This is kind of interesting: http://www.superstreetonline.com/how-to/engine/modp-1005-drivetrain-power-loss/
TL;DR: The 15% "rule" does not hold true at all and varies widely. A more powerful engine will experience a higher HP loss on a specific drivetrain due higher acceleration (dynamic drivetrain loss.)
I would guess our little 22RE platforms lose way more than 15%. Our drivetrains are built (over-built) for reliability, not efficiency.
That link triggers my malware/virus software. Looks like it tries to download something onto your computer when you open the page...?
