Engine damage

[Jaff.]

does anyone care to offer a possible explanation for this?

gonna get my injectors checked just in case for the detonation, but the pickup on the block and piston skirts is worrying me now.

Det by JaffmanRS, on Flickr

Det by JaffmanRS, on Flickr

Det by JaffmanRS, on Flickr

Det by JaffmanRS, on Flickr

Det by JaffmanRS, on Flickr

Det by JaffmanRS, on Flickr


as you can see no 1 (normal engines) cylinder has taken the brunt. would the detonation cause the pickup?
have no experience with this sort of damage

 

[Andyrg@ ClioTurbo]

ring gaps

 

[Jaff.]

any more info?

was that just a guess?

 

[Dan@SJM]

They're toast mate.

(I can do new pistons pretty cheap)

 

[Jaff.]

I'm up for that dan. If there's nothing that can be done for these...

I've got a new block on it's way so I have everything apart from gaskets required to build the engine back up then (minus the machining)

 

[RenMatt]

Last time I saw some thing like that was in the good old days of gt turbos , to much heat & incorrect fueling was the main cause . last year had a dci clio that melted the pistons to the head as in your pic that I put down to a fooooked turbo and injectors

 

[Jaff.]

It has done 7-800 miles on some old injectors that I don't know if they were good or not. The rest has been starting if up for a min or 2 with brand new Siemens deca injectors. Those 1-2 mins were barely enough to get it to overheat

 

[Shocker]

Detonation causing little bits of melted piston to stick to the bore walls seen this on lots of engines mainly stuparuus

 

[NorthloopCup]

Who mapped it out of interest??

 

[Jaff.]

I'm not bringing mapping into it a minute.

It done 7-800 miles on the standard Renault map with standard injectors. Then it's been run for a few mins here and there on a base map and brand new Siemens injectors

 

[NorthloopCup]

I'm not bringing mapping into it a minute.

It done 7-800 miles on the standard Renault map with standard injectors. Then it's been run for a few mins here and there on a base map and brand new Siemens injectors

So when you say standard Renault map are we talking original ecu?

 

[Jaff.]

Yes

 

[Jay_Kay]

Maybe revving it on the base map bring the turbo the create boost had caused this. Especially if it was on base map.

 

[Dan@SJM]

Was it seeing any positive pressure when you drove it for the 7-800 miles?

 

[WilkyWay]

It's gotta to have seen boost. You don't get det marks like that from driving off boost.

 

[Dan@SJM]

Depends how it was running. If it was at 17:1 and 40 degrees advance It could. Lol

 

[Jaff.]

When it was run for 800 miles it was just swapped into another car. So basically a low comp standard engine. It was just done to run it in.

The he only time it's seen anything from the turbo was a quick blip of the throttle when I started it the other day. I'm not talking bouncing it off the limiter btw

That doesn't explain how cyl 1 is considerably worse than the rest of them though...?

 

[Dan@SJM]

Wiring or injector issue. Leaning out that cylinder.

 

[Jaff.]

That's the explanation I came up with. But was it the standard injectors used to run the engine in or my new ones?

how can I check my wiring?

 

[Chip-mk1]

A single cylinder will always be worse than the others, even if its just a general mapping issue, as the 4 cylinders are 4 separate entities and are non identical so will react differently, and once one starts to go first it has a head start in damaging itself which means more det from oil getting into the chamber and lowering the octane rating of the fuel etc.

all 4 cylinders have marks on the head that look like det to me, so to me it simply looks like it was running lean or running too advanced.

given the lack of overall heat symptoms I dont think it just leaned out personally, I think it was too much ignition that caused it, but I am not 100% on that its just my gut feeling, if it was lean induced det I would expect the see the exhaust side of one or more pistons actually melted away


by too much ignition, I mean for the combination of boost/cr/fuel you were running.

it could have had 2 year old petrol in it for example which would do that even if the map was ok on fresh stuff

likewise if the ring gaps were too large it could be oil contamination causing it by lowering the octane rating of the fuel


too many variables and not enough information to give a definitive answer



one thing you can be pretty sure of, is that if all 4 cylinders has detted, then if you build enough to a similar spec and run it in the same conditions, all 4 will again.

 

[Jaff.]

