Just Installed UR Underdrive Pulley
05-31-2007, 02:08 PM
#1
Black Mamba
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Just Installed UR Underdrive Pulley
I have an 06 AT and after driving it for a day, I can totally feel the difference. The car feels like it has a lot more pep. The only issue I have with the pulley is that when I floor it and the RPM gets to about 5K, my shift knob starts to vibrate. I changed my stock knob to the Momo Shadow before. The vibration is almost as strong as when a cell phone vibrates. You can hear it, it's so loud. I was wondering if the vibration was because I have the underdrive pulley or maybe because I installed the shift knob wrong. I've had the knob for several months now and I've never heard or felt any vibration before. Anyone else with the same problem?
05-31-2007, 05:01 PM
#7
Registered Member
I installed a UR UDP on my former 2002 Altima SE (yes, standard with the VQ V6 engine). It increased the HP by 6.5 and the torque by 3.5 ft/lbs. I could only notice the increase in first and second gear as a very slight increase in throttle response. The negative side which was obvious and noticable was frequent belt squealing. The VQ engine did not use spring loaded accessory belt tensions. Instead, you had to set the tension manually.
There was a lot of discussion on the Altima gearhead site regarding whether or not the stock pulley was actually a true harmonic balancer. I decide with my TL not to go tis route mostly because of this issue. And also because, as I remember seeing in the Service Manual, the torque spec for the crankshaft bolt is something like 180 ft/lbs! The Altima was 140, but was actually set by degrees rather than through the use of a torque wrench.
There was a lot of discussion on the Altima gearhead site regarding whether or not the stock pulley was actually a true harmonic balancer. I decide with my TL not to go tis route mostly because of this issue. And also because, as I remember seeing in the Service Manual, the torque spec for the crankshaft bolt is something like 180 ft/lbs! The Altima was 140, but was actually set by degrees rather than through the use of a torque wrench.
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05-31-2007, 05:24 PM
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Originally Posted by WiLLrOx
The only issue I have with the pulley is that when I floor it and the RPM gets to about 5K, my shift knob starts to vibrate. I changed my stock knob to the Momo Shadow before.
05-31-2007, 05:25 PM
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Nobody else has the same problem? I've been thinking about switching to the stock diameter UR pulley because that might get rid of the vibration.
05-31-2007, 11:22 PM
#14
Call UR and tell them whats happening-you could have a problem somewhere else or a funky unit
The HP gain isnt actually ~more HP, its the approx 8 pound!! lighter weight allows freer rev and the Underdrive slows the AC and PS which opens up blocked HP already in the engine. 8-12 hp is the average advertised- difficult to tell other than accelleration.
We have short on-ramps and traffic going 80- getting fast is good
Other mods do ~add~ hp
The HP gain isnt actually ~more HP, its the approx 8 pound!! lighter weight allows freer rev and the Underdrive slows the AC and PS which opens up blocked HP already in the engine. 8-12 hp is the average advertised- difficult to tell other than accelleration.
We have short on-ramps and traffic going 80- getting fast is good
Other mods do ~add~ hp
06-01-2007, 12:29 AM
#16
other mods like exhaust, intake, etc.
This of it this way:
When the engine of ANY car is sitting on a table, NOTHING attached to it (no pulleys, no belts, nothing on the crank shaft, no intake on the throttle body, no exhaust PERIOD .. the the engine block ..) --> it's producing as much power (when it's on and running) as mechanically possible.
When the car gets dropped into an engine bay, factory intake gets bolted on, exhaust system gets bolted on, pulleys get added to the crank shaft, etc --> that PEAK crankshaft horsepower goes down. Hence this "free-ing" up horsepower you hear about no these types of threads...
TRULY adding horsepower is forced induction (turbo, supercharging), NOS (nitrous oxide injection).
This of it this way:
When the engine of ANY car is sitting on a table, NOTHING attached to it (no pulleys, no belts, nothing on the crank shaft, no intake on the throttle body, no exhaust PERIOD .. the the engine block ..) --> it's producing as much power (when it's on and running) as mechanically possible.
When the car gets dropped into an engine bay, factory intake gets bolted on, exhaust system gets bolted on, pulleys get added to the crank shaft, etc --> that PEAK crankshaft horsepower goes down. Hence this "free-ing" up horsepower you hear about no these types of threads...
