Crank pully?
08-31-2006, 08:26 AM
#21
Yeah, the thing is, the pulley is not a two-piece design connected by that rubber ring, as mentioned earlier. It doesn't go all the way through; it's just a ring of rubber that sits in a channel carved in the back of the pulley. How much can that really do on this engine? I understand all of the above, but really, in THIS application, the engine will be quite fine without that little rubber ring. Just my .02. (flame suit on...)
09-06-2006, 12:36 PM
#22
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hmm
so i dont get it....... everyone has an opinion i need solid facts ....
is the UR crank pully worth it or not
simple answer would be good.... i am searching bout the crank pully and i am half way getting the uses and the down sides of it
is the UR crank pully worth it or not
simple answer would be good.... i am searching bout the crank pully and i am half way getting the uses and the down sides of it
09-07-2006, 03:57 AM
#23
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the key way brakes from improper install or removal - nothing more. It can be broken on a stock pulley as well (as shown).
if you spend some time searching you'll see that there are TONS of people with pullies without incident. It was the first mod I did to my car 2 years ago nearly to the day, and 40k miles later, never an issue.
Yes the motor is balanced internally...and that rubber ring in the stock pulley, is as suggested, to silence the noise of the accessory belts. Not all motors are balanced without external pullies attached to them.
Yes harmonics play a huge role and yes there are lots of forces acting on the crank. That is why some motors run balance shafts internally, and some do not. But, you can easily remove these internal balance shafts, with the right internal build, and have no ill effects. The Z has no internal balance shafts BTW.
As for race teams not running it, check the rule book - they are not allowed to as far as I'm aware.
Run one, don't run one, makes no difference to me. From a personal note, it's a worthwhile mod, not expensive, has noticeable results, and on both of our own cars, both with over 40k miles, never an issue. Before installing it I asked my engine builder his thoughts - he gave it his blessing so long as the pulley we were replacing was itself, balanced. The UR one is (perfectly I might add, as I gave it to him to verify), and a such, on it went, and will remain, even with my new motor that is being built
if you spend some time searching you'll see that there are TONS of people with pullies without incident. It was the first mod I did to my car 2 years ago nearly to the day, and 40k miles later, never an issue.
Yes the motor is balanced internally...and that rubber ring in the stock pulley, is as suggested, to silence the noise of the accessory belts. Not all motors are balanced without external pullies attached to them.
Yes harmonics play a huge role and yes there are lots of forces acting on the crank. That is why some motors run balance shafts internally, and some do not. But, you can easily remove these internal balance shafts, with the right internal build, and have no ill effects. The Z has no internal balance shafts BTW.
As for race teams not running it, check the rule book - they are not allowed to as far as I'm aware.
Run one, don't run one, makes no difference to me. From a personal note, it's a worthwhile mod, not expensive, has noticeable results, and on both of our own cars, both with over 40k miles, never an issue. Before installing it I asked my engine builder his thoughts - he gave it his blessing so long as the pulley we were replacing was itself, balanced. The UR one is (perfectly I might add, as I gave it to him to verify), and a such, on it went, and will remain, even with my new motor that is being built
Last edited by Z1 Performance; 09-07-2006 at 04:08 AM.
09-07-2006, 04:28 AM
#24
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Originally Posted by MustGoFastR
Yeah, the thing is, the pulley is not a two-piece design connected by that rubber ring, as mentioned earlier. It doesn't go all the way through; it's just a ring of rubber that sits in a channel carved in the back of the pulley. How much can that really do on this engine? I understand all of the above, but really, in THIS application, the engine will be quite fine without that little rubber ring. Just my .02. (flame suit on...)
Those who choose not to believe me, that's fine. Feel free to call UR, and talk to the owners themselves about their pullies
Taken from UR's FAQ section:
4) "Is my crank pulley a harmonic/torsional/vibration damper or a harmonic balancer?"
