Looking for info on knock control

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ViperX
Posts: 3
Joined: Tue Jun 01, 2021 12:46 am

Looking for info on knock control

Post by ViperX »

Car is a 2012 V6-6MT. PCD, jpipe, exhaust, intake and P2R plenum spacer.
I have been having an issue with some pretty wild knock control swings. Running 91, I can get knock control down between 0.0 and 0.2 but it will jump up to ~1.4 almost at random. Typically the jump happens in second gear at around 30%-40%tpscmd. On A long enough drive I can get it to cycle between around .4 to 1.4. Fuel brand and octane make no difference, 87, 91 or 93 it will still jump up to 1.4.

Primary question is; is knock control adjusted strictly based on noise from the knock sensor or is it adjusted more preventatively. Basically, will the ECU adjust KC up as a preventative measure if it sees a value it doesn't like from some other sensor?

Thanks for any input.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Looking for info on knock control

Post by KTuner »

Knock control moves based on fuel quality and environmental factors.
ViperX
Posts: 3
Joined: Tue Jun 01, 2021 12:46 am

Re: Looking for info on knock control

Post by ViperX »

Are you able to elaborate at all on the environmental factors?

My intake is modified stock, so stock MAF housing. LTFTs having been becoming increasingly negative, so I replaced the MAF. Trims returned to a more normal level and this helped the Kcntrl issue some. Adjusting the maf scale to keep LTFTs at cruise slightly positive(~1%) helped even more. So far I have found trims and ambient temperature to have a very large affect on Kcntrl.

Also just to verify, would I be correct in thinking, actual knock would be visible in a log as an increase Kcntrl and also a corresponding increase in knock count? I know knock count is part of the misfire monitor but it logs all abnormal combustion events correct?

The help docs on your site say ignition timing is calculated as: ignition map + knock limit - knock retard * knock control, then the lower of the 2 between the calculated number and the ignition map is used. There appears to be another factor at play. I have logs, taken after a warm restart, where Kcntrl is recorded as 0.22 but the actual knock retard being applied is more like kcntrl = 1. Both IAT and ECT were not at a temperature that should have applied any ignition retard. My initial thought was my Ktuner failed to log Kcntrl properly but later confirmed that this wasn't the case.
On other forums, some have asserted that the Honda ECUs retard timing to reduce catalyst temperatures, can you comment on this?

Final question, I have been able to play with a few of the 8th gen V6 Accords now. The highest Kcntrl I have seen is 1.44 is this the upper limit?

Thanks for your time.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Looking for info on knock control

Post by KTuner »

If the ECU receives noise that meets the sensitivity threshold it will adjust knock control. You said seemingly random, but then go on to give a pretty specific set of circumstances. You have map trace and datalogging to help you solve possibly having too much ignition or not enough fuel in some part of the map. Hope you get it!
ViperX
Posts: 3
Joined: Tue Jun 01, 2021 12:46 am

Re: Looking for info on knock control

Post by ViperX »

Perhaps I should have described it as intermittent.
While it does indeed happen at a consistent, albeit rather large portion of the ignition map(stock ign maps), whether it happens at all on any given drive appears random. I could drive for an hour today and kcntrl will stay 0.20 or lower, I could make the exact same trip tomorrow and kcntrl will jump to 1.40 20 minutes in(all highway no city). Higher ambient temperatures appear to increase the probability of it happening.

I suspect it is a mechanical issue, knowing that Kcntrl only moves in response to knock sensor noise helps to narrow things down a great deal. I feel the issue is happening over too large of a portion of the ignition map and breadth of timings for it to be a timing issue. Logged AFRs look fine, issue also strictly occurs in closed loop.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: Looking for info on knock control

Post by KTuner »

It could very well be. Hopefully you're able to pinpoint it.
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