TRULY adding horsepower is forced induction (turbo, supercharging), NOS (nitrous oxide injection).
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06-01-2007, 11:22 AM
#18
There should be no noticeable vibration with the UR pulley. The stock crank pulley is not a harmonic dampener. It has an elastomer which is there to reduce NVH. However, the engine will run smoother and rev out quicker witht he pulley with virtually no negative side effects. I have never felt the shift knobs vibrate after a pulley install and I have done dozens of these units. It must be something with the shift knob.
06-01-2007, 11:40 AM
#19
I disagree.
Just because you've never felt it doesn't mean it's not culpabale.
Changing a shift knob on an AT wil not "introduce" vibration. Maybe a rattle if it fits shitty, but it certainly will not cause vibration.
If the heavy rubber pulley is there to reduce/counter NVH, and you remove it, you're increasing the likelihood you're going to feel some. I personally feel the reports of folks stating it "smoothed out" thier engine is bunk... and they can match that report with thier ass dyno's.
I feel a significant vibration in my floor/pedals at engine start, but smooths out when the engine reaches idle. JDM5lughatch, also noted this when coding my 2007 key. I solely attribute this to the pully. Do I think it's hurting anything? No. I've never really noticed anything in the 5K rpm range, but that's because:
1) I'd be getting on it, and that means I'm focused on shifting, clutching, and steering... 6MT has a tendency to distract you.
2) I'm lowered with 19s that are balanced kinda shitty. At 80 the ride is tight, kinda rough, with a noticeable sligth balance wobble. Noticing a small engine vibration from a pulley would be the last thing I would ever notice.
Just because you've never felt it doesn't mean it's not culpabale.
Changing a shift knob on an AT wil not "introduce" vibration. Maybe a rattle if it fits shitty, but it certainly will not cause vibration.
If the heavy rubber pulley is there to reduce/counter NVH, and you remove it, you're increasing the likelihood you're going to feel some. I personally feel the reports of folks stating it "smoothed out" thier engine is bunk... and they can match that report with thier ass dyno's.
I feel a significant vibration in my floor/pedals at engine start, but smooths out when the engine reaches idle. JDM5lughatch, also noted this when coding my 2007 key. I solely attribute this to the pully. Do I think it's hurting anything? No. I've never really noticed anything in the 5K rpm range, but that's because:
1) I'd be getting on it, and that means I'm focused on shifting, clutching, and steering... 6MT has a tendency to distract you.
2) I'm lowered with 19s that are balanced kinda shitty. At 80 the ride is tight, kinda rough, with a noticeable sligth balance wobble. Noticing a small engine vibration from a pulley would be the last thing I would ever notice.
06-01-2007, 12:44 PM
#20
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I changed the shift knob back to the stock one and I can still feel the vibration right around 5K RPM. I will call UR and let them know. Maybe it wasn't installed properly, but it seems that I'm the only one with this problem.
06-01-2007, 01:22 PM
#21
Originally Posted by Excelerate
The stock crank pulley is not a harmonic dampener.
But seriously, if the OEM pulley isn't a harmonic damper, then what does the 3G TL use to control crank harmonics?
06-01-2007, 06:04 PM
#22
acura-cl.com OG
Originally Posted by WiLLrOx
Maybe it wasn't installed properly.
i think that some of the techniques a non-acura mechanic would use to remove the crank pulley could actually be bad for the engine. i need to list mine on ebay.....
06-02-2007, 12:09 PM
#23
Originally Posted by Kennedy
I disagree.
Just because you've never felt it doesn't mean it's not culpabale.
Changing a shift knob on an AT wil not "introduce" vibration. Maybe a rattle if it fits shitty, but it certainly will not cause vibration.
If the heavy rubber pulley is there to reduce/counter NVH, and you remove it, you're increasing the likelihood you're going to feel some. I personally feel the reports of folks stating it "smoothed out" thier engine is bunk... and they can match that report with thier ass dyno's.
I feel a significant vibration in my floor/pedals at engine start, but smooths out when the engine reaches idle. JDM5lughatch, also noted this when coding my 2007 key. I solely attribute this to the pully. Do I think it's hurting anything? No. I've never really noticed anything in the 5K rpm range, but that's because:
1) I'd be getting on it, and that means I'm focused on shifting, clutching, and steering... 6MT has a tendency to distract you.
