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Old 09-18-2012, 02:23 AM   #1
toxin
Scooby Newbie
 
Member#: 51259
Join Date: Dec 2003
Vehicle:
2007 WRX
СGM

Default knock at low load/RPM

Hi everyone,

I'm breaking in my rebuilt engine after ringland crack. Driving around, I'm seeing some feedback knock corrections at low load and RPM.
The engine was built with stock internals, except the Mahle Powerpak pistons.
According to Mahle, the dish is -22cc vs stock EJ255 pistons -25cc. Thus, the compression ratio supposed to be slightly more than stock EJ255's 8.5
Could this CR increase cause the knock?

Code:
A/F IAM 	RPM	Load 	FbKC FLKC	PSI
13.44	1	1881	0.86	0	0	-4.79
13.21	1	1880	0.83	0	0	-4.5
12.98	1	1910	0.78	0	0	-4.5
12.75	1	1920	0.74	0	0	-4.5
12.63	1	1943	0.72	0	0	-4.64
12.63	1	1948	0.73	0	0	-4.64
12.52	1	1947	0.72	-1.4	0	-4.64
12.4	1	1982	0.71	-2.8	0	-4.64
12.4	1	1991	0.71	-2.8	0	-4.64
12.4	1	2013	0.7	-2.8	0	-4.79
12.52	1	2028	0.71	-2.8	0	-4.79
12.75	1	2032	0.71	-2.8	0	-4.79
12.86	1	2040	0.7	-2.8	0	-4.79
12.86	1	2081	0.7	-2.8	0	-4.79
12.86	1	2104	0.68	-2.8	0	-5.08
12.86	1	2092	0.66	-2.8	0	-5.22
12.75	1	2088	0.66	-2.8	0	-5.37
12.63	1	2113	0.65	-2.8	0	-5.51
12.63	1	2151	0.64	-2.8	0	-5.66
12.63	1	2176	0.65	-2.8	0	-5.66
12.63	1	2164	0.71	-2.8	0	-5.51
12.86	1	2161	0.72	-2.8	0	-5.22
12.98	1	2192	0.78	-2.8	0	-4.79
13.09	1	2233	0.83	-2.8	0	-4.35
13.09	1	2260	0.84	-2.8	0	-4.21
13.09	1	2260	0.84	-2.8	0	-4.21
13.09	1	2243	0.8	-2.8	0	-4.21
12.86	1	2259	0.78	-2.45	0	-4.35
12.75	1	2294	0.77	-2.45	0	-4.5
12.75	1	2319	0.77	-2.45	0	-4.64
12.86	1	2330	0.76	-2.45	0	-4.64
12.86	1	2332	0.76	-2.45	0	-4.64
12.86	1	2352	0.77	-2.45	0	-4.64
12.86	1	2383	0.76	-2.45	0	-4.64
12.86	1	2406	0.76	-2.45	0	-4.79
12.86	1	2420	0.77	-2.45	0	-4.79
12.86	1	2424	0.74	-2.45	0	-4.79
12.86	1	2436	0.76	-2.45	0	-4.79
12.86	1	2466	0.75	-2.45	0	-4.79
12.98	1	2491	0.74	-2.45	0	-4.93
12.98	1	2497	0.75	-2.45	0	-4.93
13.09	1	2500	0.75	-2.45	0	-4.93
12.98	1	2537	0.74	-2.45	0	-4.93
12.98	1	2565	0.74	-2.45	0	-5.08
13.09	1	2583	0.73	-2.45	0	-5.08
13.09	1	2588	0.74	-2.45	0	-5.08
13.21	1	2579	0.74	-2.45	0	-5.08
13.32	1	2599	0.75	-2.1	0	-5.08
13.44	1	2634	0.77	-2.1	0	-4.93
13.55	1	2669	0.82	-2.1	0	-4.5
13.55	1	2676	0.92	-2.1	0	-3.92
13.55	1	2688	0.93	-2.1	0	-3.48
13.44	1	2719	0.95	-2.1	0	-3.19
13.44	1	2753	0.95	-2.1	0	-2.9
13.44	1	2755	0.95	-2.1	0	-2.9
13.44	1	2757	0.96	-2.1	0	-2.9
13.21	1	2816	0.96	-2.1	0	-2.9
13.09	1	2841	0.94	-2.1	0	-2.76
12.86	1	2832	0.95	-2.1	0	-2.76
12.75	1	2868	0.95	-2.1	0	-2.76
12.63	1	2894	0.92	-2.1	0	-2.76
12.63	1	2935	0.91	-2.1	0	-2.9
12.52	1	2941	0.9	-2.1	0	-2.9
12.63	1	2934	0.91	-2.1	0	-2.76
12.63	1	2986	0.92	-2.1	0	-2.9
12.63	1	3001	0.9	-2.1	0	-2.9
12.63	1	3028	0.85	-2.1	0	-3.48
12.63	1	3012	0.75	-1.75	0	-4.06
12.17	1	3044	0.71	-1.75	0	-4.5
12.17	1	3079	0.7	-1.75	0	-4.93
12.17	1	3085	0.66	-1.75	0	-5.37
12.29	1	3099	0.44	-1.75	0	-7.4
12.06	1	3034	0.22	-1.05	0	-8.85
11.71	1	3014	0.11	0	0	-10.16
11.37	1	2966	0.06	0	0	-11.03
11.14	1	2931	0.05	0	0	-11.61
11.14	1	2834	0.04	0	0	-11.75
11.14	1	2768	0.05	0	0	-11.9
11.25	1	2701	0.05	0	0	-11.9
11.6	1	2631	0.05	0	0	-12.04
12.06	1	2560	0.05	0	0	-12.04
12.4	1	2454	0.06	0	0	-12.04
12.75	1	2379	0.08	0	0	-12.04
13.21	1	2304	0.11	0	0	-11.9
13.67	1	2260	0.13	0	0	-11.75

