Still Can’t Solve Knock Issue

[TheHydro]

This is my second time posting here about my knock issues. Last time a couple members reached out to me and gave me some pointers and after trying everything they advised, I’m still having knock issues. My car is a 2015 m6 with stage 2 gen 3 whipple with return fuel system. My car runs great unless I go wot in 3rd gear or higher at less than 4500rpm. If I’m under that rpm at wot I get positive knock (usually above 4 degrees and have even seen 10 degrees). This is on E85 and 91 tunes.

I beat on everything with a rubber mallet and tightened everything I could three times now. I changed my low mileage fuel pumps with brand new ones and confirmed fuel system is spot on. I told my tuner of the issue who has multiple people running my same setup on the same tune without issue. He gave me a tune to try with extremely limited timing and that tune had the same issue as my other tunes.

Thinking the worst I did a compression test and all cylinders were 210-220psi. When I’m wot from a dig or above 4500 my car rips and is scary fast. I’m just out of ideas and don’t know what to do at this point. If anyone has any ideas I’m willing to try them.

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[ice445]

Do you have oil consumption issues? Low RPM, high load situations are most likely to induce knock, and oil can exacerbate this. What are your intake air temperatures when this happens?

 

[TheHydro]

I don’t use any measurable oil on my dipstick. I use a oil catch can and it only has about an ounce in it when I change the oil at 3k miles. The iat’s have been anywhere between 40 degrees and 120 degrees. This has been an issue for an extended period of time through winter and summer. My mustang is a third vehicle so I only tinker with it when time permits.

 

[80FoxCoupe]

This is my second time posting here about my knock issues. Last time a couple members reached out to me and gave me some pointers and after trying everything they advised, I’m still having knock issues. My car is a 2015 m6 with stage 2 gen 3 whipple with return fuel system. My car runs great unless I go wot in 3rd gear or higher at less than 4500rpm. If I’m under that rpm at wot I get positive knock (usually above 4 degrees and have even seen 10 degrees). This is on E85 and 91 tunes.

I beat on everything with a rubber mallet and tightened everything I could three times now. I changed my low mileage fuel pumps with brand new ones and confirmed fuel system is spot on. I told my tuner of the issue who has multiple people running my same setup on the same tune without issue. He gave me a tune to try with extremely limited timing and that tune had the same issue as my other tunes.

Thinking the worst I did a compression test and all cylinders were 210-220psi. When I’m wot from a dig or above 4500 my car rips and is scary fast. I’m just out of ideas and don’t know what to do at this point. If anyone has any ideas I’m willing to try them.

Whats your spark plug gap set to? What plugs do you run? Does the knock stay solid or taper timing back as RPM rises?

 

[TheHydro]

My gap is set to .028 per my tuner. When I just pulled the plugs to do the compression test after roughly 1000 miles the plugs were still spot on and the color was a nice tan. I am currently running NGK but have flip flopped between Brisks and NGK while trying to figure this out. I monitor my knock on my Ngauge so as soon as I see it go positive I let out so the logs don’t really show enough to see if it is coming back down or not. What does it indicate if the knock goes down as you stay wot?

 

[sigintel]

Are you SURE the check valve in the passenger side catch can is in correctly?
Check for leaks in the evap solenoid and evap diaphragm and brake booster diaphram?
Smoke test vac lines?

No cam position codes? Check for codes that dont throw a light?

 

[TheHydro]

Are you SURE the check valve in the passenger side catch can is in correctly?
Check for leaks in the evap solenoid and evap diaphragm and brake booster diaphram?
Smoke test vac lines?


I don’t have a catch can on the passenger side. I have used my ngauge to check for any codes and none were present. I will have to look into the Evap and brake booster stuff. Thanks for the tips.

 

[TheHydro]

I am guessing you beat the crap out of your exhaust system with that mallet? Have you checked your motor mounts? Next thing I would try is a ratchet strap on the motor to make sure it’s not torquing and causing a rub.