2) I'm lowered with 19s that are balanced kinda shitty. At 80 the ride is tight, kinda rough, with a noticeable sligth balance wobble. Noticing a small engine vibration from a pulley would be the last thing I would ever notice.
Just because you've never felt it doesn't mean it's not culpabale.
Changing a shift knob on an AT wil not "introduce" vibration. Maybe a rattle if it fits shitty, but it certainly will not cause vibration.
If the heavy rubber pulley is there to reduce/counter NVH, and you remove it, you're increasing the likelihood you're going to feel some. I personally feel the reports of folks stating it "smoothed out" thier engine is bunk... and they can match that report with thier ass dyno's.
I feel a significant vibration in my floor/pedals at engine start, but smooths out when the engine reaches idle. JDM5lughatch, also noted this when coding my 2007 key. I solely attribute this to the pully. Do I think it's hurting anything? No. I've never really noticed anything in the 5K rpm range, but that's because:
1) I'd be getting on it, and that means I'm focused on shifting, clutching, and steering... 6MT has a tendency to distract you.
2) I'm lowered with 19s that are balanced kinda shitty. At 80 the ride is tight, kinda rough, with a noticeable sligth balance wobble. Noticing a small engine vibration from a pulley would be the last thing I would ever notice.
The engine does rev out more quickly and generally is smoother. That is the experience of many "ass dynos". We should trust your "ass" over ours?
Either way the harmonic damper does have an elastomer, a small rubber ring, and it is there to reduce NVH in the cabin. It may be possible that the pulley could be the culprit but I have installed a lot of pulleys on many different cars and I have never felt a vibration as the result of the pulley.
06-02-2007, 12:13 PM
#24
Originally Posted by 94eg!
It's damper, not dampener. A dampener would be a moist towel...
But seriously, if the OEM pulley isn't a harmonic damper, then what does the 3G TL use to control crank harmonics?
But seriously, if the OEM pulley isn't a harmonic damper, then what does the 3G TL use to control crank harmonics?
The OEM pulley is not a harmonic damper. The engine is internally balanced. You are thinking of old school V8's which require harmonic dampers. The stock pulley only has a rubber ring, elastomer, to reduce NVH.
06-02-2007, 03:47 PM
#25
Originally Posted by Excelerate
Yes you are right it is damper, not dampener. Typed that one too quickly without checking.
The OEM pulley is not a harmonic damper. The engine is internally balanced. You are thinking of old school V8's which require harmonic dampers. The stock pulley only has a rubber ring, elastomer, to reduce NVH.
The OEM pulley is not a harmonic damper. The engine is internally balanced. You are thinking of old school V8's which require harmonic dampers. The stock pulley only has a rubber ring, elastomer, to reduce NVH.
Sound like someone has blown some smoke up your ass about the OEM crank pulley as it has nothing to do with NVH. The elastomer built into it is in fact a harmonic balance, and removing it WILL reduce engine life. The proper way to underdrive accessories is to install smaller pulleys onto the accesory itself. And the proper way to lighten the engines rotating assembly is reduce the flywheel weight. You guys are all getting ripped off by UR racing and their cheap, easy to manufacture crank pulleys...
06-02-2007, 03:57 PM
#26
Here are some helpful diagrams detailing crank harmonics:
Crankshaft Deflection -
The Invisible Enemy
Each time the air/fuel mixture inside a cylinder is ignited, the combustion that results creates a torque spike - an extremely rapid rise in cylinder pressure. This pressure, applied to the top of the piston, becomes the force that is applied to the crankshaft through the connecting rod. Each torque spike is like a hammer blow. In fact, it hits with sufficient intensity that it not only causes the crankshaft to turn, it actually deflects or twists it. This twisting action and the resulting rebound (as the crank arm snaps back in the opposite direction) is known as torsional harmonic vibration. If not adequately controlled, torsional vibration causes rapid main bearing and main journal wear and possible crankshaft breakage.
Fortunately, harmonic vibration can be controlled by a vibration damper - which is also called a harmonic damper or erroneously a "harmonic balancer". The main purpose of a "harmonic damper" is to control harmonic vibration, not necessarily to balance the engine's rotating assembly.
