Mini F56 Balance shafts? I was looking at LAP motor sports chassis so many possibilities.... so looking into balance shafts I was surprised to see that on other engines with them when doing a performance build they are often removed. When going faster is the goal, high rpms 10,000 or so is a nice option if you can do it so wouldn’t you want to keep the shafts to cancel the 2nd order imbalance and then you can lower the weight of the crankshaft and possibly the rods and pistons if they have a generally smoother engine to work in. Or am I just missing something.

 

Ok still procrastinating and thinking about balance shafts. If you go super light on the crank shaft you loose the cushioning effect of the counter weights which were helping with harmonics from flexing and 2nd order imbalance and any other imbalance. It is always so easy to look at one part and miss the way it all fits together dynamically. Then there is the problem of timing chain stretch, the more extreme the build and the higher the RPM's the more any out of phase on the balance shafts could be trouble. So really going off the deep end how about tuning the crankshaft rigidity, there are some powdered metals used in metal die stamps that seem fun, they have super tough shock resistance and the hardness can be adjusted with heat treating. Of coarse you have to have a valve train to match. Well I think I will keep at my N14's

 

I believe that the vibrations that are caused by inline four-cylinder engines aren't generally destructive, mostly just irritating--especially at idle. With large masses moving around, the engine can really start wobbling, which is a significant negative in a daily-driver. At higher RPMs, the movement isn't as large because by the time the mass of the block and such gets going in one direction it is already being pushed in the other direction.

So as long as the vibrations induced are not enough to be destructive, the balance shafts aren't needed in a racing-type motor. Removing the balance shafts completely does eliminate their mass from the system, making high revs easier to attain. And, of course, you can still do the lightening of the other moving masses. So you've got a very easy way to lighten up the moving bits by ditching the balance shafts, plus you don't have to spend power turning them, and you lose something you don't care much about--idle smoothness.

Lots can be done with trick materials. But if you use those same techniques and also ditch the balance shafts, you're going lighter and stronger yet!