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Originally Posted by 23psi4age
It is not giving the DMW incorrect info. It is giving the DME the same info that it gets when the car is cold/ambient temperature before heat soak. You can't tell me your car does not feel faster at night or in the colder weather?! If what you were saying made sense then the factory tune would compensate to make the car always have the same power no matter the outside environment. And so if what your saying made sense, a turbo car especially, or a non turbo car, would not run faster at night or in the cold weather - it would always run the same no matter what - which is simply not true.....
It has already been documented - through instrumented testing - that at normal operating temperatures, the temperature of the intake air as it travels through the air filter / MAF sensor / intake manifold is in fact very close to that of the Ambient Air Temperature.
The Sensors and Components of the Engine and Engine Bay heat up to 140-170 degrees but the actual air intake temp because it originates from outside of the engine bay (factory intake snorkel in front of the radiator support) and is continually travelling and being ingested by the engine - is again very close to that of the outside ambient air temp.
The heat soak of these sensors adversely affects their readings of the actual air temp inside of the air intake system - and the close loop tune corrects for it, resulting in less Torque / HP. Granted it is only a small loss like 10-20HP, it is still a decline you can feel. Just like you can feel that same amount of 10-20HP gain when its freezing cold outside!
All of this is relative to Non Turbo cars as Turbo Cars inherently bake their own intake temps due to the turbo charger being literally connected to the exhaust and so actual air temps in a turbo car after the intercooler are still super hot regardless of heat soak.
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The biggest reason for an engine to make more power when it's cold is called Air Density. More Oxygen per cycle. We've had this phenomenon well before computers took control of our cars.
The Modern BMW / N52 does tailor ignition timing during higher temps but it's also constantly monitoring the knock sensors and making small changes to the stored adaptive ignition tables. Think of it as a Close loop ignition advance system. Unless you make change to the actual ignition, load or knock factors, it's going to relearn pretty quickly. I've logging a knock/noise induced timing pull in one gear and watched it pull timing in the next gear at the same RPM, without the Knock/noise. It preemptively pulled timing at that spot.
Other than extreme circumstances, You are not going to pick up 10-20 HP by simply changing the IAT location. Hell, it takes a full tune, vanos, timing, fueling to pick up 15 HP on a stock motor /N52.
Living in Florida, I have a good understanding of heat soak. I went back and looked at some of my N52 Logs, I logged everything when I tuned that car. It seems like the recorded IATs recovered pretty quickly. I'm seeing a typical 7 degree C drop in about 6 seconds. Max values, stop and go Florida traffic are about 50 Degrees C, I don't think the IAT sensors ever reach the temperatures you mention.
Ya FI motors are different beasts, stop and go traffic in the hot summer sun, I actually think my N54 IATs are lower then the N52. Some of my N52 logs show 50+ degrees in stop and go traffic, but I rarely see over 40 with the N54. Build up a little boost and that changes.