People are getting their crank pulleys confused with the harmonic dampers found on some V6 / V8 engines. "Harmonic Balancer" is a term used loosely in the automotive industry. Technically, this type of device does not exist. The "balancer" part comes from engines that are externally balanced and have a counterweight cast into the damper, hence the merging of the two terms. None of the applications we offer use a counterweight as part of the pulley, as these engines are all internally balanced.
The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that makes them look similar to a harmonic damper. The elastomer in the OEM pulley serves as an isolator, which is there to suppress natural vibration and noise from the engine itself, the A/C compressor, P/S pump, and alternator. This is what the manufacturers call NVH (Noise Vibration & Harshness) when referring to noticeable noise and vibration in the passenger compartment. It is important to note in these applications, the elastomer is inadequate in size and durability to act as an effective torsional damper. If you look at the pulleys on some imports there is no rubber to be found at all. We have samples of these, mostly from Acura/Honda, the Nissan Altima, 1.8L Eclipse, 2.3L Fords, Chrysler 2.2L's, and 1.8L VW's, to mention a few. This is not to say with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most owners who have installed our pulleys notice the engine actually feels smoother. This is result of replacing the heavy crank pulley with our crank pulley. NVH is variable and unique to every car. NVH will increase with the installation of an aftermarket intake and/or exhaust, for example. Think of OEM intake systems in newer cars, they use baffles and resonators in the intake to quiet all the intake noise. Aftermarket intakes eliminate these resonators and create dramatic increases in engine noise from the throttle opening and closing. So to most tuners, certain types of NVH can make the driving experience more enjoyable.
The purpose of a traditional harmonic damper is to protect against crank failure from torsional movement. This is not necessary in most modern engines because of the many advances in engine design and materials. Factors such as stroke length, displacement, inline, V configurations, piston dwell time, piston pin off-set, power output, etc., do determine when and how these harmonics and torsional movements occur.
Again, there is a lot of internet hearsay about crank pulleys. When engine problems occur, too often people are quick to blame the pulley first, rather than taking the time to look logically into why there was a problem. We hope that after reading this you will understand the crank pulleys better.
09-07-2006, 11:39 AM
#25
If you want solid facts, just ask a mechanical engineer in the industry. I have a BS in ME and although I don't work in an automotive industry, I can say to know somehting on this. There are several great papers you can see for yourself and download from the Society of Automotive Engineers website on crank pullies. What I posted before, and is attached below, is correct. That "little rubber ring" is designed, with the mass of steel connected to it, to cancel out the force of selected harmonics, which as I said before is just a type of periodic motion. It is the simplest type, and can easily be found mathematically. It is therefore possible to create a damper that is effective for some, not all, of these harmonics to be reduced to a net force of zero acting on the crank. This results in less stress on the crank and reduced vibration. It has NOTHING to do with the engine's accessories. Any damping that occurs is taken out in the block the accessory is mounted to and the belt. As a posted earlier, the reason people have run these lighter, smaller crank pullies without fail is the engine stil has other means of damping, such as the flywheel and torque converter in place. And again, there is NO SUCH THING as "internally dampened" The crank is balanced, this means it is designed to spin with the mass of the reciprocating assembly without any wobble. It is not designed, nor can it be designed, to automatically dampen the torsional, lateral, and vertical forces acting on the crank. Everyone keeps saying its balanced as though there aren't any other vibrations taking place. has no one noticed the engine vibrating in the engine bay, or felt the individual surges of the power strokes through their shifter? For those that may have just read to this point, again, the summary on aftermarket pullies and harmonic dampers:
Originally Posted by Resolute
The crank is obviouisly "balanced" as everyone says. But balanced does not mean there are no other forces acting on the crank that cause vibrations. This is obvious just looking at an idle engine vibrating in the engine bay, or with your hand on the shifter you can feel the vibrations. Vibrations are just a type of periodic motion. The pistons pushing on the crank and inertia pulling on the crank form the most obvious periodic motions. In other words, these are motions that occur in a repeated pattern. Some periodic motions want to cause the engine to buck on a lateral plane, others act on a vertical plane. All these periodic motions are seen as vibrations, and some are called harmonics. They occur over the entire rpm range. Harmonics are just the simplest form of periodic motions. With every engine, some harmonics are automatically cancelled out by each other, so that the net force produced is zero. Some engine designs are better at this than others, which is why straight six engines tend to feel "smoother" than V6's. In any engine though, most harmonics are not cancelled out and are transferred through the crank. The harmonic damper is that elastomer ring in the pullley designed to help eliminate some of the more devastating harmonics that transfer to the crank by cancelling them out. Lighter underdrive pullies that lack this elastomerr ring will not cancel out these harmonic frequencies. People that say otherwise are wrong.
