Crank Pulley - How do they work?

[djdnz]

There are better ways to spend your money. I installed lightweight pulleys on my last car, there was no perceivable improvement.

My personal experience is that it is not worth the money, and potential headaches that could arise.

[WolfsFang]

Originally Posted by djdnz

and potential headaches that could arise.

That will only happen if you install it wrong.
http://forums.nasioc.com/forums/showthread.php?t=444518

[JDKane527]

I didn't notice much improvement in acceleration with the GFB lightweight pulley set. Only thing I noticed was that the car's rpms drop more quickly. A lightweight flywheel, driveshaft, or wheels will yield a more noticeable difference in acceleration, but those are all much more expensive haha.

[diss7]

How do they work?

They go round and round. Put a belt around it, and it causes other pulleys to go round and round, which then power other things.

The more you know.

[Calum]

The effect a light weight crank pulley has on actual acceleration is negligible at best. On my last car though the difference in how fast the tach climbed was night and day. Enough so that I had to relearn how to launch in normal traffic.

This car seems to have a lot more mass in the rotational assembly because the difference in feel isn't that big. But it does feel sportier with the revs climbing and falling faster. This is the only real reason to put on a light weight crank pulley. If you're looking for a part to make your car faster, look somewhere else. If you want to enhance the overall driving experience this is a cheap place to start.

[InvalidJohnny5]

Ha I have a lightweight crank pulley and flywheel, goin to be installing a 12lb driveshaft soon...should be nuts to feel with my turbo haha

[diss7]

On a serious note: These do have a decent effect.

Its not straight line racing, although it does help. Its the response where you get the gain. Canyon/track battling, throttle balancing, on/off throttle action, everytime the car reponds quicker. Thats where the improvement lies IMO

Light crank pulley + flywheel + open exahust + intake/induction noise + on/off throttle driving action = win.

[brichard0625]

Originally Posted by Calum

The effect a light weight crank pulley has on actual acceleration is negligible at best. On my last car though the difference in how fast the tach climbed was night and day. Enough so that I had to relearn how to launch in normal traffic.

This car seems to have a lot more mass in the rotational assembly because the difference in feel isn't that big. But it does feel sportier with the revs climbing and falling faster. This is the only real reason to put on a light weight crank pulley. If you're looking for a part to make your car faster, look somewhere else. If you want to enhance the overall driving experience this is a cheap place to start.

I agree. i have had light weight pulleys on two of my vehicles..both were night and day. When i had the perrin pulley on my frs it felt no different
than stock. i was pretty disappointed. the only thing i noticed was that my tach dropped faster than usual but nothing too crazy. Spend your money on something else

[Sithspawn]

Originally Posted by Bg8780

I've heard these pulleys causing issues and possible damage. Anyone care to elaborate?

I'd love to, but I'll probably be ignored. Let's give it a whirl anyway.

OEM crankshaft pulleys are not simply pulleys. They are also harmonic dampers. Do not confuse harmonic damper with harmonic balancer: they're two totally different things.

A harmonic damper acts like a rotational version of a shock absorber in your suspension. A damper is used to control the motion of a spring. In reality, everything is a spring to one degree or another: including the crankshaft. It's just a really, really stiff spring. But, instead of being like a coil spring in your suspension, it's more like a sway bar since it twists as a force is applied to it (like when a piston is being forced down during the power stroke).

So what, the crankshaft twists a little on every power stroke. Big deal right? Well, yes, it can be a big deal.

Most objects have a natural frequency. In other words, when vibrated at that frequency, they begin to self excite until they break apart and stop vibrating. You know when TV dramatizes opera singers causing glasses to shatter? That is a well known example of natural frequency. The crystal (it doesn't actually work with glass) is vibrating at its natural frequency and as the opera singer holds the note, the crystal continues to vibrate harder and harder until it breaks.

A crankshaft also has a natural frequency. Now, chances are slim to none that you will hold the correct rpm (frequency) long enough to get it to vibrate at its natural frequency and shatter, but it will deflect much more than it normally would at that frequency.

That's where the harmonic damper comes into play. The OEM crankshaft pulley has a rubber portion that is tuned to cancel out the natural frequency of the crankshaft as well as absorb vibrations associated with the winding and unwinding of the crankshaft as it deflects slightly on each power stroke.

While it is true that there are tons of people that have run lightweight crankshaft pulleys with no ill effect, there exists a risk that engine damage can occur when the harmonic damper is eliminated. Now, if the FA20 is like other boxers, the oil pump is driven off the nose of the crankshaft. Excessive movement from un-damped crankshaft oscillation could cause damage to the oil pump and possibly other components over time (not to mention that aluminum pulleys on steel crankshafts can gall along with other issues).

Keep in mind that companies like Fluidamper and ATI exist for a reason. Not only are they aware of the significance of harmonic damping, but they have the equipment and knowledge to develop crankshaft pulleys that have appropriate damping characteristics for each specific engine.

The bottom line is that the almost inconsequential improvement in throttle response is not worth the risk associated with running an engine without it's harmonic damper.

