Originally Posted by Weaverman
Anotherguy - Agree. And I doubt the engineers really ever get it WRONG. They just might not have designed it exactly the way everyone wants. Engineering is definitly one of those pursuits where you can't please all the people all the time. [b]BTW, it's really the BIG bore that's limited by flame front speed, not the small bore.[b] More of a benefit of smaller bores, and part of the reason Ferrari builds V12s.
And let's not think about the times the bean counters win the war, and management tells the engineers to use the rod or other piece already in production.
It's a small bore with a wide included valve angle that needs a big dome to get even moderate compression that benefits the most from long rods.The flame front has to travel far more than the bore radius leading to some serious advance to get peak cylinder pressure at the right time. Lots of shrouding going on in that hole.Harley,BMW,Guzzi and the like. Check the rod length on an R1,GSXR ect. Mostly pushrod stuff,why would you waste a DOHC on a narrow bore? Dual pugging is cheaper and less costly in the long run and achieves the desired result.
And a calibrated DynoJet will give good HP numbers. I've run SuperFlow SF-901,FactoryPro EC997 and Dynojet from 100 to 250i. Favorite is the EC997. The SuperFlow is an awesome tool but difficult to use for motorcycles. Harleys are the easiest to mount to the 901 but not close to easy. When all is said and done the numbers only matter at the bar. Results speak far louder than numbers. The proper use of the tool is what you seek. As I alluded to earlier it's the area under the curve that gets the job done and the only way to see that is a dyno printout no matter where it comes from.