Someone Prove It

[Yak Meat]

I know that Pulleys have a negative rap on here. I know and understand the physics behind the issues that they "cause" but I have yet to see proof on any motor.

So, I challenge everyone here to prove it to me. I don't want to see anything more than bolt-ons on the motor that blew up. Going BT or having added FI does not count because there are so many added variables that could have caused something that the pulleys could not be drawn back to as the main cause.

So, show me any 2.0, VR6, 1.8t, any motor, with just bolt ons that suffered an issue from adding LIGHTENED, not underdrive pulleys please!

The motor needs to be unopened, as in no internal engine work for it to qualify. Thank you.

[Omnilith]

There is practically no point to a lightened, stock-diameter crank pulley.

The majority of the horsepower "found" through an underdrive crank pulley results from reducing the effort to drive the accessories.

Personally, I've had no issues from years of using underdrive pulleys, but I've only used them on vehicles with unbalanced factory pulleys.

[simon_C]

There is practically no point to a lightened, stock-diameter crank pulley.

The majority of the horsepower "found" through an underdrive crank pulley results from reducing the effort to drive the accessories.

Reducing the rotating mass of the engine actually does provide improvements. you just arent going to notice much on a stock engine if all you do is replace the pulley.

[Egz]

Don't issues from UDPs also tend to be from the absense of any damping devices on aftermarket pullies than from stock?

[Omnilith]

Reducing the rotating mass of the engine actually does provide improvements. you just arent going to notice much on a stock engine if all you do is replace the pulley.

Of course, but the gains from reducing the rotating mass at the crank pulley are secondary to the reduction in accessory drive effort.

[simon_C]

Of course, but the gains from reducing the rotating mass at the crank pulley are secondary to the reduction in accessory drive effort.

well thats assuming you actually get an underdrive pulley and not just a lightweight aluminum replacement.

[BostonB6]

The only issue you would have with a lightened pulley is if your particular engine requires the stock pulleys and harmonic balancer to keep the horizontal rotational mass of the engine equal.

[Jedidub]

They work

[Yak Meat]

The only issue you would have with a lightened pulley is if your particular engine requires the stock pulleys and harmonic balancer to keep the horizontal rotational mass of the engine equal.

I understand the harmonics of it but I want to see proof that a bolt-on motor with a lightened crank pulley will cause damage to the motor.

Everyone on here screams that they break things and cause issues but i have never once seen any proof. Yes, the physics is sound and I understand that but prove it... its all theory as of now.

[goin440]

http://www.atiracing.com/products/da...mper_dinan.htm

The popular method for making power pulleys on E36 engines is by removing the harmonic damper and replacing it with a lightweight alloy assembly. This is a very dangerous product because this damper is essential to the longevity of an engine. The substitution of this part often results in severe engine damage.
It is also important to understand that while the engine in a BMW is designed by a team of qualified engineers, these power pulleys are created and installed by people who do not understand some very important principles of physics. I would first like to give a brief explanation of these principles which are critical to the proper operation of an engine.

1) Elastic Deformation
Though it is common belief that large steel parts such as crankshafts are rigid and inflexible, this is not true. When a force acts on a crank it bends, flexes and twists just as a rubber band would. While this movement is often very small, it can have a significant impact on how an engine functions.

2) Natural Frequency
All objects have a natural frequency that they resonate (vibrate) at when struck with a hammer. An everyday example of this is a tuning fork. The sound that a particular fork makes is directly related to the frequency that it is vibrating at. This is its "natural frequency," that is dictated by the size, shape and material of the instrument. Just like a tuning fork, a crankshaft has a natural frequency that it vibrates at when struck. An important aspect of this principle is that when an object is exposed to a heavily amplified order of its own natural frequency, it will begin to resonate with increasing vigor until it vibrates itself to pieces (fatigue failure).

