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One apex at a time
 
Dean924s's Avatar
 
Join Date: Dec 2005
Location: MA
Posts: 773
Garage
Voltage at TPS help - MS flood clearing set up

This is part of my MS project. I am wanting to use the stock TPS on my car for flood clear. Setting it so if the TPS circuit is closed and RPM is less than say less than 500 and it will not inject fuel. For those that care you could also use it to trigger NOS or engage a clutch on a supercharger but those are things for another project.


To set up my flood clearing. I need to know how the stock circuit works. Does anyone know what the voltage is at the TPS on an na car? The other question I have is how is it wired in to the DME

I am trying to figure out if it is a 5 volt circuit from the DME using the reference voltage form the dme or if it is a 12 volt circuit from using power from the cars 12 volt system.

The other way it could be wired is resistance to ground. IE when the circuit is closed resistance (ohms) goes to zero.

Anyone with info please post up.

Many thanks!!!

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Dean

General Car Specs & Mods
Project Megasquirt 924s
Old 11-24-2010, 04:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
All Spooled Up
 
Join Date: May 2009
Location: Between NE and Central PA
Posts: 2,516
IIRC, the N/A's only use (micro)switches, no pot. There is one for idle, and the other for WOT, The TPS is powered by 5 volts from the DME.
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>gray 89 951S - K27/8, MAF, 3" intake, 3" exhaust w/separate waste pipe, 55# inj, late cam; >red 87 924S - chip, K&N, punched-out cat&muffler >black 80 924 - (sold) >maroon 77 924 - auto (sold)
Old 11-24-2010, 05:06 AM
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One apex at a time
 
Dean924s's Avatar
 
Join Date: Dec 2005
Location: MA
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Do you know if it uses the same 5v refrence from the dme (pin 9) that the AFM uses?. It apears to be the only 5v out form the DME.

I am aware of the "on/off" nature of the NA units (but thanks). I am using a MAP based system for the MS. For now the TPS would be for flood clearing only.
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Dean

General Car Specs & Mods
Project Megasquirt 924s
Old 11-24-2010, 06:59 AM
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One apex at a time
 
Dean924s's Avatar
 
Join Date: Dec 2005
Location: MA
Posts: 773
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So I pulled out the wiring diagram and this is what I got.



Anyone understand how the altitude compensation switch plays with this?

Pin 3 on the TPS is obviously the WOT switch to pin 3 on the DME

Pin 1 on the TPS goes to pin 2 on the DME. Pin 2 on the DME is the closed throttle switch.

Pin 2 on the TPS goes to pin 28 on the DME it is the ground / altitude compensation.

So to use the stock harness with the MS I am thinking I need to wire in only pins 1 and 3 on the TPS (pins 2 & 3 on the DME) to the MS. I should also leave pin 1 on the TPS (pin 28 on the DME) not connected.

A side note is I have been told I will also have to put a 1K resistor on to the circuit to prevent voltage float at the MS when the TPS switch is open (most of the time).

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Dean

General Car Specs & Mods
Project Megasquirt 924s
Old 11-26-2010, 05:45 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
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