So what? Canadian superbike allows 1000cc 4's to run with twins. Crevier (RC51) and Taylor(RC51) placing 1st and 6th overall respectively.dryheat said:If your curious how 1000cc 4-in-lines will compare with 1000cc V-twins in Superbike racing, watch the British Superbike Series. BSB changed the rules this year and they'll be competing against each other. April 1st at Donnington Park is the first race.
Fine. You don't have to wait for BSB. The point has been made:V-twins can run with 4-in-lines with the same displacement.VFRSQUID said:
So what? Canadian superbike allows 1000cc 4's to run with twins. Crevier (RC51) and Taylor(RC51) placing 1st and 6th overall respectively.
Other factors equal, a 750cc four has slightly greater valve area than a 1000cc twin. Let's compare the Ducati 998 and Suzuki GSX-R750. The two share a nearly identical bore/stroke ratio of 1.57, so that "other factor" is indeed equal. (Duc's dimensions are 100x63.5, Suzuki's 72x46).desmo079 said:The 4s have the advantage because they have more surface area of intake and exhaust. The surface area of 16 valves is greater than the surface area of 8 slightly larger valves in the twins. Thus 4s can THEORETICALLY make more horsepower.
Very well though out post. 'Course totally irrelevant once fours get to use 1000cc also.DataDan said:
Other factors equal, a 750cc four has slightly greater valve area than a 1000cc twin. Let's compare the Ducati 998 and Suzuki GSX-R750. The two share a nearly identical bore/stroke ratio of 1.57, so that "other factor" is indeed equal. (Duc's dimensions are 100x63.5, Suzuki's 72x46).
The Suzuki's cylinder cross-section area, which limits valve area, is 4071.5mm^2, with a total for its four cylinders of 16286mm^2. The Duc's cylinder cross section area is 7854mm^2, with a total of 15708mm^2. Thus the four has a 3.7% edge in cross-section area.
However, that advantage works only if the four is capable of revving high enough to exploit its valve area. And revs are where the twins seem to get the better of the fours. With its short 46mm stroke, the Suzuki should be able to rev 38% higher than the Duc. If it could, it would have more than enough extra revs to compensate for its displacement deficit.
But the extra revs don't seem to be there. Fasthrc noted that the twins revs to 13,000 and the Zook to 15,000, giving the four less than half its theoretical 38% rev margin.
Kevin Cameron wrote a column a few years ago about the quest for revs in Superbike. At that time, engine builders had reached a point of diminishing returns, where the added friction at higher revs consumed the added power produced--the marginal return from higher revs had gone negative.
I'll go out on a limb here (and, hopefully, provoke a response from someone more knowledgable than myself) and suggest that the fours may be suffering from insufficient bearing surface area. To keep the engine narrow, rod and main bearings are compromised. OTOH, a V-twin, a narrower package to begin with, can accommodate more generous bearing dimensions.