Lightweight Crank Pulley Check-In

[DashLaflash]

Hey guys I have recently stumbled across the lightweight pulleys and all of the controversy they create. There is no doubt that the 4g63 uses a rubber ring in the crank pulley to help stop the twisting of the crank. It appears that this isn't super effective because of its design as opposed to the kind that's on the 420a that attaches directly to the crank snout. It also can come apart as the rubber gets warn out over time or is a lower quality autozone pulley. Most people are too scared to use an aluminum one and end up buying a $300 fluidampr or something like it. Now every thread I read on the subject people say stay away, and that a friend of a friend of a friend had one cause catastophic engine failure. In the same thread however, someone will post first hand experience of running one for seven years without any issues. Now I know you can't believe everything you read on the internet but this is a good site for DSMers and there is a lot of mis-information on this subject. It's very frustrating. Another note is that Unorthodox has been selling their lightweight crank pulleys for 13 years and would most certainly have gone out of business if these were that much of a problem. There is a slight advantage to having a lightweight pulley as it decreases rotational mass and is a solid piece of aluminum so it will never come apart. Also you can find them much much cheaper than $300. I would get the balancing of the crank pulley double checked at a machine shop however.

So I would like people that have purchased a lightweight crank pulley to post their experiences with it in this thread, as well as how many miles they have travelled with one installed. Also post if it has destroyed your engine and you know for a fact it was from the pulley (This will be hard to prove IMO). I would like only hard facts and first hand experiences PLEASE!!!

 

[jrohner]

Just get a new OEM one. Another potential issue of the unorthodox pulley is belt slippage. I CAN NOT get mine to not squeal. I sandblasted the pulley, got a new better belt; probably had it too tight as now my waterpump bearing is loose (and it still squealed once in a while even with it that tight).

If you do get one, don't get the full kit, as the unorthodox alternator pulley is absolute garbage. They make it as light as they can, and then cut so many holes in it so close together that there's nothing left to hold it in one piece. Of the set, the bottom pulley is the only one I'm still running, and after the ew WP goes it, a stock damper is going on.

These engines rev so fast anyways, that what's a few pounds of rotating weight difference? All it does is make it even easier to spin taking off, and trickier to actually take off good.

 

[Locke]

The damage that can (and has, on the 4g63) potentially happen is catastrophic. Imagine spinning your engine at 6500rpm (or whatever) when your crankshaft breaks. If you're lucky, you may salvage the pistons and some low dollar parts, but the rest of the shortblock would be irreparable.

Some 4g63's run without harmonic dampeners for years without problems, then some explode. It's a risk, and you know the stakes. If it's worth the risk to you, do it. I'm not going to stop you.

 

[DashLaflash]

See I'm still not totally sold that these pullies cause catastrophic failure. I already bought an autozone crank pulley half a year ago without really researching about them it was just cheap. So if that one goes bad prematurely which it is likely to I might consider one of these. I know the gains are minimal but still. It just seems like internet myth to me that I would really like to clear up.

We still don't have people checking in and saying how many miles they have gone with these pullies. Maybe DSMers really do stay away from these .

 

[Locke]

http://i171.photobucket.com/albums/u291/sixbolt/album_pic.jpg

Consider it a type of "resonance disaster".

Mechanical resonance - Wikipedia, the free encyclopedia

Take a bell, dangle it from a string, and tap it with a metal striker. It rings, because it vibrates. Notice that this bell will always produce the same note, regardless of how hard you hit it. This is it's natural frequency. Strike it harder, and it will produce the same note, but louder. The bell will amplitude of the vibration and flex will increase as you strike it harder. Glue a piece of rubber to it, and strike it again. The rubber will dampen the vibrations of the bell. Even a very small piece of rubber can turn a loud ring into a thud.

http://en.wikipedia.org/wiki/Natural_frequency

This happens to your crankshaft quite a bit. Every time ignition occurs, power is most suddenly transmitted into the arm of the crank. This causes the crank to vibrate. When the rpm reaches a point where the impacts to the crank arm are occurring at the same frequency as the cranks natural frequency, the vibration and flexing of the crank will increase.

The cranks design, materials used, and manufacture process all contribute to what the cranks natural frequency will be, and at what amplitude that vibrations at the crank's natural frequency will cause it to break.

 

[turbo addict]

I have one on my mirage turbo and my limiter set to 8800rpm. I race the car all of the time and have not had any problems since I installed it in 2002. this is my personal experience in my car. I have also had 4 friends' cars fail with stock ones (rubber breaking and the pulley separating) and were left on the side of the road.

 

[pboglio]

My stocker seperated and came close to taking out the timing belt. Having said that I wouldn't run a non-damped pulley. A good lightweight flywheel and some light rims and tires makes a world of difference without the risk to the motor.

 

[Locke]

To add:

I'm by no means saying not to use one. I'm saying to weigh the risks and use your own judgment. Breaking cranks because of this almost never happens.

