# Tach wire?



## Turbo_Pumpkin (Feb 22, 2002)

I'm looking for a good tach signal on a 2003 24V VR. I would prefer one off of the ecu, but I can not find one anywhwere. I've looked at the wiring diagrams in the bentley with no success. Can someone help me out here?


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## BakBer (Apr 19, 2007)

*Re: Tach wire? (Turbo_Pumpkin)*

Why would want a tach signal?
You're going to FAIL at this. The ECU outputs CAN data to the cluster to drive the tach. This is NOT the signal that you want to use. The next problem is if you tap directly off the crank position sensor you will change the resistance in the signal you send to the ECU and you will get a faulty reading.
If anybody knows what to do here chim in!


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## .SLEEPYDUB. (Jul 28, 2005)

*Re: Tach wire? (BakBer)*


_Quote, originally posted by *BakBer* »_
You're going to FAIL

what he said, and trust me, hes tried...a bunch


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## PhReE (Sep 16, 2004)

*Re: Tach wire? (Turbo_Pumpkin)*

What exactly do you want the tach wire for?
Simple answer: There is no 'regular' tach wire you can tap into 
However depending on what you are doing I may have a more useful answer


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## Sosl0w (Aug 21, 2003)

*Re: Tach wire? (PhReE)*

He is installing Racelogic
Here are the instructions from the section i think he is on.

_RACELOGIC Traction Control Manual V3.1
1.6.3 RPM
The Black/White wire (Pin 18) should be connected to a suitable RPM signal. A suitable signal would be either 0 –12 Volts or 0 – 5 Volts.
A suitable RPM signal can be found using any of the following techniques.
• Wiring diagrams - If you have a wiring diagram of the vehicle find an RPM signal.
• *Tachometer – There is usually an RPM signal leading to the back of the dashboard. (Highly Recommended)*
• Coil signal – note, if the car has twin coils the cylinder value in the traction control menu may need to be changed. e.g. 6 Cylinder engine, twin coils, set cylinders to 3 if RPM is picked up off one coil.
• Diagnostic Connector – Some cars have a diagnostic connector, these will normally have a RPM signal. e.g. pin1 on BMW Diagnostic Socket.
• ECU – most cars will have an RPM signal coming out of the ECU.
Once a suitable RPM signal has been found, follow the procedure below for connecting the RPM wire to the RPM input of the traction control.
• Strip back the insulation of the RPM wire exposing the cores.
• Tin the cores using the soldering iron and solder.
• Strip back the insulation of the traction control wire.
• Tin the cores using the soldering iron and solder.
• Solder the traction control Wire to the RPM wire.
• Cover the joint with insulation tape.
The RPM connection can be tested using either a laptop computer or the diagnostic facility on the traction control. This is explained in Section 7.2 Diagnostic Modes._ 


_Modified by Sosl0w at 9:31 PM 4-3-2008_


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## BakBer (Apr 19, 2007)

*Re: Tach wire? (Sosl0w)*

*b/c the cluster on the 24v receives CAN data from the ECU to operate the gauge there is not a hard tach signal you can use with out tapping off the crank position sensor causing the ECU to receive a faulty signal.*
The only place that you are going to be able to get the signal you are looking for is right off the crank position sensor but it may or may not work. Try and see.


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## PhReE (Sep 16, 2004)

*Re: Tach wire? (BakBer)*

Tapping into a coil may work though. All the rest is CAN bus, as stated, which is a digital signal and you can't just tap that like you can a regular analog signal.


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (BakBer)*


_Quote, originally posted by *BakBer* »_*b/c the cluster on the 24v receives CAN data from the ECU to operate the gauge there is not a hard tach signal you can use with out tapping off the crank position sensor causing the ECU to receive a faulty signal.*
The only place that you are going to be able to get the signal you are looking for is right off the crank position sensor but it may or may not work. Try and see.

Already tapped the crank sensor and it didn't work. That's why I made this post....








It reads like 70 RPM's at idle...










_Modified by Turbo_Pumpkin at 8:07 AM 4-4-2008_


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (PhReE)*


_Quote, originally posted by *PhReE* »_Tapping into a coil may work though. All the rest is CAN bus, as stated, which is a digital signal and you can't just tap that like you can a regular analog signal.

MSD tach converter maybe?


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (Sosl0w)*


_Quote, originally posted by *Sosl0w* »_He is installing Racelogic


Way to let the cat outta the bag!







At least it's your car!


