Need help with tach signal for Audi 4.2 V8

Installation notes, Data Inputs, Tach Hook up and Software Tips
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desperado
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Need help with tach signal for Audi 4.2 V8

Postby desperado » Sun Oct 19, 2008 1:22 pm

I need to hook up tach signal on a new (2009) Audi R8. This car has TWO Bosch ECUs, one on each side of the engine bay. The owner of the car doesn't want to start tearing the car apart, cutting into the harnesses or poking holes in the firewall. Does anyone know if there is an RPM signal available on the OBDII connector, or elsewhere inside the cabin?

This should be same/similar for other Audi's with the high-perf 4.2 V8 such as RS4, etc.

Thanks in advance for your help!
Last edited by desperado on Mon Oct 20, 2008 6:17 pm, edited 1 time in total.

i_anderson
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Postby i_anderson » Mon Oct 20, 2008 10:58 am

Hi,

I went thru' similar pain when finding throttle position and RPM for my car (See thread "Ferrari 360 install notes" herein for the somewhat sordid details.....)

In summary, you need the pinout of the ECU's and the WSM. Given those (which are hopefully not state secrets the way they are on Ferrari!) it should be pretty easy to find the relevant wire(s) somewhere close to the SU - I was *amazed* at how many places the RPM (and TP) signals got sent - We found 'em running right thru the "transmission tunnel" to which the SU is mounted. Tapped into 'em with "suitcase" connectors and voila!

HTH, good luck,
Cheers,
Ian

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desperado
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Audi ECU

Postby desperado » Mon Oct 20, 2008 6:15 pm

Hey Ian,

Thanks for the reply!

I have the service manual with wiring diagrams, which includes the ECU and OBDII connector physical diagrams. However, there is not any description of what the wires DO, only where they GO. For example, a wire may go from pin X on connector A to pin Y on connector B. If there are a dozen wires from one module to another module, there is not any way that I've found to differentiate one from another unless you already know the function of the module (except for power and ground which are identified). The two ECUs have about 156 wires EACH! :(

Any idea where we would get a description of the pinouts, not just the wire gauge and destination?

Bill

i_anderson
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Re: Audi ECU

Postby i_anderson » Mon Oct 20, 2008 11:38 pm

desperado wrote:... However, there is not any description of what the wires DO, only where they GO.....Any idea where we would get a description of the pinouts....


Hmm - Remembering back to my install, the "key" was the "A0" sized blueprint from Bosch of the ECU - It's the only one that contained the "description" of each pin - The WSM simply shows, as you say, the connectors and where they go.

Now, obtaining this blueprint was, in my case at least, a *major* PITA - I have no idea if Audi also likes to keep this stuff "secret" - You may need to "bribe" your friendly local service tech (!) in order to liberate the necessary information.......

Cheers,
Ian

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Postby Track Systems » Tue Oct 21, 2008 10:17 am

You can always tap the coil-on-plug or fuel injector signal for any cylinder and select the 'Coil' setting in the TraqSync.
Data Made Easy

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desperado
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Postby desperado » Tue Oct 21, 2008 5:24 pm

Thanks, I agree this could work if we were willing to tear into the car.

... doesn't want to start tearing the car apart, cutting into the harnesses or poking holes in the firewall
desperado

09 R8 4.2 manual / 08 TT 3.2 S-tronic


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