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Anti-Vib pulley
by
Hangar5
on 17 Mar, 2009 17:09
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Swapped out the NA for an Eco-Diesel with a LDA Inj pump. It's great (also used a ACN trans ). Anyway..Recently I read that one of the turbo motor improvements was the vibration dampener pulley. No power steering on this Mk2 Golf, so I used the NA's solid single belt pulley ,not the doubleV with dampener... and was happy as a clam ,.until reading about the turbo/dampener. Can anyone tell me that I need to put the rubber pulley on before things start snapping.!
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#1
by
flapjack
on 17 Mar, 2009 18:11
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I've never seen an engine without that damper....but I guess I haven't seen that many engines
from:
http://en.wikipedia.org/wiki/Harmonic_balancer
A harmonic balancer (also called crank pulley damper, crankshaft damper, torsional damper, or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration.
Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.
To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.
Over time, the energy dissipating (rubber/clutch/fluid) element can deteriorate from age, heat, cold, or exposure to oil or chemicals. Unless rebuilt or replaced, this can cause the crankshaft to develop cracks, resulting in crankshaft failure.
There has been a trend at times by some "performance enthusiasts" to remove the harmonic balancers on their cars, usually when the balancer is attached to the crank pulley. The argument is that they aren't necessary and their mass reduces the performance of the engine. Others[who?] argue that this is not worth it, because the danger of damage to the engine from the vibrations the damper is intended to prevent is too high. Certain cars, however, do not come equipped with an external balancer on the crank pulley, and as such, can have the pulley replaced with a performance oriented product.
While net engine output can be increased without harmonic balancers, in professional race cars harmonic balancers are still commonly equipped, for reasons ranging from safety concerns to regulations. Almost all modern car manufacturers, even "performance" car makers and specialty tuners, include a harmonic balancer on their vehicles, and removal voids vehicle warranty.
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#2
by
arb
on 18 Mar, 2009 05:36
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I've laid hands on hundreds of different types of engines. The only 2 liquid engines I have not seen harmonic dampeners on were the VW 1.6L and the Subaru EA-71 & EA-82. I always questioned why this was so. Mybe they have a short enough crank they don't need one
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#3
by
Hangar5
on 18 Mar, 2009 16:49
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Thanks for the inputs. The dampened pulley is easy enough to slap back on..so ,.to error on the side caution.,I think I'll use it. I've read plenty of stories of recip. aircraft engines busting cranks because of propeller resonance feeding back. And some have crazy pendulum weights bolted onto internal crankshaft flanges to absorb resonance at specific rpm ranges.
Thanks again
Dan
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#4
by
arb
on 19 Mar, 2009 05:05
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Thanks for the inputs. The dampened pulley is easy enough to slap back on..so ,.to error on the side caution.,I think I'll use it. I've read plenty of stories of recip. aircraft engines busting cranks because of propeller resonance feeding back. And some have crazy pendulum weights bolted onto internal crankshaft flanges to absorb resonance at specific rpm ranges.
Thanks again
Dan
Have you seen what Chrysler used on some of the HEMI engines? Very elaborate pendulums - about 6 or 8 as I recall.
But, yes. Be safe and install one as long as it was for a VW. Putting the wrong one on can cause as much damage as none at all.
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#5
by
Rabbit on Roids
on 19 Mar, 2009 08:02
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uh, ive got a crank pulley off an 84 TD engine, and its got no rubber, or anything in it for that matter. its just a solid, cast aluminum double groove pulley. ive wondered about the lack of harmonic balancers on these engines also.
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#6
by
lord_verminaard
on 19 Mar, 2009 08:15
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IIRC, most of the gasser VW 8v's that I've seen didn't have them either, at least not until they started using serp belts.
My wife's 86 golf diesel does not have one.
Brendan
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#7
by
idgtd
on 19 Mar, 2009 09:39
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My gas VWs haven't had them either. According to the VW Diesel paper, the the torsional damper was added to dampen the critical 6th order vibration at 4800 rpm. I guess the NA didn't make enough torque to cause crank deflection problems at this speed, but the increased output of the turbo plus the already present 6th order vib was something to worry about. Just avoid 4800 rpm where the crank angle deflection peaks and you should be fine.
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#8
by
Rabbit on Roids
on 19 Mar, 2009 09:43
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but what if you are one of us that makes your engine see 4800 rpms every day? ive never broken a crank.. and ive done quite a few 6000 rpm burn outs when i was (just a little) pissed off. ive never even heard of a crank breaking. i dont doubt theres some 6th order vibes going on inside when you spin some r's with these little engines.
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#9
by
idgtd
on 19 Mar, 2009 09:52
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Think about it like the changes in head materials, oil squirters, etc. with the turbo engines. They added it because in certain situations, they are nice to have. Their are lots of engines out there with no dampers on them. Some of them are fine as is, some last longer with a damper added. Cranks don't just twist axially when deflected by vibrations. The throws cause them to deflect radially and load the bearings funny too. The fatigue can be cumulative, but since most people don't stay at 4800 for minutes at a time it's ok.
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#10
by
Rabbit on Roids
on 19 Mar, 2009 10:16
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true. but when did they start putting harmonic balancers on TD engines? cause like i say, ive got the stock pulley off my TD and its just a solid aluminum pulley. ive always thought a real balancer would be nice tho.
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#11
by
subsonic
on 19 Mar, 2009 10:17
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Hypothetically, if the internals received a professional balance job before assemble, would this negate the critical vibration at 4800rpm? I know this was discussed on a previous thread. Gonna try and find it.
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#12
by
idgtd
on 19 Mar, 2009 11:13
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Hypothetically, if the internals received a professional balance job before assemble, would this negate the critical vibration at 4800rpm? I know this was discussed on a previous thread. Gonna try and find it.
Not quite. 4 cyl engines are inherently unbalanced, even if all of the parts weigh the same and such. In order to achieve (in theory) perfect balance, you have to move up to an inline 6, 8, 90 degree V8, and so on. A 4 cyl engine requires a balance shaft to achieve this. But this 6th order vibration is probably not caused by a balance issue. Rather, it has to due with the torque variation inherent to piston engines and the stiffness of the crankshaft. Get the right driving frequency and stiffness and you'll have vibes.