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## BakBer (Apr 19, 2007)

*Re: Tach wire? (Turbo_Pumpkin)*


_Quote, originally posted by *Turbo_Pumpkin* »_
MSD tach converter maybe? 

maybe...


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## Sosl0w (Aug 21, 2003)

*Re: Tach wire? (Turbo_Pumpkin)*


_Quote, originally posted by *Turbo_Pumpkin* »_
Way to let the cat outta the bag!







At least it's your car!









oops


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (Sosl0w)*

I know that I can;t be the first to put racelogic on a 24V... Anyone know if the MSD tach converter will work? I don;t wanna waste the cash if it won't....


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## haenszel (Mar 14, 2004)

*Re: Tach wire? (Turbo_Pumpkin)*

jason, you can borrow my tach converter if you wire it back into my car....... its 4 wires.......


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## vdubturbo (Aug 31, 2001)

*Re: Tach wire? (Turbo_Pumpkin)*


_Quote, originally posted by *Turbo_Pumpkin* »_
Already tapped the crank sensor and it didn't work. That's why I made this post....








It reads like 70 RPM's at idle...









I could have told you that wouldn't work








Try a coil, but you're going to need to tell the racelogic somehow that the "tach" pulse isn't once every 360* or 720*, but some x/6 increment. 
That tach converter might do the trick. Worst case scenario we get a EE off my program to whip up a converter box to read the CAN BUS and generate a pulsetrain.


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (BakBer)*


_Quote, originally posted by *BakBer* »_
You're going to FAIL at this. 

I definitly won't fail at this... You'll see....


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## haenszel (Mar 14, 2004)

*Re: Tach wire? (vdubturbo)*


_Quote, originally posted by *vdubturbo* »_
I could have told you that wouldn't work








Try a coil, but you're going to need to tell the racelogic somehow that the "tach" pulse isn't once every 360* or 720*, but some x/6 increment. 
That tach converter might do the trick. Worst case scenario we get a EE off my program to whip up a converter box to read the CAN BUS and generate a pulsetrain.









stop pretending to be smart. You know you can't make that happen....


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## malezlotko (Nov 27, 2004)

*Re: Tach wire? (haenszel)*

I have never gotten my tach to work with DTA. One thing I will try is using resistors. Like bakber said when you splice into the crank sensor you are spliting the resistance in half.
first thing we need to find out is what kind of signal the actual ECU is reading to determine the speed of the engine. The variable reluctance sensor produces an AC voltage however it does not have an external power supply ie 12v like other sensors in the engine compartment. So the general question is does the ECU distinguish engine speed in terms of resistance or in terms of AC voltage. Never the less when you split the crank sensor into two you would need to stratigize a way to make sure both of those ends are still receiving the same amount of AC voltage to function properly.
Proposal: Measure the amount of AC voltage in the crank sensor signal wire prior to splicing, record this and then play with resistors with trial and error until same AC voltage is acquired after the splice in both of the leads.
-I don't really have the time to do this right now as Im away at school, but I will try this in the end of may.
-on a side note another option, dramatic but doable, is installing a secondary crank positioning sensor. This sensor can be wired to the tach reading. It will not be accurate in terms of TDC and distinguishing compression stoke but that will not be important as its sole function will be to display a tach reading which will be accurate.


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## PhReE (Sep 16, 2004)

*Re: Tach wire? (malezlotko)*

AC voltage consists of 2 things, frequency (oscilation rate) and amplitude (voltage). For example wall power is 60Hz (Freq), ~110v (Amplitude). Dont confuse Amplitude with amps though








Anyways what the CPS is probably reading is the frequency, and prolly doesnt care about the voltage much so long as it is high enough to cause a reading.
You could also tap into the cam position sensor which run either at half or double motor speed, I can't remember right now.


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (PhReE)*


_Quote, originally posted by *PhReE* »_
You could also tap into the cam position sensor which run either at half or double motor speed, I can't remember right now.

Thought about cam sensor... That's a good idea... http://****************.com/smile/emthup.gif


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## BakBer (Apr 19, 2007)

*Re: Tach wire? (Turbo_Pumpkin)*


_Quote, originally posted by *Turbo_Pumpkin* »_
Thought about cam sensor... That's a good idea... http://****************.com/smile/emthup.gif 

The cam position sensor on the 24v is a multi-angle sensor. IE it has 4 sensing points on the cam gear. The sensor takes 4 different readings every 360*
you may try using a resistor on for the signal between the crank position sensor and your new device you're wiring up..try 5.1k


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## vdubturbo (Aug 31, 2001)

*Re: Tach wire? (BakBer)*

This is getting good.


