Diesel engine Piston Damage causes?

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Diesel engine Piston Damage causes?

Postby kim0663 » Thu Mar 05, 2009 6:43 pm

I have a small assignment that i need to complete and it goes like this.
I have been given three pistons and i need to find out the cause for the damages occurred.
All damages are fuel related on some way and are diesel engine pistons. four stroke and two stroke.

Piston 1 : is a diesel engine with a concaved? piston head. half of the piston has melted and also, directly underneath the melted portion of the piston has scuff marks.
Image
Over heated? how does diesels over heat with a fuel problem?

Piston 2 : is a two stroke piston. It looks like it has been siezed and has scuffs everywhere from top to bottom of the piston skirts.
Image
Wrong oil/fuel mixture? or extended time of non operation leading to un lubricated bore surface?

Piston 3 : is of a 4 stroke piston and has had a valve brake off, smashing up the piston face. I am not sure if it is a crown type piston that has a combustion chamber within the piston or it has melted after a piece of the valve smashed a big hole into it
Image
What are the causes for valves breaking ? any other than detonation? i also think this is a diesel piston as well... please ignore that hole inside the 'combustion chamber like hole' (or is it?) as it has been drilled after the piston was taken out of the block.


Any ideas or experience stories would be appreciated... I've been researching a bit and have a vague idea of how these happened but i wanted to be sure before i start writing it up...
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Postby barryogen » Thu Mar 05, 2009 7:02 pm

rich mixture in a diesel causes high EGT... maybe if it were really rich it'd do it?
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Postby Truenotch » Thu Mar 05, 2009 7:12 pm

1 looks like it's dropped a glow plug, 3 could be the same if it's diesel.

2 looks like the piston in my scooter after a friend ran it with no piston for about a month.
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Postby Burning Angel » Thu Mar 05, 2009 7:55 pm

Truenotch wrote:1 looks like it's dropped a glow plug, 3 could be the same if it's diesel.

2 looks like the piston in my scooter after a friend ran it with no piston for about a month.


im not sure a scooter would go without a piston, maybe you mean oil?
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Postby evil_si » Thu Mar 05, 2009 7:57 pm

#1
over fuelling will cause a diesel to over heat,increases the combustion temputatures, leaking injector or incorrect spray pattern
the over fuelling has cause the piston crown to melt, damaging the skirt and bore, the over heating has also played a part in the scoring on the piston skirt

#2
2 stroke diesels dont run oil in the fuel for lubrication,
that particular piston just looks like its been overheated and picked up in the liner

#3
id say its dropped the tip of an injector and smashed that and broken the valve, the broken piece of valve has done the majority of damage,
and its suppose to have the big dish in the piston
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Postby kim0663 » Thu Mar 05, 2009 9:03 pm

can they drop the injector tips ?? wow... lol i thought i had done a bit of research but clearly NOT ENOUGH ! keep it coming guys this is great
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Postby finx » Thu Mar 05, 2009 9:19 pm

2stroke diesels are bad ass. i have worked on a few. detroit power for the win.
all of the above sounds pritty accurate to me.
i have seen damage done to pistions like no 1 due to people running a dicent mix of petrol in the fuel as well. stuffs with the cetain level and the diesels abitilty to burn/ignite.
Last edited by finx on Thu Mar 05, 2009 10:22 pm, edited 1 time in total.
daily: ep71 turbo s 2et 90hp atw 15.5sec 0-400m (stock) current 5efhte + ct9b on 6psi, 13.7@158km , torque steer??
nothing sounds like a 2stroke engine on the rev limiter
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Postby Adamal » Thu Mar 05, 2009 10:14 pm

First one looks like it could have been caused by detonation?
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Postby evil_si » Fri Mar 06, 2009 6:56 am

from my experience diesels dont suffer the same detonation effects as a petrol engine,

would also be interesting to know the brand of engines those bits have come out of
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Postby fangsport » Fri Mar 06, 2009 7:34 am

No.1 looks a lot like the last Isuzu diesil i pulled down. holed radiator, but driven till stopped. every piston melted. molten alloy on valves, through turbo and exhaust. didn't seize in the bore once cooled, but obviously tried to seize due to extreme heat.

appears to be a diesil turbo piston.

No.3 appears to have have a foreign object caught between valve and seat, and the piston has come up , made contact and broken corner off valve. the chunk of valve and 'foreign' object have been pummeled between piston top and head/valve.
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Postby Voyeur » Fri Mar 06, 2009 12:35 pm

No 1 incorrect spray pattern, directed at exhaust side of piston

No 2 Too lean, faulty injector/pump, blocked filter.

No 3 Mis-timed injector pump
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