lightweight pulleys worth having?
10 February 2014, 09:46 PM
#61
So ideally a crank would be best balanced with a pulley one side and the flywheel the other? Does anyone actually do this?. From factory are they matched or is it one part from one side of the factory bolted to a part from another.
Also, what effect does the slack on the AC and power steering pumps have on the balance of the crank?
Also, what effect does the slack on the AC and power steering pumps have on the balance of the crank?
10 February 2014, 10:00 PM
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So ideally a crank would be best balanced with a pulley one side and the flywheel the other? Does anyone actually do this?. From factory are they matched or is it one part from one side of the factory bolted to a part from another.
Also, what effect does the slack on the AC and power steering pumps have on the balance of the crank?
Also, what effect does the slack on the AC and power steering pumps have on the balance of the crank?
Factory kit will all be within certain tolerances...not balanced and blueprinted
I wonder if that's what the rubber element in the OE pulley is supposed to counteract?
10 February 2014, 10:26 PM
#63
I think we're forgetting that Subaru sell hundreds of thousands of engines every year. They are probably more interested in reliability, rather than eeking out the last ounce of performance, as any reliability issues are paid for through either warranty costs or reputational costs.
Enthusiasts, however, might take a different view of the reliability vs performance, hence we can make other choices if we wish. I.e. increase performance at the (possible) cost of long term reliability.
Personally, I chose increased performance over engine life, and when I get around to it, I'll be fitting my grimmspeed pulley that's been sat in the garage for two years. If I'm unlucky, and the engine breaks because of the pulley, I'll rebuild it.
Enthusiasts, however, might take a different view of the reliability vs performance, hence we can make other choices if we wish. I.e. increase performance at the (possible) cost of long term reliability.
Personally, I chose increased performance over engine life, and when I get around to it, I'll be fitting my grimmspeed pulley that's been sat in the garage for two years. If I'm unlucky, and the engine breaks because of the pulley, I'll rebuild it.
11 February 2014, 08:23 AM
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I think we're forgetting that Subaru sell hundreds of thousands of engines every year. They are probably more interested in reliability, rather than eeking out the last ounce of performance, as any reliability issues are paid for through either warranty costs or reputational costs.
Enthusiasts, however, might take a different view of the reliability vs performance, hence we can make other choices if we wish. I.e. increase performance at the (possible) cost of long term reliability.
Personally, I chose increased performance over engine life, and when I get around to it, I'll be fitting my grimmspeed pulley that's been sat in the garage for two years. If I'm unlucky, and the engine breaks because of the pulley, I'll rebuild it.
Enthusiasts, however, might take a different view of the reliability vs performance, hence we can make other choices if we wish. I.e. increase performance at the (possible) cost of long term reliability.
Personally, I chose increased performance over engine life, and when I get around to it, I'll be fitting my grimmspeed pulley that's been sat in the garage for two years. If I'm unlucky, and the engine breaks because of the pulley, I'll rebuild it.
11 February 2014, 08:55 AM
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I think we're forgetting that Subaru sell hundreds of thousands of engines every year. They are probably more interested in reliability, rather than eeking out the last ounce of performance, as any reliability issues are paid for through either warranty costs or reputational costs.
Enthusiasts, however, might take a different view of the reliability vs performance, hence we can make other choices if we wish. I.e. increase performance at the (possible) cost of long term reliability.
Personally, I chose increased performance over engine life, and when I get around to it, I'll be fitting my grimmspeed pulley that's been sat in the garage for two years. If I'm unlucky, and the engine breaks because of the pulley, I'll rebuild it.
Enthusiasts, however, might take a different view of the reliability vs performance, hence we can make other choices if we wish. I.e. increase performance at the (possible) cost of long term reliability.
