Golf4 vs Audi A3: ALH Engine Comparison

Does anyone know to what extent a complete engine (including auxiliary components, ESP, injectors, turbocharger, alternator, etc.) can be...?
Is a diesel engine from an Audi A3 (year 1999, ALH model) compatible with a Volkswagen Golf 4 (year 1998, ALH model)?

Specifically, it's a Volkswagen Golf IV with piston slap, and overhauling it after 385,000 kilometers, while keeping the auxiliary components, doesn't really make economic sense.

A used complete engine, including all its components, from an A3 might be available.

Hello,

It should be relatively straightforward to transplant the ALH engine from an A3 into a G4.

Best regards, Rainer.

Thanks, Rainer. Let's see what comes of it.

Hello BM!

Mechanically, I don't foresee any problems. The more interesting question is about the control unit.
As far as I know, there was a change in the generation of engine control units (ECUs) between 1998 and 1999. You can easily identify this by the last digits of the ECU designation. The older generation ends with "...018 xx", while the newer generation ends with "...012 xx".
Therefore, it is probably best to take the entire engine wiring harness from the vehicle itself, rather than from the donor engine, in order to prevent potential incompatibilities.

Regards,
Alex.

Just a side note:
Is it known what caused the piston to split? Was it due to tuning? Or perhaps leaky fuel injectors?

Quote:

Do we know what caused the piston to split? Tuning? Leaking fuel injectors?

These are called stress cracks or shrinkage cracks. They are caused by the constant temperature fluctuations in the combustion chambers, where the combustion chamber heats up unevenly, leading to localized compression (permanent deformation) in the material. When the material cools, this compressed material is no longer present in those areas, and eventually, stress cracks develop.

When this happens, it largely depends on the driving style (e.g., frequent full-throttle acceleration at high RPM on the highway followed by long periods of cruising) or thermal overload caused by poor chip tuning, etc. Damage to the fuel injection system or cooling system can also be reasons, but I personally know of no cases where this has been the cause.

However, even with regular maintenance and proper handling of the materials, there's a limit to how long something can last, and in this case, it's likely reached at over 380,000 kilometers.