[Ray_32]

Wow guys, thanks for the info! I think I've made my decision - will stay away from the crank pulleys for the time being and wait out the warranty (2.5 years to go!) before I actually have a go. Will look into other parts for now. Cheers.

[OICU812]

Originally Posted by Bg8780

I've heard these pulleys causing issues and possible damage. Anyone care to elaborate?

You heard this "WHERE"?

I consider myself a forum whore to say least, I creep this forum nightly for a few hours b4 bed and haven't even heard of a single issue other then install issues that were proven to be USER error, not a single (-) on what any of the varieties of pulleys have done.
Is there a thread or post on failures...? If someone can point me to one I'd like to see it, if it exists????

[Hawk77FT]

CAN I REPLACE THE CRANK PULLEY HARMONIC BALANCER? The harmonic balancer has the sole responsibility to retard or lessen the resonant frequencies that occur during the normal operation of any internal combustion motor. The crank is like a tuning fork for musicians; when the firing cycle hits each cylinder, its like a flick to the tuning fork. So when you see the term "harmonic", it is a literal description of what is occurring to your crank. Your crank is actually flexible, believe it or not, if it wasn't, your engine wouldn't last more then 10,000 miles. It flexes on a microscopic level to absorb the explosion from each cylinder, this flex is precisely what creates an engine's natural frequency. Some vehicle's frequencies are more violent then others due to the architectural layout of the cylinders. For example, a V6 or V8 will have higher resonance because the downward thrust of each cylinder travels through the center-line of the crank in a non-linear pattern; this actually has the ability to amplify the frequency, depending on your RPM. Compare this to an I6 or I4 and you reduce the harmonics due to the linear pulse of the cylinders approach the crank from a single direction. Finally the Flat-4, with force traveling through the crank to opposing cylinders, the frequency is reduced by its own operation. We're not saying that the frequency is completely eliminated! We're saying that of all the engine formats available, a flat-4 is the best candidate for a lightened crank pulley.

[Hawk77FT]

Originally Posted by Sithspawn

I'd love to, but I'll probably be ignored. Let's give it a whirl anyway.

OEM crankshaft pulleys are not simply pulleys. They are also harmonic dampers. Do not confuse harmonic damper with harmonic balancer: they're two totally different things.

A harmonic damper acts like a rotational version of a shock absorber in your suspension. A damper is used to control the motion of a spring. In reality, everything is a spring to one degree or another: including the crankshaft. It's just a really, really stiff spring. But, instead of being like a coil spring in your suspension, it's more like a sway bar since it twists as a force is applied to it (like when a piston is being forced down during the power stroke).

So what, the crankshaft twists a little on every power stroke. Big deal right? Well, yes, it can be a big deal.

Most objects have a natural frequency. In other words, when vibrated at that frequency, they begin to self excite until they break apart and stop vibrating. You know when TV dramatizes opera singers causing glasses to shatter? That is a well known example of natural frequency. The crystal (it doesn't actually work with glass) is vibrating at its natural frequency and as the opera singer holds the note, the crystal continues to vibrate harder and harder until it breaks.

A crankshaft also has a natural frequency. Now, chances are slim to none that you will hold the correct rpm (frequency) long enough to get it to vibrate at its natural frequency and shatter, but it will deflect much more than it normally would at that frequency.

That's where the harmonic damper comes into play. The OEM crankshaft pulley has a rubber portion that is tuned to cancel out the natural frequency of the crankshaft as well as absorb vibrations associated with the winding and unwinding of the crankshaft as it deflects slightly on each power stroke.

While it is true that there are tons of people that have run lightweight crankshaft pulleys with no ill effect, there exists a risk that engine damage can occur when the harmonic damper is eliminated. Now, if the FA20 is like other boxers, the oil pump is driven off the nose of the crankshaft. Excessive movement from un-damped crankshaft oscillation could cause damage to the oil pump and possibly other components over time (not to mention that aluminum pulleys on steel crankshafts can gall along with other issues).

Keep in mind that companies like Fluidamper and ATI exist for a reason. Not only are they aware of the significance of harmonic damping, but they have the equipment and knowledge to develop crankshaft pulleys that have appropriate damping characteristics for each specific engine.

The bottom line is that the almost inconsequential improvement in throttle response is not worth the risk associated with running an engine without it's harmonic damper.

Good stuff mate, but bear in mind this is a flat 4 not a v6 or v8...plus we're in 2013 not in the 80 when indeed some of the big engined cars needed a harmonic damper.

Maybe people from raceseg might be able to help you! @Raceseng

[Bg8780]

Originally Posted by OICU812

You heard this "WHERE"?

I consider myself a forum whore to say least, I creep this forum nightly for a few hours b4 bed and haven't even heard of a single issue other then install issues that were proven to be USER error, not a single (-) on what any of the varieties of pulleys have done.
Is there a thread or post on failures...? If someone can point me to one I'd like to see it, if it exists????

There was a thread awhile ago when the Perrin pulley first hit the market. But since then I'm pretty sure it's been chalked up to user error having to do with the seal.