Personally, I chose increased performance over engine life, and when I get around to it, I'll be fitting my grimmspeed pulley that's been sat in the garage for two years. If I'm unlucky, and the engine breaks because of the pulley, I'll rebuild it.
a) you have the necessary information to make an informed decision
b) you have the funds required to maintain the engine in the event of failure
c) you have the desire to keep going in the event of failure
12 February 2014, 12:35 AM
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12 February 2014, 01:44 PM
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got a little more frommy dad today...he even sorted the typo for you Steve
"One of the correspondents gives a figure of 2.5 kg for the standard pulley which makes me think it is designed for a specific purpose, I'm sure Subaru could have got it a lot lighter otherwise.. The flywheel design is used to reduce the cyclic speed fluctuation caused by the variation in piston forces during the 4 stoke cycle. I once had to design a flywheel for AC generator industrial application of our York diesel engine. It had to have sufficient moment of inertia to smooth out speed fluctuation to meet the specification of the 50Hz mains frequency is. Its mass was something like 3 times that of the vehicle flywheel. Reducing flywheel weight often means raising the idle speed to stop stalling due to excessive speed fluctuation during idle.
The crankshaft pulley is used to dampen high frequency vibration in the crankshaft generated by the unbalanced torsional and bending forces. The crank being an iron alloy is elastic so will vibrate and I think the pulley is tuned to the natural frequency of the crank; it's what is known as an harmonic damper. Vibration at the natural frequency can be quite destructive; the combination of high strain and high frequency can result in failure through metal fatigue. For accelerated parts testing we vibrated the component at its natural frequency because this is usually the shortest life. The best illustration of 'natural frequency' is the destruction of the Tacoma Narrows suspension bridge. On the other hand it could just be a noise damper tuned to a frequency of another vibration mode; they are used to reduce driveline ‘rumble’. I would reserve lightweight pulleys for the driven bits especially if they are running at a multiple of engine speed; the torque to accelerate is proportional to the rotation speed squared."
"One of the correspondents gives a figure of 2.5 kg for the standard pulley which makes me think it is designed for a specific purpose, I'm sure Subaru could have got it a lot lighter otherwise.. The flywheel design is used to reduce the cyclic speed fluctuation caused by the variation in piston forces during the 4 stoke cycle. I once had to design a flywheel for AC generator industrial application of our York diesel engine. It had to have sufficient moment of inertia to smooth out speed fluctuation to meet the specification of the 50Hz mains frequency is. Its mass was something like 3 times that of the vehicle flywheel. Reducing flywheel weight often means raising the idle speed to stop stalling due to excessive speed fluctuation during idle.
The crankshaft pulley is used to dampen high frequency vibration in the crankshaft generated by the unbalanced torsional and bending forces. The crank being an iron alloy is elastic so will vibrate and I think the pulley is tuned to the natural frequency of the crank; it's what is known as an harmonic damper. Vibration at the natural frequency can be quite destructive; the combination of high strain and high frequency can result in failure through metal fatigue. For accelerated parts testing we vibrated the component at its natural frequency because this is usually the shortest life. The best illustration of 'natural frequency' is the destruction of the Tacoma Narrows suspension bridge. On the other hand it could just be a noise damper tuned to a frequency of another vibration mode; they are used to reduce driveline ‘rumble’. I would reserve lightweight pulleys for the driven bits especially if they are running at a multiple of engine speed; the torque to accelerate is proportional to the rotation speed squared."
12 February 2014, 02:24 PM
#69
I know people are using the stock pulley breaking as a valid excuse to favour a solid pulley but it might be missing a point highlighted by the breaking if the pulley.
Maybe the pulley fatigues due to damping the vibration of the crank. What I'm saying is possibly they get a pounding through vibrations and the very fact they break shows they're just weakened by doing their job for the last 10/15 years. It could be that the stock pulley gives x amount less wear to the crank bearings and if it fails it might be a sign that it needs a fresh OE damper pulley to do its job, not necessarily needing a solid pulley "because the OE one broke"
Does that make sense?
I'm not saying it's true, but it's another slant on the argument for changing the OE pulley because it breaks, it might break because it's done a good job and just been worn out. And if that is true then fitting a solid pulley would be the wrong knee jerk reaction in that situation.