Now, that doesn't mean that your engine will destruct in a vibrating blaze of glory if the damper is removed. The fact is, your engine also damps these periodic motions through the dual mass flywheel and output shaft on the manual transmission cars. The auto cars fare even better as the torque converter is a massive fluid type damper in and of itself. The purpose of the elastomer ring and steel pulley is because with some calculation, an engineer can determine the specific "best" frequencies to dampen, not all of them mind you, just the most critical frequencies, and construct the damper accordingly. This is a good bit of protection for the bearings, engine mounts, etc over the course of the engine's life. Makes sense for the manufacturer to place it on the engine. Removing it will most likely lead to extra wear over the long run, but nothing too disasterous in and of itself. Combined with a lightened flywheel, these harmonic frequencies can get worse, placing more wear on the engine. Also, those people making really big power or revving higher have increased the intensity of the two forces acting on the crank: torque from compression and inertia. The greater these two forces, the greater the harmonic amplitudes can be, and the more neccessary damping them becomes. Hence, the use on racing engines with high revs and big power. Some professional drag shops have even seen power gains with a slightly heavier damper over lightened crank pullies, because at some point the power freed by the reduction in rotating inertia is lost by the force needed by the crank to overcome the periodic motions its fighting against. In other words, big power and big revs mean there are big forces the crank has to fight against, and damping them out rather than letting them amplify is good for power.
Having said all that, obviously this is not the case for stock engines, or most modified. I don't like lightened crank pullies as I don't see the marginal gains worth it, but those making big power or revving high should think long and hard about removing the stock damper. Better yet, place a fluid damper on instead because fluid dampers can cover a broader range of harmonics. Sorry for the long wind response, hope there is something salvageable in this for people,
Will
Now, that doesn't mean that your engine will destruct in a vibrating blaze of glory if the damper is removed. The fact is, your engine also damps these periodic motions through the dual mass flywheel and output shaft on the manual transmission cars. The auto cars fare even better as the torque converter is a massive fluid type damper in and of itself. The purpose of the elastomer ring and steel pulley is because with some calculation, an engineer can determine the specific "best" frequencies to dampen, not all of them mind you, just the most critical frequencies, and construct the damper accordingly. This is a good bit of protection for the bearings, engine mounts, etc over the course of the engine's life. Makes sense for the manufacturer to place it on the engine. Removing it will most likely lead to extra wear over the long run, but nothing too disasterous in and of itself. Combined with a lightened flywheel, these harmonic frequencies can get worse, placing more wear on the engine. Also, those people making really big power or revving higher have increased the intensity of the two forces acting on the crank: torque from compression and inertia. The greater these two forces, the greater the harmonic amplitudes can be, and the more neccessary damping them becomes. Hence, the use on racing engines with high revs and big power. Some professional drag shops have even seen power gains with a slightly heavier damper over lightened crank pullies, because at some point the power freed by the reduction in rotating inertia is lost by the force needed by the crank to overcome the periodic motions its fighting against. In other words, big power and big revs mean there are big forces the crank has to fight against, and damping them out rather than letting them amplify is good for power.
