Originally Posted by michaelnewmex
"Revisions include altered cam timing, compression and combustion chambers, plus, on the limited-edition HP4, an exhaust system made entirely of titanium with a “controlled acoustic valve” to boost low-end and midrange torque (all riders—touring, sportbike and racers—benefit from stronger bottom end and midrange)."
BMW HP4 Tech Updates- Features- DDC- DTC
If I can figure out how to upload the BMW press pdf, it's the most complete description of the development and engineering differences r.e. S1K/HP4.
While I agree with the poster who pointed out it's not a completely new design, it's clearly much more than "suspension, carbon and lighter wheels".
I'm told that, while the power ouput is essentially the same, the power delivery has been developed by the BMW race team in Germany over the last 3 years. Power has been mapped to allow the rider to control the bike more easily and still deliver a bucket load of power to the ground.
If you think back to the WSBK bikes even at the start of 2011, the bike was plenty powerful enough, however, the power delivery was so vicious Corsa was destroying his tyres in the first half of the race. What they've worked on is smoothing out the power so the delivery is consitent and predicatable.
I've read a few articles where the journalists has said the HP4 power is so predictable it could be safely ridden by a beginner rider. Troy Corsa has also said on camera that the bike is so fast it could have won WSBK races 5 years ago. Reference: http://www.youtube.com/watch?v=nx7-lT7tSh8
go to 4:05. Troy says the HP4 is what a Superbike was 4-5 years ago.
This is not an upgraded S1RR. It was designed from scratch as a one off superbike copy using the S1RR platform. Having ridden one a few times I can tell you the power delivery is completely different than my 2011 S1RR. Even just revving the bike in neutral it feels different.