Knock Knock Knock!

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Mada51589
Posts: 25
Joined: Thu Nov 09, 2017 3:13 pm

Knock Knock Knock!

Post by Mada51589 »

Although this ins't really a question about KTuner Hardware/Software, I figured I'd reach out and maybe others could pitch in. I've searched through many different forums and i've found little to no info regarding knock or shift knock that even remotely applies to my application.

I've been fine tuning my car for the past few months and I can't get past this. I know that some/little knock is normal, not ideal, but normal... I'm only getting a knock count during upshifts, not while idling or cruising or downshifting. NOTE: This is on a '12 TL FWD AT (Using paddle shifters/SHIFTRONIC). It really only occurs between 2nd - 3rd gear and 3rd - 4th gear between 2500 - 3500rpms. I'd have to check my datalogs again for the duty cycle %, but I'd say it's around medium load (between low and high load, and not WOT), and around 35% TP. If I lightly let off the pedal just a little to lower the TP to around 20% before the shift, it doesn't get a knock count. It doesn't get a knock count when in high load range and WOT (without letting off of the gas pedal).

I want to say that this is "normal", because after I pulled up old datalogs from when I was using the "Tune 1" pre-made tune, I found knocks in the same band range, just occurring more often. All of the tunes I've built so far have been based off of "Tune 1", as I have the exhaust mods its based on, with intake mods that are requiring fuel.

So, question is, is getting a knock count within these parameters okay or is there something I should continue adjusting?
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Knock Knock Knock!

Post by KTuner »

Rely more on the knock control, which is a better indication of what's happening regarding "noise" related to the knock sensor. If it's shooting up you can likely use some fine tuning, however it's supposed to move up and down as needed all the time.
Mada51589
Posts: 25
Joined: Thu Nov 09, 2017 3:13 pm

Re: Knock Knock Knock!

Post by Mada51589 »

Ok so I started paying attention to knock control and it was averaging around 0.11. Now, I advanced timing a little more and it’s averaging around 0.5 with much lower knock counts. Do I proceed with the advancement or go back in retard with less knock control? Which is worse, lower or higher kctrl?
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Knock Knock Knock!

Post by KTuner »

It's a catch 22. Do you know how low it would have gotten with the lower ignition? If .11 was it, then you have to weigh the actual ignition values from each run with .11 and .5 to see what's giving you the best repeatable results. Welcome to tuning.
Mada51589
Posts: 25
Joined: Thu Nov 09, 2017 3:13 pm

Re: Knock Knock Knock!

Post by Mada51589 »

I think I fully understand now. This is my understanding of what knock control means and how it's used opposed to knock counts:

The knock control can be any value, the higher the value = the more retard is applied when a "true" knock occurs (the knock control value is technically the percentage of the knock limitation table value used), but the frequency of when retard is actually applied is just as, if not more, important.

The knock control value goes down over the course of the trip IF the amount of true knocks decreases - and/or - the amount of retard needed lowers. - i.e. During startup, knocks(specifically true knocks) will occur more often and more retard will be required, causing the knock control to climb, but less true knocks will occur and/or the amount of retard required will decrease over time, causing the knock control to go down.

If the knock control value continues to increase, or sits steady at a high number without going down, or at least fluctuate up and down, then there's a cause for concern in the ignition parameters in your tune and you'd need to lower timing.

I noticed my KCtrl going from 0.16 down to 0.0 towards the end of my drive to/from work (1 hour 30 minute drive, mostly interstate&highway), which helped me make sense of your last post and how Knock control is more reliable than knock counts.

Please correct me if I'm wrong.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Knock Knock Knock!

Post by KTuner »

Knock control multiplied by the knock retard table gives a final knock retard value, so both knock control value and knock retard value are good to watch. While watching knock control in a datalog if you see it shoot up the map trace can be used to show the location specifically.

Knock control isn't based directly on knock counts, but on engine noise via the knock sensor and sensitivity settings within the ECU.
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