Knock problem 1.8 T APY with E85

EMU BLACK / CLASSIC
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Hi everyone,
I’m asking for help with an issue I’ve been dealing with for a long time and haven’t been able to resolve. The car is an Audi TT MK1 with an APY engine, various track day modifications, running on E85 fuel, and using an ECUMaster Black ECU.

The engine is semi-new and was remapped in December 2021. In February 2022, after the initial break-in period, it was used for some track testing. In the days following, while reviewing the logs, I noticed that from minute 51:35 onward, the car started detecting knock almost continuously, while the values were correct in the first part of the recording.

After that session, due to personal health issues, the car was left unused for two years. I picked it back up a few months ago (there should still be an old post from me about this same issue), and the car is still showing the same apparent knock issue, almost constantly. I’ve checked the ground connections, rechecked the ECU wiring, and everything seems to be in order.

Last week, I tested the car with a new tuner (specialized in Audi and BMW), not the one who mapped the car. While monitoring the engine using knock detection headphones during a 10 km drive, he confirmed that the engine does not have a mechanical knock issue. We also tried replacing both knock sensors with spares from the shop, but the ECU is still detecting knock on Knock Level channel

Now that I know it’s not mechanical knock, and having rechecked all the wiring to the ECU, I can’t figure out what might have happened at minute 51:35 of the first log session. Any help would be greatly appreciated. I’d like to understand whether other values also started to behave abnormally at the same time as the knock signal, or whether it could be an electrical issue, or something else entirely. What’s certain is that for the first 50 minutes, the logs looked perfectly fine — then something changed.

Any help would be really appreciated, thanks

Attached are:

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Here’s the map

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@FloorItGarage sorry to bother you, but maybe you have some hints. Thanks

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My $0.02, it looks like the shield on the knock sensor wiring failed. tune didn’t change, and if it’s not actually knocking then something is inducing voltage into the knock input.
I don’t see any noise in the other sensors that share sensor ground.

What kind of knock sensor are you using?

I’d suggest trying the 2nd harmonic frequency (14.2k ish, assuming its an 81mm bore) in the future but looking at the voltage the knock sensor is reporting, I don’t think it’s that either…

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Ahahah, sorry for the ‘call’ but I needed your advice!

Stock 3 wires knock sensors and stock wires from sensors to ECU.

Since I’ve already tried changing the sensor, and nothing changed, I think the problem could be in the wires (or in the ECU itself, but I hope not).

Yes, 81mm bore.

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all good, happy to help haha

3 wire sensor is great for this actually, you can continuity test the shield as well as both the signal and sensor ground wires to the ecu.
and then in worst case I’d try running new wiring from sensor to ECU just to rule it out