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Old 07-23-2012, 05:10 PM   #21
xixixi
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Join Date: Aug 2009
Location: St Louis, MO
Posts: 3,008
My Ride: 01 330x-xi
Quote:
Originally Posted by jared_wiesner View Post
Well, I get what you saying but I respectfully disagree. The tune is designed to read proper air temp through the manifold. If your driving down the road and flushing the engine bay with cold air, its values are very close to ambient air temp. If your sitting at a stop light heat soaking the sensor its values travel artificially high.

During Dinan's dyno testing of an M5 this difference meant a loss of close to 50 horsepower between running the car on a dyno with a closed hood and the factory IAT location. That can't possibly mean the ECU was somehow taking into account the fact that the car was stopped and heat soaking and artificially giving the IAT a higher temp. It means the ECU was getting a bad value to the tune of 50 lost ponies. Even with the hood opened, relocation of the IAT resulted in a gain of 10 horse.

Again, the idea is to provide an accurate reading of the air going into the engine at all times. The location where I have my sensor gives almost the same reading as measured in the factory location at 60MPH because of the air keeping everything from heat soaking. This is what the tune is designed for. Running the engine at speed. The air when your stopped is the same temp, the sensor is just getting thrown off because its heat soaked via conduction.

The M54 location is much better in the MAF but it's still not ideal and does provide artifically high numbers after heat soak even in this spot.

I agree with this post. Since you mentioned an M5. The e39 m5 runs the EXACT same long tube intake as these cars. Big kudos to the guy at Dinan, that engineer made his company lots of money! Only difference is the M5 uses two of these tubes. (kinda OT) I might try this. My question is, while on the dyno, how are you going to keep the fans from messing with the IAT? If you have it located down near the radiator? What would be the proper procedure to dyno with this set up? Just thinking about all this makes me think street tunes (illegal, careful) are much better than dyno tunes. If my buddy doesn't get me on the dyno, I'm gonna tune this thing on the street!
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