2jzge 2jz knocking - exceeding max retard limit and cutting fuel+ignition

[Nathanj1142]

Hi guys.

im a newbie when it comes to tuning and recently got my car done. My tuner has unfortunately got personal matters to attend to therefore cannot assist me for a few months. I don’t think there’s anything fundamentally wrong with the tune, but since driving it on the road with different load cases, issues have shown themselves.

Basically in 3rd gear sometimes 4th, the car will Rev to about 5k rpm then randomly jolt forward cause it cuts fuel and ignition (can see this active on the log files).

i also noticed the knock count increases and can clearly see where it exceeds the threshold on a few cylinders. The thing is - it’s not consistent on one cylinder - it’s completely random and I can’t really induce the issue repeatedly. My tuner tried lowering the boost from 1.6 bar to 1.4 but didn’t help. I’m running stock 2jz knock sensors (between 2 and 3, 5 and 6).

Can see in the knock settings it’s set to retard 1 degree per % - and there is max 3 degrees. Does this mean the knock is so loud it’s just blown past the max percentage? I’m starting to think it’s false knock as I have the e46 m3 box which is noisy af, but not sure how I can listen to the engine audio using the link software. Is there some specialist equipment separate to the ecu?

2jz-ge na-t (GTE headgasket). stock intake manifold. 7m-gte cam pos sensor and stock 2jz-gte crank pos sensor

BW S360 turbo, aem boost solenoid, turbosmart 45mm wastegate (14 psi spring)

r35 COP, ngk iridium BKR8EIX (2668)

FIC 1000cc injectors, aem FPR, walboro 255lph 

log file here of the knock occuring:

https://drive.google.com/drive/folders/1USfkAbgcBg3zAHiCxhTJXncp_YNtyqc-?usp=sharing

 

[Vaughan]

8 hours ago, Nathanj1142 said:

Basically in 3rd gear sometimes 4th, the car will Rev to about 5k rpm then randomly jolt forward cause it cuts fuel and ignition (can see this active on the log files).

It's hitting the rpm limit, check your rpm limit table to see what values it has in it.

8 hours ago, Nathanj1142 said:

i also noticed the knock count increases and can clearly see where it exceeds the threshold on a few cylinders. The thing is - it’s not consistent on one cylinder - it’s completely random and I can’t really induce the issue repeatedly. My tuner tried lowering the boost from 1.6 bar to 1.4 but didn’t help. I’m running stock 2jz knock sensors (between 2 and 3, 5 and 6).

Would say the noise is because of the cut not detonation

[Nathanj1142]

34 minutes ago, Vaughan said:

It's hitting the rpm limit, check your rpm limit table to see what values it has in it.

Would say the noise is because of the cut not detonation

I’ve looked and there is only rpm limits due to coolant temps in which it is 7000 at above 70 deg cel on coolant temp. The ignition cuts active due To knock noise at about 5000-5500 I think?

 

[Nathanj1142]

Checked again and there is a second table with rpm limit at 6800 when ‘virtual a’ is 0 and 2000 when virtual a is 1.

Virtual aux 1 is superknk 

[Vaughan]

What are the conditions of that virtual Aux 1 control?

[Nathanj1142]

1 hour ago, Vaughan said:

What are the conditions of that virtual Aux 1 control?

Math blocks if 1,2 and 3 knock levels exceed a mean total of 650 and 4,5 and 6 for the second math block.

(a+b+c/3)

[Vaughan]

On second look yes it looks like you've hit knock at 5000rpm and ~10psi of positive pressure in the manifold. Unrelated but when you do go back to the tuner I would recommend looking into using one of the normalised knock modes which looks for sudden changes in noise rather than looking at absolute levels, means it works consistently over a wider range of operating conditions.

12 hours ago, Nathanj1142 said:

but not sure how I can listen to the engine audio using the link software. Is there some specialist equipment separate to the ecu?

We don't currently have knock audio streamed from the ECU to PCLink but it is on the todo list at some point. A fairly common method is to bolt another knock sensor to the engine and connect an amplifier and headphones too it. An example is the Link Knock Block https://dealers.linkecu.com/G4PlusKnockBlock

[Nathanj1142]

So would you consider this a ‘real’ knock that needs addressing rather than a possible false knock or interference? Other logs have shown it occurring on other cylinders rather than 6 In this scenario. And occurs randomly 

[Adamw]

Looking at the advance commanded etc it looks about right compared to the couple of 2J's I have tuned.  Your IAT is much cooler than I normally have when tuning so my initial feeling is you should be a reasonably safe margin away from knock.  However that is assuming many things such as base timing is set up correctly, crank sensor is wired correct polarity, fuel octane is similar to what Im used to etc. 

