Hi can anyone help on the brain teaser i have come accross, does a light weight crank pulley play any part in the engines performance output, im confused with they way its ment to work/if it works at all, Do'h!
It reduces rotating mass, so has a fractional effect on performance, but it also removes the vibration damper in the centre. There are schools on whether that's a good thing or not, or whether it's neutral. Overall, not worth the bother on an otherwise fairly standard engine.
Only really applicable to motorsport prepped engines, where every last ounce of power has to be squeezed out of it. Pointless on a road car...
dont remove the damper crank pulley... results of a "lightweight" neuspeed under drive pulley on a 1.8t - no damper muchos damage dont do it, its not worth it
Nice game of crankshaft peekaboo there... Discussion closed, I think! You can lighten the standard ones a bit, I believe, and retain the damper. Personally I'd leave well alone.
whats the total weight of the thing to start with? a couple KG at the most... looks like another exercise in picking peanuts out of dog poo
F*ck a duck! That`s as bad a crank failure as I`ve ever seen ... The vibration damper (or more accurately; `resonance damper`) is there for a reason, so I wouldn`t be about to remove it to for the sake of a couple of horsepower.
Big badda boom? The main causes of crank failure would be; Torsional vibration due to the torque of each power stroke. This can match the crankshaft`s natural vibration, leading to resonance, and ultimately failure. This what the damper in the pulley helps prevent, by causing opposing vibrations though the crank to cancel out the resonance. Or; Fatigue failure; A crank will naturally `bend` in operation. If there are any weak points, stress raisers, or cracks it will ultimately fail at that point. These are more common on a crank that has been re-worked (undersized journals, crank web lightening, etc). From this pic of Bill`s; Notice where the web has failed; If it was a fatigue failure, you`d see `tidemarks` in the material radiating from the failure point. Since it`s more of a `clean` break with the internal structure unaltered, it would point more to a torsional failure IMO.
Whilst torsional stress is, of course, present, it`s not the failure mode in question. Look up `resonance` or `harmonics`. Torsional vibration builds up as a matter of course, but when it `harmonises` with the crank`s natural vibration frequency, that is when it becomes more than the material can handle, and eventually fails. Exactly the same theory as an opera singer smashing a glass with their voice... A damper (or `harmonic balancer`) sets up opposing harmonic vibrations to cancel out the natural frequencies.
AA, to all of your replys, my car is a road car an every day'er, clearly it is a bad idea, as i cant afford to have any issue if i was to fit 1!, i guess il let that idea go with the wind. Chrz!
so if you had an engine with a damper pulley, then replaced it with a non-damper pulley would you feel the vibrations? or is it the sort of thing that would go unnoticed til something broke?
Wow.!! that is some damage.!! I was looking for crank pulley lightening but staying well clear of that now.. This did lead me to finding out where and what the dampener is which sounds like the outer aux pulley is fixed to the other with rubber between.. outer wheel does dampening..?? But along the way i realised there's a small roller as part of the automatic tensioner. i've changed auto for manulal tensioner to get the mount on my aeb-mk1.. i'v seen But will foul mount.. are these as important as the bottom pulley.?? Sorry to dig up an old thread.. i was amazed by the damage caused.! Hopefully all better now.?