Maybe the pulley fatigues due to damping the vibration of the crank. What I'm saying is possibly they get a pounding through vibrations and the very fact they break shows they're just weakened by doing their job for the last 10/15 years. It could be that the stock pulley gives x amount less wear to the crank bearings and if it fails it might be a sign that it needs a fresh OE damper pulley to do its job, not necessarily needing a solid pulley "because the OE one broke"
Does that make sense?
I'm not saying it's true, but it's another slant on the argument for changing the OE pulley because it breaks, it might break because it's done a good job and just been worn out. And if that is true then fitting a solid pulley would be the wrong knee jerk reaction in that situation.
13 February 2014, 06:45 AM
#71
got a little more frommy dad today...he even sorted the typo for you Steve
"One of the correspondents gives a figure of 2.5 kg for the standard pulley which makes me think it is designed for a specific purpose, I'm sure Subaru could have got it a lot lighter otherwise.. The flywheel design is used to reduce the cyclic speed fluctuation caused by the variation in piston forces during the 4 stoke cycle. I once had to design a flywheel for AC generator industrial application of our York diesel engine. It had to have sufficient moment of inertia to smooth out speed fluctuation to meet the specification of the 50Hz mains frequency is. Its mass was something like 3 times that of the vehicle flywheel. Reducing flywheel weight often means raising the idle speed to stop stalling due to excessive speed fluctuation during idle.
The crankshaft pulley is used to dampen high frequency vibration in the crankshaft generated by the unbalanced torsional and bending forces. The crank being an iron alloy is elastic so will vibrate and I think the pulley is tuned to the natural frequency of the crank; it's what is known as an harmonic damper. Vibration at the natural frequency can be quite destructive; the combination of high strain and high frequency can result in failure through metal fatigue. For accelerated parts testing we vibrated the component at its natural frequency because this is usually the shortest life. The best illustration of 'natural frequency' is the destruction of the Tacoma Narrows suspension bridge. On the other hand it could just be a noise damper tuned to a frequency of another vibration mode; they are used to reduce driveline ‘rumble’. I would reserve lightweight pulleys for the driven bits especially if they are running at a multiple of engine speed; the torque to accelerate is proportional to the rotation speed squared."
"One of the correspondents gives a figure of 2.5 kg for the standard pulley which makes me think it is designed for a specific purpose, I'm sure Subaru could have got it a lot lighter otherwise.. The flywheel design is used to reduce the cyclic speed fluctuation caused by the variation in piston forces during the 4 stoke cycle. I once had to design a flywheel for AC generator industrial application of our York diesel engine. It had to have sufficient moment of inertia to smooth out speed fluctuation to meet the specification of the 50Hz mains frequency is. Its mass was something like 3 times that of the vehicle flywheel. Reducing flywheel weight often means raising the idle speed to stop stalling due to excessive speed fluctuation during idle.
The crankshaft pulley is used to dampen high frequency vibration in the crankshaft generated by the unbalanced torsional and bending forces. The crank being an iron alloy is elastic so will vibrate and I think the pulley is tuned to the natural frequency of the crank; it's what is known as an harmonic damper. Vibration at the natural frequency can be quite destructive; the combination of high strain and high frequency can result in failure through metal fatigue. For accelerated parts testing we vibrated the component at its natural frequency because this is usually the shortest life. The best illustration of 'natural frequency' is the destruction of the Tacoma Narrows suspension bridge. On the other hand it could just be a noise damper tuned to a frequency of another vibration mode; they are used to reduce driveline ‘rumble’. I would reserve lightweight pulleys for the driven bits especially if they are running at a multiple of engine speed; the torque to accelerate is proportional to the rotation speed squared."
Light weight flywheel = yes
13 February 2014, 01:48 PM
#74
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13 February 2014, 02:09 PM
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unless you are modifying the internal engine components then I wouldn't havethought so.
the 'wrong' oil could very well lead to increased wear which could lead to achange in vibration behaviour.
not sure where you are heading with these questions?
