Warning for GTB owners...

[alex_e3]

So... a pattern seems to be emerging regarding engine failures with GTB powered Fabia's. Mine having blown last month, Adam's last week, Kev's some time before, Silky's on another occasion etc...  Failures are tending to be knackered bottom ends, i.e. pistons melting or cracking.

 

A small group of us (including John, a.k.a. Faboka) have been discussing what the possible cause of these failures is down to. There's been suggestions such as injector failure, cyclic heat stresses, excessive cylinder pressures, stock injectors etc...  However, we're yet to come to a conclusion. Obviously we don't have VW's R&D resources to play with here!

 

My engine should be being opened up in the next couple of days to find out what has gone. Although it's likely to be a cracked piston. Southy has had his apart today and has also found a cracked piston. I'm sure he'll be along soon.

 

Now obviously these cars are being pushed to twice their standard power with some serious boost pressure. Does anyone have thoughts from proper educated knowledge on what would be causing these types of failures? My worry is that there are more and more GTB powered Fabia's appearing, and seemingly there's many ticking time bombs out there waiting to go off - ours being some of the earlier cars that have now run more mileage. Not to mention our worries of rebuilding them to have the same happen again later down the line.

 

Discuss...

[hutchysrs50]

I think steveopc also had a failed piston with his GTB.

What do the likes of Jason run then? Or is his already upgraded forged on the bottom end?

[faboka vrs]

I'm going for cyclinder pressure causing Southy's to crack.

Comparing EGT with yours and Coskev's show no difference in temps, yours being standard injectors and his being DSSR's. However this may not be telling the whole story of what's happening inside the cyclinder And it maybe the long duration (45 degrees) is causing a hot temps but as all the fuel is being used up EGT is kept low.

[vRSAnt]

Just for clarity only the biggest GTB2260 so far ? Or anyone having the same with GTB1756 also ?

[Tech1e]

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

[alex_e3]

I think steveopc also had a failed piston with his GTB.

What do the likes of Jason run then? Or is his already upgraded forged on the bottom end?

 

I didn't realise that Steve did a piston too??

 

As for Jason's, he may be along at some point given the thread title, but I was under the impression that he runs standard pistons but with forged rods. I was also under the impression that the pistons are forged as standard...

 

 

 

Just for clarity only the biggest GTB2260 so far ? Or anyone having the same with GTB1756 also ?

 

Kev melted 2 pistons big time when running his 1756. Those turbo's seem to generate much higher EGTs.

[alex_e3]

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

 

Mine is BLT, I think Southy's may be too. Kev's was an ASZ however. Not sure on any others...

[sepulchrave]

It will be a thermal stress fractures caused by the very high chamber temperature during compression overheating the piston crown.

[Tech1e]

Probably a similar reason why we also see a lot of head cracking too in the combustion chamber.

[Southy]

As Alex has already said I have suffered from a cracked piston on my BLT engine'd 2260 car. I was just casually driving home one evening last week after finishing work and put my foot down slightly to overtake a car on the by-pass. The car just lost all power as I passed said car, and started to chuck a load of smoke out of the rear.

 

This is how the engine ran after the incident occurred

http://s264.photobucket.com/user/south001/media/Fabia%20vRS/20160211_101203_zpsnt32ktig.mp4.html

 

Upon removing the engine over the weekend, and finally pulling the cylinder head today I was greeted with the following sight on No.2 cylinder (No.1 being cambelt end of the engine)

 

 

 

[alex_e3]

It will be a thermal stress fractures caused by the very high chamber temperature during compression overheating the piston crown.

 

So... this leads to the next question of... what is causing the high temperatures? As John mentioned, I was seeing EGT's of not much higher than 700 degrees on-track at Oulton. Kev was seeing slightly less with DSSR +130's. How much do the gases cool before reaching the probe?...  Does running longer durations increase the heat? If so, why?

 

Next question after that is....  what can be done to strengthen the pistons? I know there are coatings available - what works and what doesn't? I've read about this WPC treatment which is similar to shot peening, but involves higher velocities and smaller particles - which in turn makes it suitable for high tolerance parts such as pistons, apparently. Downside is that it's done in America and probably expensive.

[Jrjg]

Will be following this closely. Especially as I am due to fit a gtb1756...

JRJG

[hutchysrs50]

I'd also look at some of darksides projects, the PD engine in their Arosa is running very high power, did they change the Pistons etc in that? Might be somthing els to look into.