Any input will be highly appreciated.
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Old 09-18-2012, 08:18 AM   #2
quazimoto
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Default

I would check the knock sensor. There is a specific way it has to go on. I doubt you are seeing rell knock. Could also be piston slap. Is the car fully warmed up?
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Old 09-18-2012, 08:27 AM   #3
toxin
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Join Date: Dec 2003
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2007 WRX
СGM

Default

Quote:
Originally Posted by quazimoto View Post
I would check the knock sensor. There is a specific way it has to go on. I doubt you are seeing rell knock. Could also be piston slap. Is the car fully warmed up?
Thanks dude,
I'll see my mechanic to make sure the knock sensor is tighten per specs.
Yes, the car is fully warmed up. I can't notice any piston slap after cold start.
I intentionally bought 4032 alloy pistons for my build to set p/w clearance .0025 to avoid the piston slap.

Anton.
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Old 09-27-2012, 02:36 PM   #4
wgr73
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CAMTuning.com

Default

Can you log again, this time add total timing? Maybe your timing is too low/high in those areas?
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Old 09-28-2012, 10:45 AM   #5
bmx045
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knock sensor is extremely sensitive to incorrect torque specs.
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Old 09-28-2012, 11:01 AM   #6
lukeskywrx
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2004 Spec-C Type RA
What MAF? -Speed Density!

Default

Quote:
Originally Posted by bmx045 View Post
knock sensor is extremely sensitive to incorrect torque specs.
And stray bolts sitting on top of the engine block, I uh figured that out.
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Old 09-28-2012, 11:18 AM   #7
CrashTestRacer
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Default

Don't forget the angle, I just went through that myself:

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Old 10-08-2012, 12:07 AM   #8
04ScottWRX
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PSM

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I has to be something acoustic. There is no reason your engine should be knocking under those light loads and rich AFR's----What's up with that anyways---front mount IC?
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Old 10-09-2012, 04:12 AM   #9
NSFW
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ATP 3076, 6MT, AVO FMIC

Default

Quote:
Originally Posted by 04ScottWRX View Post
I has to be something acoustic. There is no reason your engine should be knocking under those light loads and rich AFR's
I agree, it's almost certainly not real knock.

I have a stock 09 LGT ROM in front of me, and it completely ignores the knock sensor below 0.75 g/rev. If yours did too, we wouldn't be having this conversation.
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