13 February 2014, 02:22 PM
#76
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I just wondered if a lightweight pulley had other uses other than ridding the car of a parasitic/fragile part.
13 February 2014, 02:30 PM
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http://www.atiracing.com/products/da...mper_dinan.htm
27 March 2014, 02:24 PM
#82
Subaru build cars for profit first - performance second. Most professional tuners and a lot of people on here don't operate to the same constraints or with the same objectives.
I keep hearing folks citing theoretic white papers etc as 'absolute' evidence. Not really, they are still opinion based, heavily biased, written by humans who have their own objectives. Sometimes based on empiric evidence and more often with Subaru - based on theory. Theory that if it's worked ok for the last 3 years then it must be right or at least doesn't necessitate R&D budget to change it for a better solution. The days of Subaru over engineering and ignoring costs are decades behind us.
One thing I definitely know in this case is that the OEM fails, especially on high power cars. In 16 years of running high power Subaru's I've had several rubber failures (I've actually lost count!) on crank case pulleys and never had a light weight pulley failure. All rubber failures look like torsional stress (pretty much as you'd expect thinking about it.)
Also: As I've never had a crank failure at all in either case (OEM or lightweight) I'd say I've never seend any evidence against lightweight pullies. But further to that I've never heard of any case either. So where is the evidence that removing a part designed by Subaru and replacing it with a well made improved/redesigned 'fit for purpose' part will cause damage.
For everyone saying this is a bad idea can you please cite cases where you have any evidence that lightweight pulleys have caused crank/shell failures or any other engine failure. Apologies if I have missed such citations in this thread. I'd genuinely like to know if this is a 'probability'.
I'm not having a go at anyone here or taking sides either. So cool yer boots.
I'm going on the evidence I have to hand and I'm still yet to see anything that puts me off of lightweight pulleys, just stuff that puts me off the OEM ones. 
27 March 2014, 02:51 PM
#83
One thing everyone is forgetting here is that Subaru engineers can be right muppets but also they often aren't the person who makes the design decision. The number of things that I've seen on Subarus which I've thought are an utter ****e solution dictated by an accountant NOT an engineer are endless.
Subaru build cars for profit first - performance second. Most professional tuners and a lot of people on here don't operate to the same constraints or with the same objectives.
I keep hearing folks citing theoretic white papers etc as 'absolute' evidence. Not really, they are still opinion based, heavily biased, written by humans who have their own objectives. Sometimes based on empiric evidence and more often with Subaru - based on theory. Theory that if it's worked ok for the last 3 years then it must be right or at least doesn't necessitate R&D budget to change it for a better solution. The days of Subaru over engineering and ignoring costs are decades behind us.
One thing I definitely know in this case is that the OEM fails, especially on high power cars. In 16 years of running high power Subaru's I've had several rubber failures (I've actually lost count!) on crank case pulleys and never had a light weight pulley failure. All rubber failures look like torsional stress (pretty much as you'd expect thinking about it.)
Also: As I've never had a crank failure at all in either case (OEM or lightweight) I'd say I've never seend any evidence against lightweight pullies. But further to that I've never heard of any case either. So where is the evidence that removing a part designed by Subaru and replacing it with a well made improved/redesigned 'fit for purpose' part will cause damage.
For everyone saying this is a bad idea can you please cite cases where you have any evidence that lightweight pulleys have caused crank/shell failures or any other engine failure. Apologies if I have missed such citations in this thread. I'd genuinely like to know if this is a 'probability'.
I'm not having a go at anyone here or taking sides either. So cool yer boots. I'm going on the evidence I have to hand and I'm still yet to see anything that puts me off of lightweight pulleys, just stuff that puts me off the OEM ones.
Subaru build cars for profit first - performance second. Most professional tuners and a lot of people on here don't operate to the same constraints or with the same objectives.
I keep hearing folks citing theoretic white papers etc as 'absolute' evidence. Not really, they are still opinion based, heavily biased, written by humans who have their own objectives. Sometimes based on empiric evidence and more often with Subaru - based on theory. Theory that if it's worked ok for the last 3 years then it must be right or at least doesn't necessitate R&D budget to change it for a better solution. The days of Subaru over engineering and ignoring costs are decades behind us.
