For example can you really tell me the weight ratio of the Soryu engine and the comparison with the Collins?
Don't think so.
and who in here has said that the Soryu/Oyashio drivetrain is in consideration?
there are same basic "points" here
1) The Japanese have a strong relationship with us
2) The Japanese have indicated a change in their attitude to sharing and/or exporting military technology - they have indicated also that upsetting the chinese in SEA is not in anyones interests, but that other countries may well be interested in Japanese tech for their own political needs - this is primarily but not restricted to patrol boats at the maritime level - it could also be maritime patrol aircraft, it could be digital technology, it could be sensor systems
3) There are very few conventional fleet subs that can readily be compared to the Collins mission set - the primary ones are Oyashio/Soryu and the Upholders on Blue team, after that, it goes to nukes, which are used in some of the baseline comparisons across a number of performance vectors
4) Drivetrain tech for subs in the last few years alone has changed dramatically. Available engines with similar energy figures are 1/3rd smaller and generating 50% more power
5) Subs are not designed primarily around engine systems, their capability is designed around the energy demand/requirements first, then its against likely drivetrain, then the sub is sized against that requirement. We don't design and spec a sub size and then try to squash the capability into that predetermined space - which is why the broadsheet chatter about getting 21nn class subs is utter rubbish because it immediately bypasses the capability design constraints which are operational scenarios and capability needs.
6) Conventionally powered subs are critically constrained by energy requirements, the drivetrain selection has less focus on sheer performance and is more heavily aligned to what ISR/INT roles and sensor systems are needed, churn, burn, range come after that.
As for dismissing responses as "club mentality", well when you have a number of people in here who are maritime engineers, who have worked in sub projects and/or who have worked in subs, worked in major weapons projects and then who try to impart the basics to assist in learning but then get comments thrown back which don't stand up to known real world analysis, then the courtesy issues also take a hammering.
if you're an engineer and you're making some of the comments to date as an example of engineering analysis, then some are immediately questioning competency against this subject material because they just don't add up.
subs more than any other platform are critically dependant on being designed around the concept of operations as that determines basic elements like size and powerplant
dismissing a replug on the issue of difficulty in remanaging the subs footprint, acoustic sig, handling issues etc is less than genuine comment because it conveniently ignores the fact that any replacement drivetrain options are lilely to include a drivetrain set that can offer similar energy management reqs in a smaller more efficient package - and that means that something as basic as more available internal real estate changes the dynamics and patrol options of the sub - that can mean longer patrol times, crew format issues, additional sensor capability in additional space, fuel load options etc....
so when you make throw away comments baselined against your experience in re-engining cars, then significant doubt creeps in about your engineering credentials against this capability req.
and the above is an example of considerations against one sub solution option
a mid life platform extension will be risk assessed against the 3 other options
but you don't select an alternative drivetrain based on it conforming to existing absolute weight and distribution issues.
My suggestion is that you read more, ask more questions and ratchet back on the attitude, because you haven't convinced anyone in here who is a real engineer that you understand the broader design issues.
Continuing to engage as you have been will not end well.