Acceptable Knock? Good Mitigation Strategy?

[CTWhite16Vette]

I did some logs, and on average the pulls are pretty clean, but I'm getting a few spots of low knock retard (.2-.7). The worst KR I've seen so far is 1*. If I'm reading this correctly, the ECM is is pulling exactly 1* of timing in an attempt to reduce knock, right?

I've attaches a screenshot and log for reference.

So far, I've reduced the timing in these load cell areas by 1-2* to see if that helps. I won't have a chance to flash the car and log it tonight, so looking for any other advice or confirmation what I'm doing sounds acceptable here.

Thanks!

[Redline MS]

Knock retard values are what its pulling based on knock....however knock sensors are microphones that "should" pickup the frequency of knock. However over sensitivity (common in the last 8 years) and also other noises can trigger the frequency of knock. Therefore don't get too caught up in the low values in this case. GM most likely didn't calibrate the vehicle past peak cylinder pressure so reducing the spark is not necessarily the correct thing to do....HOWEVER..... if fuel is not up to par it could be knocking but the system is designed to blend into the low octane table at that point.... if you looking at less the one degree I wouldn't sweat it... lots of howevers!

[CTWhite16Vette]

Knock retard values are what its pulling based on knock....however knock sensors are microphones that "should" pickup the frequency of knock. However over sensitivity (common in the last 8 years) and also other noises can trigger the frequency of knock. Therefore don't get too caught up in the low values in this case. GM most likely didn't calibrate the vehicle past peak cylinder pressure so reducing the spark is not necessarily the correct thing to do....HOWEVER..... if fuel is not up to par it could be knocking but the system is designed to blend into the low octane table at that point.... if you looking at less the one degree I wouldn't sweat it... lots of howevers!

Thanks. I should mention the car has a 100% stock tune. I just put LTH and X-Pipe on the car, so I started logging to ensure I don't have any knock.

The factory tune seems to have a ton of timing advance. I was hoping I'd have room to pick up some ponies by adding 2-3* timing to peak cylinder pressure areas, but if I'm knocking there and AFRs aren't bad, I'm guessing that's not gonna happen. 11.8-12.1 AFR should be totally acceptable on these cars, right? If anything I was thinking I may be able to leave it out a bit to 12.2-12.5 being its DI and I'm on 93 oct only out here. Thoughts?

[jtrosky]

I wouldn't worry about KR under 2 degrees at all. My car (2012 Impala with a 3.6L direct-injected V6) regularly sees 6-7 degrees of KR on a 100% stock motor (with 93 octane fuel). Like mentioned above, the computer will automatically reduce timing (via Knock Learn) where it seens KR - but it only does that with KR over a certan threshold, which you probably aren't even reaching (it's set to 1 degree on my car).

I wouldn't worry about the KR that you are seeing at all.

What vehicle/engine, by the way?

[CTWhite16Vette]

I wouldn't worry about KR under 2 degrees at all. My car (2012 Impala with a 3.6L direct-injected V6) regularly sees 6-7 degrees of KR on a 100% stock motor (with 93 octane fuel). Like mentioned above, the computer will automatically reduce timing (via Knock Learn) where it seens KR - but it only does that with KR over a certan threshold, which you probably aren't even reaching (it's set to 1 degree on my car).

I wouldn't worry about the KR that you are seeing at all.

What vehicle/engine, by the way?

2016 2LT Z51 Stingray - stock 6.2L LT1 engine

[sssnake]

Is it just me or does there seem to be more knock on the DI engines? Every log file of stock tunes I have looked at on DI engines has had knock.

[Higgs Boson]

Is it just me or does there seem to be more knock on the DI engines? Every log file of stock tunes I have looked at on DI engines has had knock.

It depends on what you're logging. Total Knock retard or Knock retard. It's not the DI engine, it's the E92 preventing you from spraying into spark so it retards it or it's just TM.

[jtrosky]

I too have noticed frequent, repeated KR on my 2012 Impala DI engine. However, it is a V6 and FWD with a different ECM (E39). In my case, the Knock Retard and Total Retard are always the same, so it's not Burst Knock or anything like that (in fact, burst knock is disabled on my tune, both in stock form and my custom tune).

I'll see up to 5 degrees of KR regularly and repeatedly (and up to 9 or 10 degrees at times) - even with the stock tune - whereas it seems you rarely see more than 1 degree of KR on non-DI engines.

What really strange is that when I see KR on my car, it doesn't actually reduce the timing - EVER. Not sure if this is just an HPTuner software issue or what... Since I never hear any knock whatsoever, I've learned to try and not pay so much attention to it. :-) I have a feeling that the knock sensors are just overly sensitive.

[marksstingray]

after
I installed my supercharger I was seeing some knock 1-2 especially up top even with 10 degrees of timing but it was not pulling timing so it must have been under some threshold of acceptability. Running 91 pure gas. Now with methanol and 16-17 degrees of timing I see zero knock ever. This leads me to believe there is something there not just oversensitive sensors as it went away with the addition of methanol to the system.

[Higgs Boson]

after
I installed my supercharger I was seeing some knock 1-2 especially up top even with 10 degrees of timing but it was not pulling timing so it must have been under some threshold of acceptability. Running 91 pure gas. Now with methanol and 16-17 degrees of timing I see zero knock ever. This leads me to believe there is something there not just oversensitive sensors as it went away with the addition of methanol to the system.

It pulls timing when it thinks your pulse width is too high and you don't have time to complete injection before spark. Adding meth should lower pulse width when done right.

[marksstingray]

It pulls timing when it thinks your pulse width is too high and you don't have time to complete injection before spark. Adding meth should lower pulse width when done right.

Yes it went form 6ms without meth to 5 ms with meth.