On April 7, 2018 Anonymous commented:
The official details of Russia' D49 and D42 are introduced in  and . JSC "Kolomensky Zavod" produces diesel engines on the basis of two standard sizes :
- Д49=D49 (ЧН26/26=ChN26/26; bore 260mm, stroke 260mm) D49s are V8, V10, V16 and V20
diesel engines (8ChN26/26, 10ChN26/26, 16ChN6/26, 20ChN26/26) , and are used for general,
surface Navy and submarines .
- Д42=D42 (ЧН30/38=ChN30/38, bore 300mm, 380mm). D42s are L6 and L8 diesel engines
(6Ch30/38, 8Ch30/38) and 6Ch30/38 is used for general , Navy and Kilo Project 636s.
Photo at left Fig. 6 proatom document "Diesel engines 6 ЧН30 / 38" or 6CН30/38 "slightly inferior" to Western submarine diesels?
[Pete Comment - Significantly footnote  says “In terms of their parameters, these engines are slightly inferior to foreign analogues for the submarine fleet.” That being the case, one can assume that Russia values highly assitance on submarine diesels from Rolls-Royce MTU in Russia and MAN Diesel & Turbo Russia].
 http://www.propulsionplant.ru/dvigateli/dizelnye-dvigateli/proizvodstvennoe-obedinenie-kolomenskii-zavod/dizeli-tipa-chn3038.html A turbocharger 2TK or 6TK (TK-38) is adopted, but two stage air cooling/two stage turbocharger system is adopted for 6Ch30/38 (2-7D42) for Kilo Project 636.3 .