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Old 07-08-2014, 08:49 AM   #1
tcpip4lyfe
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Default Engine Knocking at WOT

2004 WRX - EJ20 with forged pistons, rods, turbo back, TGV deletes and group N mounts running standard 91 octane.

Check out these data logs:

https://docs.google.com/spreadsheets...it?usp=sharing

In the process of an e-tune. We've gone through 15+ maps trying to get the knock tuned out. Any ideas? AF/R looks fantastic and the engine runs great but right around 5500 rpm, it's pulling up to 2 degrees of timing. Ordered a new knock sensor. What else should I be looking at?
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Old 07-08-2014, 05:36 PM   #2
mikeydrives1
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One unlikely culprit ive found is oil getting expelled into the TMIC and eventually ending up in the motor. Oil has different properties than gas and will cause knock events. This can be due to things such as bad PCV valves or even bad turbo seals. Oil naturally ends up (small amounts) in the intake tract, but excessive amounts will cause random knock events if ever pulled into the combustion chamber.

Also keep in mind, its summer. Temperatures are up and an increase in the intake temps raises the likely hood of knock. Put Intake Temperature in there on your next pull, im curious to see whats going on there when this knock happens. Also, Forged internals have been known to make false noise that is mistaken as knock.

Honestly, for your Little 2.0liter, with the parts you have listed and the tune you are running, its pretty conservative. The timing isnt crazy, AFRs are great (if thats the wideband i see in there) and your running whats basically 14lbs and letting it taper off. A stage II tune puts you into the 17psi range for allot of OTS reflashes. I can definatley see that your injectors are at the near max though. This tune should honestly be knock free

Last edited by mikeydrives1; 07-08-2014 at 05:41 PM.
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Old 07-08-2014, 05:39 PM   #3
tcpip4lyfe
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Interesting. Make's sense though. I'm replacing the knock sensor anyway so when I take the TMIC off, I'll check it for oil. Should be pretty clean. Engine only has about 2k on it. PCV has been replaced.
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Old 07-08-2014, 07:28 PM   #4
xgotboostx
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I agree with mikeydrives1. Turbo-charged vehicles are more knock prone when it's very hot outside. If your IAT's are 100+ and you're using 91 octane, expect to see knock at cruising, or you can get a good Summer tune for your car that will fix it right up, but it won't eliminate minor knocks completely.

On morning drives when it's cooler out my car does not experience any knock at all except -1.4 when at lower loads when I am suddenly increasing throttle, but for the most part no knock at all. The car is also much quicker and climbs through the RPMs faster in the morning.

On hotter days (like 95+ degrees) or when I get off work and commute back home, the RPMs climb slightly slower and knock is more active in higher gears when cruising on the freeway. I usually see 3-4 hits of -1.4 on a 30 min drive home, but that's when I am increasing throttle to keep up to speed with traffic, and occasionally get -2.8 pulled, but rarely. From what I've read this is normal since the car is running on the threshold of knock in higher gears at freeway cruising and it's the ECU doing its job.
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Old 07-10-2014, 10:31 AM   #5
tcpip4lyfe
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Well my tuner seems to think it's not normal so we'll see if swapping the knock sensor fixes it. I'm not convinced that when I built it that I torqued it down 100% and at the right angle when I put it together as well. I may have just slapped it on.
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Old 07-21-2014, 10:52 AM   #6
tcpip4lyfe
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Replaced the knock sensor and it actually looks better. Still pulling the timing -1.05 but not nearly as bad.
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Old 07-22-2014, 10:59 AM   #7
sc00ter
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Another thing to consider is that you are getting real close to maxing out your injectors. This might be limiting fuel flow in that higher RPM range. Even if this isn't the culprit I'd recommend upgrading those soon to give yourself a bit more headroom. I wouldn't feel comfortable with my injector duty cycle hitting upwards of 99%.
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Old 07-22-2014, 06:13 PM   #8
calebw15
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Is your tuner tuning stock knock sensor weighting factor on the tune? I had an issue with my hybrid picking up false knock at various loads and had to raise the weighting factor very slightly. He said you occasionally have to do it to louder engines like mine.
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Old 07-23-2014, 06:17 PM   #9
mikeydrives1
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Quote:
Originally Posted by sc00ter View Post
Another thing to consider is that you are getting real close to maxing out your injectors. This might be limiting fuel flow in that higher RPM range. Even if this isn't the culprit I'd recommend upgrading those soon to give yourself a bit more headroom. I wouldn't feel comfortable with my injector duty cycle hitting upwards of 99%.

More or less this is very true, but theres a few things to keep in mind here. The IDC # is based off of how the injectors are tuned... reason being, the stock injectors for this car should be 440cc .... the OTS cobb stage 2 tune for (02-05 wrx 2.0liter motor) tunes them as 420cc or even 400cc, fooling the ECU into thinking their actually smaller than they really are, this way they run nice and rich at WOT, esp near redline. Ive had the opportunity to play with a few bugeye WRX's, both stage 2 tunes. At about 17psi peak, with 14psi by redline, the stock injectors, tuned as 420cc, were pretty much at their limit in the high 90s. With that being said, at 14psi, the stock injectors shouldnt be at their limit, it may be the way they are tuned on the Injector Scale. Just some food for thought on that.


Quote:
Originally Posted by calebw15 View Post
Is your tuner tuning stock knock sensor weighting factor on the tune? I had an issue with my hybrid picking up false knock at various loads and had to raise the weighting factor very slightly. He said you occasionally have to do it to louder engines like mine.
This is an issue too. When you have forged internals, they tend to resonate noise differently than stock internals do. In other words, they can create more noise that is often mistaken as knock by the knock sensor, esp at WOT loads. Tuners will have to 'Dull' the knock sensor signal/calibration slightly in order to help the ECU differentiate between whats now the new norm for engine noise, and actual knocking events.
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Old 07-24-2014, 12:48 PM   #10
tcpip4lyfe
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He's taking into account the false knock but at -2, he said he would effectively be turning it off.

After replacing the knock sensor, things look much better. Only 1 event of pulling the timing off -1.05. I'm not convinced I put the original knock sensor on correctly.
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Old 07-31-2014, 11:46 AM   #11
veel86
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Quote:
Originally Posted by tcpip4lyfe View Post
He's taking into account the false knock but at -2, he said he would effectively be turning it off.

After replacing the knock sensor, things look much better. Only 1 event of pulling the timing off -1.05. I'm not convinced I put the original knock sensor on correctly.
How much force was the knock sensor torqed to?
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