Stillen Crank Pulley
09-09-2008, 04:40 PM
#196
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Ok well. The stock ECU could care less about the crank pulley weight. There is not a sensor for rotational inertia, so the ECU won't notice it either way. Secondly as is always true, less weight = less power wasted. The biggest difference though is where that rotational weight is. The crank pulley is only a few inches across at best, the flywheel on the other hand is many times larger if you consider the growth of rotational weight.
Any one here with basic math/science skills? Post up some calculations on rotational inertia so that people can figure out what a few ounces actually weighs 2 inches from centerline vs. 8 inches from centerline.
edit: oops for some reason I was thinking another motor. The earlier model G and Zs the pulley is the damper, the G37 should be the same. Unless the aftermarket unit has a damper I would not suggest replacing it.
The net gain per dollar spent might see way out of whack though if you price a flywheel which can save a significant amount more weight farther out from centerline. If you've already done a light weight flywheel and you need to save an extra hp or two then a crank pulley would be your next step before tearing into the motor to get your power back.
Warning:
1. Under drive pulleys on street cars are one of the most ignorant thing to do.
2. Removing your damper to help save weight can and will cost you actual power and can easily destroy crank/rod bearings
3. Always weigh the cost of a modification including installation vs. the actual power gains before you start on a project.
p.s. it is the worst thing in the world to have to tap a crank because some numb nuts sheared off his crank bolt. Most shops shy away from it if thats all you're doing, liability is too high.
p.p.s. why the hell people worry about crank pulleys when they have heavy *** chrome rims is beyond me (rims/tires are like 20x the rotational mass of a crank pulley x4 rims)
Any one here with basic math/science skills? Post up some calculations on rotational inertia so that people can figure out what a few ounces actually weighs 2 inches from centerline vs. 8 inches from centerline.
edit: oops for some reason I was thinking another motor. The earlier model G and Zs the pulley is the damper, the G37 should be the same. Unless the aftermarket unit has a damper I would not suggest replacing it.
The net gain per dollar spent might see way out of whack though if you price a flywheel which can save a significant amount more weight farther out from centerline. If you've already done a light weight flywheel and you need to save an extra hp or two then a crank pulley would be your next step before tearing into the motor to get your power back.
Warning:
1. Under drive pulleys on street cars are one of the most ignorant thing to do.
2. Removing your damper to help save weight can and will cost you actual power and can easily destroy crank/rod bearings
3. Always weigh the cost of a modification including installation vs. the actual power gains before you start on a project.
p.s. it is the worst thing in the world to have to tap a crank because some numb nuts sheared off his crank bolt. Most shops shy away from it if thats all you're doing, liability is too high.
p.p.s. why the hell people worry about crank pulleys when they have heavy *** chrome rims is beyond me (rims/tires are like 20x the rotational mass of a crank pulley x4 rims)
Last edited by UpRev; 09-09-2008 at 09:57 PM.
09-09-2008, 09:53 PM
#198
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A good choice might be either the ATI or Fluidampr replacement dampers. I would have to check for the actual weight difference between them to see if there was any rotational mass difference, the sizes should be identical to the stock pulley size. The difference is in the ability to damp the crank vibrations. Fluidampr's website has a good visual to explain some of the things that happen to your crank. We've noticed a 2-4hp difference on the civic our friend runs, stock H series motor, just in going to the Fluidampr from a stock damper even though they are the same weight. Simply reducing the harmonic issues of that motor helps it that much. Imagine where that extra 1-2hp goes without the Fluidampr... simply engine wear and stress.
Last edited by UpRev; 09-09-2008 at 10:06 PM.
09-09-2008, 11:19 PM
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Ok well. The stock ECU could care less about the crank pulley weight. There is not a sensor for rotational inertia, so the ECU won't notice it either way. Secondly as is always true, less weight = less power wasted. The biggest difference though is where that rotational weight is. The crank pulley is only a few inches across at best, the flywheel on the other hand is many times larger if you consider the growth of rotational weight.
