Crank Pully Picture

[Elliott]

Originally Posted by sowise

"GT2RS10-18-2003, 11:21 PM
Contacted Perrinperformance and here's what they have to say...

The argument that the reduced weight and removal of the rubber ring will destroy the front main bearing is wrong! The rubber ring between the two halves of the stock pulley is to make up for mfr. differences. Two cheap cast pieces pressed together with rubber allows for additional slop in both. If Subaru chose to install a pulley like ours would add significant cost to the engine and is not cost effective for a production piece. The rubber ring is NOT a harmonic balancer! You should go to your car and let it idle. Raise the hood and note how the belts will track side to side and up and down. This is a result of the much less than precise pulley found from the factory. This causes undue stress and wear not only on the pulleys but on the belts and accessories as well. Installation of our pulley will result in smooth, true, and long lasting belt wear and accessory lifespan is increased. Plus, throttle response, HP and torque are all increased dramatically for such an inexpensive painless part.

Crank bearings, and rod bearings are much more prone to premature wearout from increasing boost than from installation of a precision made billet pulley. This should not be a concern."

Wow, I think I will put that company on my "Do not buy from ever" list, there are so many things wrong there that it makes my head hurt. They seem to be proof that many aftermarket manufacturers are just hacks and OEM stuff is better in many cases. They seem to truly believe their little $2 chunk of aluminum is better than what OEMs spend tons of money in R&D to make, they probably put more effort into marketing than they did into the R&D of their lightweight pulley. There was a time when engines didn't have harmonic balancers and just had a pulley on the front of the crank, but just about everything in the last past 60 years has one, that alone should let you know that they must be needed.

I need to start an aftermarket parts company, my first product will be lightweight hollow ball joints to reduce unsprung weight, then maybe some aluminum drilled and slotted brake rotors to reduce unsprung weight, rotating mass and increase heat dispersion. As long as I have a disclaimer in the fine print, I should be fine.

If you want a good aftermarket pulley, go for the Fluidampr, they do make great stuff that is well engineered. You get what you pay for. I don't even see anything stating the Perrin pulley is SFI approved.

[sowise]

Wow TurboIQ you should take a chill pill I posted one link that was a response from Perrin, whether you agree with it or not. I could have posted links from Subaru master techs and engineers who have posted or been asked and support it similarily. The rubber is at most dampener not a balancer. The rubber doesn't do crap for balancing the pulley. Then you go and get in a tizzy and post in red but offer little to nothing to back up your opinions other than your own comments and open ended questions. Once again these engines and these pulleys DO NOT have a Harmonic Balancer! The rubber is more of an isolator and helps with NVH (Noise, Vibration, & Harshness). This is more for what you would hear and feel from inside the passenger area. As for the Fluidampr it looks like a nice option but not very economical, as long as those who have it feel it is $$ well spent I have nothing negative to say about it. I think that the hundreds (or possibly thousands) of people who have a lightened pulley are very happy with them. I have seen many posts with guys saying don't do it because blah blah but haven't seen one where there is any damage claimed from one. The guys who put them on the H4 engines seem to love them and thats enough R&D for me. Make your own choice but quit *****ing about mine.

[Elliott]

I think most people, including me, use harmonic balancer as a generic term. If I walk into the local speed shop and order a "harmonic balancer" for a Chevy 350, they are not going to argue that the 350 is an internal balanced engine and has a harmonic dampener and a Chevy 400 would have a harmonic balancer, they are going to ask which one I would like. It is a widely accepted and fairly interchangeable term.

That rubber is there for a reason, if it wasn't needed, Subaru would save the money and make a cheaper pulley.

[sowise]

I see your point Elliott but there is a difference between the two functions of balancer and dampener and the term does get interchanged alot I agree but so does theory of functionality. If the SOA crank was the end all be all design that some think it is, I don't see it. They could keep the same design and gone to a lighter weight but didn't they chose to use steel. Subaru didn't design everything in these cars for performance, there are many things they did to these cars hardware, software etc that individually didn't offer much increase or decrease in performance or fit, form, and function. But added up there are little power leaches all throughout. Just because it didn't get done during manufacturing doesn't mean it isn't worth doing. Like replacing the radiator with aluminum or adding external filters or coolers. They didn't offere a 4.44 geared version but most people prefer them over the stock.
If people disagree that's fine really, I am just not fond of the idea or argument that if the manufacturer didn't do it then it shouldn't be done or it is bad. It is all part of personalization and modification. To each their own though.

[Elliott]

Originally Posted by sowise

I am just not fond of the idea or argument that if the manufacturer didn't do it then it shouldn't be done or it is bad. It is all part of personalization and modification.

