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May 04, 2012 1:55 PM

WSBK » BMW dominates opening test at Monza


I believe the difference between V, L and i is crank acceleration and rate of change of acceleration, matched with thrust curves (the gearing). You want to have a torque/bhp curve with a nice, gradual rate of change as you come out of a corner, no big dips or bumps (like an R6). This is something that GSXR-750 does VERY well, in the rev range that we normally come out of a corner at. Also, a i4 flat/180deg crank is well balanced. An i4 crossplane is actually 2x i2's put together, it has bad balance and needs a balance shaft. So the crossplane engine runs/feels 'rough', perfect for coming out of corners.

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May 04, 2012 1:43 PM

WSBK » BMW dominates opening test at Monza


It is all about the 'feel' for racers. Journalists speak *ull**** and say *hit because they 'think' they have to say it. If you take rpm and gearbox ratios and sprockets, even at lowish revs, you have peppering the rear tyre with firing pulses. Mr Yoda (ex Yam, now Kwak) engine believes piston motion makes a big difference to feel and an inline helps handling, tipping in etc. A V4 centralises the mass. V2/L2 are comparing apples and oranges. Race rules gave more cc's and Ducatis are better spec'd bikes. Imagine what a $40,000 GSXR would be like?

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May 04, 2012 1:33 PM

WSBK » BMW dominates opening test at Monza


Unfortunately most of what is written is plain wrong. First up, the Yam is NOT Big Bang. Big Bang was a couple of V4 2stroke NSRs. They eventually raced a version that fired ALL 4 cyl in about 70deg of crank rotation. Top end? Have a look at the torq & power curves for a crossplane Yam - not much different to a flat/180deg crank four (Suz, Kwak, BMW). Torque is torque. Power is torque times time (or speed)(torque pulses per second). With a flat/180deg crank, there is a big rocking motion every 180deg, when all pistons slow, stop, change direction and accelerate again (2x at TDC, 2x at BDC). A Yam crossplane spreads this out, so there is no big rocking motion of the spinning crank, rods, pistons.

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May 04, 2012 12:55 PM

WSBK » BMW dominates opening test at Monza


"..With the V4, making power pulses much like the V2, it has fantastic mechanical grip, meaning it uses a lot more of it's power compared to the i4's..." @Nick636 I just wonder what piece of science, engineering or research that backs those statements up? Each cylinder makes torque, the same torque whether it is in a V, L or i. The firing order subtly spreads the firing pulses in a different order. Across the normal rev range and with final drive gearing, these pulses are peppered across the tyre. It makes *ugger all difference to mechanical grip.


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