Confused about N20 Wiring for MS2/E

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Jon k
Super MS/Extra'er
Posts: 1256
Joined: Fri Oct 14, 2005 10:28 am

Confused about N20 Wiring for MS2/E

Post by Jon k »

The MS2 docs say "An arming input signal (ground active) is sent to the Megasquirt CPU when the power is on and the safety switches are closed"

But the diagram shows a +12v signal being passed through the RPM switches and it looks like there is a pullup transistor there PE0/JS7. So, am I using a 12v input that switches the PE0/JS7 to ground via the transistor or is there a conflict in the wiring?

Sorry I suck at reading diagrams.
1992 BMW 525i M50 Non Vanos 24v Turbocharged
Stock COP Wasted Spark
MS2/E v3
wes kiser
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Location: Charlotte, NC

Post by wes kiser »

Essentially, the circuit is pulling the pin low when the nitrous is armed. You hook the circuit up as shown. When 12v is applied to the transistor you installed, it will ground the appropriate pin on the CPU. The pull-up resistor is to ensure the pin is high until it is low (instead of floating around and potentially getting triggered randomly). I hooked mine up with the input EXACTLY as shown, and the Nitrous relay hooked directly to IAC 1B.
86 Rx-7, swapped to 2.3 ford turbo (BW EFR 6758), ms3/ms3x sequential fuel /waste spark, ls2 coils
88 Tbird 2.3t, Microsquirt Module (PIMP), TFI ignition
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