Tach Sensor wire

yowsaboss

Member
Country flag
Wanting to install a small round 2.5" tach on my 2015 Cup. Typically these aftermarket tachs have a green wire that's the sensor or trigger wire. The tach is powered up and properly wired, except it doesn't read rpm. I tried to connect the green wire to the coil ground as suggested for typical installations, but that's not working. I'm sure someone out there has done this, I'm not the only one dissatisfied with the pathetic OEM dash RPM readout.

I know the tach works, or at least functions, because the needle swings up to 10K rpm when I power it up, then swings back to zero.

Do I need to tap into a trigger wire coming out of the ECU? Pull the dash and tap into the wire that actuates the normal RPM display? If so, which wire? The service manual wiring diagram is equally pathetic, doesn't actually identify the connections to the dash- the various parts of the display, like coolant temperature, etc. So if I pull the dash or the ECU I'll have no idea and no way of determining which of those dozens of wires I'm looking for.
 

Icehax

Member
Country flag
Did you ever figure it out? Im trying to build an rpm and afr logger and i just cant find that damn rpm signal cable lol
 
Did you ever figure it out? Im trying to build an rpm and afr logger and i just cant find that damn rpm signal cable lol
if you don't access the rpm signal or info from ECU to dashboard, you can access insead the ignition or injection signal. It is also periodic, based precisely on rpm
 

yowsaboss

Member
Country flag
Did you ever figure it out? Im trying to build an rpm and afr logger and i just cant find that damn rpm signal cable lol
I did not. There must be hundreds of people out there who know this. I'd like to install a real tach (track bike)
 

Fasteddy

Member
Country flag
Did you ever figure it out? Im trying to build an rpm and afr logger and i just cant find that damn rpm signal cable lol
The MOSFET inputs of the Arduino can be triggered by wrapping 10 or 15 turns of wire around the spark wire BTW...
 

Icehax

Member
Country flag
The MOSFET inputs of the Arduino can be triggered by wrapping 10 or 15 turns of wire around the spark wire BTW...
that's good to know, i resorted to just splitting the ignition coil cable open and running the 12v through a voltage divider. i will test my code this weekend as i dont have access to the bike during the weekdays unfortunately :(
 

sumit9246

New Member
Country flag
that's good to know, i resorted to just splitting the ignition coil cable open and running the 12v through a voltage divider. i will test my code this weekend as i dont have access to the bike during the weekdays unfortunately :(
Did you test it? I'm trying to make a sequential shift light for my Ktm rc 200. I'm looking for an rpm signal source too. Please help me out brother! @Fasteddy said there's a black wire connecting the console and ECU at pin 8 and 2 respectively. Please try it if you can and post the results here
 

Icehax

Member
Country flag
Did you test it? I'm trying to make a sequential shift light for my Ktm rc 200. I'm looking for an rpm signal source too. Please help me out brother! @Fasteddy said there's a black wire connecting the console and ECU at pin 8 and 2 respectively. Please try it if you can and post the results here
I spliced the ignition wires and connected a multimeter and was able to detect a variable voltage. I have not tried connecting it to the arduino yet but ideally the signal should resemble a 12v square wave and thus should be fairly easy to pick up with the arduino and the right voltage divider. I have no use to the ecu pins since I have a newer gen 2 RC with updated wiring.
 

sumit9246

New Member
Country flag
I spliced the ignition wires and connected a multimeter and was able to detect a variable voltage. I have not tried connecting it to the arduino yet but ideally the signal should resemble a 12v square wave and thus should be fairly easy to pick up with the arduino and the right voltage divider. I have no use to the ecu pins since I have a newer gen 2 RC with updated wiring.
Thank you for lighting fast replies. A dumb question..
When you say ignition wires, which specific wire are you talking about? the Positive/negative wire on the ignition coil? You must not be talking about the spark plug cable right? coz that pulses above 20k volts.
 

Icehax

Member
Country flag
Thank you for lighting fast replies. A dumb question..
When you say ignition wires, which specific wire are you talking about? the Positive/negative wire on the ignition coil? You must not be talking about the spark plug cable right? coz that pulses above 20k volts.
I am talking about the two wires that feed the ignition coil (input), those are 12v signals. They have a white plug iirc.
 
Top