Examples of det damage

[macca]

I thought these might interest the more technical of you out there. Some examples of why det is bad (mmm kay?) and what it can do to the precious insides of your engine:

http://www.i-macca.co.uk/stuff/detdamage.jpg
This is a piston from a 2JZ-GTE Supra twin turbo engine, you can see the top right edge of the piston has suffered from fairly bad detonation which has damaged the piston ringlands where the rings sit. This is what detonation usually looks like, especially when the rods haven't given way as well.

http://www.i-macca.co.uk/stuff/detdamage2.jpg
This piston is from a 3S-GTE Celica GT-Four and looks like a standard ST205 model piston (these were ceramic coated). This has suffered severe detonation which has become so aggressive and hot it's actually melted the piston ringlands.

http://www.i-macca.co.uk/stuff/detdamage3.jpg
This looks like another ST205 3S-GTE standard piston that really has been damaged very baldy by sever detonation. Too much boost, too much ignition and not enough fuel = bye bye engine :no:

You can see that the det always targets one area of the piston instead of happening broadly across the cylinder. Could be many reasons for this, spray pattern, inlet design, cylinder design etc. etc.

Det can also damage head gaskets, especially if thicker head gaskets have been fitted as this becomes a weak point and the det will concentrate there.

[AndysR]

Not nice especially that last one, the owner must have heard the det on that surely? :not:

What was the cause of the det on yours? To much boost? or incorrect fuel/ignition advance.

[macca]

Those pics weren't mine, just ones 'borrowed' from forums when I've seen them as I have a morbid fascination with it :)

They would have been able to hear the det on all three of those, that kind of damage happening is definitely audible. Whether they understood what they heard is another thing, most people wouldn't expect it to be the piston saying goodbye. And to be honest when it gets that loud you've not got much time to stop things, the damage is already done.

[macca]

I'll try and find some pictures of what happens to your pistons with mild det, as this also causes damage but not as catastrophic.

[AndysR]

Whether they understood what they heard is another thing, most people wouldn't expect it to be the piston saying goodbye. And to be honest when it gets that loud you've not got much time to stop things, the damage is already done.


Good point!

Would be interesting to see the pistons from engines which have been suffering from mild detonation. :)

[Tricky-Ricky]

There is an interesting explanation of how and why det is caused here, plus where in the cylinder its most likely to effect and damage, sharp edges etc that can get super heated.
Most references are for V8s but interesting anyway.

http://www2.zhome.com:81/ZCMnL/PICS/detonation/detonation.html

[macca]

Great link, thanks Dick!

Explains it a lot better than me!