNETTYRACING]

Originally Posted by LiqTenExp

Ted,

I am willing to learn something here, and would like to figure out why all my evidence below is incorrect.

I just went down to my car and pulled the MAF connector. Both IAT1 and IAT2 report -40°F, MAT was 80°F something. I ran the car for a little to bring up MAT over ambient. I shut off the car and brought it back to the run position (not started). When I reconnected the MAF (while logging) IAT1 and IAT2 jumped to near ambient at the same time and MAT didn't flinch.

This was the basis of my believing IAT2 doesn't exist as a physical sensor. This is also a heat soaked engine so I would have expected IAT2 to be hotter than IAT1... see attached log. I don't see how IAT2 could be within 1° of IAT1 if it was sitting in drivers side bank of the heat soaked blower.

Everything is on a +200° to -50°F scale below

I wish it was as simple as unplugging a sensor to prove your theory but trust me it is not.

I too have been tricked by this before.

I had mentioned earlier about the PID addresses and it seems you are not logging the correct PIDs

I log hundreds of ZL-1 and always see the difference between IAT1 and IAT2 they are never the same except on a stone cold start.

It took several tries to find the correct PIDs to log but this is a software issue not a hardware issue.

I have found were you log different PID and get same data.

This one will surprise you, certain pids logged at the same time cancel each other and you get no data.

So what you should see when logging correct PID is, if you Idle the car IAT2 will climb above IAT1 significantly then when you get air flow through the supercharger IAT2 will come down.

MAT is very stable and moves much slower due to the calculation of all the sensors involved.

Also note, we can log MAT on an SS which does not have a Tmap.

[LiqTenExp]

I went back and checked, 2128 is what HP Tuner calls IAT2 and is what my data I've been presenting is using. My prior post had the incorrect value typed, I fixed it for posterity. There is only 1 entry with IAT2 listed under airflow.

What are you logging as a PID for IAT, IAT2, and MAT? I don't want to be posting incorrect info if for some reason I'm using an incorrect PID, I don't believe that is the case, currently I'm using:

• IAT1: 2127 (shown under CCM) / 15 (shown under ECM, SAE)
• IAT2: 2128 (ECM)
• MAT: 2126 (ECM)

I agree with your statement, IAT1/2 match at startup and they separate is my observation. If you watch them they trend together and do not make any sense to represent post blower temp.

As far as MAT on LT1, I agree there is no TMAP (4 wire) only MAP (3 wire) and if it shows up it must be a calculated parameter. I don't have an LT1 log to verify this but I have a service manual to verify the physical wiring matches your description. There is only 1 temperature sensor in the airflow path on LT1 and that is in the MAF sensor. On LT4 the service manual shows two physical temp sensors, one in MAF and one in TMAP.

Here is another log showing vehicle speed vs. MAT. You can easily correlate the near stopped MPH with a rise in MAT (less air flow). IAT2 just trended along with IAT1, it should have started to show signs of heat soaking when the vehicle stopped, it did not. MAT jumped up when vehicle was stationary, ECT had a near linear trend and IAT1/2 barely moved. I just wonder how if MAT is calculated where it's inputs come from then.

Also attached is a plot of temperatures measured in the car and I don't see any with enough variation to provide an input to a calculation that would cause MAT to display as it does. Something is directly driving MAT and I assume it is TMAP. The delta (plotted in excel) between IAT1 and IAT2 is roughly 7-11 degrees the entire log, why so static, how could they influence MAT as a calculation at all? MAT may be still a calculation (I cannot prove this one way or another) but it sure isn't based on IAT1/2 but TMAP sensor.

[JANNETTYRACING]

Originally Posted by LiqTenExp

I went back and checked, 2128 is what HP Tuner calls IAT2 and is what my data I've been presenting is using. My prior post had the incorrect value typed, I fixed it for posterity. There is only 1 entry with IAT2 listed under airflow.

