pinging/detonation - what is it and the cure?

[MANWHORE]

i've heard people saying that they ping if the timing is set too advanced, or if they are running a to small a spark gap. I have also heard that it melts the pistons and/or the rings? is that correct? how do i know if it's pinging or detonating?

[Roy]

Well since noone has answered and as an owner of a turbo car its pretty important that you are able to identify it, ill give it a go.

Basically pinging is uncontrolled burning of the air/fuel mixtures in the combustion chamber of your engine. Controlled is when the spark plug ignites the mixture, uncontrolled is when for any number of reasons such as poor fuel, excessive heat, excessive boost/ignition that the mixture ignites without spark, which is a bad thing as the piston isnt in the right position and isnt ready for the ignition/expansion part of the process. ie piston tryin gto go up, yet combustion of mixture wants to send piston down and something has to give usually a piston, sometimes a rod out the side of the block.

So thats what it pinging / detonation is. What it sounds like is small pins dropping inside a metal tin. It is not always audible, but in extreme cases its pretty hard to miss with audible tell tales, plus puffs of smoke from the exhaust and sadly dead pistons, rods etc etc.

Typically if an engine starts to ping, by the time you can hear it, its time to address it immediately, and is usually mated with a slight to sometimes severe drop in power.

How to fix it, take it to the experts to rectify. It can be as easy as rigging up a good cold air intake to drop inlet temps, improved intercooling, reduction in back pressure, running different spark plugs, tweaking fuel & ignition maps... or any combination of these things.

But i would be ensuring that the engine is breathing properly with nice exhaust and inlet flow, and oil and water temps are being properly controlled before you fiddle with the fuel and ignition tuning of the engine, as ultimately you could be masking a defeciency in your engine if you simpy wind out ignition, drop boost or add fuel etc.

Hope that helps!

[TurboX]

I generally agree with ROY, but you can experience Detonation when the ignition of the Air/Fuel charge is initiated at the correct time by the correct means - the spark at the plug.

This is one subject that there is a lot of talk about that is not always correct as there are so many variations on cause and effect known by many different names.

I dont profess to understand it completely, but I do know that it is important to do everything in your control to try and prevent it.

Roy's last paragraph is good advice, and I belive that there are many other things to do that can reduce the chances as well,

including ensuring your Timing & Air/Fuel ratios are correct under boost on a dyno, your fuel filter is not more than 2/3 yrs old or not partialy blocked, injectors clean, decent fuel pump at right rail pressure, no oil soaked blowby going into your intake via PCV, Pod filter sucking hot underbonnet air, dirty Air filter, dirty Fuel pump filter, low voltage at fuel pump under load, and my personal favourites, no sharp edges in combustion chamber!

This includes Spark Plug Threads, valve reliefs in pistons, head shaved edges, valve seat machining, piston indents etc.

Unfortunately the head has to come off for these extreme measures but I think it all counts towards more safer power and if you have it off to be ported etc why not do it?

It does reduce your Comp Ratio slightly, but that lets you run more boost safely.

[MANWHORE]

ok, thanks guys for the response. I now have a rough idea of what it is. From what your responses, it seems that mild cases cannot be readily heard, and by the time you can hear it badly, it's too late. Damage is done.