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Old 04-29-2008, 12:22 PM   #7 (permalink)
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Originally Posted by MetroMPG View Post
The sensor mod PLUS actually increasing the intake temps may result in potentially greater fuel savings than just the sensor mod (assuming detonation is avoided, as usual).
Thats assuming a lot. Intake temperature is just as critical to knock control as octane. If you pay close attention to the autospeed article, they were using 98 ron fuel in a car that requires 95 ron in order to avoid knock. The Insight they were using is already equipped with a forward facing cold air intake which was also shown to both increase power and improve fuel economy.
Its pretty obvious that what they are trying to keep the intake air as cold as possible. This whole warm intake theory flies in the face of reason and all my experience with 4 different cars.

The only rigorous comparison test between cold and warm air intake I can find didn't show an advantage for warm air intake.

I think autospeed is on to something with this IAT resistor and I'll give it a try on my BMW. From my service manual:
A 3-5k ohm pot should do the trick. The problem is this engine is not equipped with a knock sensor and the spark timing map is very conservative. BMW recommends using only 91 octane in this engine. I'll use the IAT to advance timing, forward facing cold air intake and a water mist spray to make up the octane difference.
A resistor in the engine coolant temp sensor circuit could also be useful to trick the engine into closed loop sooner after a cold start.

Last edited by tjts1; 04-29-2008 at 01:06 PM..
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