3) Fatigue Failure
Fatigue failure is when a material, metal in this case, breaks from repeated twisting or bending. A paper clip makes a great example. Take a paper clip and flex it back and forth 90° or so. After about 10 oscillations the paper clip will break of fatigue failure.

The explanation of the destructive nature of power pulleys begins with the two basic balance and vibration modes in an internal combustion engine. It is of great importance that these modes are understood as being separate and distinct.

1) The vibration of the engine and its rigid components caused by the imbalance of the rotating and reciprocating parts. This is why we have counterweights on the crankshaft to offset the mass of the piston and rod as well as the reason for balancing the components in the engine.

2) The vibration of the engine components due to their individual elastic deformations. These deformations are a result of the periodic combustion impulses that create torsional forces on the crankshaft and camshaft. These torques excite the shafts into sequential orders of vibration, and lateral oscillation. Engine vibration of this sort is counteracted by the harmonic damper and is the primary subject of this paper.
-continued-

the gist: remove the harmonic balancer and the engine can potentially tear itself apart. At what point that is, how many miles, rpm, ?? Likely a repeated exposure weaking the part over time.

[MJZman]

My situation doesn't meet your "criteria", but I will share anyways.

I put an undampened lightweight pulley on my 92 Eagle Talon. It originally had a harmonic balancer. I got a great deal on it so I threw it on there for the hell of it. I had an upgraded turbo, and a bunch of bolt-ons at the time. Anyways, after about 2000 miles when I was doing a street tune, I heard this nasty knocking\rattling sound so I immediately shut the engine down and towed it home, sounded like a spun bearing

Upon further inspection, the flywheel bolts had backed out and caused the flywheel to rotate ****-eyed and destroyed the clutch, the input shaft bearing, and cut some nice gashes in my transmission case. I am almost certain it was from running an undampened pulley. I bought an ATI Fluidampr to replace it and I have not had a problem since. People may think, "oh, you didn't torque the flywheel bolts" or something like that, but I have a digital Snap-On torque wrench and used red loc-tite, with ARP Flywheel bolts. YMMV, but I wouldn't run any sort of pulley that isn't of the OE design, or at least maintains the function of the OE unit. Cheers

[Yak Meat]

The last two posts were very good, helpful, and informative.

thank you for posting the physics behind it.

However, MJ your motor was significantly modified it seems, thank you for realizing that. I have little doubt that it was not the pulleys in your case, however, there are too many variables to consider. Your motor had significant work and while the pulleys are an obvious suspect, the amount of work done and other things that could have caused it are also abundant. That is why I am looking for a bolt-on motor at most.

Regards and for the two previous posts.

[Vash350z]

Great idea for a thread. I have always understood the physics behind why they are dangerous, but what concerns me is it is usually thrown around by a company that sells harmonic balancers...

[SVTDanny]

The last two posts were very good, helpful, and informative.

thank you for posting the physics behind it.

However, MJ your motor was significantly modified it seems, thank you for realizing that. I have little doubt that it was not the pulleys in your case, however, there are too many variables to consider. Your motor had significant work and while the pulleys are an obvious suspect, the amount of work done and other things that could have caused it are also abundant. That is why I am looking for a bolt-on motor at most.

Regards and for the two previous posts.

An upgraded turbo has no direct effect on flywheel bolts backing out. Removing a harmonic balancer does, however.


Why anyone does this crap, I don't understand. Waste of money.

[ATL_Av8r]

Going BT or having added FI does not count

I've had Bluetooth on 3 vehicles now and it has never affected the pulleys.

[Yak Meat]

adding a BT/FI most likely means that you have altered the interior components of the motor. You have changed rods, pistons, taken things apart, looked at it, either way the motor has been opened which means it is very easy for something else to become loosened/not tightened properly/ not torqued, or anything along those lines, that is why I am looking for a strictly bolt-ons at most. I want to minimize the variables present. Adding FI or Cams, or touching the internals adds to many.