I'm not saying everything they did was right and the only way, but just because something can be modified doesn't make it a good idea. They have a lot of engineers and a lot of money, do you think that some random guy with access to CAD and a CNC manufacturing facility knows more?

Sure they did many things for practicality and reliability over performance. It would have been easy for them to make a pulley without rubber, most likely it would have been cheaper. Now if this did not hurt reliability and could possibly increase reliability because there would be no rubber to degrade, why wouldn't they do it? It would be more practical (easier and cheaper), it could be more reliable and it would have the side effect of freeing up a couple extra HP that they could put on the spec sheet to entice buyers. Wouldn't it make perfect sense for them to have a pulley like this at the factory if there were no drawbacks?

The way I see it, they designed this H6 engine from the ground up, if it was some kind of magical engine that does not have harmonics, why design a pulley like this in the first place? One that just happens to fit along with the designs commonly accepted as a dampener to reduce harmonics. Doesn't the new EZ36 still have this dampening pulley? It seems Subaru thinks there is a legitimate reason to have a dampening pulley if they are still using them on such a naturally well balanced engine.

[Boxersix]

Originally Posted by sowise

Plus:
"The main reason for a dampener is to help prevent crank walk and since the engine does not have to fight gravity in its running cycle there is no crank walk and hence no need for a dampening system."

That is so wrong it's scary. The main reason for a harmonic balancer is to counteract harmonic forces traveling along the centerline of the crankshaft created by forces against a mass.. First, second, and third order vibrations occur due to different circumstances and occur in ANY rotating mass, even your alternator has a first order vibration.

Going point blank to a flat six......it's one of the most balanced motors in existence, second only to that of a 60 degree v12(and some super rare boxer 8's). The design implemented into the motor naturally counteract first and second order vibrations. First order vibration is virtually all but eliminated by dynamic balancing and the counteracting nature of the flat six. Second order vibration occur from the rotational mass effect of a rotating mass with 2 or more poles(ends of mass) and is a vibration that occurs twice per revolution.. However again the inherit nature of the flat six design parameters all but eliminate this effect. It cannot be balanced out, therefore it's built into the design of the engine.

There has not been a flat six in production that has a harmonic balancer in place. Even the new raw performance Porsche GT3RS's with their 3.8L screaming well beyond 8500rpm in stock trim do not have a harmonic balancer. They use a solid billet pulley.


Take this as much as you feel doing, but I've built ~30 flat six porsche race motors, not one with a harmonic balancer, and never had one come back with a failure related to harmonics...

All other motors are a different story.....

[Trevor]

Originally Posted by Boxersix

That is so wrong it's scary. The main reason for a harmonic balancer is to counteract harmonic forces traveling along the centerline of the crankshaft created by forces against a mass.. First, second, and third order vibrations occur due to different circumstances and occur in ANY rotating mass, even your alternator has a first order vibration.

Going point blank to a flat six......it's one of the most balanced motors in existence, second only to that of a 60 degree v12(and some super rare boxer 8's). The design implemented into the motor naturally counteract first and second order vibrations. First order vibration is virtually all but eliminated by dynamic balancing and the counteracting nature of the flat six. Second order vibration occur from the rotational mass effect of a rotating mass with 2 or more poles(ends of mass) and is a vibration that occurs twice per revolution.. However again the inherit nature of the flat six design parameters all but eliminate this effect. It cannot be balanced out, therefore it's built into the design of the engine.

There has not been a flat six in production that has a harmonic balancer in place. Even the new raw performance Porsche GT3RS's with their 3.8L screaming well beyond 8500rpm in stock trim do not have a harmonic balancer. They use a solid billet pulley.


Take this as much as you feel doing, but I've built ~30 flat six porsche race motors, not one with a harmonic balancer, and never had one come back with a failure related to harmonics...

All other motors are a different story.....

Very interesting and informative post.

The rubber cushion dampens only rotational stresses generated by, or imposed upon the crankshaft. The effect either way is directly relates to the load driven by the pulley. The load can impose erratic rotational stresses on the crankshaft. The design of the pulley may not in fact be related to the crankshaft.

It would appear that the pulleys for various Subaru engine designs are similar. Subaru may well have used a stock standard parts book item, rather than produce a special, in spite of knowing that the flat six did not need crankshaft dampening.

The purpose of the pulley in general, could well be to insulate the crankshaft from a driven external unbalanced load. Rather than utilise a load as a means of crankshaft dampening. Only someone directly involved in the design of production engines can provide the answer.

The after market claims relate to weight and performance. The weight involved and the rotational diameter means that their claimed advantage is minute and exaggerated.

