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Discussion Starter #1
Given equal displacement and HP, would the power curve be the same or different, i.e. where the most torque or peak HP lies? Or are these configurations meant to be purely aerodynamic, such as I4 being wider and short, and V4 being narrow and long, and thus no difference in power curve like v-twin vs I4.

Except VFR, why is there such lack of interest in making more bikes with V4 engine in them?

For their superbikes, why did Honda go from V-twin to I4 when equal displacement was given, instead of going back to V5 such as RC45? Don't V configurations supposedly give the "extra" grunt, which is why Honda chose V-5 for RC211V, when most others on the grid are big bang I4? Thanks.
 

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a 90deg V should be better balanced in theory, then an inline. So performance alone, should be superior. However...
V4 would be a nightmare for designers. While the output is good, they are considerably bigger, physically, thus more difficult to package. The spread the weight out in between their two banks, thus taking away from the mass centralization concept. They also have two heads instead of one, which makes them heavier and more expansive... It isnt a performance thing thats keeping them away, its the practical issue of it all.
 

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Discussion Starter #3
IC, do V4s also inherently have longer stroke than inlines but shorter than v-twins? What makes them better balanced in theory than I4? I always figured that 90 deg V-2s were primarily balance but require counterweights for secondary balance, where as inline, the imbalance is controllable without sacrificing much power or adding counterweights. Does V4 function differently or better? Like I6 or V12 has been known to be best balanced among engines.
 

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I dont believe any of the above mentioned configurations have any stroke requirment. You could build a very short stroke Vtwin, it would just not do you any good.
As for balancing, well its abit over my head. V4 will use a crank much like the Inline, so each cylinders rotation can be controlled seperatly. The impact comes on two axis, so that could be utilized to better cancel out any unwanted vibrations.

Obviously a better balanced engine would be the flat 4, but again packaging becomes an issue.
 
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