sjanes

I have a DL-1 data logger in my track car (87 911) and want to feed a signal for rpm into it. Is there a wire on back of the tach that I can tap into?

The DL-1 has analog inputs that can take 12v input for signals.

Lorenfb

Use the black & violet wire on the tach, which is the wire from the DME pin 21.
This signal is a 0-12 volt square wave (1000 RPM = 20ms = 50HZ).

hmd

I have a DL-1 and just take the signal from the back of the tacho and put it in the low voltage rpm input on the DL-1.

EDIT: works really well.