[MJZman]

The last two posts were very good, helpful, and informative.

thank you for posting the physics behind it.

However, MJ your motor was significantly modified it seems, thank you for realizing that. I have little doubt that it was not the pulleys in your case, however, there are too many variables to consider. Your motor had significant work and while the pulleys are an obvious suspect, the amount of work done and other things that could have caused it are also abundant. That is why I am looking for a bolt-on motor at most.

Regards and for the two previous posts.

I agree on there being a lot of variables. However..

At the time, the engine was internally stock, with the exception of ARP headstuds and a MLS head gasket. The engine had seen nearly 20,000 miles on the clutch and flywheel setup, so I feel as if it was something I did wrong, it would have presented itself much sooner. Either way, I feel as if the crank pulley is something that should be left alone if your car sees any more than occasional street use. No sense in trashing your bearings or any other components! We are all on the same page here I feel. I realize my example wasn't in your criteria, but nobody else had really posted anything first hand besides the snippet from ATI, which was great, so I figured I'd at least throw that out there.

There is a thread in the Mk5 R32 forums about a guy whose flywheel bolts backed out, and no body can put a finger on why it happened. I realized in a "gruven parts aluminum pulleys" thread that he was one of the first people to have them. He was also the first person I've ever heard of to have flywheel bolts back out. In his case, it destroyed the block, and the crankshaft, as well as the DSG transmission I believe, not good and very expensive. It was never figured out what actually happened, but from my own deductive reasoning I see that the aluminum pulleys are the only thing on the engine that is out of the norm, and could have possibly caused that.

OP, may I ask why you'd like to see proof? I am just curious as to if it is a mod you are interested in doing, or trying to dispel an "urban legend". There are a lot of them out there in the automotive realm.

[deucestudios]

Great Car Lounge thread.

[deadernie]

I didn't know they made them like that. My under drive pulley set, the crank pulley is SFI approved and still functions l like the factory harmonic balancer. I would not put one on a car that was not designed this way though.

I also don't fit any of the other criteria except UDPs are my only engine mod at the moment. Almost 60K miles with no issues.

[Yak Meat]

I agree on there being a lot of variables. However..

At the time, the engine was internally stock, with the exception of ARP headstuds and a MLS head gasket. The engine had seen nearly 20,000 miles on the clutch and flywheel setup, so I feel as if it was something I did wrong, it would have presented itself much sooner. Either way, I feel as if the crank pulley is something that should be left alone if your car sees any more than occasional street use. No sense in trashing your bearings or any other components! We are all on the same page here I feel. I realize my example wasn't in your criteria, but nobody else had really posted anything first hand besides the snippet from ATI, which was great, so I figured I'd at least throw that out there.

There is a thread in the Mk5 R32 forums about a guy whose flywheel bolts backed out, and no body can put a finger on why it happened. I realized in a "gruven parts aluminum pulleys" thread that he was one of the first people to have them. He was also the first person I've ever heard of to have flywheel bolts back out. In his case, it destroyed the block, and the crankshaft, as well as the DSG transmission I believe, not good and very expensive. It was never figured out what actually happened, but from my own deductive reasoning I see that the aluminum pulleys are the only thing on the engine that is out of the norm, and could have possibly caused that.

OP, may I ask why you'd like to see proof? I am just curious as to if it is a mod you are interested in doing, or trying to dispel an "urban legend". There are a lot of them out there in the automotive realm.

I greatly appreciate you sharing your personal experience as well as noting others you have heard about.

The purpose is exactly as you said, I am trying to dispel an 'urban legend'. It seems many tuner for many different cars and makes have after market light weight pulleys available for cars. And on most forums I have seen there is the typical split of people who have them and like them or don't have them and throw physics around trying to prove their negative effects without having any concrete proof other than formulas, theories, and forum physics. So in an effort to quiet these rumors. theories, and everything surrounding the pulleys, I am trying to build a thread with examples of both good and bad or at least some proof one way or another of their effects.

