Here is another wacky thought. what if i put the original ignition control module in the circuit from the ME7? put the ME7 output and input it into pin 5 on the ignition control module as if it was the original hall sender on the distributor than rewire the rest of the module as if it was like OEM because the module is essentially an amplifier and the tach signal does come from the module from the factory and not directly off of the coil.

I attached a little quick dirty diagram of my idea.

Ignition module does not generate voltage, it's only job is to ground or not to ground.
If you want high voltage, you need coil also.
You are making this problem way way more complicated than it really is.

tach is original to the car which is a 1982 audi 4000 FWD non quattro that had a 1.7L 4 cyinder CIS mechanical fuel injected engine. the distributor on the original engine is a simple hall effect sensor thats wired to an ignition control module. the trigger wheel inside the distributor has 4 windows. very basic setup. every time a window opens, spark. 4 window openings per 1 revolution of the distributor. every time a window opens the coil is told to spark. the negative side of the coil is also tied directly to the tach input on the cluster. its clearly not bullshit as you say. its how it worked originally. must not be very well versed on cars from the 1980's as you are modern ones.

How many revolutions does the crankshaft make when the distributor makes 1 revolution?

Back to school boy.

so what your saying is they change the code to send the signal that would normally go to pin 37 and make it go to pin 47 for the MIL light instead? im alright with IDA but im not very well versed with the assembly language for the C167. i cant find where the output to pin 37 actually happens in the code. seems to be very difficult to populate the RAM completely for the 032HS ECU. everything for tuning the ecu is defined in RAM but beyond that nothing pertaining to this is and i have yet to find A2L that indicates anything about this output pin. over all if your right than my initial idea of making some other output thats 12V-0V work for this is still a possibility.

Post your bin, I will do it

i got it to work and this is how i did it. i went through the ME7.5 schematics and found that the evap purge canister which i am not using is output through the same chip as the injectors and has the over all same circuit as the injectors do. than i looked at the other schematic and see that ECU pin 64 is fed processor pin P7.3. so i went into the BIN and searched for every single instance of P7_3 in IDA pro and noted it down. than i looked for every instance of P2_13 which is the original output of the RPM signal on ECU pin 39. i went through the binary and made every reference to P7_3 CC 00 which is NOP or no operation. after that i changed every instance that P2_13 to reference P7_3 instead so the RPM signal code was than output on ECU pin 64 instead of ECU pin 37.

after doing this and loading the file to the ECU i checked pin 64 with my oscilloscope and seen an extremely clean signal but not one strong enough to drive the tach. i took a spare micro relay i had laying there and wired it so that ECU pin 64 triggered the ground side the relay, gave it switched 12v and the through wire is also switched 12v. in the end when pin 64 grounded the relay the relay sends 12V to my tach. works perfectly and matches exactly with what the ECU says in VCDS measuring blocks!

hope this helps someone else avoid buying costly tach converters as it is obviously not necessary. thanks for all the help guys!!


also forgot to mention that i did this mod to the tach board itself in this thread though i dont think its necessary.  https://forum.autosportlabs.com/viewtopic.php?t=3046

So in the end, the info provided to you was correct.
Also a mechanical relay won't work for any period of time, you either need a transistor or a solid state relay.