knock sensors

[stevnoof]

can turning traction/advance trac on or off have an effect on how much knock your seeing and how much timing advance you have?

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[ahl395]

Nope, no correlation between the two.

Timing will advance if no knock is seen (up to a certain amount). Knock sensors "listen" for knock or pre-detonation from the engine and will retard timing as necessary until it goes away.

Traction control/Advance trac simply monitors individual wheel speed and watches for major differences between them, and will reduce power until they are equal again. Simplified explanation but basically the way it works.

 

[GTBOB]

This is correct ^^^^ But something to consider...

If the nannies are turned on, you are more susceptible to wheel hop oscillation due to the system intervening abruptly. This "rattling/chattering" will cause the sensors to pick up this false knock. Overall timing will be pulled back.

 

[Grimace427]

This is correct ^^^^ But something to consider...

If the nannies are turned on, you are more susceptible to wheel hop oscillation due to the system intervening abruptly. This "rattling/chattering" will cause the sensors to pick up this false knock. Overall timing will be pulled back.

If the traction/stability control is actively trying to stop wheelspin it won't allow WOT anyway so max timing isn't a priority.

 

[markmurfie]

don't think of timing in max and min terms. There is only the correct timing everything else is wrong. If its too high or too low you are not at the correct spark advance. This makes reading logs much easier.

The knock sensors job is to give a feedback loop to the spark advance telling it its too high or too low. Even if it does a horrible job at that sometimes, thats its purpose. As monitoring spark plug ionization gets better, knock sensors should become less and less of a source of head ache in the future.

Traction control and other limiters can use fuel cuts, spark cuts, upshifts in an auto, and/ or throttle cuts to reduce power. None of which should cause knock sensor activity as the knock advance is disabled in these modes, knock is still sensed, but should not happen as the engine isn't being pushed to the borderline.

An unexpected drop in spark is usually correlated with a spark source or knock sensor activity to determine why it happened.

In short: If you still have positive knock sensor activity or it gets worst in a traction control event its most likely false. If positive knock goes away its most likely real.

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