Help with nitrous activated timing retard
05-07-2004, 04:02 PM
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Help with nitrous activated timing retard Hi guys,
I am trying to use a relay and resistor to trick the IAT into thinking the temp is 178* F when the nitrous is activated. When nitrous is not activated, the IAT should read normally.
The thing is, it works fine with the car engine off and ignition on, but not when I run the car up to 3k rpm and hit the gas. In fact, sometimes the IAT plummets instead of pegging at 178*
There are two wires going to the IAT - purple and tan. purple is ground, and tan is PCM signal (5v)
Here is how I have it hooked up by relay posts:
30: Purple wire that was going to IAT sensor was cut and rerouted here.
85: Ground to window switch
86: 12v signal from TPS switch
87a: continuation of purple wire to the IAT sensor
87: wire with 330 ohm resistor inline, spliced into the tan colored IAT sensor wire. This places the line in parallel with the IAT sensor.
Does this sound right? I thought it was fine, and I get a good accurate signal out of 87a, I just cant seem to get the right IAT when post 87 is active instead. Should I have fed the tan wire into post 30 instead of the purple wire?
I am trying to use a relay and resistor to trick the IAT into thinking the temp is 178* F when the nitrous is activated. When nitrous is not activated, the IAT should read normally.
The thing is, it works fine with the car engine off and ignition on, but not when I run the car up to 3k rpm and hit the gas. In fact, sometimes the IAT plummets instead of pegging at 178*
There are two wires going to the IAT - purple and tan. purple is ground, and tan is PCM signal (5v)
Here is how I have it hooked up by relay posts:
30: Purple wire that was going to IAT sensor was cut and rerouted here.
85: Ground to window switch
86: 12v signal from TPS switch
87a: continuation of purple wire to the IAT sensor
87: wire with 330 ohm resistor inline, spliced into the tan colored IAT sensor wire. This places the line in parallel with the IAT sensor.
Does this sound right? I thought it was fine, and I get a good accurate signal out of 87a, I just cant seem to get the right IAT when post 87 is active instead. Should I have fed the tan wire into post 30 instead of the purple wire?
Last edited by Draco; 05-07-2004 at 04:31 PM.
05-10-2004, 11:21 PM
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I thinking that the 12 volt source from the TPS sensor can't supply enough current for the relay. This is creating the relay to bounce (on-off-on-off) rapidly, giving you a intermitent readings of zero ohms. Personally I would never use a PCM suuplied source. The PCMs boards were never designed to be used as a power supply. The 12 volt signal supplied to the TPS sensor is used as a "reference" ,if you wanna call it that, and is never really loaded under normal operation. Try the same setup with a alternative 12volt source just to see if the results are different. Perhaps use a normal WOT switch and see what happens.
