Engine failure AFN :-(

Unfortunately, my TDI AFN engine failed on Thursday while I was driving home, after being under full load for less than 2 seconds. "Oh great, the turbocharger is blown!"
I drove the last 1.5 kilometers home, feeling completely frustrated. He only ran for...
3 cylinders, but sufficient for 1.5 km. Left a really beautiful brown flag about 50 meters behind the front door.

So, it had happened. I actually hoped that the motor would last at least 100,000 km with that performance. Intake hose ripped off, but all the turbine blades are still there.
Turbo not broken , at least on the compressor side.
The next day, the compression was measured. Result.
Cylinder: 1, 27 bar.
2 26 bar
3 28 bar
4 1.9 bar
The head must be removed... cause found.
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Now I'm wondering what I should do with this block of time. Mileage approximately 110,000 km.
One thing I know for sure is that this unfortunately won't be cheap.http://www.franken-online.de/Steffarn/Kolben%20A4%20Tdi.jpg{MARKER}

'It seems like 1.8 bar of pressure was probably too much.'

Try to investigate how the damage occurred, specifically where the crack originated and why.

CU Gremlin.

Why do you want to throw away the block?

New pistons with reduced compression ratio, and that's it!

Regards,

Manuel.

Gremlin wrote:

Those 1.8 bar were probably too much...

1.8 bar is probably not sufficient on its own, but rather works in conjunction with a higher fuel injection volume.

It could also just be a dumb coincidence that the piston had a manufacturing defect and would have failed anyway, even without any modifications.

@Steffarn: Approximately how many horsepower (HP) and Newton-meters (Nm) did the engine produce before?

Manuel Thomas wrote:

Why do you want to throw the block away? New pistons with reduced compression ratio, and that's it!

I completely agree.

If the tread and bearings are in good condition, I would use this tire in every application. With 100,000 km (approximately 62,000 miles), the engine block has lost its initial casting stresses and is at its peak stability.

In the 1970s, BMW sought out such old engines at high prices in order to build a 1.5-liter F1 turbo engine with an output of 1000-1500 horsepower. Today, the blocks used for such projects are artificially aged.

Maybe 1.8 bar was too much.
1.8 bar is probably not sufficient on its own, but rather in combination with a higher fuel injection volume.

Did you make a joke?

without a 'compelling' reason, he probably won't drive it at 1.8 bar .

CU Gremlin.

As announced, nothing happened regarding the damage.
The engine was almost at operating temperature, and then I wanted to give it some gas.
Then, at around 2600 RPM, the boost pressure gauge started to fluctuate significantly, and I immediately took my foot off the accelerator.
Then he drove out, arrived at the intersection, and while stopped, he was shaking violently. So, it was only running on three cylinders.
At first, I thought the turbocharger had broken it apart, and then it sucked up the debris and forced it through the valves, which would prevent compression if a valve was bent.
However, that wasn't the cause; the turbo is still working fine.

That about the 1.8 bar is actually correct.
The engine control unit (ECU) was adjusted to a boost pressure of 2800 mbar, as per my request.
and the injection volume is approximately 60 mg per injection.
Power output: approximately 200 horsepower and 400 Nm of torque at 2300 RPM.

It's highly likely that the tuning contributed to the piston failing so quickly. But perhaps he had material damage from the very beginning (as Ulf already mentioned).

I'm not sure if I should completely disassemble the engine block and have one of the cylinders re-bored.
or all four at once. What do you think?
The Mahle pistons cost me 136 euros each. (This is the first oversize.)
Honing the cylinders: €140.
And unfortunately, it's about 40 hours of work that I will, of course, complete myself. (I've already saved up some money ).

@stefarn

Condolences.

I would overhaul the block. If I were to do it, I would do all four cylinders, possibly grind the crankshaft, and rebuild the cylinder head. If you do it yourself, you know what you've done and that your work is correct. If you go to a repair shop you don't know, you have no guarantee that the block was properly rebuilt. A rebuilt short block generally costs at least €1700-€1900, and that's without knowing exactly what work was done or not done. A completely rebuilt engine, ready for installation, costs a minimum of €2700. An alternative would be to find a block from a car that was totaled but has low mileage, but that's often difficult to find.

I was also looking for an ABN (presumably a specific part) for my boss's Audi. It involved a lot of phone calls and haggling. Due to a lack of time, etc., I ended up buying a rebuilt short block. I'll eventually rebuild the old block and use it as a spare engine for my own A4.

So, a replacement engine block or a complete engine are definitely not an option; they're outrageously expensive.

I hope the best-case scenario is that only the four pistons need to be replaced.
The pistons will probably need to be replaced with the first oversize size.
On this occasion, I'll also replace the needle bearings.

Hi,

I've heard, through the grapevine, that cracked pistons are a common problem in TDI engines that are heavily stressed.

This suggests that it would be best to replace all the pistons.
However, engines can also be repaired. Whether the remaining three cylinders will be included in the repair is another matter, but if the cylinders appear to be in good condition, which is easily visible by the honing marks, I wouldn't have them re-bored. How well the engine will perform after the repair depends heavily on the skills of the person doing the work. Apart from the enormous amount of work involved compared to simply replacing a piston.

If I were in your position, I would replace the piston rings and connecting rod bearings during the disassembly process.

Please post the bearing surfaces of the connecting rod bearings.

Otherwise, our condolences and best of luck.

Hello Steffarn,

Since 200 hp/400 Nm is pretty much the maximum you can get out of the 1.9-liter engine, wouldn't it be possible to bore it out to 2.0 liters at the same time?
It's another financial problem.

Sure, here's the translation:

"Hi!!"

Drilling? Are we talking about engines now?

Increasing the engine displacement is achieved by modifying the crankshaft, connecting rods, and pistons. But should we drill it?

Regards,

Manuel.

Regarding that topic, I recommend you take a history lesson about VAG engine blocks...
Bertil wrote something down somewhere around here...

Drilling is risky when it comes to performance, as the wall thicknesses are already not ideal.

CU Gremlin.

I don't really think drilling is a good idea. I don't have any experience with that either.

What might also be considered are tuning pistons, of a certain kind.
The surface of the pistons should be specially coated to withstand higher combustion temperatures.
And if, for some reason, not all of the fuel from the injector sprays into the combustion chamber, the piston shouldn't be affected.

I have absolutely no idea where one could find something like that.
Let alone what they would cost.

What is the cost of 4 original pistons from Mahle or similar? Alcan already costs 550 euros + tax.

I definitely paid my dues with that car.
I will definitely continue to post updates on what I'm doing.
Thank you for your sympathy.

"Excuse me, what did you say?"
What is included with the 550? Rings + bolts?

Best regards, Robert.

The piston rings are being installed. That's it .