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## Mr. Rictus (Sep 25, 2004)

*Re: Tach wire? (vdubturbo)*


_Quote, originally posted by *vdubturbo* »_This is getting good.









What do you have to contribute?








I know nothing about any of this stuff... reading this is like a whole new world to me.


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## .SLEEPYDUB. (Jul 28, 2005)

*Re: Tach wire? (Mr. Rictus)*

im just ready for them to figure it out so i have a working tach








ill buy a







for whomever figures it out first...we could make this a competition http://****************.com/smile/emthup.gif


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## PhReE (Sep 16, 2004)

*Re: Tach wire? (.SLEEPYDUB.)*

Sleepydub, it shouldnt behard to get your tach working... I think it has been mentioned a few times, you just need to leave the ecu connected enough to provide the tach signal to the cluster. You dont need to worry about hacking the CAN bus signal or anything. Go ask some of the 1.8T BT guys running SEM and see how they are doing it -- theres a lot more 1.8T guys than us so I think you got pretty good chances one of them will know.


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## BakBer (Apr 19, 2007)

*Re: Tach wire? (PhReE)*

The problem isn't finding the signal. The 034 harness uses a splitter to divide the tach signal between the stock ECU and 034 ECU. The 034 steals most of the signal and the stock ECU never receives the signal from the crank position sensor. 034's "solution" is to use a pair of 5.1k resistors in line with the 034 ECU to give more of the signal back to the stock ECU but it doesn't seem to work very well on the 24v VR6 were as other engines too ok with it b/c 1.8t and 12v VR6 owners have a hard tach signal to the cluster and not the CAN bus set up like we do. The 24v ECU is just picky with this issue.


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## need_a_VR6 (May 19, 1999)

*Re: Tach wire? (BakBer)*

You won't be able to share the crank sensor signal without additional circuitry, almost any loading of the stock signal freaks out the ecu. 
Your best bet to get a tach signal is to tap into to one of the coilpacks trigger wires and use that. It's a 0-5v signal that goes high to trigger the coilpack. You'll have to configure the Racelogic system for something stupid like a 4 stroke 1cyl to get it to read correct rpm.


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_You won't be able to share the crank sensor signal without additional circuitry, almost any loading of the stock signal freaks out the ecu. 
Your best bet to get a tach signal is to tap into to one of the coilpacks trigger wires and use that. It's a 0-5v signal that goes high to trigger the coilpack. You'll have to configure the Racelogic system for something stupid like a 4 stroke 1cyl to get it to read correct rpm. 

That's basically what they said at Racelogic: 
_Well the first thing I'd try is the negative side of a coil pack, and then altering the 'Number of Cylinders' field in the TC software so that the RPM values are correctly interpreted.

If no joy there, you might be able to get the signal from CAN and convert it to voltage. We have a product that can do this, but I don't know if we'll have the CAN identifier for RPM._
We'll see.


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## RipCity Euros (Sep 23, 2007)

*Re: Tach wire? (Turbo_Pumpkin)*

F**K CAN-BUS


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## gc (Mar 19, 2000)

*Re: Tach wire? (RipCity Euros)*

You might be able to get a tach signal at the orange 10 pin connector in the intake plenum. I believe that there was a period of time where some but not all systems were using the CAN-BUS and so a discrete RPM signal was sent on the wire that goes from the ECU to pin 9 of that 10 pin terminal.
GC


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (gc)*

I got it all figured out. I pulled a signal from a coil trigger wire, and manipulated the software so that it was accurate. Everything has been up and operational for a couple weeks now.... http://****************.com/smile/emthup.gif


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## illadelph-vr6 (Jul 22, 2008)

*Re: Tach wire? (Turbo_Pumpkin)*

i was wondering if you could tell me where you hooked up the green wire that comes from the tachometer. it would be much appreciated if you could tell me
i got an 04 gti 24v vr6.


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## BakBer (Apr 19, 2007)

*Re: Tach wire? (illadelph-vr6)*


_Quote, originally posted by *illadelph-vr6* »_i was wondering if you could tell me where you hooked up the green wire that comes from the tachometer. it would be much appreciated if you could tell me
i got an 04 gti 24v vr6.

There is no way dude....did you read what this guy had to do?
Sorry..

