This GD False Knock...

[Obsol3te]

Can anyone help shine some light on this subject for me? I put my car back in the air today to try and find out where this false knock is coming from after my LT header swap. I can't see a damn thing that it could be contacting. The only thing I found was one of the O2 sensor harness' didnt clip back into a chassis support hole so I zip tied it off and HOPED that was my issue. Just did a datalog and im looking at it now on the laptop, as soon as I peg the throttle in third gear at about 3000 rpms, i let it climb to about 7k. It's doing great from 3000-4100 RPM, I get up to -4.5º knock. But as soon as I pass 4k rpm, the knock starts moving back toward the positives.
By
4200rpm its at -2.38º,
4300 -1.38º,
4400 -.68º,
4500-4900 is 0.91º
5000-6100 1.58º
6150-6350 1.33º
6400-6750 2.02º
6800-7000 3.02º


I know my car makes peak power around 6.5kish. But still, why the hell is it knocking?!

I've tried Torco, I have a Passenger side oil separator. I've tried different gas stations. Everything appears to be tight and I cant see anything close to hitting.
I dont really want to drop it off for a shop to try and diagnose and figure out and it end up costing me a grand for a simple fix. But anything? anyone?
I have plenty of clearance with Kooks on that AC bracket too.

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[Rhinogt]

What's your spark where you have positive knock?

 

[Nick@JDM]

We had a customer come in with a 2016 GT and his Magnaflow cat-back was making contact with part of the parking brake cable mounts if I remember correctly. Some of the early Magnaflow kits have slight fitment issues.


I know you said you didn't see anything to note, but it can be hard to see unless carefully examined on a lift.

 

[Obsol3te]

What's your spark where you have positive knock?

From 4000RPM it hits a max of 24º timing, then drops to 19º at 5000
Climbs to 22º at 6100 and levels off again at 23º at 6800

 

[Obsol3te]

We had a customer come in with a 2016 GT and his Magnaflow cat-back was making contact with part of the parking brake cable mounts if I remember correctly. Some of the early Magnaflow kits have slight fitment issues.


I know you said you didn't see anything to note, but it can be hard to see unless carefully examined on a lift.

Definitely looking at that ASAP. TY!

 

[Nucdancer01]

Did you look for contact with the AC line bracket, on the passenger side pipe?


Sent from my Oxford White 2015 GT PP, Prem

 

[Obsol3te]

Did you look for contact with the AC line bracket, on the passenger side pipe?


Sent from my Oxford White 2015 GT PP, Prem

Yes, plenty of clearance with Kooks. I know thats a common problem with Stainless Works(i think it was)

 

[Tugger50H]

I feel your pain. I have been dealing with this shit for months. Spent countless hours testing fuels, and checking clearances. Finally got it to start adding timing this weekend with a dyno tune.

 

[Rhinogt]

24 at 4000 sounds ok. My car only likes at most 22, usually more like 20 around there. 23 at redline seems a little low since you said you've tried torco. I'd ask your tuner. Maybe the vct you're running doesn't like anymore spark? What's the lambda for the pull?

 

[Obsol3te]

It wasn't the E-Brake cable sadly... There's is a good amount of clearance there. However I have maybe an inch to play with between the back part of the X pipe and where my driveshaft connects to my rear end. I dont think there would be that much play there though.

I feel your pain. I have been dealing with this shit for months. Spent countless hours testing fuels, and checking clearances. Finally got it to start adding timing this weekend with a dyno tune.

TY for the PM. I am going to check plug gaping ASAP. Just need to go get another gapping tool. What is the recommended gap. And if theyre too far out, am I just buying new plugs at that point?

24 at 4000 sounds ok. My car only likes at most 22, usually more like 20 around there. 23 at redline seems a little low since you said you've tried torco. I'd ask your tuner. Maybe the vct you're running doesn't like anymore spark? What's the lambda for the pull?

Lund tuned the car, and says the tune is spot on. So im clueless... I really dont know what Lambda is, i've heard it a few times though. I know it has to do with Air/Fuel. But im fairly certain it was fine there too.

 

[Tugger50H]

I think maybe I confused you. Wish I understood this tuning stuff better myself. I didn't gap the plugs but the tuner adjusted the spark advance through the tune. I think he called it spark tip in angle:shrug:

 

[Rhinogt]

I would assume you're lambda is fine then since Lund tuned it. Basically, FYI, lambda is related to air/fuel. It is based off the stoich. 1.0 would be right at stoich. Typically at WOT these cars should be between .82-.84 lambda NA. Next time you log the car, I would check it just to be sure, but I doubt that's the issue.

 

[Obsol3te]

Yes!!! Ok looks like Lund is pulling through for me. He richened up the tune a little bit and pulled a little timing. .52º was my max knock in a 3rd gear pull... the knock was im guessing the initial blip on the throttle on the second pull. Did two back to back,First pull was from 3k-7k -4.08º at 4.8k and dropped to -1.02º by the time i hit 7k. ZERO KNOCK. Second pull was -1.69º knock at the 7k mark(rose from a min of -4.49 at 4.7k then slowly dropped back down to -1.69 toward the end of the pull.
Hopefully i can get a little more timing out of the car and we can stop there

 

[Ultrakla$$ic]

So when we are driving our car and watching the PID related to knock it should always be in the negatives???

 

[Obsol3te]

So when we are driving our car and watching the PID related to knock it should always be in the negatives???

When it's in the negatives you car is adding timing(atleast thats what I understand it as) so negatives are a GOOD thing. When it's above zero is when you are having issue and the car's not making the power it should. Either from Detonation, Shitty fuel, oil blow-by or false knock from exhaust rubbing etc.

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