What are you logging as a PID for IAT, IAT2, and MAT? I don't want to be posting incorrect info if for some reason I'm using an incorrect PID, I don't believe that is the case, currently I'm using:

• IAT1: 2127 (shown under CCM) / 15 (shown under ECM, SAE)
• IAT2: 2128 (ECM)
• MAT: 2126 (ECM)

I agree with your statement, IAT1/2 match at startup and they separate is my observation. If you watch them they trend together and do not make any sense to represent post blower temp.

As far as MAT on LT1, I agree there is no TMAP (4 wire) only MAP (3 wire) and if it shows up it must be a calculated parameter. I don't have an LT1 log to verify this but I have a service manual to verify the physical wiring matches your description. There is only 1 temperature sensor in the airflow path on LT1 and that is in the MAF sensor. On LT4 the service manual shows two physical temp sensors, one in MAF and one in TMAP.

Here is another log showing vehicle speed vs. MAT. You can easily correlate the near stopped MPH with a rise in MAT (less air flow). IAT2 just trended along with IAT1, it should have started to show signs of heat soaking when the vehicle stopped, it did not. MAT jumped up when vehicle was stationary, ECT had a near linear trend and IAT1/2 barely moved. I just wonder how if MAT is calculated where it's inputs come from then.

Also attached is a plot of temperatures measured in the car and I don't see any with enough variation to provide an input to a calculation that would cause MAT to display as it does. Something is directly driving MAT and I assume it is TMAP. The delta (plotted in excel) between IAT1 and IAT2 is roughly 7-11 degrees the entire log, why so static, how could they influence MAT as a calculation at all? MAT may be still a calculation (I cannot prove this one way or another) but it sure isn't based on IAT1/2 but TMAP sensor.

I too am willing to learn something, and we appreciate your hard work at trying to decipher the sensors and what roll they play.

I feel like we all may be battling Labels and not physical sensors, (who's responsible for labels) Someone at Hptuners? the guy who wrote the operating system?, SAE?

Why is the IAT in the CCM?? Ambient Temp sensor in the Grill? Shares circuit with MAF? IAT1 and IAT2

Those same sensors may be labeled different in the SS Ambient and IAT.

We know IAT 2 in a Gen 5 Camaro is 100% in the supercharger post Intercooler, but based on our research that is not the case on this platform.

On the ZL-1 I always tune working off MAT, on the SS I work off IAT in MAF simply because trends show they are the main factor in IAT timing control.

On the LT4, MAT is Primarily derived from the Tmap there is no question on that, but from what I know it does also take in to account ECT, IAT, Intake valve temp, time from start, EGT, Altitude/baro, Humidity, etc.

The operating system determines what roll the sensors play.

Ted.

[LiqTenExp]

I don't know why HP Tuners has IAT1 under ECM and CCM. It could be that the physical sensor wiring goes to CCM and then just passes the data up to ECM (hence the dual PID). I don't have a service manual in front of me at the moment to verify.

This happens a couple more times:

• There is an additional sensor for ambient air temp PID: 2125 under CCM and PID: 70 under ECM (SAE). This is its own physical sensor.
• There is also the ambient barometric pressure sensor PID: 2341 under CCM and PID: 51 under ECM (SAE). This is its own physical sensor (driver's side rear of engine bay if memory serves me correctly).

When I have an opportunity I'm going to isolate my TMAP divorced temp sensor and purchase an equivalent 2 wire temp senor to play with. I can do some experiments that would let us figure out if it is straight temp or temp+math going on. I don't doubt there is some math going on based on how "smooth" the temp curve is for it compared to something like IAT1. IAT1 data looks a little more raw and glitchy as if it was reading just straight 0-5 VDC. MAT looks a little too smooth to be just straight 0-5 VDC the more I stare at it.

I just hope we can agree that MAT is the closest thing to post intercooler temperatures. I don't disagree that may have some math on it. It is what is used to drive IAT Advance (timing retard). The lower MAT is the better.

