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Old 11-05-2004, 03:57 AM   #1
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Default Electrical engineers, lets do this!

Looking for adjustable timing here. Damemorder and I were discussing this yesterday, and i was at Radio Shack and started thinking too much, so i didn't buy anything....

Basic info.. The IAT sensor detects incoming air, the colder the air coming in is, the more advanced your timing is. The resistor "chips" on ebay do this, but the PCM readjusts. The **** is nice for that race on the street you wanna do, and have a small advantage, or when you decide to do a spirited run somewhere.

The IAT is a thermistor, @ 140* it'* letting no current through at all. @ like -29 (i think) it'* letting the full 5v input pass through.

So less resistance = more timing.

Went to go get a Pot, a guy there suggested a Linear taper 10k ohm one. (does this sound good?) After some thinking, i realised that if you ran "normal" on no resistance in the pot, and turned it up, you'd kill your timing.

So my question is, should we integrate the Pot into the circuit just straight up, and hope the PCM accomodates the resistance of it in the "normal" position?

Or should we build a circuit that uses the IAT sensor'* voltage, as input, and output equals that resistance, but part of that resistance is the Pot set to "normal", so we can turn the pot'* resistance down, to add timing?
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Old 11-05-2004, 04:36 PM   #2
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I'm kinda catching your drift, but I am thinking to my self ...WTF is a POT? Is POT a acronym, or am I going blonde?
Sorry, I'll have to look it up on google.


<----Hmm!! Does that # say ONE-FIVE-DUBELOH???
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Old 11-05-2004, 08:48 PM   #3
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Quote:
Originally Posted by OLBlueEyesBonne
.WTF is a POT? Is POT a acronym, or am I going blonde?
Potentiometer
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Old 11-06-2004, 01:07 AM   #4
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You would need to replace the IAT with the POT, not add it to the circuit. I read somewhere that 57 degrees F requires a 4.7K ohm resistor. I think that you would only gain one or two degrees of timing no matter how low you went. If you had any KR, this could be harmful in the long run.
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Old 11-06-2004, 04:40 AM   #5
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It'* only for short bursts, when you want the power for a race, or spirited section on a road. The PCM will supposedly figure it out. I was considering just the Pot instead of the IAT completely, with an external Temp readout inside.
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Old 11-06-2004, 10:10 AM   #6
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Quote:
Originally Posted by BonneMeMN
It'* only for short bursts, when you want the power for a race, or spirited section on a road. The PCM will supposedly figure it out. I was considering just the Pot instead of the IAT completely, with an external Temp readout inside.
Another idea would be at add a switch that would redirect the current through a fixed resistor instead of the IAT. That would give you your temporary control.
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Old 11-06-2004, 04:09 PM   #7
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When you are running on the pot, you should disconnect your o2 as well. The comp is gonna see your running too rich and then that pot isn't gonna make a diffrence.

O yeah ONLY do this for shot periods since you'll clog the crap outta your cat running a little rich.
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Old 11-06-2004, 04:17 PM   #8
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Running rich can be as bad as running lean.

Temp/resistance specs are in Techinfo. Remember that if you put the pot in parallel, you decrease the overall resistance of the circuit. Run the pot full high for normal running (but ket a 100k or higher pot). As you decrease the pot, you increase your timing, as the current has two paths to travel through.
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Old 11-06-2004, 04:26 PM   #9
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Yeah that would make sence to short it.
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Old 11-06-2004, 04:51 PM   #10
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Two 10 ohm resistors in parallel equal 5 ohms. Two 10'* in series are 20.
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