I'm pretty sure my failure was down to an injector fault,as it did show 'injector fault cylinder two' on VCDS,so I'm thinking mine doesn't really have anything in common with Alex's (if it's cracked a piston) and Adams.

Mine melted the piston two,and had started to melt piston three aswell,but this could have happened from the massive melt down of piston two as the engine seized solid braking at circa 70mph after a WOT run.

http://smg.photobucket.com/user/coskev3/media/Mobile%20Uploads/2015-07/IMG-20150703-WA0010_zpsdrbqognl.jpeg.html

 

Yes, your situation is totally different, but the faulty injector in cylinder two can't have caused the problem in cylinder three as well.

I'm running a DS tubular manifold and Alex is running a cast manifold so we can't put it down to a heat issue caused by the manifolds. Essentially both mine and Alex's are the same setups apart from the manifolds, we are both using the same mapper (Faboka) and same supplier of the turbo (Xman)

 

Are you both running 2.5bar on stock injectors also? sorry to hear about the engine but sure you will be back on the road soon. Makes me slightly concerned now however i have only done 2k miles on mine so far. 

My ASZ bottom end has been really solid.  In fact if I am switching to a low mileage BLT bottom end (in a 2 litre conversion) I might make sure the 2 litre pistons are a good design / strong.  I'll be using BHW pistons so not sure how decent they are.  Perhaps I should be considering using uprated forged ones?

 

My head has been off probably 3 times now.  Due to upgrading the head mainly but the last time due to low throttle smoke which turned out to be a cracked head (and turbo seals going) - new head on and its better now but still does it a bit.

 

Each time the head has been off, the state of the bottom end has always impressed me - nice clean pistons, cylinder bores looking decent - The last change was with the engine at 155,000 miles, and the engine has been 220bhp since 7,500 miles, and steadily increased over 10 years or so to the 300 (and something) it is now.  So I am following this thread for morbid curiosity but have never suffered [touch wood].

 

There's only one thing I can think of that might be to blame, and its clutching at straws, but from early days - probably around 7 years and from about 50,000 miles I've been using uprated injectors of some sort.  Started with Bosio R783 +30% ish.  Upgraded to Firad +80s for a fair while and currently using DSSR130%.  I don't know the mechanics of big injectors or how mapping is affected, and how it may affect combustion process.

Edited 16 February, 201610 yr by devonutopia

The larger injector flow more so the window of injection (duration) is reduced.

Kev's dssr 130 is running 24-25 degrees of duration compared to my stock 22.5.

I'm saying its heat in the cyclinder (not exhaust) caused by long duration of the standard injectors.

What's the split with ASZ and BLT?

ASZ pistons always looked stronger to me. The crown design of the Euro 4 BLT was always going to be a bit of an Achilles heal

Adams looked up replacement after market pistons and its listing the same piston for both ASZ and BLT,so if he asked at skoda they would list ASZ different to BLT?

I'm saying its heat in the cyclinder (not exhaust) caused by long duration of the standard injectors.

 

Now I have zero engineering skills, but it was the one thing that seems to separate my setup from the odd other setup - and I have caned my engine very hard at times, but the bottom end has been so reliable.  Yes, I have blown turbo seals (2.8 bar boost will do that....) and there's been other wear & tear, but the block has been immense.  It's one reason despite having a low miles BLT block to use for the conversion, I am reluctant to go 2 litre until I really have to.

As Kev has said I have looked in the piston catalogue we have at work and the ASZ and BLT pistons are both under the same listing. Any idea what differences there are from factory?

Well engine is stripped down fully now and I have a few better pics of the bore and piston itself.

It's not 100% clear from the photo, but the crack has spread down to the gudgeon pin area and the bronze bush has spun and that is what has rubbed on the cylinder wall.

Dang!! :(

The bottom ends of the ASZ and the BLT are identical. Block, crank, rods and pistons are all the same.

Haven't most failures been on stock injectors or most of them? I'm going with stock injectors being pushed too hard in terms of duration etc.

But not due to high EGT like everyone makes out but for a different reason.

High EGT knackers turbos not engines, DUH!

Most definitely high cylinder pressures would ceramic coating pistons be an option?

I'm heading towards cyclinder pressure, so the obvious would better/coated Piston

Would not lowering compression have a similar effect ?? I know it's a little say.... Tricky as dervs work off compression but would it be worth a try but again it would be hard to test

I don't know much about compression but the Chap who runs an overseas porting company said not to fiddle with it (eg fitting a 3 hole gasket when 1 hole applicable) so I made sure I got the right gasket

Stronger pistons are the obvious answer as they are seemingly the weak link in the chain.

 

I've also been scouring the net looking for uprated forged pistons for the PD lump and while lots of people make them for the various VAG petrol turbo units, none I have found list them for the diesel.

 

Other than looking at other manufacturer for an uprated piston I think it would be nigh on impossible to get the dimensions of the combustion bowl, piston height, gudgeon pin placement etc etc. I know some other brands can cross match, ie Vauxhall c20let pistons into Ford Zetec turbos

Stronger pistons are the obvious answer as they are seemingly the weak link in the chain.

 

I've also been scouring the net looking for uprated forged pistons for the PD lump and while lots of people make them for the various VAG petrol turbo units, none I have found list them for the diesel.

 

Other than looking at other manufacturer for an uprated piston I think it would be nigh on impossible to get the dimensions of the combustion bowl, piston height, gudgeon pin placement etc etc. I know some other brands can cross match, ie Vauxhall c20let pistons into Ford Zetec turbos

 

I thought standard where forged?

I think they are but so are the standard YB cossie pistons and you can buy stronger versions of those.

 

Limited options it seems when going to the lengths these big power guys are at like Coskev and Jason etc etc :|

I think lack of demand means no options generally. How many people tune tdis to how many ramp up cossie engines?

Edited 17 February, 201610 yr by devonutopia

Of course supply and demand will always be a factor.

 

Custom made pistons would "probably" be available but are the costs worth it? Where do you draw the line?

 

Alex - would the fitment of the 16v head have any reduction in cylinder pressures due to the faster gas flow of the better head or does the 16v bottom end differ enough internally to say its deffo stronger?

Thinking about it running lots of duration then having to increase soi to get a good eoi would increase cylinder pressures maybe going bigger on nozzles would help massively really thinks it's down to too much soi lowering compression would help but would that cause problems at low throttle?

I don't know much about compression but the Chap who runs an overseas porting company said not to fiddle with it (eg fitting a 3 hole gasket when 1 hole applicable) so I made sure I got the right gasket

I'm personally running a 3 holed gasket instead of 2 but this was because I skimmed my head last year when my cambelt went.

I've looked into the piston specs and the recess for the valve cutout on the BHW 2.0 piston is .7mm compared to 1.1mm on the 1.9 piston.

Also the 2.0litre piston has a slightly taller compression height of .03mm.

The piston chamber volume of the 2.0 is also slightly smaller at 23.3ccm compared to 24.2ccm on the 1.9

Has any been able to measure peak combustion temperatures? EGT temperature don't give the whole picture.

Also for those who have cracked a piston, have they cracked the same direction as southy.

mine cracked no4 and that was with a mdx 376 turbo no problem with gtb turbo with tubular mani