As far as IAT2, I just ignore it, it never shows me anything useful on LT4. I agree on LSA/LS9 type motors IAT2 was the post intercooler temp.

[JANNETTYRACING]

Originally Posted by LiqTenExp

I just hope we can agree that MAT is the closest thing to post intercooler temperatures. I don't disagree that may have some math on it. It is what is used to drive IAT Advance (timing retard). The lower MAT is the better

Never once debated this, Like I said it is what references the IAT table.

What people have to understand is Timing is Dynamic and needs to take in to account every possible input that effects burn rate/speed of the Air/fuel charge.

Just because timing is reduced does not mean your making less power.

A good example would be 2 600 hp engines, 1 small block chevy, one LS, they both make 600 hp, but the small block runs 38 degrees timing and the LS runs 23 Degrees timing.

The LS won't make more power at 38 degrees it will implode.

So in this example timing is not directly related to Horsepower, it is a function of what lead is needed in each combination to create peak cylinder pressure at 15 degrees After top dead center so it can do the most work on the piston.

Ted.

[EDFHOBBIES]

I went over to my tuner yesterday and wanted to get some clarity..

As I mentioned I was curious to why I had 3 IATs and a MAT for my ZL1 and what to monitor now that I have these gauges that monitor and data log.

I was told that the IAT 3 (I believe in HP tuners he said its listed as MAT) this is what he uses primarily for timing yes the others factor in as well. I was also curious to see if I needed to install that FI chiller I picked up. If you remember I was told by the 3 magnunson bros. Toohighpsi Shizzysupra and Lanly15 that my edelbrock 2650 will never cool as well maggi 2650 even if I had a FI chiller. Of course that's horse manure from all the people I'm seeing with the 2650R it looks pretty close most of those guys are 800s not 1000 plus. I think its another misconception about edelbrock since they had that LS3 2300 turd. I saw when CSP did there 4 or 5 blower review and down played it but never really tested head to head just general hypothesis from the passed LS3 turds.. I've been seeing a ton of builds at RPM with it and Fran has no problems with it. The past is the past but its hard for me to drop it cuz those guys were saying such negative things and that there the best.. what ever! I'm just giving ya back ground and wanted other opinions as well for my IATs.

BTW I maybe wrong but on my car running e85 if the IAT3 reaches 168 timing is pulled and 93 its 150 degree he told me to make 3 hard hits in a row on the way home and if the IATs are far from 170 chillers not really going to do much.

On the way over to the shop I was just monitoring IAT1 and IAT2 and out side temp were 99 degrees..

Cruising:

IAT1 99/100
IAT2 108
IAT3 N/A

At the shop I added IAT3 to the gauge

Idling for 30 min in 100 degree temps with AC on while we looked at some haltech data i notice the gauges reading this:

IAT1 140s
IAT2 170s
IAT3 144/145

leaving the shop on country road with a limit of 45 mph within 3 miles i was back down to:

IAT1 100
IAT2 115
IAT3 133

Made it to the Highway where I ran 70 mph within 3 or 4 min my readings were:

IAT1 100
IAT2 108
IAT3 124

4x 4th gear Hard pulls from 60 to 150 something I saw:

IAT1 100/99
IAT2 108 fall to 103
IAT3 126 fall to 124 but rose to 133 to 135 after I let off then 1/2 mile later back to 126

I couldn't get the IAT3 in the 140s I'm sure if I was doing that at the strip with longer wait times and less air movement making passes and sitting it would get fairly high. I guess there is really no way to recover with no air movement and driving hard for a 1/4 mile its no wonder they use ice in the reservoir and chillers. For my purposes a daily and roll racing I think its dialed in with no chiller needed.

what ya think?

[KingLT1]

What I think: MAT is the most important air temp parameter to log for LT4 stuff because that is what the ECU references for spark correction.