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Old 02-19-2009, 09:38 PM   #1
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Default Knock with Super Retarded Timing

For some reason, I keep getting knock, even with ridiculously retarded timing. It always happens in the 3k-4k RPM region. Once out of there, the KnockSense goes quiet and stays that way all the way up to redline.
KnocksenseMS is tuned to just go off from noise at ~7k RPM steady cruise.

Datalog is attached at the bottowm, but here is a picture of a pull:
knock_log.jpg?t=1235092551

I checked my base timing, and verified the crank pulley is properly aligned to TDC by sticking a long stick down CYL1. I'm not sure if it might be a rich misfire (would that even set off the knock sensor?). I gapped my plugs (BKR6E's) down to .025 to .028" with no help. I'm also running ~97octane fuel blend, and ambient temps are the mid-30's.

Verifying the cam timing is next on my list, but before doing that I wanted to consult you guys in case I'm being stupid and missing something.
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File Type: zip datalog200902182019.zip (131.3 KB, 24 views)
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Old 02-19-2009, 09:48 PM   #2
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for what its worth, ive heard that too little timing can cause knock also. I see you were at 1.3* ... might be too late.
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Old 02-19-2009, 10:14 PM   #3
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Post your msq. It's probably not knocking and the knocksense is giving out a false reading. Again, post the msq so we can see what you're running.
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Old 02-19-2009, 10:19 PM   #4
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Yeah, it's stupid low, like my tuning skills. I had it at ~20-13 deg @ 120kpa-170 kpa (respectively) when I started tuning this issue, but while gradually retarding timing in this area, there's no improvement. The car will hesitate a little in the RPM range, and once over 4k it smooths out and just pulls.

Damn good thing this isn't my day job...
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Old 02-19-2009, 10:23 PM   #5
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Pats -- Here is my latest MSQ.
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Old 02-19-2009, 10:29 PM   #6
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Your spark table is pathetic. Needs major work. If I had to guess, you don't have the knocksense adjusted properly. I'd unhook it, turn of knocksense crap, and get a decent/safe spark table in there and see how it runs.
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Old 02-19-2009, 10:30 PM   #7
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Pull your cat out of the car and see if it gets better. Exhaust restrictions drive EGTs up and cause knock. Excessive retard caused by the knock sensor going off will then drive the EGTs up even further, etc.

Check your timing belt as well. My car ran smooth with the intake cam retarded two teeth. Made buckets of power up top, no power down low, detonated everywhere.

My spark map used to look like yours, 5-6 degrees of timing in boost everywhere. Fixing the timing belt and ditching the cat let me jump up to 12-13 in boost, 15 at redline.
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Old 02-20-2009, 03:09 AM   #8
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Quote:
Originally Posted by Savington View Post
Check your timing belt as well. My car ran smooth with the intake cam retarded two teeth.
*pissed*:
DSCF3048.jpg?t=1235112791

Exhaust cam is good @ TDC:
DSCF3050.jpg?t=1235112808

Intake is retarded. Camera angle's bad; it's worse than the pic shows:
DSCF3051.jpg?t=1235112841

Fixed the issue w/o too much trouble. Removed the water pump pulley, upper plastic front cover and intermediate plastic front cover to get access to timing belt tensioner. Put a zip tie on the exhaust cam to make sure it doesn't slip:
DSCF3052.jpg?t=1235112868
then loosened the tensioner to adjust the intake cam.

Had to re-tension the belt, too, as it was a bit beyond the upper limit of tension spec.

The more I work on this car, the more janky mistakes I find from the original owner...

So very .

Thank you Savington, for the good suggestion.
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Old 02-20-2009, 03:42 AM   #9
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Good thinking Sav
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Old 02-21-2009, 12:00 AM   #10
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I was about to suggest worn crank keyway, that's how mine acted before I welded it in place.
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Old 02-21-2009, 12:29 AM   #11
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Sav knows all about shitty cam timing and detonation. When I bought my 99' I knew something wasn't quite right. I did all the maintenance and then when I decided to to a TB I checked, and sure enough, exhaust cam was a tooth advanced. Fixed it and it helped power, but after pulling the head from poping a head gasket (100 shot at idle FTL...), all the exhaust valves leak a spec. Advanced exhaust cam timing = higher valve stem temps = worn valve seats and faces. :( Gonna rebuild it this summer when I do the most badass miata head and block port you bitches have ever seen. (yeah, I said port the block...)
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Old 02-21-2009, 03:29 AM   #12
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Quote:
Originally Posted by patsmx5 View Post
Gonna rebuild it this summer when I do the most badass miata head and block port you bitches have ever seen. (yeah, I said port the block...)
Whaaa -- block port?? Like port where the combustion chamber edges meet the top of cylinder walls? Never heard of this before. Keep us posted on the updates. It sounds like a badass build.

So I drove my car around today with ~3-4 deg extra spark in the 3k-4k region and OMG the difference in low & mid RPM torque is amazing!! 3k RPM, 2nd gear, 1/2 throttle and the rear end started squirming around. I can't even imagine how frustrating Sav's motor must have been with 2 teeth off. Pretty excited about tuning now... I'm thinking of throwing in FM's spark map and seeing how the car likes that. KnocksenseMS was completely silent and the power was butter smooth... like a buttery freight train. MAP signal cleaned up quite a bit, and I was able to turn AE back on. I saw more CLT stability under boost, and lower EGTs by 100-200F.
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Old 02-21-2009, 05:15 AM   #13
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2 degrees is crazy low. With the TB corrected, and your base timing reset, you should be able to run at least 12 degrees at 13psi. Glad you found the issue.

My car was pretty shitty with the intake retarded 2 teeth, though. I dynoed 219/201tq with a boost peak of 14+psi. 14+psi and only 200tq = failz.
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