Tuning: ZK Screws & Fasteners

Hello,

It is well known that excessive compression ratio and/or an excessively early injection timing (achieved through tuning) can lead to head gasket failures, and this also applies to the design of more powerful factory versions of existing engines.

Probably that's why the ARL engine received stronger connecting rod bolts (038 103 384 C, strength 12.9, if I recall correctly) compared to the other PD engines (038 103 384 / 10..

The 160 hp BPX engine, being the most powerful 1.9-liter production engine, still, according to the records, only uses the "softer" 038 103 384 screws.
Okay, one might think: a mistake in the records.
But now there's also the Sharan with a 150 hp 1.9 PD engine called BTB. And for that engine, only the standard 038 103 384 screws are listed in the records... I really don't want to believe anymore that there are two identical errors listed in the records .

So, how is this to be understood? Why were only the ARL models fitted with the extra-strong screws, when engines of the same or even greater power could manage with the standard parts?

I haven't seen any MSG files from BTB yet, but the BPX has the same PDE values as the ARL, the same starting pressure settings, and 50 mbar more maximum load pressure. Therefore, in my opinion, the stress on the screws in the BPX cannot be lower than in the ARL.

Do the standard screws of the "smaller" 1.9 PD engines actually offer higher tuning potential than one might expect, considering the ARL parts?

Hi Ulf,
It's possible that they were still afraid of using the ARL and then eventually realized that the cheaper ones also work.

Best regards,
Rudi

Hi Ulf,

Take a look at the dress code.
It's possible that the "softer" approaches are the key to avoiding greater damage.

In the Cosworth turbo engines of the 90s, during (extreme) tuning, the standard screws were intentionally milled to create a tapered shape. This reduced the (maximum possible) tensile forces on the screws, but increased their flexibility (which is particularly important at high temperatures). The goal was to avoid expensive cylinder head damage and instead sacrifice the cylinder head gasket. However, these modified screws required slightly higher torque settings.

Bertil wrote:

Take a look at the dress code. Possibly, the "softer" approaches are the key to avoiding greater damage.

Hi Bertil,

According to my research and inquiries, the same dress code applies to the ARL as it does to the rest of the TDIs .

Do you think that too many ARL-ZK components were damaged due to the hard screws, which is why softer screws were used in subsequent versions?

Then it would be consistent to also change the "Akte" – that is, to replace the ...C screws with the universal parts and to include this information in the documentation for the ARL as well, just as it was supposedly done with the first PDE ball joints (which still had the ball joint surface curved upwards, so that the oil always ran out instead of collecting inside)?

I don't know why the Sharan came with soft suspension, but when you get the chance, replace them with stiffer ones.

The parts even fit on a Golf 3, if you use special washers .

It's simply necessary when you increase the engine's power output twofold; otherwise, the head gasket will fail after only 20,000 kilometers.


There are also specialized titanium bolts (e.g., from DRV) that are extremely strong, last a lifetime, and are reusable... but they cost €200 for a 4-cylinder engine.
On the one hand, spend 200€ once and be done with it, or on the other hand, replace the cylinder head gasket every 20,000 km...