This is also why I am limiting the examples to bolt-ons at most. I have no doubt that it is on the rare side for someone to mess up putting an engine back together after a rebuild with new internals, however, there is always that possibility and the variables greatly increase with built motors being allowed as examples. A Motor that has never been opened up but has pulleys and has failed would be ideal.

[Yak Meat]

I didn't know they made them like that. My under drive pulley set, the crank pulley is SFI approved and still functions l like the factory harmonic balancer. I would not put one on a car that was not designed this way though.

I also don't fit any of the other criteria except UDPs are my only engine mod at the moment. Almost 60K miles with no issues.

What pulleys are u using on what car?

[dunhamjr]

There is practically no point to a lightened, stock-diameter crank pulley.

this is like saying that getting lightweight wheels or a lightened flywheel will not help.
less weight to rotate is less weight to rotate.

will you notice 1 lb off each wheel more then 1 lb off the crank pulley? sure.
doesn't mean its not helpful.

but i do agree, that underdrive/overdrive is where MOST of the gains people would see come from.

[AKADriver]

The purpose is exactly as you said, I am trying to dispel an 'urban legend'.

There's no "urban legend" here. This is not "forum physics", the engineering behind them is sound and has been around for many decades. The nature of the damage that's caused by omitting a harmonic balancer isn't such that you'll ever get a satisfactory "I added one and the engine exploded the next day" story. It's additive damage over many years and miles. Most people break something else or sell a modded car after that long.

You're looking at this completely backwards - this is an engineering problem which can be characterized perfectly "on paper" - but unsatisfied with that, you're looking for unsubstantiated anecdotes instead.

No one ever blew their engine from removing the plastic radiator air ducting or exhaust heat shields, or running a K&N or a Fram oil filter either, but I would still never use those filters or remove those parts because I know that it's unnecessary added wear.

[AKADriver]

this is like saying that getting lightweight wheels or a lightened flywheel will not help.

Lightweight wheels actually don't help very much in instrumented testing. I'm all for them, mostly because the bulk of non-lightweight wheels are just ugly chrome crap anyway, but there aren't massive gains to be had there. On an engine/car with other modifications, reducing driveline mass gets lost in the noise.

[karl_1052]

Harmonic balancers are used to balance a cranshaft externally.
Using the wrong weight or just an UD pulley will upset the balance of the crankshaft, unless the crankshaft is internally balanced.

On a ford 302, if you use a pre 79 balancer on a 79+ 302, the crank will be damaged, as the early motor uses a 28oz balance weight and the latter a 50 ox balance weight.

it doesn't sound like a lot, but it will make a huge difference to the rotating parts of the crankline(crank, main bearings, flywheel)

[SVTDanny]

I greatly appreciate you sharing your personal experience as well as noting others you have heard about.

The purpose is exactly as you said, I am trying to dispel an 'urban legend'. It seems many tuner for many different cars and makes have after market light weight pulleys available for cars. And on most forums I have seen there is the typical split of people who have them and like them or don't have them and throw physics around trying to prove their negative effects without having any concrete proof other than formulas, theories, and forum physics. So in an effort to quiet these rumors. theories, and everything surrounding the pulleys, I am trying to build a thread with examples of both good and bad or at least some proof one way or another of their effects.

This is also why I am limiting the examples to bolt-ons at most. I have no doubt that it is on the rare side for someone to mess up putting an engine back together after a rebuild with new internals, however, there is always that possibility and the variables greatly increase with built motors being allowed as examples. A Motor that has never been opened up but has pulleys and has failed would be ideal.

The internals of the engine produce frequencies during operation. The harmonic balancer is designed to do just that - balance the harmonics. If you remove it, then you have a crankshaft spinning to 7,000 RPMs without being in balance. Over time this will cause bolts to back out, trash bearings, or worse.

