Yes thats right. But you do batter the crankcase to death as well slacken the flywheel gland nut, when revs and slight mods allow the engine to be revved past 4500rpm. For speeds greater than this you need to give CB, Gene Berg, Scat, etc a call for a counterweighted crank!
What! It's got nothing to do with frequency, it's to do with the number of power strokes per revolution of the engine. The more bangs per rpm the smoother the engine is. There is no engineering reason why 6's or 12's should rev any different to a 4 cyl. It's all to do with the mass of the crank/piston assembly in relation to the rpm. A 2.4 litre 4cyl will never rev that high due to the high individual mass of each piston, to atain 600cc pre cylinder. Where as a 2.4L V12 could easily be made to rev much higher due to each piston being tiny needing to only achieve 200cc per cylinder.
Only the 1200 cc, which isn't worth tuning anyway, because of the lack of counterweights! But if you do chose to tune the 1200, the first step is to get counterweights welded on.....
Honda do have a major bore x stroke advantage when it comes to high rpm's, which plays out as a disadvantage for low rpm torque....
This comment is un-called for and totally un-related to knife edging IMO. VF do a good job, that's why they balance a few F1 cranks! I think you'll find if anyone's doing "not a great job", it's the engine builders, who quiet often don't even realise how well balanced some stock engines are these days! And by "these days", i mean later than 1989 in some cases! I'd bet a lot of money that the problem with the "less apparently balanced engine", was not a result of the work from Vibration Free.
Not exactly. The reciprocating pistons cannot be balanced by a rotating mass. The pistons are arranged so that they counteract each other through the crank though. Which is why in a 4 pot there are always 2 up and 2 down and also why when building an engine you balance the pistons to each other, and not to the counterweights. But this is only true at the fundamental frequency, the higher order frequency components from the pistons need to be balanced or counteracted by weights running at 2x engine rpm in an in-line 4. I couldn't agree more.
Loving this thread! More info please I have a knife edged steel eurospec crank in my engine coupled to pauter rods, je pistons inconnel valves and schrick cams Dont know anything about it apart from the fact that it revs real good and fast, and is smooth as at 8k + rpm
Amazed at some of the misinformation here. To clarify: - straight 6 and flat 4 are inherently balanced configurations (2nd order forces cancel out) so don't need counterweighting on the crank - inline 4 isn't balanced (2nd order forces), this is due to the rod angle making the piston velocity non-sinusoidal. It can be compensated for by a balance shaft running at 2x crank speed. - The VW inline 4 doesn't have a balance shaft, it has an intermediate shaft (drives oil pump, (some cars) fuel pump, (some cars) distributor). - cross plane V8 is not inherently balanced either, but its able to use large counterweights on the crank to achieve reasonable smoothness. Flat plane V8 is similar to 2x 4cyl engines in terms of balance - configuration, not number of cylinders, is mainly responsible for an engine balance. a flat 2 is inherently balanced in terms of its mechanical components (but not torque delivery).
