Autosport Labs

Two quick questions...

Does the tach out on the MJ unit give a pulse-per-revolution, or a pulse-per-ignition cycle (o.e. 2 per rev for 4 cyl engine)

Whats the voltage on the tach out pin..?

Looking to drive a LM2917 frequency to voltage chip

Cheers

Pete

It's pulse per ignition event. It's a 12V square wave.

Regards,

2 per rotation on a 4 cyl 4 stroke... that works out at 33.3333Hz at 1000RPM. I have used the LM2917 in the bargraph section of my DIY rev counter and it works spot on with the MJLJ tach output.



More info on my rev counter here:

http://www.ford-capri.fsnet.co.uk/white ... ounter.htm

http://www.ford-capri.fsnet.co.uk/white ... xt_gen.htm

Cheers !

Yours was one of the designs I had seen and wanted to know more about.

Do you drive the circuit straight onto the -ve coil input that you have marked on the circuit diagram..?

I'm looking to run 20 leds, so will be driving 2 IC drivers

Thanks

Peter

I was running it before I went MJLJ, so where it says coil LT -ve, wire to MJLJ tach output.

brentp wrote:It's pulse per ignition event. It's a 12V square wave.

Regards,

sorry, to revive this old thread. will the tach output on the MJ be compatible w/ the stock tach lead on the corolla (4age) or will i have to apply the "high-voltage kick back pulse" suggested in the "How To" section under "Installation"?

Use the HV circuit- that's what I have on the MR2. The toyota electronics seems to need this to operate the tach correctly.