There is no "myth" here. If it was a "myth," then OEM's wouldn't spend the time or money to create a harmonic balancer on every engine that they put out.

[Yak Meat]

The last three posts are good and I understand them execpt for 2 parts.

1) I want proof... Show me a motor that has run pulleys for 100-150k miles and has suffered a failure related to what you speak about and i will believe it. Sure the harmonics are there but maybe they are not enough to make a difference.

2) You mentioned that 1) Lightweight wheels don't make a difference in performance - Wrong. 2) You mentioned lightening the internals - wouldn't that change the harmonics and therefore cause the current damper to be incorrectly weighted? So we can change the weight of internals and there is no issue, but when you change the pulley there is?

Forum physics: applying physics to only the areas you are concerned with and screaming about the negative effects without taking into account the entire system or how great the affects are.

You just did it right there... Internals lightened = fine, Pulley lightened - not fine...

Beyond this, because we are getting away from what I want, I am not looking at a modified engine internals wise... I want a closed engine with bolt-ons at most that blew up from a pulley being added/lightened/changed.

And if no one can prove it then the response to the age old question of "Should I get pulleys" is now:

If you do not plan on going BT or Adding FI there is little to no conclusive evidence that says a lightened pulley will damage your motor. However, if you do plan on going FI or adding a BT, the harmonics of the motor become more important and while I have no examples off hand, everything is getting stressed that much more, therefore, you have a greater chance of having those harmonics getting thrown further out of whack. That combined with the significant increase in stress across the engine system could result in a failure.

~~~~

Once again guys, PROVE IT! I dont see any hard examples of a bolt-on motor being destroyed because of a pulley. Hell, Ive seen 2 stories of BT and added FI guys with lightened pulleys having failures related to the pulley, and one posted above. Another was the Mk5 R32, i tracked the thread down and read it some.

[SVTDanny]

You just did it right there... Internals lightened = fine, Pulley lightened - not fine...

Internals are balanced. Lightened pulleys are not weighted specifically to balance out harmonics.

I doubt you'll find a motor that has been destroyed, and the failure was traced back specifically to lightweight pulleys. What is indisputable however, is that a lightweight, non-harmonic balancing crank pulley will cause excess wear over the stock unit.

[AKADriver]

1) I want proof... Show me a motor that has run pulleys for 100-150k miles and has suffered a failure related to what you speak about and i will believe it. Sure the harmonics are there but maybe they are not enough to make a difference.

Again, you're searching for an anecdote when we've given you science. That's backwards reasoning.

You mentioned that 1) Lightweight wheels don't make a difference in performance - Wrong.

Grassroots Motorsports has run the experiment a few times, most recently in 2011 using their STR Miata. They saw no appreciable lap time change between wheel weights - and that's a best-case scenario, where the car is both accelerating and cornering, and on a lightweight car without much power. I have seen dyno tests showing +/-5hp or so from a wheel change, but like I said, when you're making substantial engine mods that gets lost in the noise.

For a race engine that gets frequent rebuilds but where every thousandth of a second counts, driveline mass is more critical and omitting the harmonic damper might be worth a look.

You mentioned lightening the internals - wouldn't that change the harmonics and therefore cause the current damper to be incorrectly weighted?

Possibly, if the damper also acts as a balancer, though engine builders will generally seek to balance the new rotating assembly the way the factory designed, even if the new parts have different masses.

There are two different functions you're conflating here. A harmonic balancer has an offset weight to balance the rotating assembly. Not all cars have this on the crank pulley; some are internally balanced, and some use the flywheel assembly for this. A harmonic damper has an elastomer band separating the hub from the heavy outer rim, allowing it to vibrate out of phase with the crankshaft, which in turn damps the crankshaft vibration. Any production engine in the modern era has a damper. The tuning of the damper isn't as exacting as the balancer.

