Anyone move the IAT on a L99?

[06MonteSS]

yeah... it starts pulling timing out at 86*...

starts at 86*, pulling out 3* of timing... then as dsteck said, it gets more aggressive the hotter it gets... will pull 4, 5, 6, 8, and up to 10* of timing as the temps get up there...

[wirebender]

I purchased and installed the HSRK unit from Vector, however...no data on actually how well it performs. Seems to do good though, for what that's worth.

[2SSCAMARO]

Originally Posted by DSteck

That timing gets pulled for a reason... Just because you aren't knocking doesn't mean you're at max brake torque. I typically leave that IAT table alone unless I really have the opportunity to tweak it for MBT (which is rare). One problem with IAT breakout kits is that the new intake temperature sensor may not actually match the temperature calibration in the PCM. You can modify the reported temperature based on resistance in the PCM. I don't know how close the breakout IAT sensors match the factory calibration, but there's not really much purpose for doing them. If you want to actually do something productive, insulate the MAF housing. The IAT sensor is built into your MAF, and will actually cool down pretty quick when there is air moving over it.

If you want to help your heat soak situation, then in addition to insulating your MAF housing, find a way to get lots of fresh, outside air to your air filter. Just because you relocate your IAT sensor doesn't mean you're suddenly not pulling in 150º F engine bay air.

The bummer with the heatsoak issue especially with long tubes that radiate tremendous heat under the hood is that when you are in the staging lanes the ECM is receiving pretty much correct IAT data but when you leave the starting line, for the next 12 or 13 seconds, the ECM is receiving IAT data that is skewed to the high side because the sensor is so slow to sample, sense, calibrate, and send the TRUE temperature of the fresher and cooler air flowing through it. I've logged many times while doing stop and go driving. After sitting at a red light for a minute or two in hot weather, it sometimes takes over 60 seconds to get the IAT back down to within 2 to 5 degrees of ambient which the CAI maintains in cruise condition.

[Matt TuneTime]

It is usually better to lessen the amount of timing in the IAT table slightly instead of try to fool it bottom line the temp in the MAF is the TEMP in the pipe and the car is Calibrated for that so it will not knock ...

[Silver Ice Man]

Just a thought, and please don't flame me, as I am no professional, but would wrappaing the intake tube with some of that reflective insulation possibley deflect, or aleast slow down the heat saturation of the metal intake tubes???

[DSteck]

Originally Posted by Silver Ice Man

Just a thought, and please don't flame me, as I am no professional, but would wrappaing the intake tube with some of that reflective insulation possibley deflect, or aleast slow down the heat saturation of the metal intake tubes???

Yes. In Corvettes, the air bridge goes right over the upper radiator pipe, so some people use some material with very low thermal conductivity to stand the intake off of that radiator pipe, and others also use heat reflective material around it.

On the topic of waiting for IATs to come back down, mine come down pretty quick. Leaving from a red light is a little different from a balls-out launch at the drag strip, where you're going to hit 50-60mph very quickly. My car has the duct in the front bumper, so I get a direct fresh air source, which probably helps mine drop IATs faster, but if you can get a more direct path of outside air to the filter element, that'd be the best thing to do.

[wirebender]

Originally Posted by 2SSCAMARO

The bummer with the heatsoak issue especially with long tubes that radiate tremendous heat under the hood is that when you are in the staging lanes the ECM is receiving pretty much correct IAT data but when you leave the starting line, for the next 12 or 13 seconds, the ECM is receiving IAT data that is skewed to the high side because the sensor is so slow to sample, sense, calibrate, and send the TRUE temperature of the fresher and cooler air flowing through it. I've logged many times while doing stop and go driving. After sitting at a red light for a minute or two in hot weather, it sometimes takes over 60 seconds to get the IAT back down to within 2 to 5 degrees of ambient which the CAI maintains in cruise condition.

The HSRK from Vector sends data (I think its like 5 or 10 times) faster than the stock sensor so more accurate and timely info is being sent to the ECM.

[DSteck]

Originally Posted by wirebender

The HSRK from Vector sends data (I think its like 5 or 10 times) faster than the stock sensor so more accurate and timely info is being sent to the ECM.

Sorry, but that's snake oil. A guy with a Trailblazer SS tested that out on his own.

http://www.ss-shootout.com/hsrk-results.html

I can't say for sure, but part of the reason the Vector IAT reads lower could be a different calibration scale. I'd be curious to record output values in a controlled environment for the MAF's IAT and the Vector IAT.

Beyond that, both your coolant temperature and intake temperature are used to determine your manifold air temperature, which is effectively the temperature of air entering your combustion chamber. It's biased towards one or the other based on airflow (the theory being that at zero airflow, the air inside the manifold is the same temperature as your coolant temperature, whereas at infinite airflow, the incoming air has no time to absorb heat from the engine, so it is effectively the same as the intake temperature). It'd behoove everyone to simply tweak the IAT timing table, but I tend to leave that table alone and look for mechanical solutions instead (ie: better air supply).

As far as the factory sensor being slow to "sample, sense, and calibrate"... It's just a variable resistor, basically. At different temperatures, it changes resistance. The resistance across the sensor is constantly being measured and accounted for. Your PCM is sampling faster than you'll ever notice... When it takes a while for IATs to drop, it's because you're still getting a good chunk of air from the engine bay. Insulate the everlasting crap out of your intake, and run it so the filter is outside the car... See how fast your IAT drops then.

Also, for kicks, here's the IAT timing reduction table, as well as the two multiplier tables in the factory calibration:




The ECT multiplier ends up not affecting everything too much, aside from making slightly less timing come out at higher ECTs. The IAT multiplier vs. engine speed is where you can see that the full timing listed in the IAT reduction table starts being taken out at 158* F, but begins to aggressively hit the reduction table around 130-140.

For reference, most people will be in the 0.70-0.90 g/cyl engine load range during a WOT pull.

[Duke]

DSteck hit the nail on the head when he said insulate the MAF/IAT. As far as the PCM goes, the temperature downstream of the IAT sensor is irrelevent. So, insulating the whole intake pipe won't do anything as far as reducing the timing pull.

Thanks DSteck, this is my next mod.

[Slowhawk]

There are many things you can do but you have to be smart about it.Just moving the sensor could cause alot of damage IF the air is hot going into the motor. Luckilly most cars have a decent cold air setup so the high IAT temps are from heat soak.This is ussually not a problem while cruising around but affect timing alot while sitting in traffic or more important - in the staging lanes at the track.

If the heat soak is minimum you can adjust the timing table in the tune.Moving the sensor to the filter is 1 good option.

As for myself on my 99 TA that I race alot. We put them in the front fog light hole to measure outside air temp.This way it doesn't pull timing on launch.

[JANNETTYRACING]

Dstek, Excellent Posts, not sure if everyone gets it so the bottom line is.

Don't Move your Air temp sensor Leave it alone, it is where it is for a reason.

Ted.

[DSteck]

Originally Posted by JANNETTYRACING

Don't Move your Air temp sensor Leave it alone, it is where it is for a reason.

Winner winner, chicken dinner!

[hot ss]

heat is thine enemy, its good to know how close the enemy is, and accurately.

[aj2ssrs]

Originally Posted by JANNETTYRACING

Dstek, Excellent Posts, not sure if everyone gets it so the bottom line is.

Don't Move your Air temp sensor Leave it alone, it is where it is for a reason.

Ted.

Do you think it's a problem that ADM moves the sensor from the stock location to the inside of their air box?