Any one here with basic math/science skills? Post up some calculations on rotational inertia so that people can figure out what a few ounces actually weighs 2 inches from centerline vs. 8 inches from centerline.
edit: oops for some reason I was thinking another motor. The earlier model G and Zs the pulley is the damper, the G37 should be the same. Unless the aftermarket unit has a damper I would not suggest replacing it.
The net gain per dollar spent might see way out of whack though if you price a flywheel which can save a significant amount more weight farther out from centerline. If you've already done a light weight flywheel and you need to save an extra hp or two then a crank pulley would be your next step before tearing into the motor to get your power back.
Warning:
1. Under drive pulleys on street cars are one of the most ignorant thing to do.
2. Removing your damper to help save weight can and will cost you actual power and can easily destroy crank/rod bearings
3. Always weigh the cost of a modification including installation vs. the actual power gains before you start on a project.
p.s. it is the worst thing in the world to have to tap a crank because some numb nuts sheared off his crank bolt. Most shops shy away from it if thats all you're doing, liability is too high.
p.p.s. why the hell people worry about crank pulleys when they have heavy *** chrome rims is beyond me (rims/tires are like 20x the rotational mass of a crank pulley x4 rims)
Any one here with basic math/science skills? Post up some calculations on rotational inertia so that people can figure out what a few ounces actually weighs 2 inches from centerline vs. 8 inches from centerline.
edit: oops for some reason I was thinking another motor. The earlier model G and Zs the pulley is the damper, the G37 should be the same. Unless the aftermarket unit has a damper I would not suggest replacing it.
The net gain per dollar spent might see way out of whack though if you price a flywheel which can save a significant amount more weight farther out from centerline. If you've already done a light weight flywheel and you need to save an extra hp or two then a crank pulley would be your next step before tearing into the motor to get your power back.
Warning:
1. Under drive pulleys on street cars are one of the most ignorant thing to do.
2. Removing your damper to help save weight can and will cost you actual power and can easily destroy crank/rod bearings
3. Always weigh the cost of a modification including installation vs. the actual power gains before you start on a project.
p.s. it is the worst thing in the world to have to tap a crank because some numb nuts sheared off his crank bolt. Most shops shy away from it if thats all you're doing, liability is too high.
p.p.s. why the hell people worry about crank pulleys when they have heavy *** chrome rims is beyond me (rims/tires are like 20x the rotational mass of a crank pulley x4 rims)
Some people think their butt dyno can tell the difference. Preparation H would probably cure that.
BTW, the stock ECU does care about the pulley. I had a long talk with mine and finally got the truth after pouring a few beers on it. They've been seeing each other since the car was built and thought nobody knew.
09-09-2008, 11:51 PM
#202
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The pulley is the same size but weights 7lbs less. There should be no negative affect on the motor since the pulley size is not different. How much of a difference it will make? I do not know yet. I will be doing a before/after dyno when I get mine installed though just to see if there is a difference. UpRev or someone else, please explain how this will damage the engine. That doesn't make sense to me from what I've been told.
09-10-2008, 12:30 AM
#203
The pulley is the same size but weights 7lbs less. There should be no negative affect on the motor since the pulley size is not different. How much of a difference it will make? I do not know yet. I will be doing a before/after dyno when I get mine installed though just to see if there is a difference. UpRev or someone else, please explain how this will damage the engine. That doesn't make sense to me from what I've been told.
"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."
09-10-2008, 12:42 AM
#204
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From Wikipedia-
"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."
"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."
A more trustworthy source such as a engine manufacture site would be cool if you can find that. 
09-10-2008, 12:58 AM
#206
Any other source other than Wikipedia? Not saying that wikipedia is not true but any paper that I write in college is not allowed to use wikipedia as a source because the material that it contains is questionable. If I use wikipedia I get a grade deduction. A more trustworthy source such as a engine manufacture site would be cool if you can find that.
