Lightweight crank pulleys?
Dec 28, 2009, 03:44 PM
#1
Lightweight crank pulleys?
I've been doing a bit of reading on lightweight crank pulleys lately and am finding conflicting information. Some of which says they're a very bad idea since they can't absorb any of the noise/vibrations but other info stating the stock pulley with rubber ring does nothing more than try and quiet down engine noise (it is called a harmonic damper after all). I know underdrive pulleys are available too but I'm not really concerned with them, mainly just looking for info on solid aluminum vs. dampened (stock or Fluidampr for example).
My other thought is, can the little stock pulley with a rubber ring really do much good at absorbing vibrations when there is the much larger and solid flywheel at the other end of the crank?
I've also read about the vibrations potentially damaging the oil pump, but, does the stock damper even affect the oil pump since that's driven off the timing belt and not accessory belt?
Maybe I'm just confused as to what vibrations the dampened pulley is actually absorbing that couldn't otherwise be absorbed by the rubber belt and tensioner. How exactly is it able to protect the engine bearings from vibrations?
My other thought is, can the little stock pulley with a rubber ring really do much good at absorbing vibrations when there is the much larger and solid flywheel at the other end of the crank?
I've also read about the vibrations potentially damaging the oil pump, but, does the stock damper even affect the oil pump since that's driven off the timing belt and not accessory belt?
Maybe I'm just confused as to what vibrations the dampened pulley is actually absorbing that couldn't otherwise be absorbed by the rubber belt and tensioner. How exactly is it able to protect the engine bearings from vibrations?
Dec 28, 2009, 04:56 PM
#3
A lightened crank pulley is not recommended.. its a very small mass and not worth any gain vs the damage that MAY occur.. The balancers like a fluidampr is a HARMONIC balancer for engine harmonics at higher rpms.. not something a belt is going to absorb.. A simple google search explains it all..
http://en.wikipedia.org/wiki/Harmonic_balancer
and some more info..
http://www.fluidampr.com/HOWITWORKS.htm
http://en.wikipedia.org/wiki/Harmonic_balancer
and some more info..
http://www.fluidampr.com/HOWITWORKS.htm
Dec 28, 2009, 05:00 PM
#4
I recall one dedicated racer in here who resolved all his rapid bearing wear issues simply by going from a solid aluminum pulley back to a dampener. That was convincing enough.
Grab onto a steel pipe and have someone hit it repeatedly with a ball peen hammer. Those ringing vibrations that make your hand hurt get transmitted to critical friction surfaces. That rubber ring absorbs those vibrations as they reach the nose of the crank. A Fluidampr is even more efficient. In fact, there was an article in a magazine not long ago whereby it was demonstrated that both the ATI and Fluidampr increased power as compared to a solid pulley on a V8 engine.
Crank driven oil pumps tend to suffer premature failure when the crank is undampened. This isn't a problem with a 4G63, but it demonstrates what crank harmonics can do.
In summary, there isn't any way I'd run a high torque engine without a dampened crank. There's nothing to be gained from it, only something to be lost.
Grab onto a steel pipe and have someone hit it repeatedly with a ball peen hammer. Those ringing vibrations that make your hand hurt get transmitted to critical friction surfaces. That rubber ring absorbs those vibrations as they reach the nose of the crank. A Fluidampr is even more efficient. In fact, there was an article in a magazine not long ago whereby it was demonstrated that both the ATI and Fluidampr increased power as compared to a solid pulley on a V8 engine.
Crank driven oil pumps tend to suffer premature failure when the crank is undampened. This isn't a problem with a 4G63, but it demonstrates what crank harmonics can do.
In summary, there isn't any way I'd run a high torque engine without a dampened crank. There's nothing to be gained from it, only something to be lost.
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Dec 28, 2009, 09:28 PM
#8
Many people have used pulleys for years without issue and that rubber ring is for NVH of which I have not noticed any additional.Also that rubber ring will not may deteriorate and break as almost all dsm owners can attest.when mine broke it was at idle lucky me.Cobb makes them as well as Perrin and a host of others and stand behind them.
Last edited by PlanoEvo; Dec 28, 2009 at 09:54 PM.
Dec 28, 2009, 10:09 PM
#11
The magazine test I quoted previously was independently conducted. Crank vibrations were measured and logged. The Fluidampr sharply reduced the harmonic losses, and picked up 10bhp at the 400bhp level vs. a plain hub.
Dampers are used from virtually every conceivable OE application to sanctioned racing. How they work and why they work is thoroughly understood and proven. It isn't like debating the cause of global warming.
FYI
Dampers are used from virtually every conceivable OE application to sanctioned racing. How they work and why they work is thoroughly understood and proven. It isn't like debating the cause of global warming.
FYI
Dec 29, 2009, 08:33 AM
#12
Taking a test on V-8's and assuming its the same for an inline-4 isn't really saying much at all. On Evo's there have been documented cases of power gains with a solid pulley so that goes against what your test shows. I'm not trying to argue with you, but rather get to the facts and figure out if there is fact behind these opinions or if its just knowledge carried over from the muscle cars and is assumed to be right for lack of better information.