Crankshaft Deflection -
The Invisible Enemy
Each time the air/fuel mixture inside a cylinder is ignited, the combustion that results creates a torque spike - an extremely rapid rise in cylinder pressure. This pressure, applied to the top of the piston, becomes the force that is applied to the crankshaft through the connecting rod. Each torque spike is like a hammer blow. In fact, it hits with sufficient intensity that it not only causes the crankshaft to turn, it actually deflects or twists it. This twisting action and the resulting rebound (as the crank arm snaps back in the opposite direction) is known as torsional harmonic vibration. If not adequately controlled, torsional vibration causes rapid main bearing and main journal wear and possible crankshaft breakage.
Fortunately, harmonic vibration can be controlled by a vibration damper - which is also called a harmonic damper or erroneously a "harmonic balancer". The main purpose of a "harmonic damper" is to control harmonic vibration, not necessarily to balance the engine's rotating assembly.
06-02-2007, 04:30 PM
#27
94eg!,
God bless ya. I went down this road too. Search for my posts on this topic.
BMW's dinaan has a great article on this topic as well.
It's really been beat to death here if you search around.
I went ahead with the mod because I can't find 1 credible reference demonstrating journal bearing wear, and there are literally dozens of these installed on 2G TL's with up to 100K miles... and no known issues.
God bless ya. I went down this road too. Search for my posts on this topic.
BMW's dinaan has a great article on this topic as well.
It's really been beat to death here if you search around.
I went ahead with the mod because I can't find 1 credible reference demonstrating journal bearing wear, and there are literally dozens of these installed on 2G TL's with up to 100K miles... and no known issues.
06-02-2007, 06:47 PM
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Guys....
A Crank pulley swap should NOT produce any noticable vibration...especially the way the OP has described. There is something else going one here....make sure all the bolts are tightened to spec and in the process of puttings everything together you didn't leave something undone somewhere somehow....I've seen some pretty crazy install goofs.
Bottom line is, your shifter is probably loose....and rattling. Or if the shifter is of multi-peice construction, something internally could be broken or loose. I'd double check that its all in order....go over your pulley install....
I've never heard of a pulley install producing any amount of vibration, much less that would be that noticable. If anything, the cars seem to accelerate smoother.
Good luck.
A Crank pulley swap should NOT produce any noticable vibration...especially the way the OP has described. There is something else going one here....make sure all the bolts are tightened to spec and in the process of puttings everything together you didn't leave something undone somewhere somehow....I've seen some pretty crazy install goofs.
Bottom line is, your shifter is probably loose....and rattling. Or if the shifter is of multi-peice construction, something internally could be broken or loose. I'd double check that its all in order....go over your pulley install....
I've never heard of a pulley install producing any amount of vibration, much less that would be that noticable. If anything, the cars seem to accelerate smoother.
Good luck.
06-02-2007, 06:58 PM
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Kennedy,
One thing you need to remember as well is that an Inline 6 as mentioned or referenced in the Dinan articles is inherently the most succeptible to harmonic balancing issues due to the length of the crank. Its a very different with a V6 or I4....same laws apply of course, but not to the same degree.
And crank pulleys were ok to run on street I6 BMWs as long as the factory flywheel wasn't replaced with a lightweight aluminum unit. They ran fine as long as either end remained "weighted". The only crank issues or bearing failures we saw on the race cars were on those with BOTH lightweight aluminum crank pulleys and flywheel....and these were cars being beat to hell, pushed to the limit, and driven between sustained 5500-7000rpm.
Installing a crank pulley on a street driven V6 is really a non-issue....and the opposing bank's reciprocating assembly does most of the harmonic damping anyways, not to mention the honkin'30lb flywheel out back.
One thing you need to remember as well is that an Inline 6 as mentioned or referenced in the Dinan articles is inherently the most succeptible to harmonic balancing issues due to the length of the crank. Its a very different with a V6 or I4....same laws apply of course, but not to the same degree.
And crank pulleys were ok to run on street I6 BMWs as long as the factory flywheel wasn't replaced with a lightweight aluminum unit. They ran fine as long as either end remained "weighted". The only crank issues or bearing failures we saw on the race cars were on those with BOTH lightweight aluminum crank pulleys and flywheel....and these were cars being beat to hell, pushed to the limit, and driven between sustained 5500-7000rpm.
Installing a crank pulley on a street driven V6 is really a non-issue....and the opposing bank's reciprocating assembly does most of the harmonic damping anyways, not to mention the honkin'30lb flywheel out back.
06-03-2007, 08:53 AM
#30
Registered Member
Originally Posted by 94eg!