For me personally, the gain is not worth the risk. My 1g got a new stocker when the previous one failed.

 

[pboglio]

Ahem.....mine just seperated on the way home today. Tink..tink..tink...tink...was the sound I heard of the inertia/dampening inner ring rolling down the street. Luckily the pulley itself is still intact. Pics to follow but damned if I don't get annoyed with this failure. Seems to be failing at 60,000 mile intervals on the dot. I may go with the fluid filled harmonic dampers this time around.

 

[DashLaflash]

http://i171.photobucket.com/albums/u291/sixbolt/album_pic.jpg

Consider it a type of "resonance disaster".

Mechanical resonance - Wikipedia, the free encyclopedia

Take a bell, dangle it from a string, and tap it with a metal striker. It rings, because it vibrates. Notice that this bell will always produce the same note, regardless of how hard you hit it. This is it's natural frequency. Strike it harder, and it will produce the same note, but louder. The bell will amplitude of the vibration and flex will increase as you strike it harder. Glue a piece of rubber to it, and strike it again. The rubber will dampen the vibrations of the bell. Even a very small piece of rubber can turn a loud ring into a thud.

Resonance - Wikipedia, the free encyclopedia

This happens to your crankshaft quite a bit. Every time ignition occurs, power is most suddenly transmitted into the arm of the crank. This causes the crank to vibrate. When the rpm reaches a point where the impacts to the crank arm are occurring at the same frequency as the cranks natural frequency, the vibration and flexing of the crank will increase.

The cranks design, materials used, and manufacture process all contribute to what the cranks natural frequency will be, and at what amplitude that vibrations at the crank's natural frequency will cause it to break.

Hey I agree with you Locke. I've seen all those articles and read both sides of the story and they make sense in theory. You do have to admit that the stock damper is not as good as it should be though. I also always see that picture posted as well as maybe one other. I would also like to add (if I remember correctly) that crank that broke was a remanufactured crank and the guy was trying to run 300hp. He just happened to have one of the pulleys and people jumped to the conclusion that it was the cause.

Pboglio you should definately get a Fluidampr seeing how many of those you go through . Or maybe try the undampened .

 

[SBR Joe]

First off, yes i know that there may be some very strong opinions about this subject so take it easy those who may disagree, but i myself have a strong belief that running the aluminum crank pulleys has no ill effect. Two reasons, one being the fact that every car i ever had made over 400whp, and ran one of these pulleys. All were daily drivers, all saw thousands of miles of abuse, never once did i have an issue, not even the belt squealing ones.

Second, the theory of it sounds good, theres no doubt about it, but not once was i ever convinced that not having a dampened pulley created any crank breaking/bearing failures as a direct result of it. Ive seen the same things happen to guys running ATi pulleys, it could be a number of various things causing said circumstances, not necessarily the crank pulley. I have known many many big names in the industry with very fast cars running the same pulley i have been for many years now. Its a great mod, much less rotating weight and will yield noticeable gains, and will not ever come apart. I will probably never be convinced that on 4g63's, an undampened pulley is any sort of liability. Rebuttals welcome, this is just my .02.

 

[debbie]

OK my initial thoughts on this were your crank was connected to you’re timing belt via a sprocket on the crank not the crank pulley, so you could In theory run you engine with out a crank pulley. If you could find a way to charge it that is.
So how important is it that the pulley needs to be dampened?

Well that was until I found this.

Harmonic balancers are designed to prolong the engine life by reducing wear on the main bearings and main journals and preventing crankshaft failure. The harmonic balancer or the vibration damper is a piece of equipment connected to the crankshaft which job is to lessen the harmonic vibration. Each time a cylinder fires, the connecting rod pounds the crankshaft journal as the force turns the crankshaft, causing energy to be dispersed through the engine. The front of the crankshaft takes the brunt of this power, so it often moves before the back of the crankshaft. This results to a twisting motion and after that, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Even if this ?unwinding process? is somewhat diminutive, it causes harmonic vibration.

The harmonic balancer is made up of three parts. The inner part is bolted to the crankshaft. The center part is a rubber ring which dampens crankshaft vibrations, and the outer part with the timing marks and pulley cuts for the belts. When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but it ends up twisting the rubber or discs that connects the two parts of the damper. The front of the crank can not speed up as much with the damper connected; the force is utilized to twirl the rubber and speed up the damper wheel, keeping the crankshaft operation in control.

When the harmonic balancer fails, the timing marks drift. What causes the harmonic balancer to work inefficiently? Age is the number one factor why your harmonic balancer started to work inefficiently. Another is the deterioration of its parts ? the rubber will dry out and crack and will separate from the metal sections, leading to a condition where the outer grooved ring will spin separately from the hub. Once this happens, it will have to be replaced ? for obvious reasons.

I’m now thinking that there needs to be an extra item added to the Timing belt change kit.