Generally when I have problems like this I start over completely with the simplest thing first and work towards the hardest to solve. Forget all the things you have done and start from scratch.

4500 is close to peak torque so that’s the most movement you will get out of the engine.

Do you have factory or long tubes?

I went to town on the exhaust with a mallet and it is solid. I am running stock manifolds with cat deletes because I didn’t want to have false knock issues with headers, lol.

The only other thing I can think of is my diff is through bolted with billet steeda inserts. I have a dynotech driveshaft and an mgw shifter. I don’t know if any combination of that can produce the consistent knock I’m seeing.

 

[sigintel]

I went to town on the exhaust with a mallet and it is solid. I am running stock manifolds with cat deletes because I didn’t want to have false knock issues with headers, lol.

The only other thing I can think of is my diff is through bolted with billet steeda inserts. I have a dynotech driveshaft and an mgw shifter. I don’t know if any combination of that can produce the consistent knock I’m seeing.

ABove I was loking for anythign that could leak a small amount of air that might slightly lean you out at lower RPM, but the lean error gets diluted by higher RPMs to where it doesnt cause knock.

!! driveshaft !! - totally possible the drive shaft mounting joints might need to be reclocked?
Fast check: Get a couple large hose clamps from Tractor Supply. You are going to test adding small amounts of imbalance on the drive shaft to see if a slight change in resonance changes the knock RPM threshold? - Run into this before...

 

[WildHorse]

My car runs great unless I go wot in 3rd gear or higher at less than 4500rpm.

Hmmm... so with a giant vacuum cleaner on the engine, going WOT under 4500 RPM in a 11:1 engine and you get knock on E85. Above that it's as right as rain. You don't say.

 

[zero_chance]

One of my customers was tuned by Lund and they were trying to tell him the same thing, some knock evident so it must be something loose. I asked my guy to inform the tuner we were in Arizona, as soon as he found that out, tuner said you’re good to go. Why? The gas out here sucks, you’re a state away. Your gas sucks too. I think you might be chasing a ghost my friend. If you weren’t creeping on your gauge all the time, how does the car feel to you? If you didn’t know there was timing being pulled, were you thinking oh something must be wrong while driving? Or are you just looking at a gauge, seeing the car do what it’s supposed to do and saying there’s gotta be something wrong?

 

[TheHydro]

One of my customers was tuned by Lund and they were trying to tell him the same thing, some knock evident so it must be something loose. I asked my guy to inform the tuner we were in Arizona, as soon as he found that out, tuner said you’re good to go. Why? The gas out here sucks, you’re a state away. Your gas sucks too. I think you might be chasing a ghost my friend. If you weren’t creeping on your gauge all the time, how does the car feel to you? If you didn’t know there was timing being pulled, were you thinking oh something must be wrong while driving? Or are you just looking at a gauge, seeing the car do what it’s supposed to do and saying there’s gotta be something wrong?

It pulls so much timing it falls on its face and you can feel it right away. This does it on pump E85 that tests at E80 which is what it was tuned on. I’ve reached out to several tuners who all said the car shouldn’t be pulling that kind of timing on E80

 

[WildHorse]

It pulls so much timing it falls on its face and you can feel it right away. This does it on pump E85 that tests at E80 which is what it was tuned on. I’ve reached out to several tuners who all said the car shouldn’t be pulling that kind of timing on E80

LUND or PBD ?? What'd they say about it ?

 

[sabtaj1]

Maybe try pulling your belt and checking all of your pulleys, try turning the supercharger by hand while at it. Seems like you have tried everything. Turn waterpump as well. Just a thought

 

[Stage_3]

Nothing hitting the chassis of the car? Bolts/washers? Nothing that vibrates is touching in or around the engine to make the engine pick up false knock?
Believe it or not, a cai can cause false knock if touching the radiator shroud from vibrations.

Good luck!!

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