Need help with knock (logs available)

backman_66

I'm in the process of getting my G37 etuned via Ecutek and my car is showing a bit of knock at this point.* My tuner has asked me if I want to raise the knock thresholds if it's false knock, or to pull a bit of timing.* I am no expert and I don't know what to do.

Would anyone be willing to look at a few of my logs and tell me their opinion please? My fuel is 93 pump gas with 8oz of Boostane which roughly makes the octane 98-99.* I mix the same every time I fill up.* The car wasn't showing hardly any knock but I recently did a "Reset ECU" to clear the long term fuel trims, and after doing that, there are a few places where it's pulling 3 degrees of timing.

https://drive.google.com/file/d/18pS...ew?usp=sharing

Thanks for your time!

Spooler

Are you NA? What brand fuel are you running and what is the octane?
You may need to get a set of catch cans. If you have oil vapor coming back into the intake it will decrease the octane level you are running.

backman_66

Yeah I am N/A.

2.75" intakes with bellmouths and velocity stack filters
Ported stock TB's
Ported upper and lower IM
2.5" RHFC
2.25" CBE
Ecutek tuning

I'm using Exxon 93 octane because there aren't many other options during COVID since some places stopped carrying 93. I'm also using 8oz Boostane Professional to raise octane to 98-99ish every fillup.

Spooler

Ugg, that is part of your problem. Fuel up with either BP or Shell. Exxon is terrible. Takes some logs again and see what you see. You may have some blowbye and need to install catch cans to solve it. That has happened before.

JARblue

What tuner are you using and why are they leaving this up to you, the uninformed client?

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backman_66

I'm using one of the best tuners! Eugene @ Enthusiast Auto Care, aka Bythabay on the forums. I'm not trying to undermine his ability or talk bad about him cuz he's awesome, but he did leave this decision up to me and I don't know what to reply back, I just want him to do whatever he thinks is best cuz he's the knowledgeable one.

He showed me the few parts on the logs where it knocked but I can't make a decision whether to change the thresholds or pull timing. I thought it was odd that he's leaving the choice up to me.

Rusty

Sounds like he doesn't want to take responsibility if things go south.

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SG4247

My car would knock at the exact same rpm, in the same gear everytime, no matter what fuel was in it (even E100), or timing used. All the logs showed the same knock at the same point. This is engine noise picked up by the knock transducers.

Based on this data, I was convinced it was ghost knock. I had the tuner raise the threshold on knock detection and been happy ever since.

I have had the engine light flash (mil gauge highjack knock indicator) a couple times on 89 cheap gas when pulling away from a stoplight with light throttle. If I see that, I pull timing on the oil temp gauge with the cruise toggle, and go add some 93 oct.

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NA on E85 - 12.402 @ 112 mph
100 shot E85 - 11.589 @ 117 mph
JWT C2 cams rev Base Circle & Titan Valves

backman_66

Good info! Thanks for that. I'll be getting more datalogs to see if I can reproduce the knock and see at what rpm's it happens at. I'm still in the tuning optimization process for normal driving conditions so I have a lot more datalogs to collect, but I always make sure to do some pulls while I'm at it.

Someone on the myg37.com forums said that G's in the 330whp+ range often have to raise the thresholds a bit to make the car happy, so maybe that's just a common issue.

My car only has 42,500 miles on it so I would assume the internals, plugs etc are all in good condition. When I replaced my factory intake manifolds with ported ones, I didn't notice excessive blow-by in the intake tracts but who knows if that is affecting knock or not?