Google is my (or your) friend...
You are making some serious accusations here regarding the Germans. How about some reputable sources to back said claims up please. I really am quite interested.
If you 'google' with 'German submarine diesel engine china' then results are:
CORRECTED-SPECIAL REPORT-Chinese military's secret ...
reuters /.../breakout-submarines-special-report-p...
2013/12/20 - Most of China's advanced surface warships are powered by German and French-designed diesel engines. Chinese destroyers have French sonar, anti-submarine-warfare helicopters and surface-to-air missiles. Above the ...
Exclusive: China trying to undercut Germany on submarine ...
reuters /.../us-china-egypt-submarines-exclus...
2015/09/15 - China is trying to sell two submarines to Egypt that are cheaper than vessels on offer from Germany, industry ... long had friendly ties, and China supplied Egypt with four Ming-class diesel-electric submarines in the 1980s.
Why China's Submarine Force Still Lags Behind | The ...
thediplomat /.../why-chinas-submarine-force-still-l...
2015/05/28 - The bulk of China's conventional sub armada consists of 13 Song-class (Type 039) diesel-attack subs and 13 ... the Song- and Yuan-class attack submarines are equipped with German-made state-of-the-art diesel engines ...
European Companies Are Supplying China With Billions In ...
businessinsider /european-companies-are-su...
2014/04/30 - Military experts believe the ship relies on diesel engines produced by German firm MTU. ... German-designed engines chosen for their quietness power virtually all non-nuclear Chinese submarines and several classes of ...
China to build 15 more Yuan-class submarines with German ...
chinadailymail /.../china-to-build-15-more-[/url]...
2013/04/11 - In comparison, “China may plan to construct 15 additional Yuan-class attack submarines, based on German diesel engine purchases. “It is said the Yuan-class submarines could be equipped with air-independent propulsion ...
The first result shows French involvement in addition to Germans. They are using interesting excuses to sell their hardware. Sonar? No, it's a fish detector!
Or these diesel engines are for commercial surface ships with unique requirements.........
Sorry can' post url's, yet