_Quote, originally posted by *Turbo_Pumpkin* »_I got it all figured out. I pulled a signal from a coil trigger wire, and manipulated the software so that it was accurate. Everything has been up and operational for a couple weeks now.... http://****************.com/smile/emthup.gif


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (BakBer)*


_Quote, originally posted by *BakBer* »_
There is no way dude....did you read what this guy had to do?


There is always a way... Don't just accept defeat. 
Illadelph-vr6,
I sent you a PM on your options... i found a solution for what I needed, but there is a way that you can do what you need to as well...







Just remember that the tach in the cluster has to run on something, and it's not hopes and dreams, it's voltage. It just depends on how hard you want to work to get a tach signal. Good luck... http://****************.com/smile/emthup.gif


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## need_a_VR6 (May 19, 1999)

*Re: Tach wire? (Turbo_Pumpkin)*


_Quote, originally posted by *Turbo_Pumpkin* »_I got it all figured out. I pulled a signal from a coil trigger wire, and manipulated the software so that it was accurate. Everything has been up and operational for a couple weeks now.... http://****************.com/smile/emthup.gif 

Glad you got it working http://****************.com/smile/emthup.gif


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## illadelph-vr6 (Jul 22, 2008)

*Re: Tach wire? (Turbo_Pumpkin)*

its true the you can not edit the tachometer like yours. but ive heard that if you set the tach as 2 cylinder engine instead of the six it fixes that. so where is the the coil wire 1. actuallly where is the ecu cuz ive looked online and they only like to have info on 12v vr6s. :/


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (illadelph-vr6)*


_Quote, originally posted by *illadelph-vr6* »_its true the you can not edit the tachometer like yours. but ive heard that if you set the tach as 2 cylinder engine instead of the six it fixes that. so where is the the coil wire 1. actuallly where is the ecu cuz ive looked online and they only like to have info on 12v vr6s. :/

If you are asking where the ECU is then this may be a bit over your head. I'm not trying to sound like a d*ck, but making a tach wire is gonna be kind of complicated on a can bus car.


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## Turbo_Pumpkin (Feb 22, 2002)

*Re: Tach wire? (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_
Glad you got it working http://****************.com/smile/emthup.gif 

Thanks! So is the owner of the car!


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## oilpangasket (Dec 5, 2007)

*Re: Tach wire? (Turbo_Pumpkin)*

wouldnt someting like this work as well to send a tach signal to your traction control or whatever?
http://www.msextra.com/manuals...s.GIF


_Modified by oilpangasket at 2:50 AM 9-16-2008_


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## koko5869 (Feb 15, 2006)

*Re: Tach wire? (oilpangasket)*

so ill bring an post back to life.....
how was the racelogic?
and most importantly, was it worth the ~grand it cost?
guessing the big power guys would benefit the most with it.
just curious about it all


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## Tor_m (Feb 13, 2010)

Ill bring this one up again to! 
Turbo-pumpkin, did you just splice a trigger for the coil? How was it to manipulate the software? Pretty new using standalone to. 
Maybe there is other solutions now after a couple of years?


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## dubjettaa (Jan 5, 2012)

i know this is old and i too have been trying to do the same damn thing with no luck at all, ecu wont work, cluster wire wont work...if anyone is still watchin this i have the 03 24v gli as well, u said u used a wire of one of the coil packs? could u specify which wire? and what software?


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## dubjettaa (Jan 5, 2012)

someone recommended using one of the 3 lilac wires off the coils to me, is that what you used to get it to work? and i couldnt find any soilid wires but there are 3 larger purple/black ones not sure if those are it


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## Clay.0 (Jan 12, 2005)

I know this thread is old, but when searching I was not able to find any info, so here's what we found...

24v swap into mk3, mk4 ecu and harness spliced into mk3 CE2 wiring.

For the tach signal - Pin 37 of the T121 ECU harness is a green/brown wire that goes to the Orange T10 - pin 9 connector.

In a mk4 this is a signal for the climatronic unit, however when connected to the tach input wire on an OBD2 VR6 mk3, it works perfectly. Does not work with an OBD1 cluster.


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## Dubstuning (Nov 1, 2007)

Clay.0 said:


> I know this thread is old, but when searching I was not able to find any info, so here's what we found...
> 
> 24v swap into mk3, mk4 ecu and harness spliced into mk3 CE2 wiring.
> 
> ...


Works in a corrado. Not the best tach signal but gets the job done.


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