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Old 04-06-2009, 09:33 PM   #1 (permalink)
wstar
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Location: Houston, TX
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Default Intake air temp data (Stillen Gen 3, need stock)

I got bored today with nothing else to do to my car today, and I logged some info on intake air temps with the Stillen Gen 3 intakes just to validate that they are in fact drawing cold air (not that I expected any different). Results are unsurprising. I was using a little handheld OBD-II unit that can log a minute or two of data at a time for review, so it took a few passes (and a few minutes of just watching live data as I drive).

Outside temps were around 61-65 F through the drive according to the Z's little info display. Intake air temp (IAT) dropped to about 66 within two minutes of getting on the highway at 70mph+ speeds. Coolant temps were around 195, oil temp similar, maybe 5 degrees higher on average (this was a very non-aggressive drive). Even when I slowed down onto the feeder road (~45mph), the IAT stayed down. When I got down to parking lot speed, the temps went up a few degrees, but still stayed under 70. A couple of WOT runs didn't phase the IAT either (just in case the increased engine airflow caused them to suck hot air from the radiator fins or something). Nothing I could do driving seemed to raise them. I was looking for ways to cause some kind of airflow or pressure problem - very high speeds, long slow curves, driving behind another car vs not, etc.

The only way to get them to raise significantly was to park the car and idle. Took about 12 minutes of sitting in a parking lot idling to get the IAT up to 115 degrees (and the coolant temp was cycling between about 200 and 214 as the fans kicked in and out). Leaving the parking lot and driving again, it takes a minute or two for the IAT temps to get back down to "normal". I suspect this is because the sensor responds slowly to rapid changes like that, as there's really no other rational explanation.

If anyone else has a generic OBD-II tool that can show them live IAT on a stock 370Z intake, it would be interesting for comparison to see how it does. I'm kicking myself now for not thinking of this two days ago before I installed my intakes. Given the design of the stock inlets (which is really pretty good for factory stuff), I imagine it does pretty well, although perhaps not as good as the Stillen setup.
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