Logging a second IAT sensor? HPT 3bar OS

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
Wanted to break this topic off of my build thread...

Anyone out there in TCG land know if you can add a second (stock) IAT sensor to a fbody PCM and log data from it?

I need to start logging ambient air temp. This seems like a logical thing to do via the PCM... maybe with the EGR or old MAF inputs?

I'm WAAAAAY outside of my understanding of the PCM at that point... I guess I'd have to see what signal the PCM expects from both of those sensors under normal operating conditions, figure out how to make the IAT sensor output its data in the same format, then figure out how to "convert" the data on the other end....

That sounds like a PITA... anyone know an easier way!? :rofl:
 

Pewter-Camaro

Well-known member
Joined
May 28, 2011
Messages
2,108
Reaction score
41
Location
NW Chi town Suburbs
Its been years though since I've done it so I don't remember the details on how to do it but I used to log trans temps pre and post Cooler when I was trying to find a really effective place to mount it. Its just like logging a Wideband on HPT you have to plug the output of the sensor directly into the HPT box and set the parameters in HPT accordingly. No need to go through the PCM though.
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
YES you can...kinda sucks that hpt nor dhp cant touch the BCM/HVAC controls dataset as there's an ambient sensor in most systems to provide data for auto climate controls (as well as a cabin air temp)
i was gonna run Hk's into the EGR position input or the TFTemp signal wire with a switch
 

Handsome Jesus

A V6? What a ripoff...
Donating Member
Joined
Jun 9, 2007
Messages
9,169
Reaction score
24
Location
Carpentersville, IL
EGR voltage runs on a 0-5V signal typically, so if the sensor works based on that, you just need the transfer function.

should be simple-ish.
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
shit thats right i think thats why i started looking into the TFT signal as it was easier and iirc the resistance range was comparable

edit: like i said i looked into this stuff a while back
 

SleeperLS

Desert Racer
Donating Member
Joined
Oct 19, 2008
Messages
10,993
Reaction score
134
Location
Sandia Mountain
The AC can also be used as well as the egr. I have tried both in efforts to hook up my wideband inline with no success. It is a bit of a pain. Good luck.
 

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
Hrmm 5v signal... should be able to drop this straight into HPT then with one of its inputs...

 

Yaj Yak

Harbor Master
Donating Member
Joined
May 24, 2007
Messages
90,400
Reaction score
1,346
The AC can also be used as well as the egr. I have tried both in efforts to hook up my wideband inline with no success. It is a bit of a pain. Good luck.
My wideband is hooked through my egr... Was really easy iirc
 

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
Yeah, I think you can do that too... WB isn't bad tho, cuz you can program its output to read what you need to see @ the PCM.

I just need to find ONE link out there showing how someone else did it... :s00ls:
 

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
Most folks only run WB data through the EGR if they don't have the inputs at the scan tool from what I recall... I have 4 or 5 inputs with the HPT pro scanner though... wondering if its just easier to pipe it in directly rather than dick with getting it piped into the PCM...

Anyone have a wiring diagram for the stock IAT? :dunno:
 

Yaj Yak

Harbor Master
Donating Member
Joined
May 24, 2007
Messages
90,400
Reaction score
1,346
I dont have pro hpt

Isnt the air temp sensor just a simple dealio what harm could you do in hookin er up
 

Yaj Yak

Harbor Master
Donating Member
Joined
May 24, 2007
Messages
90,400
Reaction score
1,346
I may have my stock one from my car sitting somewhere since I have a metal one in the charge pipe now
 

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
Yeah, I think I might just give it a whirl... I setup a custom input in HPT... maybe just wire one up? I THINK I have a stocker IAT somewhere. Will have to locate it.

Do I just ground one side and run the other side to the scanner then?! :dunno:
 

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
1999+ LS1 PCM EGR Pin-Out:
Blue Connector:
Pin 41 - Black, EGR Pintle Position Ground - Grey wire
Pin 47 - Grey, EGR Pintle Position Sensor 5V Reference - Black wire
Pin 55 - Brown, EGR Pintle Position Sensor Signal - Blue wire

Here's the sensor and wiring, only 2 wires...


Would I only need Pin 47 (5v reference) and Pin 55, for signal if I wanted to route it into the EGR?

Otherwise... for routing to HPT, maybe I can steal 5v from something else and feed one side of the IAT sensor with that and then pipe it straight into the AUX input on the HPT MPVI box?
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
you need the 5v reference and the easiest 2 wire setup i found was a spdt switch on the tft circuit.
hell you could install a rotary switch and have the potential to log the temp of your farts.
i just always figured that with a pre and post ic sensor if you did 6 runs at 3 each position that enough data to get an average....the more runs the better you can toss erroneous data

some info from alldata
IAT
Intake Air Temperature Sensor
The Intake Air Temperature (IAT) sensor (3) is a thermistor which changes value based on the temperature of air entering the engine. Low temperature produces a high resistance (100,000 ohms at -40°C/-40°F) , while high temperature causes low resistance (70 ohms at 130°C/266°F) . The PCM supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the PCM calculates the incoming air temperature.
The IAT sensor signal is used to adjust spark timing according to incoming air density. The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold, and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the IAT sensor temperature and engine coolant temperature should read close to each other. A failure in the IAT sensor circuit should set DTC P0112 or DTC P0113.


