Haltech Haltech tacho ouput
Thread Starter
Joined: Mar 2001
Posts: 266
Likes: 2
From: San Francisco, California
Haltech tacho ouput
Ok I'm probably over thinking this but anyway. How does the Haltech tach ouput work?
I am upgrading my E6K to a Haltech Sprint RE and redoing the wiring. Now I have a Racepak IQ3 data logger/dash so no stock tachometer whatsoever. Right now it's hooked up to the trailing coil - yellow/blue wire and works just fine. Racepak gets the tach signal, rpms displayed, shift lights works, data logs good.
Now since the Sprint RE has CAN BUS there are couple ways I can get the RPMs signal on the Racepak dash when I upgrade. The easiest being I remove the wire hooked up to the trailing coil and just get the RPMs right over the CAN BUS. Or two, I can leave the wire as is or three, I can hook up the Racepak wire to the TACH ouput on the Haltech.
So this got me wondering about how the Haltech gets the RPM signal in the first place and outputs it to the Tacho wire output of the Haltech. Is the signal derived from the Crank Angle Sensor and just measures the rotation and the Haltech converts it internally to a RPM value? Or is it actually using the ouput to the ignition coils and that is the RPM value?
Reason I ask is I am probably going to use BOTH the CANBUS RPM value and the Trailing Coil output and can data log both! In theory, I should be able to use this as a diagnostic aid in case I ever have a no spark problem (which will probably be very rare). One RPM value is what the Haltech "sees" while the other is the actual coil "ouput" value. They should be pretty much identical on in the logs right, and if not I might have a problem - like sloppy CAS or Coils taking a bit longer to fire?
Yeah I know - I'm overthinking it but it's not much work to hook the single wire up when I got it all apart.
By the way this is on a S4 RX-7.
I am upgrading my E6K to a Haltech Sprint RE and redoing the wiring. Now I have a Racepak IQ3 data logger/dash so no stock tachometer whatsoever. Right now it's hooked up to the trailing coil - yellow/blue wire and works just fine. Racepak gets the tach signal, rpms displayed, shift lights works, data logs good.
Now since the Sprint RE has CAN BUS there are couple ways I can get the RPMs signal on the Racepak dash when I upgrade. The easiest being I remove the wire hooked up to the trailing coil and just get the RPMs right over the CAN BUS. Or two, I can leave the wire as is or three, I can hook up the Racepak wire to the TACH ouput on the Haltech.
So this got me wondering about how the Haltech gets the RPM signal in the first place and outputs it to the Tacho wire output of the Haltech. Is the signal derived from the Crank Angle Sensor and just measures the rotation and the Haltech converts it internally to a RPM value? Or is it actually using the ouput to the ignition coils and that is the RPM value?
Reason I ask is I am probably going to use BOTH the CANBUS RPM value and the Trailing Coil output and can data log both! In theory, I should be able to use this as a diagnostic aid in case I ever have a no spark problem (which will probably be very rare). One RPM value is what the Haltech "sees" while the other is the actual coil "ouput" value. They should be pretty much identical on in the logs right, and if not I might have a problem - like sloppy CAS or Coils taking a bit longer to fire?
Yeah I know - I'm overthinking it but it's not much work to hook the single wire up when I got it all apart.
By the way this is on a S4 RX-7.
Right now you're getting a signal generated by the trailing coil. You're right in all of your assumptions. Not sure you can have two RPM channels, but why not try? Worst case you would name the 2nd RPM channel something else, like wheelspeed or driveshaft speed.
Since you're upgrading the ECU, now is a great time to go to the FFE crank trigger kit and eliminate all possibility of the sloppy CAS.
Since you're upgrading the ECU, now is a great time to go to the FFE crank trigger kit and eliminate all possibility of the sloppy CAS.
