Climbing IAT's in stanging lanes = slow E.T.'s

[charcoal03silvy]

Since the weather has gotten warmer, my times have slowed down over half a second... I feel like my truck should be able to run 14.999999, but last time at the track i couldn't get down past 15.5. Finally, I logged a run with my HPT scanner and saw that my IAT's were reading 125*+ by the time i waited in the staging lanes and got to the tree... Truck was pulling 7~ish degrees or more of timing due to the high IAT's from heatsoak.

I know there's a table in HPT that advances/retards timing based on IAT vs G/CYL... I mellowed out the 77* to 113* cells, but it seems like I need to mellow out the whole damn table for a track only tune... I know that once i do the burnout and when I'm making a pass, the IAT's aren't really that high, but the IAT sensor is just heat soaked...

Thoughts?

[jimmyblue]

I recommend you get the IAT out of the engine bay
entirely, and make sure you have a ducted cold air
setup that makes in-taken air temp equal ambient.
Then the only error will be at low airflows where closed
loop fuel trimming can take it out real-time, from a
rich (safe) initial error.

[charcoal03silvy]

The IAT is in the MAF.. So I'd have to extend my "cold air intake" down into the fender and extend the MAF harness down there as well

[FarShot83]

The IAT can be wired and installed into the CAI at any point. You need an IAT thats seperate from the MAF of course. I used the one from my 2000 gmc jimmy 4.3v6. Cut and routed the wires IAT wires at the MAF to hook up where I wanted it. Thats it.

[charcoal03silvy]

I have read about installing an IAT sensor in the EGR port of the truck intakes.. (mine doesn't have EGR, just a block off plate) I do use nitrous occasionally, so wouldn't that be better, so the IAT sensor is seeing the temps the cylinders are seeing?

[charcoal03silvy]

Just like having the IAT sensor down stream from where you'd inject meth at on a turbo app?

[FarShot83]

Put it away from the heat of the engine. The closer to the engine it is the more accurate. Key to success is get air in from outside the engine bay. Vent the heat out of the engine bay. Wrap headers, use an Electric fan bypass switch to manually turn your fans on, etc..

My IAT is at the center of the cone filter. Probably a little cooler there but it stays stable.

[HoP]

scale the iat sensor

[charcoal03silvy]

scale the iat sensor

explain

[murphinator]

good news you have identified high Iat's as an issue.

how about some thoughts outside tuning that may help ? (yes I know its a tuning forum)

even if you change iat location and adjust tables to gain timing which will likely help you are still not getting the benefits of colder denser air which will make more power.

Personally I have always gotten quicker et's by making fewer passes with more cool down time between them with the hood up facing into any wind.

on a typical pass I start and shut off my engine about 20 times in the staging lanes ( wearing out starters hasnt been an issue) only run to move , shut it down if your stopped.

every tracks rules are different but typically if you havent entered into the burnout/staging area yet your hood can be "popped" not fully open but on the release catch just make sure you close it before you burnout/stage, if your vehicle is going to be stopped waiting for your lane to move again open it all the way up and keep it shut off.

when I turn off the track onto the return road I pull the hood release ( check to make sure yours is functional) and maintain speed/slow steady to the time slip shack and back through the pits to try to keep rpm's low while keeping air flowing through the engine bay - dont get on the bumper of the guy in front of you on the return road or pits rather let the next car pile up behind you - you want that unrestricted airflow from not having a car in front of you whenever possible to get any cooling you can.

[FarShot83]

Those techniques should help but...

I had my vehicle hitting 130+ IAT and it was 10 degrees out. Thats why I seperated my IAT from the MAF. It still raises a little but its stable and reflects the actual intake air temps.
They cost 7 - 16 on rockauto.com Don't get a brass one.

Your vehicle should be able to maintain levels of heat. Depending on the build, colder/hotter than others. If you have IAT issues, move it to get true intake temps. If heat soak is affecting the IAT then its an issue that should be addressed. You want cooler dense air in and you want the PCM to know what its getting.

IMO...focus on controlling engine and engine bay temps. Electric fan upgrade, better E-fan controls, better radiator, low temp thermostat, BE COOL additive, etc...

IAT is probably getting heat soak and most likely you could get cooler air into the engine. Your going to need to experiment to get the best results. I put about 6 flat stick-on thermometers in the engine bay. I also use a laser temp gauge to find and correct hot spots and target cooler air in.

You can easily get this fixed the right way. You just need the right tools and techniques. Do it any way YOU want but, do it right the first and only time. Everyone has different methods. Hopefully others share better methods...

[gn2beatu]

Put it in the intake, and then cover it over with some aluminum tape like youd use on household AC ducting. This will insulate it from the hot air coming from the fan wash. You can even paint it flat black so its not so ugly. Just gotta keep the hot underhood air from the sensor body to prevent heat soak. Now if this is a show car, or something you dont want as ugly under the hood, then pull the intake, and put the sensor in the back, and then cover it back there where no one can see it. If you have to lengthen the wires, solder them, dont just twist em together, and dont use crimp connects. They will add resistance to the circuit and temps wont be as good after a while. Lastly, after the car has sat overnight and before starting it, check the temp outside, and check the temp the sensor is reading with the key on in HPT. You may need to scale it a touch. You asked what that was before. If outside temp is 40 and you read 44 in HPT, your off by 10%. Find the IAT sensor cal table, and reduce it by 10% and recheck the temps again without starting the vehicle. Do this til its spot on. Bet that clears up any issues.