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Tach Signal problem... losing my mind.

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Volkswagen 2.0T TSI (CCTA engine). Car makes 400whp all day without issues. Good solid running car, only 50,000KMS on it. I've now added a 5th injector and I'm using a Torqbyte CM5-LT to control it. My issue is i can not get a clean tach signal to the unit. I've wired it a million different configuration to ensure there's no noise from other wires. In fact I have it wired in it's simplest form right now for testing (in the engine bay, short wires and simple, power, ground, switched, and tach signal wired).

I've tried pulling tach signal off multiple coils, and injectors, and have the signal currently pulled 6" away from the ECU to eliminate chances of noise in the harness. Ground is good, but I've also moved it many times to other very good grounding points for testing.

I've tested the unit (datalogged in the software) on my Audi 2.0T FSI and it works exactly as it should, so it's not the unit, software. I've disconnected the stereo gear in the faulty car and there are no other accessories like WOT boxes or anything like that wired into the ignition system. I've also tried the coils, and plugs from my Audi in the faulty car and still no go.

One of the common things that's happening with the faulty car is I have a 95-100% clean signal when I first take the car out for a test drive, after about 10 mins of driving and the car gets up to temp... the tach signal gets progressively worse (datalogging it in the Torqbyte software). This could just be an odd coincidence but it's something I've noticed.

One other weird thing is that when it was wired in the working car the "pulses per revolution" needs to be 0.5 which is what Torqbyte states it should be. When I wired to the faulty car I need to switch the "pulses per revolution" to 2.0 in order to get the output (what's displaying in the software) to match what the actual RPM is.

I can't tune this car any further at this point as the signal is so erratic. I require RPM/MAP for the fuel table. So, I'm reaching out for any out of the ordinary issues any of you may have seen with logging RPM.

Unfortunately I do not have an oscilloscope, or do I know anyone who has one as I tried to find one.

Any ideas, or things to check would be greatly appreciated.

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