Nice idea Vecko, keep up your good work
Talking about the engine ratios/speed graph, was in-game data measured with TDW's engine ratio patch enabled?
Even with it enabled, there were still some dicrepancies between expected and measured speeds, especially for back speed orders, though I can't remember all the details now. I suggest you having a good look into old posts of TDW's patch thread.
Something I remember for sure is that, according to historical data, engine rpm and u-boat speeds had a linear relation:
http://www.subsim.com/radioroom/show...postcount=1677
http://www.subsim.com/radioroom/show...postcount=2258
http://www.subsim.com/radioroom/show...postcount=2254
SH5 uses a sigmoidal function for calculating maximum theoretical speed over engine ratio:
http://www.subsim.com/radioroom/show...postcount=2291
http://www.subsim.com/radioroom/show...postcount=2292
http://www.subsim.com/radioroom/show...postcount=2314
What is odd to me is that max speeds set in boats' sim files don't show in the above algorythm and that actual speeds in game don't follow its graph