Engine Knock Can't Seem To Get Rid Of It

[Michael's R33]

Hi Guys Im running a Rb25 with op6 highflow set on 20psi tuned by insight motorsport

The car picks up knock readings of 80+ on my pfc this is my second engine and i don't quite want to do an engine swap any time soon and before it gets asked i did get this motor retuned after the engine swap could it be bad fuel? or anything else?

I now run half a bottle of octane booster per tank to keep it from knocking at the moment?

I havent checked cam timing ill pop the cover off today and see if it has jumped any teeth.

thanks any help is appreciated

Michael

[89CAL]

The Power FC's (especially the older ones) tend to pick up 'false' knock.

As an example I had an old power FC on my car when I had the gt2835KAI (think it wasa v2.20) which I replaced with a brand new one. Same tune on both, with the old one I used to see 20+ knock on startup and randomly get spikes of knock at really random times. With the new one, only ever got about 6 knock on startup and never really had any knock issues

Im not suggesting that its nothing to worry about and your Power FC is lying to you, but its worth mentioning

The tuner needs to put a standalone knock sensor on it and have a proper listen for knock. Log the point where it knocks if you can or at least remember where it is then get the tuner to go for a drive with you and listen for actual knock. There may be no problem at all, or it may need a retune

This is the only way to prove it for sure

[breaker1845]

What Cal said is perfect, if you follow that and you are still getting knock but no signs of it through the tune then there is the chance that it could be a false reading. Having said that you might want to lower your tune to a safer limit while you work out what the issue is as you could be damaging your motor.

[Blackkers]

The factory knock sensors are pretty old too.

I had a knock cut come in around 4500RPM on the haltech due to knock readings over 100.... I was on E85

[Dose Pipe Sutututu]

which RPM are you picking up this knock at?

[iruvyouskyrine]

New nissan knock sensors are ridiculously expensive. Is there any new alternative that doesn't require too much dicking around? Most knock kits use the Bosch or GM donut sensors, could these be incorporated into the ECU?

[Michael's R33]

The Power FC's (especially the older ones) tend to pick up 'false' knock.

As an example I had an old power FC on my car when I had the gt2835KAI (think it wasa v2.20) which I replaced with a brand new one. Same tune on both, with the old one I used to see 20+ knock on startup and randomly get spikes of knock at really random times. With the new one, only ever got about 6 knock on startup and never really had any knock issues

Im not suggesting that its nothing to worry about and your Power FC is lying to you, but its worth mentioning

The tuner needs to put a standalone knock sensor on it and have a proper listen for knock. Log the point where it knocks if you can or at least remember where it is then get the tuner to go for a drive with you and listen for actual knock. There may be no problem at all, or it may need a retune

This is the only way to prove it for sure

Its pretty random I have had high knock levels pop up just putting around 2000-4500 barely hitting boost then i get them at WOT but with octane booster i see nothing over 30. makes me think there is carbon buildup in the cylinder

which RPM are you picking up this knock at?

its pretty random but if i had to pick it would be up top 6000+ WOT

New nissan knock sensors are ridiculously expensive. Is there any new alternative that doesn't require too much dicking around? Most knock kits use the Bosch or GM donut sensors, could these be incorporated into the ECU?

im interested to know i would love to update them

[Dose Pipe Sutututu]

could just be mechanical noise you're picking up, usually from my personal experience most knock occurs where peak torque is reached, unless timing up top is pretty strong and there could be a chance it's knocking there too.

[jiffo]

I've never seen an Rb jump a cam belt.

Any odd cam timing I've come across can always be traced back to a poor/incorrect belt install.

You've got a hand commander, pull a few degrees timing out of it and note the results.

Go Setting, Ign/Inj and either add fuel or pull timing. (I'd pull timing)

As soon as you turn the engine off those temporary changes are gone and she's back exactly where it was. A very conventient function for test/tune.

A lot easier than farting about with octane booster, plus you can give some accurate feedback to your tuner.

Paul's big PFc story is a mine of useful information, have a read of the hand commander section.

How's the tuner going to do a tight tune with some unknown ratio of octane booster still in your tank.

[XGTRX]

could just be mechanical noise you're picking up, usually from my personal experience most knock occurs where peak torque is reached, unless timing up top is pretty strong and there could be a chance it's knocking there too.

I would be checking AFRs too but johnnilcte pretty much summed it up.

[MrStabby]

I now run half a bottle of octane booster per tank to keep it from knocking at the moment?

Is that a statement or a question?

If you are running octane booster and the knock goes away, then you can confirm its real knock. If you want to play around with the tune, then follow Jiffo's advice. If you dont want play around, then just take it back to the tuner to fix.