Here are some helpful diagrams detailing crank harmonics:
Crankshaft Deflection -
The Invisible Enemy
Each time the air/fuel mixture inside a cylinder is ignited, the combustion that results creates a torque spike - an extremely rapid rise in cylinder pressure. This pressure, applied to the top of the piston, becomes the force that is applied to the crankshaft through the connecting rod. Each torque spike is like a hammer blow. In fact, it hits with sufficient intensity that it not only causes the crankshaft to turn, it actually deflects or twists it. This twisting action and the resulting rebound (as the crank arm snaps back in the opposite direction) is known as torsional harmonic vibration. If not adequately controlled, torsional vibration causes rapid main bearing and main journal wear and possible crankshaft breakage.
Fortunately, harmonic vibration can be controlled by a vibration damper - which is also called a harmonic damper or erroneously a "harmonic balancer". The main purpose of a "harmonic damper" is to control harmonic vibration, not necessarily to balance the engine's rotating assembly.
Crankshaft Deflection -
The Invisible Enemy
Each time the air/fuel mixture inside a cylinder is ignited, the combustion that results creates a torque spike - an extremely rapid rise in cylinder pressure. This pressure, applied to the top of the piston, becomes the force that is applied to the crankshaft through the connecting rod. Each torque spike is like a hammer blow. In fact, it hits with sufficient intensity that it not only causes the crankshaft to turn, it actually deflects or twists it. This twisting action and the resulting rebound (as the crank arm snaps back in the opposite direction) is known as torsional harmonic vibration. If not adequately controlled, torsional vibration causes rapid main bearing and main journal wear and possible crankshaft breakage.
Fortunately, harmonic vibration can be controlled by a vibration damper - which is also called a harmonic damper or erroneously a "harmonic balancer". The main purpose of a "harmonic damper" is to control harmonic vibration, not necessarily to balance the engine's rotating assembly.
See these for a reference;
http://www.partstrain.com/ShopByDepa...ncer/CHEVROLET
http://en.wikipedia.org/wiki/Harmonic_balancer
06-03-2007, 11:53 AM
#32
Registered Member
Originally Posted by BASELINE
Its a good thing we're talking chevy's.....
06-03-2007, 11:58 AM
#33
Registered Member
In any case, 94eg!'s response post above is very interesting. I have heard of this before, but like many of us, it tends to get lost in the shuffle. There was some discussion on the Altima gearhead site I used to belong to about this very thing. And as I recall, the dynamics which 94eg! has shown here were part of the discussion. Also there was some talk about BMWs and whether or not to use ultra-light UDPs with them, the argument being due to the length of an inline 6-cylinder crankshaft and the harmonics involved with it and internal combustion.
06-03-2007, 12:01 PM
#34
Registered Member
Gentlemen, this is good stuff.. regarding posting of the pro's and con's of using a super light UDP on the TL engine. None of us wants to trash a $6000+ street engine for a $200 after-market performance item, I would wager. So I say this discussion is right on the money and may help those members who are sitting on the fence as to whether or not they decide to go this route.
Well done!
Well done!
06-03-2007, 03:08 PM
#35
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Definitely a great discussion.....agreed!
I maintain that if installed correctly, an UD LTW pulley is safe on this car. I run a lightweight flywheel and lightweight pulley on my 01.5 S4, I make over DOUBLE the stock power and have been running this now for over 30K without any problems (knocks on wood). Its also a short crank (V6)...but if truly was a detriment to the ability of the engine to run properly, it would manifest itself in conditions such as these.
Cheers.
I maintain that if installed correctly, an UD LTW pulley is safe on this car. I run a lightweight flywheel and lightweight pulley on my 01.5 S4, I make over DOUBLE the stock power and have been running this now for over 30K without any problems (knocks on wood). Its also a short crank (V6)...but if truly was a detriment to the ability of the engine to run properly, it would manifest itself in conditions such as these.
Cheers.
06-03-2007, 08:33 PM
#36
The fact still remains that you can get the exact same results with underdrive pulleys on the accessories themselves, and a light weight flywheel without eliminating the OEM harmonic damper...
It's there for a reason. It's not like it's some sort of selling gimmic that Honda puts on the car to steal your money.
It's there for a reason. It's not like it's some sort of selling gimmic that Honda puts on the car to steal your money.
