392 IAT (long) sensor virtually cured my heat soak issue

[rayzazoo]

Originally Posted by 84Laser

Does anyone know if 2012 cars are using this new long IAT sensor from the factory?

Originally Posted by BigDaddyWiz

If I had to venture a guess I would say yes. The 2011 charger intake tube that I ordered to replace my 2009 tube (that has a resonator) came with the longer temp sensor installed in it already.

Originally Posted by hemifever

My 2011 has the new long sensor

All 2011+ models that utilize the new airbox design have the new, longer IAT sensor. There have been no changes in the design between the 2011 and 2012 model year.

For $4, this is a very good modification to do and will work even better with relocating your sensor away from the throttle body as mikeychallenger did. The newer sensor is insulated better than the previous. Essentially, putting the sensor in the middle of the tube reduces the potential of the sensor reading intake tube sidewall temperatures rather than the actual intake temperature going through the tube.

Also to mention, this is not one of those "butt dyno I think I'm feeling more horsepower" modifications. You might not notice it as much in a 6-speed vehicle, but in the automatics, your transmission shifts during acceleration and deceleration are much smoother and less abrupt. Here is an example theory of what you can expect by doing this mod.


You're driving around town all day, you engine is already heatsoaked. You've been going in stop and go driving, you pull up to a stoplight and you have the following readings. Sensor is in the stock location.

[EDITTED] - thread post reference for actual data

So the lag in acceleration in heatsoaked conditions is caused by sensor inaccuracy. This explains why we loose 20+ lbs/ft of torque in stop and go driving and why we get excessive engine knock and timing pulled in heatsoaked conditions after consecutive runs at the 1/4mi track. The air/fuel mix is leaned out because the PCM injects the improper amount of fuel for the actual air temperature entering the combustion chamber. As a point of reference, you'll get a lean air/fuel mixture if your sensor reads higher than actual air temperatures. This also results in the "spark trim", as Chrysler calls it, where the engine will use less spark advance to compensate for engine knock that resulted from an improper air/fuel mix. You'll also get a rich air/fuel mixture if your sensor reads lower than actual air temperatures. This results in the lag in acceleration from too much fuel. Notice how your peppyness of the Challenger is in cold vs hot weather.

Mikeychallenger showed us a few things.

- relocating the sensor away from heat sources allowed for a more accurate reading of the actual air flowing through the intake tube
- the difference in results showed that 20 lbs/ft torque is lossed

Some things that I have observed are
- as the engine heatsoaked, engine knock was detected as a result of an inefficient air/fuel mixture
- when the engine fans came on at idle, an unshrouded filter will heat up 10-20 degrees in temperature

I too verify the engine knock as I race down the 1/4mi track. I did 3 runs and the first run I had no engine knock. As I got to my 3rd run, I had engine knock detected on initial launch, and with every shift their after. My engine torque between the 1st run and the 3rd run was reduced roughly 20+ lbs/ft. The result was that I lost 2/10ths in the 1/4mi: same 60fts at 2.0x, 1st run: 12.7 @ 110, 3rd run 12.9 @ 108.

With this in mind, we increase sensor accuracy by moving it away from heat sources, which is exactly what the new sensor design does. We also increase sensor accuracy because the wire insulation on the new design is better than the old design.

I plan to do datalogging this weekend to see the difference between the two sensor readings to verify what mikeychallenger has pretty much proven with the relocation of the IAT sensor and how it reads more accurate.

The end goal is for the sensor to produce the most accurate actual air flowing through the tube temperature reading without reading the temperatures of the materials surrounding it.

[sam95ta]

Here is mine installed in a Stack Bullet CAI.Good find rayzazoo

[rdockery_3]

How exactly does a sensor fix the heat soak issue? Do the colder readings cause the ECM to add fuel?

[rayzazoo]

Originally Posted by rdockery_3

How exactly does a sensor fix the heat soak issue? Do the colder readings cause the ECM to add fuel?

What this modification does is improve the accuracy of the IAT reading. This results in your engine running more efficiently and ensures that you aren't loosing power due to detonation/knock and spark trim from a higher than actual temperature reading. A more accurate reading will cause the ECM to add the correct amount of fuel for the actual air temperature (ECM will calculate an air density) entering the combustion chamber.

