bore vs stroke

[lukeb1961]

It's because the longer rod 'works' better. Even a stock Banshee with just the 115mm rod swap feels torquier to ride. Something to consider for your PE

I believe that the 3rd birthday is coming up - any chance of it progressing? 

[Lozza]

Your call has progressed in the queue...................... stand by for the nearest available operator...................................
(will get some answers for you)

[lukeb1961]

Your call has progressed in the queue...................... stand by for the nearest available operator...................................
(will get some answers for you)

I bet I get put through to some kid in Bangalore!
That Irving chap has a way with words. Good stuff.

[pancho]

 All very interesting. Who is this Irving dude who has a name that makes me think he should know what he is talking about?
 I found his last sentence interesting if not revealing.
 I would love to talk to him face to face about some of his ideas and conclusions that appear to be 'drawing a long bow.'
 His paragraph stating ' Maximum cylinder pressure is reached at an early phase of the power stroke, and the longer rod ensures that high cylinder pressure is developed and held when the crankpin is at a greater angle, leading to improved thrust'.
 To my understanding, by the time that the 'leverage angle' is at its most productive, effective pressure has dissipated...... Not like a diesel.
 not arguing learning.
cheers pancho.

[Lozza]

He's a automotive engineer I dunno if he is any relation to Phil Irving (maybe go the the Rapid Bikes forum and ask), as I said before pancho, Ian has it correct and you have it arse about. The ideal angle for peak cylinder pressure is not long after TDC, having the piston dwell at TDC longer gets greater thrust. I don't think all the F1 engine builder, Aprilia , KTM and HRC all got it wrong.

[firko]

I've known Ian Irving for a number of years (although haven't spoken to him for quite a while) and he's indeed a very cluey individual. He used to have a little tuning shop across from the Tollgate Hotel in North Parramatta back in the late 90's. I worked around the corner and used to enjoy dropping in for a beer and a bench race and sucking up his amazing knowledge. He built an impressive big bore GPZ1100 powered Bimota that was as trick as they come in 1995. Jeez that bike was quick......BTW..no relation to Phil

[Gerard De Ruyter (Twistandshout)]

i forgot all about asking this question till tonite.  um. wow.  there's some answers there isn't there.  while most went right over my head, i sort of get it now - everything interdependant.  not in buddhist sense (tho they're on the money there), but design factors.  longer stroke gets you more time to get more mixture in and out (and other impacts too), while bigger bore gets the same thru broader ports/bigger valves (and other impacts too).  the other impacts relate to torque and hp.  and reliability/longevity.  and the article by that irving guy....longhand way of saying 'om' i reckon.