I've postponed some other tasks and re-factored Engine Beat effect as you had asked.
New FX is available in fresh published beta version 2.28
Group-box Engine Beat now features a new small button [>] which means "More Options available for this FX".
When you press it a new More Options window will be opened.
Default value of a threshold to trigger FX is 65% of Max RPM reported by a game, since I've tried to implement the new FX according to Mr Latte submission. By default the FX gain will increase from about 5 % when it's triggered proportionally to RPMs and will reach 100 % at max engine RPMs. You can disable that gain change by "Constant Gain" checkbox.
The algorithm is the same for both JetSeat and bass-shakers.
If you set "Start Effect at % of Max RPMS" value to 0 the FX will work as it worked before. Just in case if anybody will miss it.
Important note: new FX uses samples 7.wav(uwv), the old one still uses samples 2.wav(uwv).
I've tried the new FX out with just Assetto Corsa yet. Let's try it out with other games.
Please keep under control your antiviral software while application updates and starts for the first time, especially if it's Windows Defender. I'd prefer to spent more time on further developing of the application, than explain again and again how to restore it after Windows Defender attacks.
Happy racing to everyone :)