How do pistons fail on a turbo car?

[squeekyduck]

I have just been wondering about this over the last few days and maybe some of ye people might know. Basically everyone says not to turn up the boost on an engine past a certain ammount because the turbo is not rated for the pressure and the internals will go pop. Now my question is: is it the pressure created by the high spooling turbo that makes the pistons go boom or is it the high temperatures?? Can anyone shed some light on this please.

 

[Franza1]

It's Nearly always the high temperatures combined with the extra combustion pressure put on the pistons that cause them to fail,

Heat = Expansion
Expansion = Stress on components as they are too tight

 

[squeekyduck]

It's Nearly always the high temperatures combined with the extra combustion pressure put on the pistons that cause them to fail,

Heat = Expansion
Expansion = Stress on components as they are too tight

makes sense frankie. so if you introduced water cooling this would help?? no. obviously forgies and lower boost are the best, just thinking other options here.

 

[Franza1]

makes sense frankie. so if you introduced water cooling this would help?? no. obviously forgies and lower boost are the best, just thinking other options here.

I would allow you to push up your break horsepower that much further but you would run into a brick wall again pretty soon, Best thing is forging as it would give you alot more room to play with,

Pistons would be a must where as Rods wouldn't be as essential, most people do both as it would give them that much more peace of mind and you may aswell do all of the engine instead of half if you know what i mean

 

[Dave@TM-developments.com]

Detonation is the biggest cause on a turbo car

 

[Monkfish]

Detonation is the biggest cause on a turbo car

Correct. My understanding of det is this...

As the piston travels up the cylinder, just before Top Dead Centre (TDC) the spark plug fires, igniting the air/fuel mix in the cylinder and pushing the piston back down. Detonation is where the temperatures in the cylinder are too high, and as the cylinder compresses the petrol, it explodes early before the piston gets to TDC. The effect on the piston is that it's trying to be forced down while it's still on it's way up. It wrecks the bottom and and will crack the piston/rings.

IMIRITE?

 

[Nwimie]

does anyone on here run oil squirters or water injection kits ?? would be interesting to see the results.

 

[sx_turbo]

mostly piston damage is done because of to little fuel, the fuel helps cool the piston down, when there is not enough fuel is when piston damage occursas it gets to hot.


@monkfish- wot u described was wrong timing, if to far advanced you will get preignition which is another form of piston damage.


generally its only really turbo cars that have been tuned that suffer engine failure.

 

[Sharagath]

I had the same question and my enginebuilder gave ma a little lesson in keeping your engine working.

Detonation is exploding fuel before the spark plug fires. This does not happen directly trough heat ,but trough a to high boost. The compression rizes and gets to the point were the fuel wil burn on its own(like a diesel but at the wrong moment).
Mercedis Benz is worikng on a engine with twin charging and controled detonation in low revs for fuel economi(detonation happens at the right mixures of fuel and air).

Killing a turbocharged engine;
- wrong AFM(running lean)
- Running to high REVs
- Detonation because of wrong AFM and to high boost

these things are ale temp related, high temp will melt valves and pistons.

Boost will give great force on the crank and rods, the weakest point will always be the baerings of these.
Boost could give detonation, but could be fixed by lowering compression or running rich.

 

[Monkfish]

@monkfish- wot u described was wrong timing, if to far advanced you will get preignition which is another form of piston damage.

No, I was on about det, hence the...

"Detonation is where the temperatures in the cylinder are too high, and as the cylinder compresses the petrol, it explodes early before the piston gets to TDC."

Not advanced timing, just the mix exploding too soon. Sharagath described it better with...

Detonation is exploding fuel before the spark plug fires. This does not happen directly trough heat ,but trough a to high boost. The compression rizes and gets to the point were the fuel wil burn on its own(like a diesel but at the wrong moment).

 

[sx_turbo]

i apologise monkfish

 

[Monkfish]

No problems, easy to misunderstand...

Hell, I struggle myself!

 

[Sharagath]

does anyone on here run oil squirters or water injection kits ?? would be interesting to see the results.

this info i got form my engine builder.

water injectors will lower your inlet temperature and exposion heat.
Oil squirters are jusefull if you are going to run for longer times in high revs. there are people wo take them off and make more HP, they don't drive autobahn.

circuit driving and drag racing give your engine enough rest to cooldowm before the next acceleration.

 

[slostar]

no no, detonation isn't caused buy the fuel being ignited before the spark plugs are fired. that's preigniton - ignition happening before its spose to. but can lead to det

detonation- very simplified way of explaining it: when the fuel mix erratically combusts due to excessive cylinder pressure, at the time the mix is lit... ignition timing, fuel octane, boost pressure, in cylinder temps. will all have an effect on detionation threshold. plus clyinder head design, but we're all talking e series here
so if the mix is lit too soon. be it a hotspot, (pre-igniton) or too much igntion advance. the cylinder pressure will be way too high, due to the fuel mix exploding, and the piston trying to compress the explosion at the same time. then we have some detonation and some nicely cracked ringlands.
the colder the air and higher octane of the fuel will prevent the above happening to a point.

its very hard to explain, and theres alot more to it than that. but gives you an idea









so many people give the standard pistons a bad name for being "weak" after they crack one from detonation.

 

[HYBRID]

Every material has its rating, the stock internals are pretty strong, however like we said everything has a limit... now since nobody runs the perfect conditions all day long, for ex intake air temp, it is much harder to say how long an oem piston will last... thats y u have an average rating for each internal.. iv seen a person crack a combustion chamber but the piston was still intact.. later found out one of the valves was sticking..

there are so many variables that its impossible to state an exact list of what causes what to go.. All it takes is a drop in oil pressure or a little extra oil temperature & u could b on ur way to havin a serious problem..

Kon