lightened flywheels...

 If you want more acceleration, especially in lower gears, lightening crankshafts and flywheels is a good idea...it will NOT give you any more power, so top speed, will remain unchanged.  It WILL allow more power to reach the wheels under accelerating conditions because less energy is being wasted accelerating the engines rotating parts up to speed!...it may also result in a slightly lumpier idle, but will give faster throttle response when you blip the pedal!  Much like a motorcycle, because they have no flywheels....the gains are quite small and expensive but like all engine tuning you have to decide what you are trying to achieve....and everything should be a good balance of modifications that matches...The job of the flywheel is to smooth out firing pulses, stop vibration harmonics, and torsional twist. The most economical way for the factory to do this was to make the flywheel the weight it is stock.

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Originally Posted by 340i so the flywheel is weaker than it was before, but it will presumably be getting more abuse? is that safe? i dont want to freak you out, but have you seen what happens to flywheels when they break? byebye feet...

i wonder about this...and while a flywheel flying apart isn't my real concern...engine performance and engine longevity is...i have a new m10 rebuild and a fresh transmission rebuild but i have yet to put in the clutch kit and flywheel togther...i had the flywheel resurfaced but not lightened...i considered an aluminum flywheel but after talking with a lot of trusted friends...the conversation always turns toward comments about manufacture's proportions and engine balance, engine longevity, and the money spent on engineering and design by the factory...i know that the racing circuit has successfully lightened flywheels for years...but in the end i DID NOT lighten my flywheel YET...

i am seriously wondering what to do about it...should i...or shouldn't i...that is my question...i put a 292 cam in the engine so i expect that to increase some performance...but for a summer DD where is the "end point" of modifications is what i'm wondering...where does the line between performance enhancements and engine longevity meet?...is lightening a flywheel to much? if so...how much is too much lightening...what does experience say? i don't know these answers and i am not sure where to find them...i have discussed this with my machine shop and IE...and neither answer the question...at least the way i want them too...probably because there are so many possible variables...

any thoughts on this?

Consider The Following:   if we are serious about lightning bits and pieces to get a free revving engine what about a carbon fiber drive shaft?...it would rotationally flex more that the metal counterparts and reduce strain on the engine . . .if a metal drive shaft breaks parts can be thrown through the car!...a carbon fiber drive shaft is stronger but if it does break...it would generally only leave a 'broom' into 'harmless' fibers and little damage will be done to the car...and the same effect is achieved...lthough the uninitiated might only see the obvious lightweight advantage offered by a carbon-fiber driveshaft, there is areally a great deal more to it than simple weight reduction...along with being roughly 50 percent lighter than a steel unit, carbon-fiber driveshafts offer greater fatigue life, superior vibration damping and a much higher critical speed...the most obvious benefit of carbon fiber is its weight...unlike other weight-reduction measures, such as fiberglass hoods or ditching the A/C, carbon-fiber driveshafts actually aid acceleration, and deceleration...

this is just a theoretical question is am posing...i am highly suspect that using a lightened flywheel with a stock, non counter-weighted crankshaft requires using an equalizer pulley to dampen the harmonics, bending, torsional twist and vibration...without doing so would seem to cause premature case, piston, rod bearing and even possible crank damage...particularly, at high rev's which is the ultimate reason intended with lighten a flywheel...between a lightened flywheel, and lumpier cam in the 320i i am restoring...drive ability is my concern...while not actually increasing speed...it would increase response...but at the cost of consistent flow through acceleration and deceleration...not advisable for a summer season daily driver...