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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 01-11-2014, 11:45 PM   #1
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Brainstormers Please: Knock

What might cause excessive knock in 1 cylinder? I have found an extraordinary number of knocks in cylinder 4, seemingly randomly, and almost no knocks in any other cylinder except for occasionally cylinder 1. Fuel rail being short of fuel seems out..., as the knocks would get worse farther from the FPR, which is opposite of the case save for cylinder 1.
The injectors are indexed and flow matched.
AFR is under control. Ignition advance has not changed, and yet, logs are showing worsening knock tendency.
Someone awhile ago suggested that perhaps the head bolts were getting loose at the corners and coolant was seeping in just enough to throw off the ion count.
Any ideas? Anyone have this happen to them? What was the solution?
Thanks,
-Cm
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Old 01-13-2014, 11:09 AM   #2
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During regular driving or under WOT?
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Old 01-13-2014, 11:34 AM   #3
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Try moving the injector to another cyl. and see if it moves.

Run some Seafoam or Techron through it, maybe there is some carbon built up somewhere.

Compression & leakdown test if you can, those might be helpful.
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Old 01-13-2014, 12:20 PM   #4
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How about shuffle spark plugs too. Then try different DIC. It may not be real
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First T7 19T turbo setup. First T7 Deka 80lb. injector setup.

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Old 01-14-2014, 09:31 PM   #5
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1) I'll get a(1) occasional knock scattered around the vacuum range, but it occurs most repeatably during boost, and interestingly, not during wot, but I get niggles in the .5, .75, and .93 boost ranges, right between 32xx and 3920rpm. I have reduced ignition in this realm over and over again...I think I am at stock or slightly retarded of stock at this point.

2) I bought a new DIC (10/0, from a low mileage car. I threw it in and the car drove like 1 billion dollars for exactly 4 days. Zero knocks. Now, it is back to it's old habits, of cylinder 1 and/or 4 knocking. Silence from 2&3, which are typically the hotter cylinders. The old DIC favored cylinder 1 for most knock counts; the new one likes #4 by a factor of 7 EG cylinder 1 will have 3 knocks, #4 will have ~20, and the middle two offer nothing but smiling 0's.

3) This problem, of 1&4, has persisted through an engine rebuild, stg3-6tunes, stock and Deka 630 injectors, and two ecu's.

4) It manifests ONLY after driving around for a while on my current tune. For example, if I disconnect the battery, re-write the SRAM via CANusb, and then go for a drive, maybe it'll knock 4 times across multiple load areas, and while at first it's dumb, it'll pull like a Saturn 1 after a good pull or two. Once it sits overnight, bam, it becomes a loud (engine becomes DEAFENINGLY loud), slow, stinky paper-weight that knocks copiously.

5) I just put new plugs in: BCPR7es 11 gapped to ~.034. I gapped #4 to .031 with the hopes of creating a smaller flame nucleus and thus less chance of knock, but, it appears for naught. I also put "silicone dielectric" in the boots. First time i've ever seen/used "silicone" dielectric.

Thanks for the help! I know this is tedious and boring and I appreciate it!
I've been tearing my hair out over this and getting external input is awesome
-Cm
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Old 01-15-2014, 07:33 AM   #6
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Well, its time to start swapping parts around. Put on another DI, swap injectors around, etc.
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Old 01-15-2014, 08:29 AM   #7
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prob wouldn't hurt to retorque the head
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Old 01-15-2014, 09:42 AM   #8
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So you're not actually hearing knock correct? If not, try reducing the knock sensitivity to almost zero as a test, see what it does.

Right now my long shot money's on a harness/ground/connector issue somewhere near the DIC.

Do you have access to an insulation tester?
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Old 01-15-2014, 10:05 PM   #9
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So you're not actually hearing knock correct? If not, try reducing the knock sensitivity to almost zero as a test, see what it does.

Right now my long shot money's on a harness/ground/connector issue somewhere near the DIC.

Do you have access to an insulation tester?
I have reduced knock sensitivity to ~50 across the board for boost; vacuum is ~19. I have never actually heard knock. Closest thing I ever got was when I had spark-out on an old DIC at high boost; I almost had a heart attack until my brain caught up. I have heard knock in a car with a bad MAF, and that was obvious and wince-evoking.
The old DIC used to make this compressor surge sound at full tilt. New DIC has no such sound even at 30psi (I went wot in 4th from down low, just to see what happened)

I don't know if this helps, but I have been reading the archives at ECU project, and I found several threads on Kadapt_load, rpm, time, etc. While interesting that the kadapt load range is so low (.05 bar is max), the rpm sites for this are apparently supposed to match the spool of the turbo?
But I digress...

I have a very good Fluke multimeter; the internet seems to consider a multimeter an insulation tester as well. I'll also have you know that I've grounded my LC-1 to the intake manifold where the loom grounds itself, which may or may not interfere with the DIC.
-Cm
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Old 01-20-2014, 12:46 PM   #10
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Originally Posted by Drew in Houston View Post
So you're not actually hearing knock correct? If not, try reducing the knock sensitivity to almost zero as a test, see what it does.

Right now my long shot money's on a harness/ground/connector issue somewhere near the DIC.

Do you have access to an insulation tester?
Tentatively, it would seem that you were correct. Which, most assuredly, means you are a freakin' genius!!! I found the harness for the DIC to have frayed against the lift-hoop, though the wire insulation seemed intact. The attached picture shows where, but this is not my bay, though I am jealous. But I digress; I wrapped the wires and moved the cable off the abrasion point and so far only one knock at high boost after 400 miles of driving.
-Cm
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Old 02-01-2014, 08:55 PM   #11
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Yeah the knock adaptation should be done properly, factory tune is more suited to the smaller turbo obviously. If it's off you could pick up some phantom pinging.
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Old 02-04-2014, 11:36 AM   #12
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The problem is back Seems to correlate with key cycles and running closed loop. So, unplugging the battery, reflashing, and then going for a drive in open loop yields good performance. Turning it off, and then driving again in open loop yields blistering performance. At which point, I usually think the problem is fixed and let it derp in closed loop. It will run beastly in closed loop for ~2 key cycles, after that, it gets dumb and loud, and knocks.

I have yet to turn knock sensitivity to zero to see what happens. The fact that it runs so well after the battery has been disconnected for the first few runs makes me wary of variables I do not yet understand...

Also, comtrang, I alluded to the low load zones of knock_adapt--how could changing these for a bigger turbo make a difference? Also, the rpm is supposed to correspond with the spool of the turbo, but then why is the pressure so low?
-Cm
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Old 02-09-2014, 12:35 PM   #13
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Changed knock_adapt_low to higher rpm range (2200-->3300) and seemingly, it knocked a lot more. Changed it back and a few less knocks.

Turned knock sensitivity to 20: still knocks in the same ranges at the same boost, though, maybe 1-2 fewer knocks. I have yet to hear anything though knock wise. No knocks in any other cylinder except #4.


-Cm
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