Dec 29, 2009, 09:52 AM
#13
Taking a test on V-8's and assuming its the same for an inline-4 isn't really saying much at all. On Evo's there have been documented cases of power gains with a solid pulley so that goes against what your test shows. I'm not trying to argue with you, but rather get to the facts and figure out if there is fact behind these opinions or if its just knowledge carried over from the muscle cars and is assumed to be right for lack of better information.
I have been an early user of underdrive pulleys for many years now but only learnt about the detrimental effects of harmonics in the 4G63 engine not too long ago.
Try replacing bearings every single race like I do and you will know that the problem lies more than just tolerances and balancing. Have been building 2.0 on the DSM's for years now and the inherent bearing problems but thank god I nitrided my cranks ( thus am able to save cranks even with worn out mains) and 2.3 strokers in my Evo 6 which kills absolutely every single mains running only 6 to 7 passes on a single event. And both makes over 700WHP. Both have not run harmonic balancers and without balance shafts. And yes, the engine DOES make a little more vibration without the balance shafts. Funny thing is that while the main bearings are worn out badly, the conrod bearings remain perfect, almost untouched....
Have recently completed a race on the stroker and will remove the main bearings shortly to compare previously on which I have ran no dampener and this time with the dampener. This will at least confirm some how on the effects of the dampener.
Am only relating my experiences with the harmonics that are killing the engine and I don't think Mitsubishi would be putting one on if it didn't need one...
If I recall in one of many early forums some long time ago, even Bushur runs the stock dampener and doesn't use pulleys....
Try replacing bearings every single race like I do and you will know that the problem lies more than just tolerances and balancing. Have been building 2.0 on the DSM's for years now and the inherent bearing problems but thank god I nitrided my cranks ( thus am able to save cranks even with worn out mains) and 2.3 strokers in my Evo 6 which kills absolutely every single mains running only 6 to 7 passes on a single event. And both makes over 700WHP. Both have not run harmonic balancers and without balance shafts. And yes, the engine DOES make a little more vibration without the balance shafts. Funny thing is that while the main bearings are worn out badly, the conrod bearings remain perfect, almost untouched....
Have recently completed a race on the stroker and will remove the main bearings shortly to compare previously on which I have ran no dampener and this time with the dampener. This will at least confirm some how on the effects of the dampener.
Am only relating my experiences with the harmonics that are killing the engine and I don't think Mitsubishi would be putting one on if it didn't need one...
If I recall in one of many early forums some long time ago, even Bushur runs the stock dampener and doesn't use pulleys....
Sorry for my late reply on my findings with my motor. Took it apart yesterday and the results are indeed very interesting. After running at over 8000 rpms on this stroker 2.3 motor and at 35 psi making 750 WHP/656 ft/ib WTQ, the bearings were in good reasonable condition and take note, this motor was run WITH a brand new stock Mitsubishi harmonic damper, crank pulley. I swear what I saw was surprising on what I revved the motor to ( 8500 rpm at times on the track). To add to the topic of balance shafts, this motor was built without balance shafts at all. The motor has seen done 40 dyno pulls and 10 full on passes down the track at the drags..
On my earlier post, I mentioned that the mains were worn right down to metal at a lower power level ( 670 WHP) and at less rpms at the track. This was on a brand new rebuilt motor with only 7 passes down the track and about 30 dyno pulls.
The above findings I found was on the same motor except that I replaced a set of brand new Clevites on it and the new Mitsubishi crank pulley and I was all ready to replace it again yesterday but hey there you go guys.... there is no dispute that the damper is there for a reason and for a very good reason in fact.... no more aluminium pulleys for me...
On my earlier post, I mentioned that the mains were worn right down to metal at a lower power level ( 670 WHP) and at less rpms at the track. This was on a brand new rebuilt motor with only 7 passes down the track and about 30 dyno pulls.
The above findings I found was on the same motor except that I replaced a set of brand new Clevites on it and the new Mitsubishi crank pulley and I was all ready to replace it again yesterday but hey there you go guys.... there is no dispute that the damper is there for a reason and for a very good reason in fact.... no more aluminium pulleys for me...
The engine was pulled apart and I can say that my mixture was perfect since there was ZERO detonation and the pistons and combustion chamber was in perfect condition. I was running the 37R with this and there was no tune difference except that it was maybe .2 of an A/F leaner with the C16.
It's all in the crank damper. I have been using the aluminium underdrive pulleys for the last 10 years and I never had an engine failure with it but it now explains why I have less life span in my motors especially big power and boost is concerned.
It was Carmela from Jackson's that warned me against using a pulley. I took her word and there we go...the difference is obvious especially in a 2.3 stroker.
It's all in the crank damper. I have been using the aluminium underdrive pulleys for the last 10 years and I never had an engine failure with it but it now explains why I have less life span in my motors especially big power and boost is concerned.
It was Carmela from Jackson's that warned me against using a pulley. I took her word and there we go...the difference is obvious especially in a 2.3 stroker.
Apparently the aftermarket dampers work at all rpms whereas the factory piece is more ' tuned ' at a higher rpm. This is what I was told and I have recently purchased a Fluidamper for my Evo and it is an awesome looking piece, bit heavy though but what the heck, it saves my motor...
There you go guys, guess most of us found out the hard way...even myself..
There you go guys, guess most of us found out the hard way...even myself..
