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Discussion Starter #1
Why does some skylines knock? I understand knocking to be detonation (when the fuel-air mix spontaneously explodes)
This is not a good thing for the internals so how do I cure it?
It sounds like a tapping noise, I've tried cooling her down and adjusting boost???
 

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if it is coming from the area where your injectors are then i have been told that this is normal as i posted a similer thread:)
 

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nope its not, well atleast i dont think so, i know the injectors make a tapping noise because if the springs but I think its not coming from there.
 

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Discussion Starter #5
lol alright mate, cheers for ya help.
was your spark plugs marked when you bought the car or did you do them yourself?
 

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a loud tapping on boost is knock or detonation

the injectors you will hear if you listen closely to the engine, but not when driving...when you would normally get detonation

detonation is caused by lack of fuel, inlet temp too high, too much ignition advance, crap fuel etc
 

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Upgraded injectors tick loudly, this is not 'knock'.. get your engine mapped by a reputable ecu tuner, 'knock' is only audible with det cans, you wont hear it with the engine running normally, silent killer ;) (Bit more expensive than the farts at school tho) ;)
 

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ahh yes a visit to the tuner, when ever i go there, i find my self buying something else and spending more money lol :D
 

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if you have detonation do not go out on the road and full throttle it just to listen to the noise because it will break your engine and cost you thousands to repair

fix it before it starts killing engine parts....take it to a tuner
 

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As many here said,go to someone that knows his stuff,you cant hear det when putting you foot down in a high gear,no way,you need special equipment(detcans,knocklink etc),and driving the car full throttle doesn´t cure the problem,so please:

Dont give the guy the answer he should do it himself.
 

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what about pops and bangs then out of the tailpipe that get my knock sensors shooting up to 50 on my Power FC? I've never heard any pinking sounds (mice tap dancing on piston crowns?) but my car's been popping a lot at WOT at high rpms - I talked about this in a different thread. Is this a hijack? Maybe I just can't shut up about my car's engine. <sigh> :p
 

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Discussion Starter #15
i found the octane thred and f*ck me im not reading all that!

cheers guys, Im taking it to a tuner next week, should i not drive it until after then?
 

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On older engines knock can also be caused by carbon buildup. If little soot particles start to glow, they can ignite the mixture before the spark does and cause detonation and unwanted pressure waves that can kill the engine.
I don't know if it is mentioned ( I guess it is) but anyway, if you have a too hot grade sprak plug it can't dispose the heat of the combustion enough and it is going to glow / melt. This couse detonation also and burn holes in your piston..

The engine's resistance against knock depends of:
- Copression ratio:
lower compression ratio = less knock

- Combustion chamber design:
At the rb26 the squish area can be removed for more controled combustion.
On places where the flame front can't reach eaysily the unburn't mixture has a higher risc for detonation, that's why a smooth camber design is prefered above a chamber with a lot of angles > places that are harder to reach by the flame front.

- Pollishing of the combustion chamber / valves:
can give less carbon builup and thus some kind of extra knock resistance, it also reflects a bit of heat( But this is probably as long as the pollished chamber stay's clean,)

-Spark plug grade:
as mentioned above ( should always be right)

-Intake temperature:
lower intake temps give a more controled burn, water injection can reduce intake temps and detonation down.

- Boost:
Higher boost:
will give a higher end compression pressure and so the risc for detonation is bigger.

- Head gasket:
The head gasket is a weak point in the combustion chamber and is often the part that dies fisrt when the car detonates. A thin head gasket is prefered above a thick one cause you'll have a bigger weak spot and a little less ideal
combustion chamber shape.

- Fuel:
The thing that gives the fuel more resistance against knocking is the RON or MON number, the higher the number, the higher the resistance against knocking.

- Igniton timing:
The ignition advance depends of the engine's resistance against knock, the more resistance against it, the more advance you can cun, and ignition advance results in more power (roughly said)
 
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