Engine Knock: General info

[worldwalker]

I've got an engine knock on a bigport 4AGE. Though the situation involving this 4AGE was the instigator for my question, it's more a general question about engine knock so that I can get a better understanding of detonation with this era of engine.

The engine itself is a tired old 4AGE that is just limping my AW11 along until the new engine is rebuilt. I've been progressively replacing parts in an attempt to solve the knock but because it is a temporary engine, they're very temporary solutions. Basically the engine wont knock on warm up but the hotter the engine gets the worse the knock gets. After playing with the timing and changing the plugs, leads, AFM, ECU etc I thought I'd replace the fuel filter and while I was at it, replace it the injectors with higher flowing injectors just to see what happens. The whole idea of the bigger injectors was just to see how a stock 4A copes (poorly as it turns out) and to keep the girl limping along while I wait for the new engine.

So the result is 7MGE injectors dumping bucket loads of fuel into the engine black spark plugs and its still pinging its head off.

My question is now, what would be the possible causes, to go from no problems other than a bit of hesitation to sounding like a cement mixer (almost instantly) despite guzzling more fuel than a Saturn V rocket? This extends to the question, what are all the possible (reasonable) causes of detonation with this era engine?

Cheers,

Nick

[wa5]

Just to be clear, your are reffering to Pinging (or Pinking if you prefer).. the fuel air mix detonating prior to the piston reaching top dead centre..

as opposed to a "big end knock" caused by conrod bearing failure...

My guess would be timing to far advanced.

[worldwalker]

Yeah talking about detonation. Timing is my suspicion but it no matter where I set it in diagnostic it's still pinging. The cams are aligned correctly etc too.

[oldeskewltoy]

It might not be detonation.... it might be ring land failure.... Stock 4AGE pistons don't take well to detonation, and presented with a lot of it, the ring lands tend to break

[worldwalker]

I would have thought that'd result in a continuous noise though? The sound isn't there at idle or off load, and only once the engine has warmed up.

[dnegative]

You would be surprised how different things can sound when everything is cold;
4AGE's don't suffer prom pre-ignition, you can run them on old shitty E10 without issue. To induce it, you have to really crank the shit out of the timing and run poor fuel for pinging to occur.

Sure its not a different knocking noise?
Record a video if you can

[Hurricane]

im thinkin a video would be good also, hard to say with out knowing the noise first hand.

what did you set the timing to?

maybe what you were reading was/is not the true reading (timing marks incorrect, timing light faulty)

excessive carbon build up can cause pre ignition, along with shape edges in the compustion chamber