I hope I don't be arrogant to be persistent, but IMO You are wrong. Both fighters are in no relation to each other for several reasons:
- all current fighters from CAC - J-10 and JF-17 - use engines with the engine's gear-box mounted on the bottom of the engine. That's the reason to differ the AL-31F (in the J-11) and the AL-31FN (in the J-10). The same is for the JF-17 (and J-31 as well), that uses the RD-93 which is a gear-bog on the bottom version of the RD-33 as used in the MiG-29.
In contrast to these types, the Flanker-series still uses engines with the gear-box on top namely the AL-31F or the WS-10A ... to make the WS-10 compatible to fit the J-10 it needed its gear-box on the bottom, which resulted in the WS-10B (see:
http://4.bp.blogspot.com/-9UsWX4031qs/UA3IHyYpbLI/AAAAAAAAANw/WYzvusK2TII/s1600/WS-10B.jpg and
Chinese Military Aviation: Fighters II). Therefore it does not make any sense to assume that the J-20 would use an engine with the gear-box on top, simply excluding all the AL-31F as well as the WS-10A ... only the WS-10B could fit, but by all information I have so far it is not ready yet.
- China DID not stop to import Russian engines, since there was especially a huge order of additional AL-31FN Series III (see below) especially for the current J-10B to replace the older AL-31FN.
- the WS-10A/B is a product of Shenyang Engine Corp. with the aim of delivery priority for SAC types ... whereas CAC has a good connection to Salut since years.
- as mentioned already, both engines - the AL-31F and FN and the WS-10A and B - are really different. The number of pedals on the afterburner is different, the inner structure of the flame-holder is different as well as the sound ... but even if painted or treated in that strange silverfish colour the J-20's engine is more akin to the J-10A's engine and not the Flanker's one ... as such I'm sure (100% to say so) that it uses an AL-31FN version.
No ... there is indeed a version called Series III, that has a slightly higher thrust (nit much) and a higher reliability (operation time to first maintenance after 750 hours)
FEDERAL STATE UNITARY ENTERPRISE «GAS-TURBINE ENGINEERING RESEARCH AND PRODUCTION CENTER «SALUT» | NEWS | NEWS | The FSUE “GTE-RPC “Salut”-produced AL-31FN series-3 engine receives code letter “O1”
To admit ... even if I agree that there might be a WS-10G under development ... so far there is NONE ! I know these rumours since the J-20's maiden flight but after all these years I've been watching the scene I'm sure there is only the WS-10A for the Flankers operationally (gear box on top) and the WS-10B under test for the J-10B (gear box on the bottom) but no WS-10G.
Otherwise if You have other information ... I would be very interested to learn more about.
Cheers,
Deino