I posted this question here because I figure some of you have scrapped the stock instrument cluster in favor of other gauge setups ...

My friend is making a tachometer for his 93 civic cx with a 95 b18c1 conversion. The ECU is the stock unit from a 95 gsr.

So, here's the question ... what is the form of the signal coming out of the tach wire out of the ECU? Wave shape (sin or square wave), whether it's voltage or current coming out of the ecu, and how does the signal behave (I.E. increase in voltage with increase in RPM, decrease in voltage with increase in RPM).

Thanks for the help or any leads

 

I never looked at the tach sig going to the OEM instrument cluster, but I do know that the Engine RPM, and vehicle speed sensors send a square wave to the ECU that has a frequency proportional to the speed. I "think" on my car the engine speed is a 0 to 5v square wave and the vehicle speed is a 0 to 12v square wave.

 

borrow an osciliscope from someone and check it out.

 

sounds good Thanks for the help. I'll see if I can get an oscilloscope to check the raw and processed signals.