So we can change the weight of internals and there is no issue, but when you change the pulley there is?

It's only not an issue to change the weights of the internals if they are then correctly balanced. It's only not an issue to change a pulley if the pulley is also correctly balanced and the damper is left in place. There are aftermarket pulleys that contain dampers.

Forum physics: applying physics to only the areas you are concerned with and screaming about the negative effects without taking into account the entire system or how great the affects are.

You're not even understanding the depth of the problem if you think anything we're saying is as simple as "Internals lightened = fine, Pulley lightened - not fine".

And if no one can prove it then the response to the age old question of "Should I get pulleys" is now:

You're not an authority on this. Neither am I. You're not only grasping for anecdotes in the face of real information, though, but you're using the lack of those anecdotes to prove a negative. There is "conclusive evidence" that says a missing harmonic damper or balancer may cause long-term damage. Some engines are externally balanced and require a balancer. All crankshafts vibrate and tis vibration can be damped with a damper. There are no anecdotes which provide a tidy "I installed a pulley and blew my stock engine" story, sorry.

[Yak Meat]

I am merely playing the other side of the argument. And still no one has provided proof.

I am trying to fully understand the physics behind everything and I did mix up the damper verse the balancing aspect. My mistake.

I am not disputing the physics or science behind it. It is completely sound and I stand behind it. Hell I am the first person to shout science at people with regards to almost anything. However, as this discussion (thank god it has remained a discussion and not turned into an argument) has evolved the only thing I am stuck on is the fact that there is no evidence, hard proof, that pulleys on a stock-ish motor will cause issues.

Yes, the science is sound, and definitely true, my argument isn't with the science, but my point is that, on our motors with only bolt-ons (1.8ts, VR6s, ect) the harmonics are not affected enough to cause issues. The magnitude of the affect harmonics and imbalance is not enough to cause failure within the foreseeable lifetime of the motor. Once you start adding the additional stresses of FI or BT, I can see my position being thrown out the window, however, until someone shows me evidence, not just science that a stock-ish motor has had issues, I will not support the pulley bashing.

Guys, just to clarify, I started this thread so we can post it when someone asks about pulleys and have conclusive information regarding the side effects of the pulleys. I am just playing the advocate role. (I will never put a lightened crank pulley on as I track my cars and they see a lot of additional stresses.)

[PowerDubs]

I'd say manufacturers install them more for NVH than for engine longevity purposes.

[karl_1052]

2) You mentioned that 1) Lightweight wheels don't make a difference in performance - Wrong.

No, they don't make a big enough difference.

http://www.carcraft.com/projectbuild...ls_comparison/

In this article they dropped 82lbs of unsprung weight and the car only gained 1/10th

[04VR]

so i have lightweight pulleys on my car, its a 2004 gti vr6. ive had them on for probably close to 100,000 miles now. never had a problem. but, there is one thing, the crank pulley i took off, was just that, a pulley. there is no external harmonic balancer to be found on my motor. i think the problem are people removing the balancer for a pulley. there is a reason those balancers are on there. do u think car companies would be putting them on for decades if there wasn't a reason?

[drecian]

Once again guys, PROVE IT! I dont see any hard examples of a bolt-on motor being destroyed because of a pulley.

I don't really understand what kind of engine failure can be proven beyond a doubt to be caused SOLELY by the pulley. The case with the flywheel bolts backing out could be due to many other causes. Two cases could still be coincedental with difference causes.

Its like saying that lighter wheels reduce wear on brake components. Everyone understands the science behind rotating mass and inertia, but outside of controlled experiments, too many other uncontrolled factors are in play.

My $0.02

[MJZman]

No, they don't make a big enough difference.

http://www.carcraft.com/projectbuild...ls_comparison/

In this article they dropped 82lbs of unsprung weight and the car only gained 1/10th

Go outside and run down the street. Rest up until you are ready to do it again then try it with 20 lb lead boots on. See where I am going with this?