Lots of Knock, is it real??

[maudyZ28]

Hi guys,

Well got an idle pinned down, WB still says rich, but back in closed loop fuel triming does its thing and idle is fine in N, it does also blip up before going in gear and hold nice idle in gear too.

Anyways, set the fueling to about 12.6 to be on safe side, ramps down from 13.5 at 2000 to 12.9 at 4000 then to 12.6 after that. Doing a few WOT plus with Z06 timing table (low at wot as it is 22 deg) as a baseline, then I intend to change from here.
Problem is i'm getting knock all over, not saw tooth but just jumps of knock here and there. Thing is once it has done it do sensors get more sensative as it random knocks more and more then, either when i change gear/ driveline clunks?, randomly, exhaust banging?? or could it be eating Oil throguh bad PCV? Could it be my coolant lines under LS6 intake (ls1 to ls6 conversion that are banging the block??)

I've got a oil catch can and renewing PCV than is inline too. But any idea what the other knock could be. I've dropped timing to 17 at 4000+ and it STILL pulls timing.
I'm not happy as car feels no faster and is possible slower over the md range than when I didn't have 253 heads and cam (LS1 camaro, 253 ls2 heads, 228R cam).

I also have high octane spark table in low octane table the same? and it still pulls timing ???

BTW plugs are TR5 gapped at 0.04" and all looks good, no fouling etc and leads ok, all cylinders fire (could I do plug out test on head to check spark strength?)

[joecar]

Hi Maudy,

Can you post some log files showing KR.

Oil ingested thru PCV is a big problem, check the floor of the intake manifold for oil (open throttle blade and peek in with flashlight, use long screwdriver to see how wet the floor is). Does the oil level seem to change much after each drive...?

Post pics showing PCV plumbing.

Sometimes the knock sensors pick up exhaust headers banging on chassis or valvetrain noise or other noise.

[maudyZ28]

hi joecar,

yeah there is oil in the manifold, i do keep checking, but oil level not really gone down, just a thin film in intake. Not nearly as bad now i put catch can in though and it didn't knock this bad before. The PCV route is stock with oil catch inline, correct baffled one and does stop oil as I drain it every 500-1000 miles. New PCV are on the way too just incase.

11807

11808

11809

11810

Few log files above, all that is changed is spark and fueling to try get a none knocking combo, but still knocks. I know though for a fact that when stationary in gear the exhaust bangs, and think this could be a cause, and maybe the knock every gear change?

190811_firstrun... fuel from 13.1 to 12.8 with timing from 22 peak torque to 26 at top
190811_2run... is interesting, 2 full throttle with nothing, then went nuts?? z06 spark, 22 deg flat
220811_speedrun ... fuelling richened by 0.2 accross the board, timing pulled to 18 at torque and 20 at peak, still there
220811_madmilrun .. as above but down hill, all above are on flat run over a mile or so stretch

cant really get a good run on same road to compare time thoguh gears cause knock is changing timing all over :(


I also didnt log my MAF dyn air, if my MAF cal is NOT smooth and jumps a little, (cant tell in tune) but is more than burst knock parameters could this be the cause also???

[joecar]

If KR is sawtoothed shaped then it is real knock, and HO2Sx1 dropping below 900mV supports this (avoid this by setting PE to EQR 1.17 or higher).

BEN looks good.

I see some KR at gear shift, this is probably exhaust banging chassis (if this can't be fixed the it may be time for poly motor mounts).

[maudyZ28]

thanks for taking the time to look joe,

Yeah so i'll bring fueling even richer to more than 12.6 (EQ 1.17 is about 12.5 AFR)

I'll see how I can sort exhaust, strange that 253 heads are a little wider at exhaust mount so my exhausts bang, never did with ls1 853's ??

So you do think the bit of saw tooth is real, even though the timing is so far down? I did read about having too 'hot' a plug as I run TR5's, although the colour looks ok, do you thing regardless of timing that they could be causing the pre detonation?

Final question, one of my O2 sensors is 30 mv lower at WOT (only about 7 mV at stoich) just wondered if one injector maybe lagging. Ill check plugs again for colour and swap sensors over, see if there is still same issue :D

[maudyZ28]

right, still waiting on new PCV but edited the tune a bit.

Changed the burst knock due to MAF fluctuations to 0.2, I have a sneaky feeling this still needs increasing as knock seems to appear at about 4000 rpm right when fueling becomes MAF only. Maybe I need to recal MAF and VE to check ?

Check all Plugs, look fine -> Running TR5 though which ate gapped at 0.038". These plugs maybe too HOT or are too small a gap. Do you think re-gapping to 0.05" would be better.

Put timing upto what I want it to be at for now with the Edited Z06 table and increase fueling to 12.2 to try stop knock. Car still doesn't feel as powerful as I think it should? Maybe I expected too much of 253 heads and 228R cam change??

latest log file:
11867

before tune:
11869

After Cam tune file:
11868

If anyone would like to share a good spark table or something that works well (as I'm unsure if I have the torque dip in the correct area - purely a guess but I know LS1 have a given rpm range where they are at peak torque)

[maudyZ28]

just to put an end to this, think my problem was the plug, no matter how much timing pulled r fuel added the car was the same, and really running bad

my plugs I was given were TR5, Ive had them before and they've been fine, however plug gap is 0.035". I'm guessing they were not burning all fuel corect at WOT, anyways, regapped them to 0.05" and the knock has gone :) happy days.

now I can actually try to tune for power

[joecar]

Hey Maudy, thanks for posting your results :cheers:

[etmotorsports]

What did you a/f do after you re-gaped the plugs?

[maudyZ28]

i've not realy investigated yet, i'd put car back in closed loop STFT only, they were +/- 1% before gapping, but I was getting knock regardless of pulling timing down to ~15* and fuel upto 12.0:1.

I'll re-do my auto VE and auto MAF next week sometime and see how much it has shifted. I'm not sure it will have change significantly, if at all.
I believe that as my plugs are TR5 (NGK standard - stock heat range) and were gapped small 0.035" and overheating the plugs to the point of pre-igniting the fuel