06-03-2007, 09:29 PM
#37
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Originally Posted by 94eg!
The fact still remains that you can get the exact same results with underdrive pulleys on the accessories themselves, and a light weight flywheel without eliminating the OEM harmonic damper...
It's there for a reason. It's not like it's some sort of selling gimmic that Honda puts on the car to steal your money.
It's there for a reason. It's not like it's some sort of selling gimmic that Honda puts on the car to steal your money.
PS... I had a UR underdrive pulley on my 2000 TL for about 30,000 miles with no problems on it whatsoever. It definitely revved easier with it.
06-04-2007, 10:28 AM
#38
94eg!
The stock crank pulley is not a harmonic damper/balancer. Honda's engines are internally balanced. The stock crank pulley has an elastomer (rubber ring) to reduce Noise Vibration Harshness. So replacing it with a UR crank pulley is fine. However, if you are pushing 3-4 times your stock HP and are revving the car 2-3k over your stock redline you would need an aftermarket harmonic balancer which some companies make. At this amount of HP and at these revs you create different frequencies that even the stock crank pulley doesn't know what to do with. In fact, UR is releasing a harmonic dampener for B and D series engines and other highly modded engines, but they are set up to deal with those higher revs (and thus different frequencies) and the torsional vibrations associated with those circumstances. But for all of us who aren't pushing that kind of hp ( I push almost 2.5 times my stock HP and I run the pulleys myself without a problem; everything in my motor looked good when I pulled it apart) then the UR pulley is a great mod that helps the car rev out quicker. And there are many many people who have been running the crank pulley for tens of thousands of miles without a single problem. There have even been oil analyses showing no difference in metallic content with the pulley installed.
There is a lack of anyone to produce any substantial evidence that what you are saying is true. There are only theories. However, there are many people running these pulleys for many years without any issues. UR has been in business for over a decade and they are also developing harmonic dampers for engines that require them.
The stock crank pulley is not a harmonic damper/balancer. Honda's engines are internally balanced. The stock crank pulley has an elastomer (rubber ring) to reduce Noise Vibration Harshness. So replacing it with a UR crank pulley is fine. However, if you are pushing 3-4 times your stock HP and are revving the car 2-3k over your stock redline you would need an aftermarket harmonic balancer which some companies make. At this amount of HP and at these revs you create different frequencies that even the stock crank pulley doesn't know what to do with. In fact, UR is releasing a harmonic dampener for B and D series engines and other highly modded engines, but they are set up to deal with those higher revs (and thus different frequencies) and the torsional vibrations associated with those circumstances. But for all of us who aren't pushing that kind of hp ( I push almost 2.5 times my stock HP and I run the pulleys myself without a problem; everything in my motor looked good when I pulled it apart) then the UR pulley is a great mod that helps the car rev out quicker. And there are many many people who have been running the crank pulley for tens of thousands of miles without a single problem. There have even been oil analyses showing no difference in metallic content with the pulley installed.
There is a lack of anyone to produce any substantial evidence that what you are saying is true. There are only theories. However, there are many people running these pulleys for many years without any issues. UR has been in business for over a decade and they are also developing harmonic dampers for engines that require them.
06-04-2007, 10:57 AM
#39
Originally Posted by blokhead
I disagree. You won't get the same effect from underdrive pulleys on the accessories, most of the performance gain is from the lightened weight of the pulley and the reduction in mass of the rotating assembly. If there was significant gains in underdrive accessory pulleys, don't you think UR or any one else would sell them and claim massive horsepower increases?
PS... I had a UR underdrive pulley on my 2000 TL for about 30,000 miles with no problems on it whatsoever. It definitely revved easier with it.
PS... I had a UR underdrive pulley on my 2000 TL for about 30,000 miles with no problems on it whatsoever. It definitely revved easier with it.
Lighten the rotating assembly by installing lightweight flywheel. You'll drop a lot more weight, and rev much quicker than some cheap-ass pulley!
Under-drive the accessories by installing larger under-drive pulleys directly on them!
And for some reason, Exelerate still seems to think that the a Harmonic Damper and Crank Harmonics in general have something to do with the balance of the rotating assembly. Simply put, crank harmonics is the twisting action of the crank. No amount of balancing can stop the twisting force of combustion. Here is a history lesson about crank harmonics: http://deviantmethods.com/bigmoose/p..._vibration.htm
