Charley

question regarding intake temperature and octane



i was told by someone that decreasing the engine bay temp, leading to lower intake temps gives you a theoretical octane boost because decreasing engine bay temps/IATs may allow your ECU to advance the timing/inject more fuel due to the raise in air density.



can anyone confirm/ deny, or explain?

Red Raspberry

Lower IATs will allow the ECU to boost timing as the timing is usually pushed to the point of spark knock then pulled back. At least if you have a knock sensor.



But the thing is how to get there and do you know what your IAT and spark values were/are before and after any changes?

krazytib

I made an adjustable IAT. It's really only beneficial if you have an ODB II scanner to make sure you have it adjusted properly. If the temp is set 20 degrees above or below ambient temperature then the car runs shitty.

Red Raspberry

The Gen Coupe has a MAP sensor before the throttle body. The IAT comes from a MAP sensor in the intake. So people have moved the IAT to the pre throttle body area. Personally I don't like this as you are not getting a true intake air temp IMHO. Their thoughts are the hot intake is heating the plastic of the MAP and artificially raising the temp reading.