TFT range
Sensor Resistance Hot 70 ohms at 266 deg F Sensor Resistance Cold 1000,000 ohms at -40 deg F
The transaxle fluid temperature sensor is a thermistor which changes value based on the temperature of the Transaxle fluid. A high transaxle fluid temperature may cause the vehicle to operate in Hot Mode. While in Hot Mode, shift points may be altered, 4th gear disabled, and TCC forced ON in 2nd gear.

A failure in the TFT sensor or associated wiring should cause DTC P0712 or P0713 to set. In this case, a value based on engine coolant temperature will be substituted for the TFT sensor value, and the Transaxle will operate normally. Refer to Diagnostic Trouble Code Tables. See: Powertrain Management\Computers and Control Systems\Testing and Inspection
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
just label sensor location and assign a number and just give the number of revs tps increases at the start of your log and youll always know what sensor was in use on that log

replace your radiator dammit, im telling you even an oem replacement will be better than that gunked up junk
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
im guessing that if you te'd the 5vref through a resister into the sensor signal then just ran sens signal and ground to the egr sensor inputs youd be close...if you knew the exact resistance on the IAT/TFT 5v ref resisters you could have it damn near the original temp pid equation

meh im not really thinking too hard about it, im staring at my garage mess and drinking coffee, so just take these as ramblings

now that im thinking about it your probably gonna have to calibrate/test your sensors at several different temps to make sure you have a matched set to elimnate variables ...at least without switching sensor locations, which id figure to be a cunt, so its worth walking into the parts store with three thermos's of hot warm and cold water and a dvom :rofl:
 

Eagle

Nemo me impune lacessit
Super Moderator
Joined
Mar 1, 2008
Messages
62,583
Reaction score
107
Location
Woodsticks, IL
just label sensor location and assign a number and just give the number of revs tps increases at the start of your log and youll always know what sensor was in use on that log

replace your radiator dammit, im telling you even an oem replacement will be better than that gunked up junk
But i'm talking IC cooling issues, not radiator issues... :io:
 

rocket5979

Gearhead
Joined
Nov 15, 2005
Messages
6,575
Reaction score
6
Location
Round Lake, IL
Most folks only run WB data through the EGR if they don't have the inputs at the scan tool from what I recall... I have 4 or 5 inputs with the HPT pro scanner though... wondering if its just easier to pipe it in directly rather than dick with getting it piped into the PCM...

Anyone have a wiring diagram for the stock IAT? :dunno:
I would pipe directly to HPT. It will be easier to just do it direct and you have more freedom of movement to set your own custom formula with that versus doing a semi-ghetto rig through another sensors circuit.

Yeah, I think I might just give it a whirl... I setup a custom input in HPT... maybe just wire one up? I THINK I have a stocker IAT somewhere. Will have to locate it.

Do I just ground one side and run the other side to the scanner then?! :dunno:


The IATS does not have a polarity since it is just a thermistor. You can hook up either pole to your 5v feed wire and send the other pole to your HPT MPVI to log. All resistors, except the diode kind and possibly a few others I am not thinking about, are not polarized.

I made a Powerpoint slide a while back for the different IATS resistance values at different temperatures for some nitrous timing tuner box stuff I was building then but it will work for you too. Between this and the voltage table also in the powerpoint it should give you all the information to set your formula up in HPT VCM Scanner. Let me know if you don't have Microsoft Office and I will convert it for you. I attached a few pictures from the slides that you may find most helpful. The regular calibration data that comes with the GM external IATS is:

Temperature Ohms
48 degrees F 7000
87 degrees F 1930
146 degrees F 560

The following IATS calibration tables are from the tunefile calibrations in those car's just to be used as examples. The last table that appears fuzzy is a Ford IATS calibration table whose IATS reads different resistance per a given temperature. But since their IATS operates off of 5v ref you can use the resistance and resulting voltage values at said resistance to set your formula for your GM IATS logging.
 

Attachments

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
with what im saying about blocking off all airflow except through the IC im wanting you to know you gonna have to make sure the radiator can easily reject heat into the hot air leaving the IC
im 99.68f250 sure that thing has crud coating the insides of each crossflow tube, ive been seeing it forever now
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
ps with additional IAT sensors (or just ziptieing them in a new spot) you can check how well your radiator is pumping out heat, ambient/pre ic roadway air temp, post ic temp, then a post radiator temp

then the other two you just put on the IC inlet and outlet

it would let you see how well everythings working

over-engineered and actually probably fairly cheap aside from the sensor purchase of a matching set
 

SleeperLS

Desert Racer
Donating Member
Joined
Oct 19, 2008
Messages
10,993
Reaction score
134
Location
Sandia Mountain
My wideband is hooked through my egr... Was really easy iirc
Do you have hpt? If so you must teach me the way. I tried following a write up online but couldn't get my wideband to read in hpt. I am wondering if my egr isn't even wired up from the swap though. Anyone know which pinout number the egr signal wire is? Might be the problem
 

Turbocharged400sbc

Welllllllllll ya knowwwwwww.....
Joined
Jun 16, 2007
Messages
26,499
Reaction score
12
Location
hangover park IL
Do you have hpt? If so you must teach me the way. I tried following a write up online but couldn't get my wideband to read in hpt. I am wondering if my egr isn't even wired up from the swap though. Anyone know which pinout number the egr signal wire is? Might be the problem
you figure out those oil feed fittings? i can give you the wiring info but considering how you can judge thread size....:drums::jg:
 

Create an account or login to comment

You must be a member in order to leave a comment

Create account

Create an account on our community. It's easy!

Log in

Already have an account? Log in here.

Top Bottom