Originally Posted by BuckeyeSRT
I am not following the temp increase after an extended drive. How does it increase when moving? Isn't that like saying the (cooling) fan is more likely to come on when you are moving than when are idling? I have never owned a car where the under hood temp has not been close to or the same temp level as the outside air when moving.
The WK2 engine compartment is sealed better than those of a few years ago.
Even without the sealing, the air in my engine compartment is always quite a bit warmer than ambient, there is a lot of radiant heat from the engine as well as all that hot air being pulled through the radiator. There is just not enough air moving to cool things down.
Years ago we used to punch holes in the hood and connect hoses to route the cooler outside air to the carbs. How many shows have you seen where they cooked dinner on the engine while that are moving.
Anyway, the difference between metal and plastic pipes is dramatic as more heat is conducted through the metal pipe to the air inside as well as directly to the sensor than with plastic pipes. You wouldn't think it would be much as the outside of the pipe is just as hot (it is more uncomfortable touching a hot metal pipe than a hot plastic pipe), but in practice it is dramatic, even without relocating the IAT sensor to get a truer air temp reading.