moosestang

I was data logging today and noticed the spark adder dmr was showing -3 when my tires started spinning in 2nd gear. I was only at 56% throttle and 3400 rpms.

So my question for you tuning experts is can wheel spin cause false spark knock? I wouldn't expect any knock when your tires are spinning, because load is less.

I did google false knock caused by wheel spin and got a few hits, but nothing conclusive. My theory is the vibration from the tires is transmitting through the drive line to the engine. I did a test on my dirt road and could not duplicated the knock readings even giving it 80% throttle. There's very little vibration from spinning my tires on the dirt. it will dig in and get sidewayz, but it's like spinning on a wet road.

Cobrakev

My guess, but dont know 100%. If the computer detects one wheel spinning faster, the TC will start to try and fix the wheel spin. (This is where my guess starts.) Cutting back cylinder's(spark) is a way for the TC to fix wheel spin. Is this what you were seeing during the data logging? Just guessing.......

moosestang

I don't think so. Traction control was off.

siggyfreud

Can you see the actual knock counter in your datalog?

moosestang

I was datalogging the spark adder array, so not the actual knock count.

siggyfreud

Would just be curious to know if you're actually getting knock counts during the burnout. It would make sense that something is vibrating in a manner to trigger the knock sensor, but would be good to validate by actually seeing the knock count rise.

moosestang

I'll do another datalog and figure out which pid is the actual knock sensor count. I'm going to datalog 1st gear and stand on the gas pedal from a stop! This should be interesting, I've never even given it full throttle in first on the street.

siggyfreud

If it's anything like my car, you'll hit the rev limiter in about half a second.

AMWill

Heavy vibrations can trigger false knock easier then you think. Even radical naturally aspirated camshafts have been known to trigger false knock during low cylinder air-mass/ low rpm cruise. I don't see any reason why a light throttle burnout couldn't do the same thing. It's possible your Mustang had a slight wheel hope or just any other vibrations during a burnout causing the knock sensors to pull timing.

A good test would be to go WOT up hill in 3rd gear so there's no wheel spin and heavy load. If you experience any pulled timing then back out right away. If not, then you were definitely having false knock.

Hope this helps!

Shane

moosestang

Thanks Shane, It didn't pull any timing at full throttle in 3rd.

I couldn't get it to knock again by spinning the tires. Must have been a fluke.