Thanks for your input chip.
If it helps I've always smelt fuel when it's been running and the oil in the pan has always looked slightly contaminated when I've taken the sump off (I put this down to a lifter issue I had when I was first trying to start it)

another explanation I thought of was a bit of bore wash to have caused all that pick up? But that went against the lean running idea...

 

[Chip-mk1]

I think that its had too much timing more than too little fuel personally.

It may be that what happened was:
bore wash
oil contaminated incoming charge air by getting past rings
det caused by poor fuel quality (cause its got oil in it)

or it could be that the det is unconnected to the bore wear, the det certainly doesnt look bad enough to have caused that, its not like its going to have nipped all the rings for example, so it might be that you have two seperate problems.

 

[Jaff.]

Your right the rings look (to the naked eye at least) perfect.

do you concur that these pistons are dead? Or do you think they can be saved?

 

[Chip-mk1]

pistons have had it, even if you skimmed the top to clean the det marks off there, the skirts are gone.

 

[Jaff.]

They are oversized so can they not be turned down to standard size? Or does that offer other problems?

Ive be pretty much resigned myself to buying new pistons anyway I'm just wondering

 

[Chip-mk1]

They are oversized so can they not be turned down to standard size? Or does that offer other problems?

The piston skirt isnt straight its slightly tapered, so it would be a hell of a machining job to do so, then the grooves would be needing to be redone as they would no longer be shallow enough etc, and any heat treatment the finished piston had would need to be repeated etc.

It might be possible, but its got loads of potential issues and when you can avoid the whole lot as cheaply as 400 quid for a set of new pistons it seems utterly silly to try IMHO

Ive be pretty much resigned myself to buying new pistons anyway I'm just wondering

You need new pistons. new block. and potentially a new head too as even if you skim it enough to clean it you will need to get it hardness tested as it might have gone soft and you risk running into issues with it being too thin from the skim and messing up CR etc.

You look like you can probably use the valves, rods and crank again after inspection, but thats about it.

 

[Jaff.]

The head is being re-used. I've got a new block coming. I'll order some pistons (don't know where you're finding them for £400 though)

the rest as you say is fine. I'm just apprehensive about spending again because there's no definitive answer to how this happened

 

[Chip-mk1]

What recitification work are you planning on doing to the head before you use it?

just a skim or are you going to get it hardness checked?

 

[Jaff.]

I was gong to get it skimmed. Take the absolute minimum off it as it's been done before. I don't know any requirements about hardness testing you saying that is the first time anyone has mentioned it. I suppose I could look into that. I really don't want to scrap this head as it's had a lot of money spent on it and I don't have a spare. So unless it's completely necessary I plan on keeping it

 

[Chip-mk1]

Why was it skimmed before?

That would ring even more alarm bells for re-using it for me TBH

 

[Jaff.]

It was sent to a specialist for porting and polishing it was skimmed as a matter of course to ensure it was entirely flat

 

[Chip-mk1]

Thats good then, was worried it was cause it had overheated.

 

[Jaff.]

No history of overheating mate.

Your ignition ion timing idea would sit well tbh as my crank sensor isn't the most secure and any movement could cause advanced ignition, plus with no knock sensor the ecu wouldn't know to pull it back.

I'm going to get my injectors checked, new block, new pistons, skim the head, new gasket (can you advise with this? I went 1.6mm last time but not sure why) check my wiring ( any way to check it's not breaking down when it's running?) and just get if mapped straight away

 

[Chip-mk1]

what cc is the head, what is the piston dish, what is the piston deck height and what CR are you aiming for?
if any of those figures is missing I cant advise at all on gasket.

 

[Jaff.]

I don't have those figures

 

[Chip-mk1]

then i cant help as the thickness of the gasket to get the correct cr is entirely dependant on those factors.

 

[Jaff.]

Is it essential?

 

[Chip-mk1]

Is it essential?

If you want to end up at a particular cr rather than just "think its lo comp mate" then yes.

 

[Jaff.]

Ok so how do I get these figures? Piston figures I imagine come with the pistons? How do I check the cc of the head?

 

[Chip-mk1]

You use a buerrette mate, or you can get close enough with a syringe TBH if you dont mind if its like 0.05 CR out or whatever.