One thing I definitely know in this case is that the OEM fails, especially on high power cars. In 16 years of running high power Subaru's I've had several rubber failures (I've actually lost count!) on crank case pulleys and never had a light weight pulley failure. All rubber failures look like torsional stress (pretty much as you'd expect thinking about it.)
Also: As I've never had a crank failure at all in either case (OEM or lightweight) I'd say I've never seend any evidence against lightweight pullies. But further to that I've never heard of any case either. So where is the evidence that removing a part designed by Subaru and replacing it with a well made improved/redesigned 'fit for purpose' part will cause damage.
For everyone saying this is a bad idea can you please cite cases where you have any evidence that lightweight pulleys have caused crank/shell failures or any other engine failure. Apologies if I have missed such citations in this thread. I'd genuinely like to know if this is a 'probability'.
I'm not having a go at anyone here or taking sides either. So cool yer boots.
I'm going on the evidence I have to hand and I'm still yet to see anything that puts me off of lightweight pulleys, just stuff that puts me off the OEM ones. Wise words !
27 March 2014, 04:43 PM
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One thing everyone is forgetting here is that Subaru engineers can be right muppets but also they often aren't the person who makes the design decision. The number of things that I've seen on Subarus which I've thought are an utter ****e solution dictated by an accountant NOT an engineer are endless.
Subaru build cars for profit first - performance second. Most professional tuners and a lot of people on here don't operate to the same constraints or with the same objectives.
I keep hearing folks citing theoretic white papers etc as 'absolute' evidence. Not really, they are still opinion based, heavily biased, written by humans who have their own objectives. Sometimes based on empiric evidence and more often with Subaru - based on theory. Theory that if it's worked ok for the last 3 years then it must be right or at least doesn't necessitate R&D budget to change it for a better solution. The days of Subaru over engineering and ignoring costs are decades behind us.
One thing I definitely know in this case is that the OEM fails, especially on high power cars. In 16 years of running high power Subaru's I've had several rubber failures (I've actually lost count!) on crank case pulleys and never had a light weight pulley failure. All rubber failures look like torsional stress (pretty much as you'd expect thinking about it.)
Also: As I've never had a crank failure at all in either case (OEM or lightweight) I'd say I've never seend any evidence against lightweight pullies. But further to that I've never heard of any case either. So where is the evidence that removing a part designed by Subaru and replacing it with a well made improved/redesigned 'fit for purpose' part will cause damage.
For everyone saying this is a bad idea can you please cite cases where you have any evidence that lightweight pulleys have caused crank/shell failures or any other engine failure. Apologies if I have missed such citations in this thread. I'd genuinely like to know if this is a 'probability'.
I'm not having a go at anyone here or taking sides either. So cool yer boots. I'm going on the evidence I have to hand and I'm still yet to see anything that puts me off of lightweight pulleys, just stuff that puts me off the OEM ones.
Subaru build cars for profit first - performance second. Most professional tuners and a lot of people on here don't operate to the same constraints or with the same objectives.
I keep hearing folks citing theoretic white papers etc as 'absolute' evidence. Not really, they are still opinion based, heavily biased, written by humans who have their own objectives. Sometimes based on empiric evidence and more often with Subaru - based on theory. Theory that if it's worked ok for the last 3 years then it must be right or at least doesn't necessitate R&D budget to change it for a better solution. The days of Subaru over engineering and ignoring costs are decades behind us.
One thing I definitely know in this case is that the OEM fails, especially on high power cars. In 16 years of running high power Subaru's I've had several rubber failures (I've actually lost count!) on crank case pulleys and never had a light weight pulley failure. All rubber failures look like torsional stress (pretty much as you'd expect thinking about it.)
Also: As I've never had a crank failure at all in either case (OEM or lightweight) I'd say I've never seend any evidence against lightweight pullies. But further to that I've never heard of any case either. So where is the evidence that removing a part designed by Subaru and replacing it with a well made improved/redesigned 'fit for purpose' part will cause damage.
