Knock problems (boosted)

Elmo370z

Weird question you have a catch can?

Martijn_b

No i dont, i placed 2 filters (vent to air) on the tubes from the valve covers (which normally go into the intake pipes)

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Elmo370z

Gotcha. I’m not boosted yet but I had a similar issue with my car pulling timing like your car, installed a catch can and poof no more timing issues, but what spooler linked in that would be a issue. I’m tuned by Seb

Martijn_b

What was your original setup? Venting back into the intakes?

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Spooler

That would be caused by a ring sealing issue causing excessive blow bye. You had a motor issue and didn't know you had it. Still do. Good thing you are going for a new motor soon. How do you like the SOHO catch can? Did you get the one with the drain back mounted to the dipstick tube?

The Weapon

Seb had me add two more filters. When I pulled off the hoses there was a quite a bit of oil in them.

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Elmo370z

Yes, when I swapped manifolds is was quite a bit of oil residue.

Elmo370z

Mmmm interesting. No I didn’t want the blow by to go back into the oil. I like the set up. Seems to be helping to catch the blow by my
Motor was producing rather efficiently

Martijn_b

So you plugged the 2 openings on the intake manifold, and put an air filter on the hoses?

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The Weapon

Yes but i put the filter on the driver side directly on the port. The passenger has a small piece of hose since the fuel line didnt allow the filter to fit.

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Boosted Performance Comp Turbo - Tuner- CJM Fuel Return- Modified Berk CBE- ZSpeed Stage 4 Clutch - Southbend Flywheel - Tuned by Seb ~650whp - HKS Coilovers - SPL - Focal Audio 4 way Active - Audiocontrol DSP - Work CR 2P

Martijn_b

Alright, little update:

- vented all hoses which come from the head and manifold to air
- took out the dilkar8a8 gtr spark plugs and put the stock ones back
- performed a compression test; 240-250psi across al cylinders
- moved ign coils and injectors around

No result, still knock.

Next up im thinking to drive the car back with the original software, open the wastegates and disconnect intercooler piping. Bring it back to the previous state (which had no issues) about as much as i can.

I inspected all pistons with a boroscope. Validated the knock, its visible on all 6 pistons. To me this means that whatever the cause is, its not tied to one single cylinder.



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Martijn_b

Another suspicion could be carbon build up. Now the intake valves are really clean, but the pistons look a bit black to me.

Is this normal for an engine with 50k miles?

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Rusty

Your intake valve is really clean. Most times, there is a carbon build up on them. Same with your pistons. what you are looking for is small potholes in the top of the piston and cracks around the edge. When a engine has detonation bad enough. It will turn the tops of the pistons into silly putty and melt a hole through. Look at some of the pictures on google.

https://www.google.com/search?q=engi...ih=578#imgrc=_

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Martijn_b

Drove the car on stock map and injectors and without boost. I experienced no audible knock. Couldnt see if the ECU retarded timing as the stock rom doesnt support ecutek data logging.

Next up is cleaning the pistons with some sort of seafoam/combustion chamber cleaner. Put back the id1050 injectors and run again.

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ByThaBay

Knock often times cannot be heard with the human ear, I would carefully plot the signals and check for spikes for each cylinder vs the threshold. In the rom settings you can disable racerom timing and this will let you run the stock calibration but with additional diagnostic parameters to fully understand the problem. Your tuner can set up the rom for you to do this. This will allow you to see if the ecu is pulling tuning, etc.