Repeatable knock at 8200 & 8600 Cylinder 3

FlashPro questions & answers specific to the 2006-2009 (US, UK, Asia) S2000
Post Reply
futureal33
Posts: 3
Joined: Wed Apr 21, 2021 11:28 pm

Repeatable knock at 8200 & 8600 Cylinder 3

Post by futureal33 »

Hi all,

My first post here and looking for some opinions if what I'm seeing is cause for concern.
My tune is not yet finished, but I am now tuning WOT and in particular the 6000+rpm areas.

I am seeing a repeatable knock on cylinder 3 at 8200rpm, and 8600rpm where my knock count increases by 2 each time it passes this rpm but only when in 4th gear. Strangely it doesn't seem to happen in 2nd or 3rd.

Ignition timing is 29degrees and AF is around 13AFR

I haven't yet tried individual cylinder trim on cyl.3 but that was my next plan

I am just trying to get some opinions if knock is likely at that high of an RPM - it seems most people experience high load / low rpm knock
Cheers

*also, for info, iAT was 11c and I am using Shell 99RON fuel - as good as I can get*
EFICU
Posts: 631
Joined: Mon Feb 25, 2019 10:14 pm

Re: Repeatable knock at 8200 & 8600 Cylinder 3

Post by EFICU »

The car experiences more load in fourth, so the knock you see is most likely real. I would remove 2* ignition in those areas and reinspect. It’s common to not see knock in third but get it in fourth, all part of the process sometimes. Keep us in the loop.
futureal33
Posts: 3
Joined: Wed Apr 21, 2021 11:28 pm

Re: Repeatable knock at 8200 & 8600 Cylinder 3

Post by futureal33 »

Thanks for your reply,

So the timing has been reduced from 29 degrees to 27 degrees, but if anything the knock is worse.

I am now seeing a knock count of +10 from a 4th gear pull, but all the knocks start at 8400rpm
AFR has been richened a little to 12.9AFR

I've looked for anything loose which could be giving me false knock, but can't see anything.

Am I right in saying that it shouldn't knock with these settings?
Cheers
EFICU
Posts: 631
Joined: Mon Feb 25, 2019 10:14 pm

Re: Repeatable knock at 8200 & 8600 Cylinder 3

Post by EFICU »

Can you post a datalog showing the knock events and the calibration you’re driving on? That would help to see on our end to try to help. You can always take a bigger swing at the ignition just as a test. Put it down to 20* in that area. If the knock goes away you can always creep back up. From the sound of it, it almost seems like a false knock. But you’re being smart by testing to find the issue if there is one.

Are you tuning with a wideband or the stock sensor?

At 11c (51.8F) you shouldn’t be having any knock when the ignition is set right, so it doesn’t seem IAT compensation is a problem. If the temps were hotter I would say add some compensation in the tables. But at those temps there shouldn’t be any. Are you tuning with the knock control bypassed so the ecu isn’t adding knock retard?

All your engine mounts are stock OEM? You don’t have a “stiffy” engine mount where it bolts from the engine to the strut tower like this one in the link? https://www.carousell.sg/p/honda-s2000- ... 248546852/

Every car is different so it’s hard to make a blanket statement that it shouldn’t knock at these settings. One car might, another may not.

If you can post a datalog and the calibration that would be ideal.
futureal33
Posts: 3
Joined: Wed Apr 21, 2021 11:28 pm

Re: Repeatable knock at 8200 & 8600 Cylinder 3

Post by futureal33 »

Thanks for your reply again :)
I've attached a screenshot of what I'm seeing - this was from a 2nd-4th WOT pull to 9000rpm in each gear - notice the knock count in particular - notice how theres zero count until the very top end of 4th where the cursor is placed.

All the other data is on the screenshot, iAT was a bit warmer today 25c/77f

All my engine mounts are OEM - my only mods are K&N FIPK and a 63mm test pipe. Everything is factory. Its a 2006 UK Spec (AP1 F20c engine) car.

Im using the OEM AFR sensor which is a wideband (drive by wire model) - and is a brand new OEM Denso unit, replaced when I purchased the Hondata a month ago.

I really hope its false knock.... 8600rpm and full load isnt a good place to get a load of knock counts!!
Attachments
hondatascreen.png
hondatascreen.png (317.66 KiB) Viewed 229 times
EFICU
Posts: 631
Joined: Mon Feb 25, 2019 10:14 pm

Re: Repeatable knock at 8200 & 8600 Cylinder 3

Post by EFICU »

futureal33 wrote: Fri Apr 23, 2021 12:50 pm Thanks for your reply again :)
I've attached a screenshot of what I'm seeing - this was from a 2nd-4th WOT pull to 9000rpm in each gear - notice the knock count in particular - notice how theres zero count until the very top end of 4th where the cursor is placed.

All the other data is on the screenshot, iAT was a bit warmer today 25c/77f

All my engine mounts are OEM - my only mods are K&N FIPK and a 63mm test pipe. Everything is factory. Its a 2006 UK Spec (AP1 F20c engine) car.

Im using the OEM AFR sensor which is a wideband (drive by wire model) - and is a brand new OEM Denso unit, replaced when I purchased the Hondata a month ago.

I really hope its false knock.... 8600rpm and full load isnt a good place to get a load of knock counts!!
That helps a little bit, a datalog and calibration helps more, but it's a start. In my thinking, a false knock would most likely show up just as much on your third gear pull as it would on your fourth gear pull. Meaning that a vibration causing a noise would see similar environment to cause the audible noise the knock sensor hears. Hopefully that makes sense, haha. I just mean that an audible noise caused by a vibration or some entity would be caused for third and fourth gear scenarios. I would reduce the timing to 20* around the around the area of knock and reinspect. If the knock goes away in fourth then we know it should be real. Then increase it by 2* until the knock in fourth returns. That is how I would address it if you were my customer, or anyone I normally help on this forum.

25c/77f is the ideal temperature for normal driving. It's right before compensations start to pull for ignition and fuel. So this is a good temp to test everything as you have been.

Yeah the stock sensor converts as wideband, but Hondata says stock sensor isn't accurate enough to fine tune the AFR. You should still be in the ballpark though, and how you're seeing knock in only one place would make me believe the afr isn't impacting the knock event.

The positive side to the knock being at high rpm is you can still drive the car without worrying about knock. The cars that knock like crazy in the normal portions of the tables are the ones that make you nervous. But I know what you mean, knock up top like that is concerning, but at least you can avoid those rpms until you get it sorted.

One thing I noticed in the graphs you posted, you apparently modified the WOT lambda table. The vehicle isn't entering open loop operation during your WOT pulls. I don't think this is impacting the knock, but it is something that should be addressed. If the vehicle doesn't enter open loop during WOT operations, the fuel trims can be added to the fueling. The commanded afr is 12.9 in your datalog, it has to be at least 12.46 to make the ecu enter open loop operation when you go WOT. That way it goes by your fuel tables for fueling without input from l trims and s trims.

If you don't want to post your calibration on here, you can always email it to me. You can PM your email address and we can exchange it through email. Honestly a datalog and the calibration would really help, so I can see what all you're working with for commanded afr and all that.
Post Reply