A more trustworthy source such as a engine manufacture site would be cool if you can find that. http://www.automedia.com/Performance...ht20020501pd/1
http://www.circletrack.com/techartic...per/index.html
Also, I called GT Motorsports about this once and they said something similar.
Last edited by Buddy Revell; 09-10-2008 at 01:18 AM.
09-10-2008, 01:02 AM
#207
Pay no attention to the man behind the curtain! He's obviously using the original laws of physics!
Some people think their butt dyno can tell the difference. Preparation H would probably cure that.
BTW, the stock ECU does care about the pulley. I had a long talk with mine and finally got the truth after pouring a few beers on it. They've been seeing each other since the car was built and thought nobody knew.
Some people think their butt dyno can tell the difference. Preparation H would probably cure that.
BTW, the stock ECU does care about the pulley. I had a long talk with mine and finally got the truth after pouring a few beers on it. They've been seeing each other since the car was built and thought nobody knew.
DOMO
09-10-2008, 01:11 AM
#208
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I called GT Motorsports about this once and they said something similar.
http://www.automedia.com/Performance...ht20020501pd/1
http://www.automedia.com/Performance...ht20020501pd/1
09-10-2008, 02:34 AM
#209
This is from all the research I've done, and compiled before buying and installing the UR pulley.
The crank pulley is not a harmonic balancer. Our engines are internally balanced. From what I understand UR does not make pulleys for vehicles that use the crank pulley as a harmonic balancer. The crank pulley has a dampener on it. It is a rubber (or some other material) piece pressed on the portion of the pulley that sits in the engine by the crank case. It is used NOT to balance, but to lessen the vibration and noise from our accesories. The UR pulley DOES have a pressed on piece on the same location, and is the EXACT dimensions of the stock pulley. UR has gone through great lengths not to damage our engines, and I've never had problems with their products in the past. I've had UR pulleys on my previous 3 cars, and had zero problems. This isn't some crappy P.O.S. product trying to get a free $200 from us for a crappy piece of metal that will ruin or engines.
The crank pulley is not a harmonic balancer. Our engines are internally balanced. From what I understand UR does not make pulleys for vehicles that use the crank pulley as a harmonic balancer. The crank pulley has a dampener on it. It is a rubber (or some other material) piece pressed on the portion of the pulley that sits in the engine by the crank case. It is used NOT to balance, but to lessen the vibration and noise from our accesories. The UR pulley DOES have a pressed on piece on the same location, and is the EXACT dimensions of the stock pulley. UR has gone through great lengths not to damage our engines, and I've never had problems with their products in the past. I've had UR pulleys on my previous 3 cars, and had zero problems. This isn't some crappy P.O.S. product trying to get a free $200 from us for a crappy piece of metal that will ruin or engines.
Last edited by AZg37; 09-10-2008 at 02:40 AM.
09-10-2008, 02:43 AM
#210
I found this, should clear things up a bit. It's straight from UR themselves:
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 that is 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 that we offer utilize a counterweight as part of the pulley as these engines are internally balanced.
The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that looks 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 that in these applications, this elastomer is somewhat inadequate in size, as well as life span, to act as an effective torsional damper. If you look at the pulleys on some of the 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 that with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most who have installed and driven a vehicle with our pulleys will notice the engine actually feels smoother. This is a natural result of replacing the heavy steel crank pulley with a CNC-machined aluminum 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.
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 that is 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 that we offer utilize a counterweight as part of the pulley as these engines are internally balanced.
The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that looks 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 that in these applications, this elastomer is somewhat inadequate in size, as well as life span, to act as an effective torsional damper. If you look at the pulleys on some of the 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 that with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most who have installed and driven a vehicle with our pulleys will notice the engine actually feels smoother. This is a natural result of replacing the heavy steel crank pulley with a CNC-machined aluminum 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.