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MG MGF Technical - engine speed waveform

i am fitting the epas system from an mgtf 2003 into another car and am having problems with it enabling. i think the problem is with the engine speed signal i am sending the ecu.does anyone know what waveform/signal type the engine ecu sends to the epas ecu. i currently have it connected to my tacho line but the warning lamp refuses to go off and there is no assistance at rest.

please help

d siepka

I think the epas signal comes from the speedo not the engine ecu - maybe this is where it is getting confused. No Idea of the waveform shape though - try contacting Deiter if you can find him on another thread, surprised he hasn't popped up yet....:-)

to generate the speed input i have a screw in type transducer , this would normally feed both the epas and the speedo but mine only feeds the epas(i have a different speedo fitted on it's own transducer).

the wiring diagram shows the engine speed signal coming from the main engine ecu.

how do you search for a member ?

d siepka

the ecu is run on the tacho output (black with a white stripe, or the other way around). I think this signal is a clone of the signal used to drive the coil, I assume that means it is a square wave with a constant mark and variable space ratio, two rising edges per revolution.
Will Munns

someone will know for sure soon :)

Dieter, Hersfeld, Hesse,
...His website may have it somewhere.

Pre-2000 Model year MGFs used a Reed-switch generated signal from the speedo - which was mechanically driven and resulted in a square wave-formed signal.

Post 2000MY cars use an electronic speedo, with an electronic sender mounted on the gearbox. I *suspect* that this results in a square wave form signal too - but I am not sure...?

Darren, are you using a compatible signal generator for your EPAS installation?
Rob Bell

Nope Rob, that's for the speed sensor, the RPM comes directly from the ECU
Will Munns

Rob Bell

Did a simple NE555 circuit many years ago for my "F".
Simply added the 10-15Hz pulses from that gadget over the ones comming from the reed relay. It seemed not to matter if they "collided" as the car came up to speed.Probably all pulses was integrated and smoothed for the EPAS electronics to determine the actual "fake" speed....
The aim of all this was to get rid of most of the EPAS assistance at the flip of a switch without to much wiring into that system. / Carl
Carl Blom

This thread was discussed between 02/07/2007 and 09/07/2007

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