For those wondering how is the noise of a WW2 uboat engine, here's the answer
(there are 10 pieces in total)
I don't know where this video has been shot. As video says, it's the propulsion unit of a type XXIII coastal uboat. In front of the engine, it's possible to recognize the electric motor/generator attached to it.
The type XXIII employed a MWM RS134S six cylinder diesel engine. Unlike many large diesel engines which are direct injection, it employs a pre-combustion chamber. Bore dimension is 260mm, stroke 340mm. Power output is 630HP at 850rpm.
Attached to the shaft, there is a large DC electric motor which works also as generator. The GU 4463/8, made by AEG, is an evolution of the electric motor used on type VII uboots. It develops 580HP at 240V.
A pair of MWM RS134 where employed as generators aboard the large type IXD-2 uboats. This way, it was possible to recharge the battery banks without using the main engines. This engine was later installed in the type XXIII along with the DC motor/generator made by AEG. The power developed by the duo was enough to propel the small submarine at 12.5kts underwater.