[Boxersix]

Originally Posted by Trevor

Very interesting and informative post.

The rubber cushion dampens only rotational stresses generated by, or imposed upon the crankshaft. The effect either way is directly relates to the load driven by the pulley. The load can impose erratic rotational stresses on the crankshaft. The design of the pulley may not in fact be related to the crankshaft.

It would appear that the pulleys for various Subaru engine designs are similar. Subaru may well have used a stock standard parts book item, rather than produce a special, in spite of knowing that the flat six did not need crankshaft dampening.

The purpose of the pulley in general, could well be to insulate the crankshaft from a driven external unbalanced load. Rather than utilise a load as a means of crankshaft dampening. Only someone directly involved in the design of production engines can provide the answer.

The after market claims relate to weight and performance. The weight involved and the rotational diameter means that their claimed advantage is minute and exaggerated.

Correct. The rubber insert in those pulleys is simply there to dampen harmonics isolated in the accessory belt drive, whether created from the belt itself or the driven accessories. They are first order vibrations from the rotating masses of the PS and AC pumps, and the alternator. The drive belt itself can too impart a vibration, but one outside of that consistent with 1st-inf vibrations.

I don't know the exact lineup of the drive pulley on all these motors but all EJ's and the EG share this pulley. The related accessories are different between the EG and EJ motors, but share the same drive offset dimensionality and reach this through use of specific brackets(EG and EJ specific)

Your third paragraph.......while not a production engine designer myself I can agree with that. One can go about eliminating all first order vibration from accessories w/o much effort in reality. Balancing the alternator stator is already done but can be done to a more perfect result, as too can the rotor assembly in the PS pump. The PS pump itself wouldn't generate enough 1st order vibration to impart a wave to the crank even if so off balance it destroyed itself. Just not enough mass to it and the belt itself would likely dissipate a majority of it anyway.. The alt on the other hand can, but again most are balanced beyond any typically measurable means.


As far as gains from the addition of a lightened pulley, I've yet to see any serious gains from adding one. I simply do it to simplify the front of the motor(tidy it up) and often on some car giving more room to work around(due to thinner fore/aft profile). This is doubly true on most fan cooled Porsches, which run a V-style belt rather than a serpentine. Pulley is only ~3/4" wide to start with. Negligible means in reality performance wise. There is an in depth formula for calculating power "free" by reduction in the weight of a rotating mass, but it basically boils down to about 2.2hp per pound of weight removed. And that's at the crank, not wheels.

Again this is ONLY applicable toward flat sixes and 60 degree v12's. Any other motor is subject to varying 1st-3rd order vibrations that really require a dampener to cancel and in those cases a proper fluid type dampener should be used. I6 motors are the next of the balanced motors but they suffer badly from 2nd order. BMW's line of M series motors(M52, S50, S52 etc) are notorious for snapping the cranks at RPMs exceeding 8000. Typically they'd snap the drive snout right clean off, sending a tensioned and spinning 10 lb drive pulley/crank trigger assembly FLYING. God awefull when they let go at speed on the track. BMW knew this and solved the issue on the design of the Mclaren F1 S70-2 engine by making the drive snout a completely separate part that is fastened to the front of the crank via four 12x120mm yielded fasteners. This design was later carried over to the E46 M3 S54 engine(3.2L) and onto subsequent V8 and V10 M-car engines

[oab_au]

Adam, I take it that you don’t believe, that Torsional Harmonics are a problem in the SVX crankshaft? Just believe that the damper is there to counter, ‘out-of-balance’, accessories?

You can see for yourself, just look at the crank signal on a scope, while you run it up on the dyno. Without the damper, there can be 5/8* displacement over the length, this plays havoc with the crank pos sensors. The damping weight is there to prevent this.

Look at what happens to the crank pulley on the SVX when it is not torqued up. Shatters the key, destroys the keyway, damages the crank end. That damage is caused by rapid torsional vibration.

It is the length and the construction of the crankshaft that produces torsional vibrations that travel up and down the shaft. Produced by the firing pulse that twists the shaft as it turns the flywheel.

As the engine speed rises, the natural frequency, of the shaft, will be out of phase with the pulses, so that a twist travelling down the shaft, will meet a twist travelling up the shaft. Where these pulses meet, the shaft can fatigue to crack. The Harmonic damper is there to add load to the free end of the crank, to dampen it free oscillations. The rubber fitted between the hub and the mass is to reduce the shock loading to the crank end, which can break the end off.

The effect becomes greater as the crankshaft becomes longer. The SVX crank is a very compact looking item about 24" long, but if it was straightened out, (24"+ 6x3" throws), it would be about 42" long. It's the torsional length that gives rise to problematic harmonics.

