God Forgives I Dont

Well I went ahead and relocated my IAT to hopefully help make all the input variables that the PCM is using to calculate the formulas so the PCM can adapt.

Initial results look good and it didn't take very long to do either.

It was sitting at exactly the reported temperature before I started the car and didn't move at all and I let it sit at idle until the engine was at operating temperature and still the IAT didn't budge.

I know what you’re thinking! It's fried or I did a bad splice job. Nope, I took a hairdryer and while the motor was still running idle I pointed the hairdryer at the IAT and by the time I could get back to read the dash it was at \150* F (max). I then turned the hairdryer off (left car running at idle) and watch it as the IAT dropped all the way back to the baseline of 73*.

You'll have to detach the pics attached to this if you use IE because it looks really bad if you view it in IE.

slow

iTrader: (7)

why did you move it?

the stock location measures the air coming into the motor, the only place it really matters.

Ryan

blacktransam

iTrader: (13)

hers my question.. I like the idea.. but i can see that you did the free ram air mod which we know raises IAT.. so isn't that basically sending the comp false signals?? cuz the air entering the motor is much hotter

WS6FirebirdTA00

iTrader: (33)

tahts cool and all but the reason it was in the air lid was to measure the air after it was filtered. there are some quick temp chagnes and that will give false readings. that will give ambient temps not intake temps IMO. you have to account for ALL air taken in not just the air at the front of the box.

RedWS6 00

I'll be considering locating the IAT myself.
Leaving the car on idle, I seems to be measuring high temps as the IAT is above the radiator. Is the AIR temp really that high or its it conducted temperature from the rad below? Perhaps two sensors would be better, or perhaps moving it to just before the TB? I was considering putting it before the IAT filter. I'm not sure, but it does seem I get false readings where it is in the Whisper lid.

If I'm in SD mode on idle it just gets leaner and leaner, as its opening up the IAC to allow more air in as it thinks its less dense due to high temps.

2002_Z28_Six_Speed

iTrader: (19)

If you look at your car you will realise that air ahead and behind of the rad support are two completely different temps.

This will only really help SD cars.

jimmyblue

iTrader: (11)

Question is, is the air at the TB face the same, higher or lower,
and how consistently related to the sensed air temp. Conductive
("heat soak") thermal input skews the air temp reading while not
changing the air stream any, which introduces a variable error.

I prefer the integrated IAT of the 85mm MAF but the stock
F-body one was a real whack-job when located in a back corner
of the air lid where it got no flow and plenty of backside cook
from the engine compartment. Your airflow has to overcome
any of that, for sensed to equal actual.

It would be fabulous to get to a -manifold- absolute temp
scheme with all the prediction and other numerical fudging
stripped away. But good luck with that.

YellowToy/A

iTrader: (1)

I think it is important to measure the air temp going into the motor. This is a great mod. I have tried about 3 places with mine. Including on top of the intake manifold. I put it in the plastic that is front of the rad down low.

The conducted heat from the rad warms every thing up top. The air at the wall of the pipe does not move. Only the air in the center does. The IAT sensor becomes heat soaked at idle. Once more air starts in the engine the sensor is still heat soaked because of the slow air movement at the wall. The Air/fuel ratio is lean. I have more that a few logs that show a much better A/F ratio with the sensor reporting close to ambient.

If you want to see this, here is way. With the out side air below 60 deg and IAT in the lid, let the car idle. The temp will go up to 110 or so. Now monitor the IAT. Run the car hard and watch the temp. I will tell you for sure that any air in the filter or pipeing will be below 70 in a sec or 2 of full throttle. Look to see what the sensor reports.

2002_Z28_Six_Speed

iTrader: (19)

I like to think of the IAT as an outdoor temp sensor. Hopefully, the PCM doesn't pull magic tricks on the numbers to figure out the temp at the intake manifold. If they did it would be a waste of processing time because it would be different for each vehicle depending on the intake config.

Weight it towards ECT during idle.

Weight it towards IAR during high airflows.

Solved all my problems.

YellowToy/A

iTrader: (1)

But under High throttle what is IAT? Do you know do? Do you have any data?

slow

iTrader: (7)

I am not sure on the ls1/ls2 cars, but the magic tricks you talk about are most certainly used for things like infered fuel rail temperature on ford applications.

Ryan

miami993c297

iTrader: (6)

After many testing of different locations,I am fine with my actual IAT Sensor location:





And here are the data, reaction time is less than 1 second (outside temp was ~ 70*):



Christian

Slowhawk

iTrader: (12)

Moving the sensor to the front works pretty good. The reason I've done them is that some of our street/race cars would heat soak real bad with temps hitting 150 degree's on the sensor which hurt the launch at the track.Also it would affect idling in traffic.Since moving it to the front the results have been good.

miami993c297

iTrader: (6)

Hi Slowhawk,

The maximun temp I ever recorded with the sensor in the Fast Intake in this position in stop and go traffic of Miami on a 98* outside temp August afternoon is a 112*...which is fine on a 2002 ZO6 with the stock Bias Table:



Christian

Slowhawk

iTrader: (12)

I like your setup but I won't drill a FAST intake like that or risk the sensor end coming off and going into a cylinder. Thats just me though.

gametech

iTrader: (1)

The ideal IAT position would be on top of the intake valve. Everything else is just a compromise that causes the need for extra computer calcs. Since that position is impossible, pick your poison. Farther away needs better tuning, and in the intake risks blocking airflow/sending pieces into the motor. I see the possibility of nearly endless arguments on this subject.

YellowToy/A

iTrader: (1)

My friend has his mounted in the Fast intake. It is forced induction. Not a bad place. It will still heat soak some.

2002_Z28_Six_Speed

iTrader: (19)

Maybe.


At WOT you have high airflow. That means it doesn't have time to pick up much heat from the enviroment. The IAT relocation mod might be better. At WOT the outside ambient temp ~= temp at the intake valve. The temp has to be correct cause the O2s arent working. If the IAT sensor is off you will never get it dialed it, right?

At part throttle lets say the IAT sensor relocation mod makes the temp wrong because contact with the enviroment skews the real temp. Oh well the O2s will make it up.

Without the relocation mod the air is almost always less dense meaning you are running lean. I think it is best to pick the setup that will help you at WOT when tuning matter more and when the O2s cant help you.

I did the IAT relocation mod because I run OL all the time. Screw paying all that money for Nbs when I already have a WB. I thought it was a joke and it didn't make a difference but it helps me.

fact9c1

iTrader: (8)

interesting

jimmyblue

iTrader: (11)

The thing is, the stock PCM is "massaging" the IAT and ECT
data to get to manifold air temp. No matter where you move
it this will still go on. Question is, given the downstream PCM
hoodoo, what is the quantity you really want to be feeding
it?

This is what I have not seen explained. Though Marcin
(redhardsupra) has been working on methods of tweaking the end
result, and I believe MAT may be coming as an available scanner
output (if it's not here already) for HPT.

Maybe somebody with a spare thermocouple could stuff one
down the manifold (EGR port, MAP grommet, unused nitrous boss,
etc.) and get a correlation between IAT (various schemes) ->
MAT (PID) and the logged thermocouple manifold temp. This
would let us all know what's what (for the given hardware at
least).