Answer pretty much covered above between dmf and smf.adsgreen wrote:The issue is that the flywheel is both an energy store and a damper.Spectre wrote:WTF - all this 'cos the guy cannot spell particularly well but is proud to be making a decent living anyway? If he is paying his taxes, he has my respect. Sheesh - let's move on and get back to talking cars?
Am I wrong in thinking that the point of a lightened flywheel is to reduce the effort needed by the motor to build revs (since there is less weight to rotate) therefor making the motor rev more freely, with the possible downside being that revs drop faster too? (ie. losing speed faster) Thinking logically, I cannot see why would a lightened flywheel would cause any problems elsewhere. Perhaps the design of the engine relies on the fact that there is a certain amount of weight related resistance to balance the nature of the engines components? Thoughts?
Mak.
The crank in our cars sees 4 pulses of acceleration every rotation.
You need the stored energy to keep the crank turning in between cylinder pulses otherwise the crank would slow down dramatically before the next combustion event due to other cylinders being compressed.
The damper aspect is that the flywheel also reduces the "peaks" of the acceleration events. So instead of the crank accelerating quickly the flywheel also smooth's things out.
Dual mass flywheel is a way of dealing with high compression engines - high compression engines like ours and diesels have proportionately larger acceleration (and deceleration) events. This would normally need a larger flywheel to cope but then this transmits a lot to the geartrain. So if the fly wheel is effectively split in two with one side connected to the crankshaft then other to the gearbox and linked with a spring damper. With the car in neutral the engine "sees" the whole flywheel mass so has a nice low steady idle. When in gear the engine "sees" only the inner mass and the transmission is damped with the outer mass meaning the engine is reasonably free to pick up speed and the transmission is damped to make it quiet.
Overall the DMF is a really elegant solution to the problem however as is pretty well documented, elegant but fragile.
A lighter single mass flywheel will obviously reduce the rotating mass of the system which has benefits. You don't want to go too light though as lighter wheels will accelerate faster but in a similar vein will also decelerate faster before the next "event".
But you do loose the gearbox damping which is why some get a degree of gearbox "chatter". You'll also need to adjust (probably by only a small amount) launch rpm as the engine will be more prone to stalling.
As for the crank? well you are putting more stress on the crank as the acceleration events will be less damped. As to say if will cause a failure? Hard to say - the crank is strong in our cars as are the bearings given the high rpm and with 8 cylinders the time between combustions is also lower than say a v6 or inline 4. I think there are now plenty of people using them for a long time without issue so I would say that it should be ok.
However this thread reminded me of the good ole Harry Enfield sketch load'sa money:
https://www.youtube.com/watch?v=gXuRvthgn4U
gave me a good ole giggle, top work.