Having said all that, obviously this is not the case for stock engines, or most modified. I don't like lightened crank pullies as I don't see the marginal gains worth it, but those making big power or revving high should think long and hard about removing the stock damper. Better yet, place a fluid damper on instead because fluid dampers can cover a broader range of harmonics. Sorry for the long wind response, hope there is something salvageable in this for people,
Will
09-07-2006, 11:49 AM
#26
Originally Posted by MustGoFastR
Yeah, the thing is, the pulley is not a two-piece design connected by that rubber ring, as mentioned earlier. It doesn't go all the way through; it's just a ring of rubber that sits in a channel carved in the back of the pulley. How much can that really do on this engine? I understand all of the above, but really, in THIS application, the engine will be quite fine without that little rubber ring. Just my .02. (flame suit on...)
09-07-2006, 01:02 PM
#27
Originally Posted by Resolute
Doesn't need to be two-piece design. Two piece designs are designed to have the outer piece of steel "slip" under severe torsional load. A four cylinder or flat plane crank V8 will have this issue. A 60 degree V6 will not. That elastomer section is the same as placing your finger on a tuning fork. It simply dampens vibrations that would otherwise contribute to the amplitude of other frequencies. That's the whole point. The harmonics on our engine aren't so bad, but some, known as critical harmonics, will increase the amplitude of others, and make them worse. It is cheap and easy to calculate the critical damping on a four cycle engine, and so it makes sense to do so for reducing vibration in the crank, and as a result the block and tranny. Removing it will increase the load on the crank from vibration, or the natural harmonics acting on it.
Bottom line is there are plenty of people running pullies on this engine with no problems at all (and some that have other mods that will likely decrease engine life a heck of a lot more than an undampened pulley), but for those overly worrisome types, your info. is good justification for their stance on the matter. There are always certain risks when modding; just part of the game. If you don't wanna play, then don't mod.
09-07-2006, 04:57 PM
#28
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What's the point? A purely lightened (not underdrive) crank pulley will not have any noticeable effect on power to the ground. Intuitively this should be clear based on the masses involved, but I derived it mathemagically here for the doubters. The plugged-in numbers are for a different car, but you'll find similarly tiny results for ours.
Based on the lack of gains alone, why would one every pay money for such an item? Add to that the increased peak internal stresses from decreased inertial dampening and I see no room for debate.
Based on the lack of gains alone, why would one every pay money for such an item? Add to that the increased peak internal stresses from decreased inertial dampening and I see no room for debate.
Last edited by Mechee; 09-07-2006 at 04:59 PM.
09-08-2006, 05:45 AM
#29
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Originally Posted by Mechee
What's the point? A purely lightened (not underdrive) crank pulley will not have any noticeable effect on power to the ground. Intuitively this should be clear based on the masses involved, but I derived it mathemagically here for the doubters. The plugged-in numbers are for a different car, but you'll find similarly tiny results for ours.
Based on the lack of gains alone, why would one every pay money for such an item? Add to that the increased peak internal stresses from decreased inertial dampening and I see no room for debate.
Based on the lack of gains alone, why would one every pay money for such an item? Add to that the increased peak internal stresses from decreased inertial dampening and I see no room for debate.
09-08-2006, 09:22 AM
#30
Originally Posted by teh215
So basically what you are saying with your first post is that the power that was used to spin the 5lb heavier stock pulley when switching to a lighter pulley just disappears?
09-08-2006, 09:31 AM
#31
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I think that the pulley is simply one piece in a long list of items that could be replaced with lighter parts to reduce the mass of rotating parts on the car. Yes, the pulley alone is not going to be that large of a change. But combine that with a lighter clutch, flywheel and other drive train parts as well as wheels, tires, rotors etc. and there is going to be alot more power being put to the ground that previously was just working to make stuff turn. Am I off track?
09-08-2006, 09:42 AM
#32
Originally Posted by MustGoFastR
Actually that does make perfect sense. The info. you are posting, though, is how the stuff owrks in general and not neccessarily saying that the deletion of the dampening ring is for sure harmful in this particular application.
