erratic RPM signal

[smidge]

do any of you know exactly how the ST gets its RPM signal? as mine seems to be all over the place... its stable during idle and cruise, but when you nail it and the SC kicks in the revs jump from 9000 to 3000 to 4000 and back flicking all over the place on my display

the actual tach needle is smooth so does that explain anything?

 

[Baz]

do any of you know exactly how the ST gets its RPM signal? as mine seems to be all over the place... its stable during idle and cruise, but when you nail it and the SC kicks in the revs jump from 9000 to 3000 to 4000 and back flicking all over the place on my display

the actual tach needle is smooth so does that explain anything?

Did you tap in to the ecu?

 

[smidge]

yeah wire 39 at the ECU plug, just spliced off it

 

[Baz]

yeah wire 39 at the ECU plug, just spliced off it

HMMMM try the negative connection going to the coil?

 

[Ed]

You have the right line. You just need to filter the signal that is going into your logger. Its picking up noise. The ignition signal and tacho are shared on the ST.

 

[Baz]

You have the right line. You just need to filter the signal that is going into your logger. Its picking up noise. The ignition signal and tacho are shared on the ST.

How does that actually work?

 

[Ed]

The signal comes from the ECU pin to the ignition amp where it then goes to the coil and also to the tacho.

 

[Baz]

The signal comes from the ECU pin to the ignition amp where it then goes to the coil and also to the tacho.

Cool:grinning:

 

[smidge]

You have the right line. You just need to filter the signal that is going into your logger. Its picking up noise. The ignition signal and tacho are shared on the ST.

Ah i see! I need to investigate that AND the earthing of the logger to the other engine sensors using the 5v logic

well let ya's know how i go!