Speedo interface info

Speedo interface info

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Mr Jenks

Original Poster:

1,206 posts

280 months

Thursday 11th July 2013
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Delving into the inards of the dash of my Griff getmecoat just lately I have discovered a black box lurking behind the radio. It has a label with part no. MO559 on it which is the same as on some Chim`s, a speedo interface box. Can someone tell me what it does? I know there is a speed transducer picking up signals from the prop but I guess these would be a sine wave so does this box convert that into a digital signal, knock off the below zero wave or just split the signal to supply the speed signal to the injection ecu? I may be forced into getting a scope on it at the weekend...

Julesprivate

871 posts

158 months

Friday 12th July 2013
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I believe that's the "Speedometer Calibration Unit" (black box about the size of a fag packet with a white label on)..

It tells the 14CUX when the car drops below ~3mph (or thereabouts) and that in turn activates the stepper motor.


blitzracing

6,412 posts

235 months

Friday 12th July 2013
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It has two basic components- the first clocks the signal rate from the diff sensor and then switches on a basic pulse generator when the input signal is around 3mph. This pulse generator produces a signal that is around 35- 55mph that is then fed into the ECU. Its an all or nothing set up and pretty crude at best.

Mr Jenks

Original Poster:

1,206 posts

280 months

Friday 12th July 2013
quotequote all
blitzracing said:
It has two basic components- the first clocks the signal rate from the diff sensor and then switches on a basic pulse generator when the input signal is around 3mph. This pulse generator produces a signal that is around 35- 55mph that is then fed into the ECU. Its an all or nothing set up and pretty crude at best.
Thats good info, thanks Mark.

I guess then that it has no effect on the speedo pulse signal? The output from the sensor is passed straight through to the speedo head as a standard wave form ?

paulathome

686 posts

233 months

Saturday 13th July 2013
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Yes.
If you look inside the box the speed pulse signal goes straight through without any alterations.
Paul