Bottom line is there are plenty of people running pullies on this engine with no problems at all (and some that have other mods that will likely decrease engine life a heck of a lot more than an undampened pulley), but for those overly worrisome types, your info. is good justification for their stance on the matter. There are always certain risks when modding; just part of the game. If you don't wanna play, then don't mod.
Bottom line is there are plenty of people running pullies on this engine with no problems at all (and some that have other mods that will likely decrease engine life a heck of a lot more than an undampened pulley), but for those overly worrisome types, your info. is good justification for their stance on the matter. There are always certain risks when modding; just part of the game. If you don't wanna play, then don't mod.
"The fact is, your engine also damps these periodic motions through the dual mass flywheel and output shaft on the manual transmission cars. The auto cars fare even better as the torque converter is a massive fluid type damper in and of itself. The purpose of the elastomer ring and steel pulley is because with some calculation, an engineer can determine the specific "best" frequencies to dampen, not all of them mind you, just the most critical frequencies, and construct the damper accordingly. This is a good bit of protection for the bearings, engine mounts, etc over the course of the engine's life. Makes sense for the manufacturer to place it on the engine. Removing it will most likely lead to extra wear over the long run, but nothing too disasterous in and of itself."
There will be extra wear, just like saying making 50hp over stock will place extra wear on the engine. But will you notice it? Not likely. Over several hundred thousand miles? probably. The more power, and especially more revs, the worse the wear will be. That's physics, and it doesn't care what kind of engine you have.
As far as our application, a 60 deg V6 is a 60 deg V6, the only real variable in determining critical damping for the engine's natural harmonics is the rod length and stroke. Otherwise any 60deg V6 will have the same periodic motions. The good news, its not as bad for us as a four cylinder. It's better than us for a V8. Engine configurations are consistant in their general harmonic properties.
09-08-2006, 09:59 AM
#33
Originally Posted by teh215
I think that the pulley is simply one piece in a long list of items that could be replaced with lighter parts to reduce the mass of rotating parts on the car. Yes, the pulley alone is not going to be that large of a change. But combine that with a lighter clutch, flywheel and other drive train parts as well as wheels, tires, rotors etc. and there is going to be alot more power being put to the ground that previously was just working to make stuff turn. Am I off track?
09-08-2006, 11:27 AM
#34
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Originally Posted by teh215
So basically what you are saying with your first post is that the power that was used to spin the 5lb heavier stock pulley when switching to a lighter pulley just disappears?
09-08-2006, 12:56 PM
#35
Originally Posted by Mechee
Clearly that is NOT what I'm saying. The question is, how much power did it take to accelerate the heavier pulley relative to the lighter pulley? Was it 1000 hp, or 0.001 hp? I am saying that the effective power increases to the ground are fractions of 1 hp in anything but 1st gear, and I prove this physically in the link I provided.
of course, the energy freed rom a reduction in rotational inertia will always be a percentage, so some would argue that the 2 or 3 hp they gained to the wheel is worth more if they make more power at the crank. But as I posted above, there will be a point of diminishing return as the forces acting against the crank also increase.
09-08-2006, 01:01 PM
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Originally Posted by Resolute
exactly
of course, the energy freed rom a reduction in rotational inertia will always be a percentage, so some would argue that the 2 or 3 hp they gained to the wheel is worth more if they make more power at the crank. But as I posted above, there will be a point of diminishing return as the forces acting against the crank also increase.
of course, the energy freed rom a reduction in rotational inertia will always be a percentage, so some would argue that the 2 or 3 hp they gained to the wheel is worth more if they make more power at the crank. But as I posted above, there will be a point of diminishing return as the forces acting against the crank also increase.
09-08-2006, 01:13 PM
#37
Originally Posted by Mechee
That's the gotcha that most people never consider: decreased mechanical efficiencies of the internal assemblies from increased stresses and vibrations, which is why lightening the crank pulley can actually decrease power to the ground under certain circumstances as you suggest. However my write-up is purely arguing the decreased inertia power claims. While the "gains" are nondimensional percentages to first order, it's often easier to get the point across by instead quoting peak gains for stock motor power levels.
Will
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