Tuesday, 19 November 2013

Tacho settings

I had noticed the Rev Counter was reading very low ie 200 RPM and after a while it became apparent that the dip switch settings on the rear of the Tacho were not set right for my LS6 engine ( same for LS1). The ECU I'm using is a Delphi which is the original GM unit.
IT took a while with a few of the Chaps on the Cobra forum chipping in before we got the correct settings.


In the above picture you can see the dip switch which is behind the rubber grommet normally.
The correct settling is as follows  1 off  2 off  3 on  4off.

Settings for Smiths Rev counter link here.  new type

older type here  both supplied  by Alan :)

Happy Jim's Technical info on it
The number of crankshaft medium resolution pulses (24x pulses) to hold the tacho output high (should match {G1205} "Tacho Pulses Low").

The number of output pulses P is calculated as P=24/(N*2) where N is the value of this calibration.

Sample values for this calibration:
For 12 pulses, use N= 1
For 6 pulses, use N= 2
For 4 pulses, use N= 3
For 3 pulses, use N= 4
For 2 pulses, use N= 6
For 1 pulse, use N=12


 answer = output is 2 pulses per Rev.        ..................Switch 1 off Switch 2 off

Switch 3  in the on position...... as it appears the ECU needs a resistive load to 12v, turning on switch 3 achieves this.

Switch 4 is for calibration only hence stays in the off position.


Mac Stowt uses the above settings on his LS2 engine setup as well.


Another wee snag sorted with the help of the Cobra club lads :)


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