G.M. lab test sheets on Corvair Harmonic Balancer development. Flat six. Same trouble.
http://www.dalemfg.com/dale_026.htm

Harvey.

[Boxersix]

If the svx crank is suffering that much frequency distortion then it's due to a design parameter in the motor, or possibly due to the firing order. Our P-car motors, which are essentially the same thing as out lovely EG33, do not have such fluctuations in the crank as badly as you have mentioned, but have quite a bit different things going on inside like mainshafts, dry sump drives, etc all driven off the the crank and all affecting the final harmonics.

I have never registered that much distortion on the EG33. was the pulley new during that 5/8* register? those pulleys technically are a wear item and can create their own harmonics if dry rot. The outer sheave will actually rotate off center creating a massive first order vibration which is very bad.

3rd order vibration will rarely break a crank on 6 cylinder motors. It's damaging effect is usually so high up in the RPm range one never really sees the right frequency. This though, really depends on the design of the crank as alot of older crank with minimal counterweight mass tend to suffer badly from 3rd order vibration(like aforementioned Corvair). caused by the torque/compression force applied to the crank during firing sequence. The firing order plays a big role in this vibration as to when and where this vibration occurs.

6th order vibration is mostly from the torque force applied from the pistons and it's degree is determined by layout, crank material, and natural frequency of the crankshaft. Impossible to eliminate it but with a proper design can be minimized, or have it's "danger zone" tuned to an RPM range well outside the motors use. Hardening the crank will help dramatically as it pushes it's natural frequency up higher. Cranks hardened in the EG33???(I don't know myself)

what's the firing order of the Eg33? P-car is 162435

A balancer or drive pulley not properly torqued on any motor will do crank damage you described as a loose mass on the end of a shaft can create it's own harmonics on top of any mechanical(friction/contact type) damage that would result from it's movement. I repair this exact damage on all sort of cranks at the machine shop on a weekly basis. Seems like folks love to forget the typically huge fastener holding it on! :lol


Corvair was a failure from the start IIRC the firing order for that piece was 145236


All in all still very interesting. I'd like to know the definitive reason behind the EG33's suspected vibration and what order it's focus upon. Believe me I'm not doubting your input in this area one bit. I just know for sure fact that I wouldn't be risking ~$20K engine builds for my p-car customers knowing that they'ed grenade w/o a balancer in place.

We should look into this more as I'm very curious. I just got another EG33 engine as a spare that I can do some tests with

[Trevor]

Originally Posted by oab_au

You can see for yourself, just look at the crank signal on a scope, while you run it up on the dyno. Without the damper, there can be 5/8* displacement over the length, this plays havoc with the crank pos sensors. The damping weight is there to prevent this.

The crank signal can in no way be used to measure torsional vibration. Obviously measurement requires sensors located in at least two places. Methods are complicated and usually involve optics.

We must presume that your figure and ideas are based on engines of a different configuration to the SVX. Detail is required in order to establish relevance. Particularly as this constitutes the essence of the current argument.

It must be presumed that damping load/torque, rather than damping weight, is in fact meant or implied.

Look at what happens to the crank pulley on the SVX when it is not torqued up. Shatters the key, destroys the keyway, damages the crank end. That damage is caused by rapid torsional vibration.
Harvey.

This comparison is naive and holds no water.

[oab_au]

Not even a Subaru, it was an Australian Holden straight 6, in a boat, driving, off the nose of the shaft, through a rubber dough-nut. It had ignition problems, and this showed up during the checks, as the problem.

The crankshaft has to be considered as a torsion bar, anchored at one end to a flywheel whose angular velocity is substantially constant, and with the other end free to oscillate. Under these conditions it is subjected to a series of torsional impulses imposed by the pistons.

At certain critical speeds the frequency of these impulses will coincide with some harmonic of the natural frequency of the shaft. When this occurs the normal angular deflection of the shaft will be increased many times and if completely unchecked, would build up to such an amplitude, to result in fracturing the shaft.

The damage to the damper when it is loose is caused by the end of the shaft being let free, to oscillate inside the damper from torsional vibration.

The firing order does not really mater, as they are all the same for a flat six. Two, three cylinder engines, have to fire either 1,2,3, or 3,2,1, The only other option depends on which way the 120* crank pins are offset, so that you get the SVX’s 163254, or the Corvair’s, 145236. The Porsche’s 162435 is the same as the SVX, just a different way of numbering the block, they both fire No1 followed by No6 at opposite ends of the crank. The No1 winds the crank up one way, No6 winds it up the opposite way.

An interesting subject, though I think we have over done it.

Harvey.