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Old 03-25-2007, 07:14 PM   #1
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Default PWM 12v signal diode install

I've installed a switch so that I can switch the idle from stock ecu to megasquirt once i get everything else running the way I want. You have to install a provided diode in the 12v signal line. Now in my switched setup is there any reason I can't install the diode in the main signal line going to the valve itself.
If that is worded poorly can I install the diode in the main 12v line between the switch box and the idle valve without causing any problems with the stock ECU communicating with the idle valve. I don't want to put it in the main line if it going to interfere with the stock ecu's ability to control idle.
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Old 03-25-2007, 07:20 PM   #2
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A diode does the same thing in an electrical circuit that a check valve does in a plumbing circuit. So as long as it is a DC circuit, and the diode is oriented in the correct direction, I don't see a problem.

But I **** about MS or the circuit you need to build, so take it with some salt...

<edit> I reread--is the diode supposed to block voltage between the stock ecu and parallel ecu? If so, then NO it would NOT work. If that's the case, it would need to go between the switch and MS.
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Old 03-25-2007, 07:29 PM   #3
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I installed the Diode between the MS and the switch and I understood the concept of the diode acting as a check valve as well since it is supposed to act as flyback protection for the MS. I was just thinking about it because I initially had it installed in between the switch and solenoid but switched it earlier today. Just incase something strang might occur with the diode in the circuit for the stock ECU to control idle.
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Old 03-25-2007, 08:06 PM   #4
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Actually by nature of the switch there could not be an electrical path between ecus.
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Old 03-25-2007, 08:10 PM   #5
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i don't see how it would hurt it. but why bother with switchable idle anyway? its not something you need for a limp mode so...
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Old 03-25-2007, 08:19 PM   #6
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I did the switch because i wanted to be able to wire it all up and not have to take all the wiring out to connect idle once i had fuel and spark tuned. I just didn't want to tackle idle right off the bat and it's a PITA to get under the driverside dash to get at the ECU wiring. Makes me want to cut myself everytime I have to get under there to check or change some of the wiring.
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Old 03-25-2007, 08:31 PM   #7
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I just had the car running on all stock ecu and switched it over to MS Fuel, car ran but it ran like crap. Stoked that it was working though. Switched it back to stock fuel and then tried spark alone by itself and the car died. I still have to set the CAS to match the timing of the car though.
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