Speedo interface info
Discussion
Delving into the inards of the dash of my Griff
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...

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.
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 ?
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