[Southy]

I'd also look at some of darksides projects, the PD engine in their Arosa is running very high power, did they change the Pistons etc in that? Might be somthing els to look into.

 The Arosa is a 2.0 16v, looking through the build of it the pistons are standard, but have had a treatment of some form, with them being gold in colour. For the life of me I can't find what particular coating they have used on it.

I have searched high and low the last few days for any 'uprated' pistons for the 1.9tdi and nothing seems to exsist. 

I have even looked into cryogenic treatment to stress relieve the parts.

[hutchysrs50]

Ah right, I wasn't sure if it was the 1.9 or 2.0.

At least you know a 2.0 conversion is up to the power anyway.

[Southy]

I've contacted DS regarding the matter as I am tempted to go down the 2.0 route myself and use the BHW pistons in my block, but obviously I am now concerned that this issue may arise once again further down the line, but they assure me they have customers and there own car's running 300bhp+ on these pistons with no issues, but having had this surface just over 12months since I converted to the GTB setup, (granted the engine is 100k old now) but both myself, Alex and Kev all seem to of had these problems after a same time frame on the setups which obviously concerns us.

[hutchysrs50]

So what do you all have in common then? power goals, same supplier of turbo?

Against darksides setups. Do they use a different manifold or housing, different supplier for parts?

Any failures with different exhaust manifolds, tubular etc? I was under the impression they kept temperatures down?

Edited 15 February, 2016 by hutchysrs50

[Southy]

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)

[sepulchrave]

Looking at Southys piston the crack appears to run right across the same axis as the gudgeon pin, you can see in the third picture where the piston has smeared itself down the bore wall indicating a partial heat seizure.

You need to look at all the cylinders to see if there are similar seizure witness marks on all the bores.

[hutchysrs50]

Surely the gudgeon pin is just coincidence being centre, are you thinking compression is to high and the force is pushing it to crack?

I noticed the marks on the bore, doesn't that happen with oil starvation, or in this case a result of the cracked piston?

[hutchysrs50]

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)

Ok so... Anyone used a different supplier of turbo

And had theirs mapped by someone els

Running or failed.

[sepulchrave]

Surely the gudgeon pin is just coincidence being centre, are you thinking compression is to high and the force is pushing it to crack?

I noticed the marks on the bore, doesn't that happen with oil starvation, or in this case a result of the cracked piston?

 

No, the piston cracked because it seized, it seized because it got too hot, the gudgeon pin axis is weaker because it has a bloody great hole bored right the way through it.

What I want to know is if all the pistons show signs of seizure, this would suggest the problem is fundamental rather than isolated to that particular cylinder.

Edited 15 February, 2016 by sepulchrave

[Southy]

No, the piston cracked because it seized, it seized because it got too hot, the gudgeon pin axis is weaker because it has a bloody great hole bored right the way through it.

What I want to know is if all the pistons show signs of seizure, this would suggest the problem is fundamental rather than isolated to that particular cylinder.

 

The block and pistons will be stripped down fully tomorrow so I can report back on that matter. Given the mark on the cylinder wall, there is NO grooving actually occurred and nothing can be felt with a finger nail, so unless damage has occurred further down the bore I may of escaped fairly lucky.

 

The main damage to the piston found so far looks to of been within the bowl of the piston, there is a fairly large chunk missing out of the side of the bowl which hasn't shown up great in the pics and can just be made out in the second picture. Could the rest of the crack of formed due to this initial crack in the bowl and spread the rest of the way across the piston on it's weakest point along the axis of the gudgeon pin area?

 

[sepulchrave]

The block and pistons will be stripped down fully tomorrow so I can report back on that matter. Given the mark on the cylinder wall, there is NO grooving actually occurred and nothing can be felt with a finger nail, so unless damage has occurred further down the bore I may of escaped fairly lucky.

 

The main damage to the piston found so far looks to of been within the bowl of the piston, there is a fairly large chunk missing out of the side of the bowl which hasn't shown up great in the pics and can just be made out in the second picture. Could the rest of the crack of formed due to this initial crack in the bowl and spread the rest of the way across the piston on it's weakest point along the axis of the gudgeon pin area?

 

It could have, it's really hard to see in the pictures, I'll wait until you've stripped the lot to see what's what. need to see all the pistons and the bores before deducing what happened.

[coskev]

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

Edited 16 February, 2016 by coskev