I also dont know if there are any significant differences between the NA and GTE versions - both that I tuned were genuine GTE engines.   

The quick test to confirm if it is real knock or not without audio equipment would be to either pull 3 deg out of the ignition table around that area or put some high octane fuel in and see if it still shows high knock levels in the same area.  

Have the knock sensors been replaced with doughnut type?

[Vaughan]

38 minutes ago, Adamw said:

I also dont know if there are any significant differences between the NA and GTE versions - both that I tuned were genuine GTE engines.   

quick google says something like 9.6:1 (ge with factory pistons and Turbo headgasket) instead of 8.5:1 (factory turbo motor)

https://www.my.is/threads/compression-ratio-of-pistons.424067/

[Nathanj1142]

1 hour ago, Adamw said:

Looking at the advance commanded etc it looks about right compared to the couple of 2J's I have tuned.  Your IAT is much cooler than I normally have when tuning so my initial feeling is you should be a reasonably safe margin away from knock.  However that is assuming many things such as base timing is set up correctly, crank sensor is wired correct polarity, fuel octane is similar to what Im used to etc. 

I also dont know if there are any significant differences between the NA and GTE versions - both that I tuned were genuine GTE engines.   

The quick test to confirm if it is real knock or not without audio equipment would be to either pull 3 deg out of the ignition table around that area or put some high octane fuel in and see if it still shows high knock levels in the same area.  

Have the knock sensors been replaced with doughnut type?

Stock narrowband sensors at the moment. I have ordered Bosch donut knock sensors and will be installing soon to rule them out but not too clued up on setting them up without the audio equipment.

99 octane fuel here in the U.K. that’s all I run it on.

53 minutes ago, Vaughan said:

quick google says something like 9.6:1 (ge with factory pistons and Turbo headgasket) instead of 8.5:1 (factory turbo motor)

https://www.my.is/threads/compression-ratio-of-pistons.424067/

This sounds about right

[Nathanj1142]

just had a further investigation.

The math blocks (1 and 2) are set to calculate a mean average 'knock' across cylinders 123(MB1) and 456(MB2). the equation in this math block is a+b+c/3. if math block 1 or 2 exceeds 650, it will activate the 2000rpm limit (fuel and ign cut).

if you do a+b+c/3 in it's current form it only divides c by 3, not the other cylinders, therefore outputting the <650 requirement to enable rpmlimit2.

if you calculate (a+b+c)/3, it will output the true mean value.

i compared this too the log, where I manually calculated ~677(I think) on cylinders 456 with the current equation, then compared to the math block log which is the same value of 677.

if i calc the true mean i get something like 250, which is way under the RPM limit variable.

 

Am i correct in my understanding, and can I adjust the math block equation to the above ( (a+b+c)/3 ) safely.

cheers

 

[Vaughan]

5 hours ago, Nathanj1142 said:

Am i correct in my understanding, and can I adjust the math block equation to the above ( (a+b+c)/3 ) safely.

You can adjust the math block but whether or not it is safe for the engine would be a question for your tuner, it would be impossible to say what a safe noise limit would be for your setup without having some interaction with it. Changing it would make it reflect the intent of the person who tuned it but I would recommend having a chat to them.

[Nathanj1142]

37 minutes ago, Vaughan said:

You can adjust the math block but whether or not it is safe for the engine would be a question for your tuner, it would be impossible to say what a safe noise limit would be for your setup without having some interaction with it. Changing it would make it reflect the intent of the person who tuned it but I would recommend having a chat to them.

As I say I can’t get in contact with him at the moment. I have assumed that It is a Simple math error. Thanks for the advice, but just wanted to make sure the math block function within the link software works in the way I’ve depicted, And by adjusting to the new equation would work as intended to originally?

[Vaughan]

1 hour ago, Nathanj1142 said:

As I say I can’t get in contact with him at the moment. I have assumed that It is a Simple math error. Thanks for the advice, but just wanted to make sure the math block function within the link software works in the way I’ve depicted, And by adjusting to the new equation would work as intended to originally?

Should do, a quick check of the values while it is running should show if it is correct.