For everyone saying this is a bad idea can you please cite cases where you have any evidence that lightweight pulleys have caused crank/shell failures or any other engine failure. Apologies if I have missed such citations in this thread. I'd genuinely like to know if this is a 'probability'.
I'm not having a go at anyone here or taking sides either. So cool yer boots.
I'm going on the evidence I have to hand and I'm still yet to see anything that puts me off of lightweight pulleys, just stuff that puts me off the OEM ones.
27 March 2014, 08:03 PM
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Just to say from the start I know nothing about rebuilding engines.
I was very interested in reading this some good points.
I was just thinking about uneven forces acting on the crank shaft causing vibration.
RE the pulley: When upgrading the engine do people balance the pistons & connecting rods.I know they used to in the olden days
.
Are production tolerances so good today that it is no longer necessary?
I was very interested in reading this some good points.
I was just thinking about uneven forces acting on the crank shaft causing vibration.
RE the pulley: When upgrading the engine do people balance the pistons & connecting rods.I know they used to in the olden days
.Are production tolerances so good today that it is no longer necessary?
30 March 2014, 10:24 PM
#88
Interesting read.......
Im interested to hear of any failures of cranks/ bearings etc on cars been fitted with lightened pulleys. Thats where the proof is. If there isn't a large amount of failures on cars running the pulleys its safe to say with enough evidence that they aren't a problem.
Also there could be other causes of failures. Even on cars with lightened pulleys and the they themselves aren't necessarily the cause. Subaru are never in a million years going to endorse aftermarket parts to replace their own designed parts unless they are prodrive or similar in a partner venture.
There will always be a difference in opinion and people with knowledge will always be able to back up what they say with scientific stuff but it doesn't mean somebody else is wrong.
Personally i will run lightened pulleys but it doesn't mean an right either.
Anyway enough of my drivel.
Im interested to hear of any failures of cranks/ bearings etc on cars been fitted with lightened pulleys. Thats where the proof is. If there isn't a large amount of failures on cars running the pulleys its safe to say with enough evidence that they aren't a problem.
Also there could be other causes of failures. Even on cars with lightened pulleys and the they themselves aren't necessarily the cause. Subaru are never in a million years going to endorse aftermarket parts to replace their own designed parts unless they are prodrive or similar in a partner venture.
There will always be a difference in opinion and people with knowledge will always be able to back up what they say with scientific stuff but it doesn't mean somebody else is wrong.
Personally i will run lightened pulleys but it doesn't mean an right either.
Anyway enough of my drivel.
31 March 2014, 09:16 AM
#89
Intresting topic that didnt end up in the usual bun fight (disapointed almost) well done CDF.
As someone who works in manufacturing the only conflict I see in this debate is cost to subaru, if they thought they could get away with a massive cost saving by using a much less complicated pulley without compromise surely they would?
Thats assuming that a single peice alloy pulley is cheaper to make than a cast bonded part. Where I work we would be jumping through hoops to make a saving like that. Im using the alloy option and after seeing the pics of a failed OEM part I'm happy with my decision.
As someone who works in manufacturing the only conflict I see in this debate is cost to subaru, if they thought they could get away with a massive cost saving by using a much less complicated pulley without compromise surely they would?
Thats assuming that a single peice alloy pulley is cheaper to make than a cast bonded part. Where I work we would be jumping through hoops to make a saving like that. Im using the alloy option and after seeing the pics of a failed OEM part I'm happy with my decision.
Last edited by edsel; 31 March 2014 at 09:18 AM.
01 April 2014, 07:54 AM
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Non-damped pulleys will cause more wear to the engine but I'm not sure they would cause catastrophic failure without significant 'other' issues. This is the only uprated damper I'm aware of, the builds and builders that use them speak for themselves.
http://www.atiracing.com/products/da...dam-subaru.htm
http://www.atiracing.com/products/da...dam-subaru.htm