Minimizing the effects of Heatsoak

Heatsoak Defined

Understand, heatsoak is not fixed because of this mod. Heatsoak is inevitable, especially once you shut off your engine, however, while your engine is operating, heatsoak is reduced through engine coolant. Measures we can take during engine operation are are using a 180 t-stat to start the cooling process sooner, reducing the fan settings, and using engine oil coolers. While at the track, you can use the 25 Cent Fan Mod to turn on the fans to cool off the engine when it's shut off.

We minimize the effects heatsoak has on engine performance (specifically the air entering the combustion chambers) by insulating the IAT sensor from engine materials that store heat and pulling air that is cooler than engine compartment air from the fender. We also can reduce the effects of heatsoak by using materials in the engine compartment that have low thermal conductivity and a high specific heat (e.g. rubber, plastic). A final way we reduce the effects of heatsoak on the IAT sensor is by relocating it away from the engine block.

These same principles listed above can be seen in the redesign of the 392 air intake tube and air box. The new manifold is a plastic composite material, the new air box is made of plastic, the sensor is insulated better than the previous and reads from the middle of the airstream, the sensor is located away from the engine block (the highest heat source), and the throttle body is thermally insulated by the new manifold that is a plastic composite material.


Effects of higher or lower sensor reading than actual air charge

With the heatsoak issue, if the sensor reads higher than the actual air going through the tube, it'll subtract fuel resulting in a less than efficient burn and also you'll be more prone to engine knock/detonation. This engine knock causes the ECM to reduce spark advance to compensate thus reducing the power output.

On the flipside, if you take the sensor and let it read ambient air temperatures (lxforum sensor relocation thread did this), this won't be representative of the actual air going through the intake tube. As a result, you'll have too much fuel added and a less efficient combustion. This is also the reason why too much fuel is added as a result of a sensor that gets dirty or oil on it.

The argument has been that the IAT sensor relocation mod tricked the ECM into adding more fuel when in reality, as MikeyChallenger has shown in his thread 20+ lbs/ft torque, allowed for the ECM to read the actual air temperature flowing through the tube rather than the heatsoaked temperatures of the materials surrounding the sensor, resulting in a more efficient burn. This also helps to explain why the transmission shifts are smoother and the acceleration lag is nearly gone because of the new sensor.

Also for reference, An air temperature charge pulled from the fender well is about 4-5 degrees above ambient and the air temperature charge pulled from inside the engine compartment is 10-15 degrees above ambient. At highway speeds, I've shown that an unshrouded short ram intake can read 1-2 degrees difference from a fender pull intake.

[rdockery_3]

I think I'm going to stop by the dealership and pick one up. When its muggy outside my car feels like its down a cylinder.

[deranged]

It does make a noticeable difference on the 6-speeds as well.

How many times will you say "I only spent $4.00 to make my car run better." ?

[BrUiRcNeR]

I'll swing by the dealer for one as well. I have yet to pick up a 180 stat, but that will come soon enough. Anything that will help offset the heatsoak effects will be a welcome addition.

[BEER_ME_in_CT]

AWESOME! I was about to drop 400 bones on a diablo and Tstat. I'm going to try this first! Whoever figured this out I owe you a cheap light domestic beer!

[BigDaddyWiz]

Originally Posted by BEER_ME_in_CT

AWESOME! I was about to drop 400 bones on a diablo and Tstat. I'm going to try this first! Whoever figured this out I owe you a cheap light domestic beer!

while this will help, it wont be as effective as the tstat/fan mod. that mod brings down engine temps, which in turn keeps timing from being pulled to begin with. overall it keeps engine bay temps lower and will help the IAT sensor from being effected.

[elders10rt]

Originally Posted by Crush

Thanks to the posts put up by mikeyChallenger Heat soak eats 20+ lb/ft of torque! and rayzazoo Mystery Grey IAT Sensor Connector - SOLVED!

My car is a dog in 85+ degree weather, esp with the A/C on, so I was really excited about trying the new 392 IAT sensor PN 05149279AB. It was $3.50 and plugged right into my gray connector and into my RoboFab air tube. Today was the real test as I go home for lunch, the car heat soaks, and I drive back in 90+ degree humid temps. The new sensor really made a difference I could feel. This is in the stock mounting location. Eventually I'll get the extension cable and relocate to the air box.

Thanks for the research guys as the heat soaking was one of my biggest complaints about the car. I can't wait to see if cooler weather performance is better as well.

(I wanted to put something with a "heat soak" subject in this section for exposure.)

I ordered mine today. you mentioned an extension for the wires where do get one of these extensions? what is required to i.e. drilling etc to mount in the Air box? how does one Fill in the hole left in the intake?