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Old 10-16-2007, 07:56 AM   #1
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Default OEM temp sensor out of afm

I'd like to know more about my intake temperature, especially after the intercooler. Is there a way to use the OEM sesor out of an old AFM for that? Or does it respond too slow?

I don't need a gauge, I'd like to wire it to the ZT-2 and define a max. Value, so that I get a warning, if intake temperature gets too high...and that I can log the corresponding volt values along with boost level, tps and rpm...

Would that be possible? Does anybody know how the sensor works?
has it two cables (5v in, signal out, or is it only a mass resistor?)
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Old 10-16-2007, 10:06 AM   #2
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start here: http://miatajoe.50megs.com/index.html
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Old 10-16-2007, 10:54 AM   #3
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Thanks for the vote of faith, Brainy.

RacingGreen, I went into significant detail in that writeup as to why I didn't re-deploy the OEM AIT sensor in a post-turbo configuration, but I'll give you the short summary. It's too slow.

If you take a look at one of those sensors (and I put several good pictures of one on the link above) you'll see that it is encased in plastic. This protects the sensor, but also prevents it from responding to rapid changes in temperature, such as you would see on the outlet of a turbo, or even after an intercooler.

For something like this, you need what's called an open-element sensor. It's basically the same electronics, but without the plastic case. These devices can respond very rapidly to changes in temperature, at the cost of being more susceptible to damage. Here is an example of an open-element sensor of the type used by Megasquirt owners to monitor temperature after the turbo: http://www.diyautotune.com/catalog/o...tor-p-116.html Notice in that picture that you can actually see the metal sensor element inside? That's the difference.

As to how they work, they are simply variable resistors. As temperature increases, resistance decreases. Thus, measurement is usually done by grounding one side of the sensor, applying a regulated voltage through a fixed resistance to the other side, and measuring the voltage drop across the sensor.
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