I know I'm going to stick to a dampened one and change it with my timing belt

 

[gst fat]

I have an unorthodox light crank pulley and has not given me a problem whatsoever, but then again it depends on how u treat ## motor, I change my oil at least every 2,500 miles, I also have the supposive dreaded 7 bolt I have gone through 4 turbos on this car and it still runs like a champ! (knock on wood) so personally I've never had a problem and I run 22psi dd as well,honestly I would have never gotten it if it weren't for one of my boys that had it laying around.

So I'll give the lightweight pulley a thumbs up from experience

 

[Boosted98gsx]

I have an unorthodox light crank pulley and has not given me a problem whatsoever, but then again it depends on how u treat ## motor, I change my oil at least every 2,500 miles, I also have the supposive dreaded 7 bolt I have gone through 4 turbos on this car and it still runs like a champ! (knock on wood) so personally I've never had a problem and I run 22psi dd as well,honestly I would have never gotten it if it weren't for one of my boys that had it laying around.

So I'll give the lightweight pulley a thumbs up from experience

how you treat your motor has nothing to do with the harmonics that are inherent to the design of the engine. Eventually your crank will break because it has little to no natural damping to counter act the harmonics, and the vibrations will escalate to a point where it will just plain break.

I repeat, how you treat your car HAS NOTHING TO DO WITH IT, other than your negligence to your engine. It is a matter of time.

 

[jeff24680]

I replaced my crank pulley along with all other components on the timing side with my 75000 mild build. I replaced it with a Fluidampr Crank Pulley I have since put 10000 miles on the engine without a peep. No squeaks or any irregularities.

This is my experience so far. No complaints

 

[gst fat]

how you treat your motor has nothing to do with the harmonics that are inherent to the design of the engine. Eventually your crank will break because it has little to no natural damping to counter act the harmonics, and the vibrations will escalate to a point where it will just plain break.

I repeat, how you treat your car HAS NOTHING TO DO WITH IT, other than your negligence to your engine. It is a matter of time.

Saying that it will brake is pretty bold but hey, that's on you man, ok now here's the question?
If you have had any damage done to your engine do to an unorthodox crank pulley please post on here

 

[Boosted98gsx]

Saying that it will brake is pretty bold but hey, that's on you man, ok now here's the question?
If you have had any damage done to your engine do to an unorthodox crank pulley please post on here

Here's an analogy for ya.

Take a diving board that has a pretty high spring rate (high modulus of elasticity, ie, it can deflect a LOT before permanent plastic deformation takes place). Now bounce on it, what does it do? It deflects with a displacement directly proportional to the amount of force your body exerts on it with respect to that modulus. When you jump off, it wiggles up and down because there is no damper.

Now, take that same diving board. Make it from steel (or hell, make it out of glass), something FAR more rigid and brittle (low modulus of elasticity) and increase your weight about 1000x then jump on it. What happens? It's going to deflect far less before permanent plastic deformation (and depending on its modulus, might even be perfectly plastic, meaning no elasticity at all). Add 4 bodies onto that same board alternating so that each one takes a turn bouncing in a certain location.

There is no damper, ie, nothing to absorb the velocity of those bodies hitting the board, so what does it do? It builds up vibration on top of vibration onto infinity until it finally cracks.

This is what will happen to your crank.

 

[viperlp01]

Seriously guys why do companies even make Harmonic dampeners.. Seriously? They have no purpose.....

 

[Boosted98gsx]

Seriously guys why do companies even make Harmonic dampeners.. Seriously? They have no purpose.....

quoted for truth

 

[donniekak]

Hang 2 cranks with rope from the flywheel flange. One with the damper installed, one without. Tap them with a hammer on a weight, or the nose. The undampened rings like a bell, the dampened one thuds. Personally, I don't want a ringing bell for a crankshaft.

 

[jrohner]

Hang 2 cranks with rope from the flywheel flange. One with the damper installed, one without. Tap them with a hammer on a weight, or the nose. The undampened rings like a bell, the dampened one thuds. Personally, I don't want a ringing bell for a crankshaft.

On the one without a damper, put a timing belt pulled tight to something else and see if it still rings.

Eventually your crank will break because it has little to no natural damping to counter act the harmonics, and the vibrations will escalate to a point where it will just plain break.

I think mine would've broken by now then. I don't put on a ton of miles, but I beat my car all the time. I'm a lot harder on my car on the street than I could be at any drag strip.


I am going to put a stock damper pulley on because I'm sick of the belt squeal that I absolutely can not get rid of with the aluminum pulley (a friend of mine has had the same issue).

 

[viperlp01]

Well there is no timing belt on the crank pulleys..... There is a wobbling alternator belt on it.

Why do you think the stock dampeners fail so much.. I thought that rubber is pretty durable.. Maybe the constant vibrations it sees at very high rpms has something to do with it. I don't know..

I am a guy that believes in making more power than trying to save weight. My car has been down to bare body from the engine bay back and I went to the track last week and weighed in at 3420lbs. I will take my full weight 2g into the 11s with a OEM dampener and OEM flywheel. The rotating mass helps launching the car and keeping the revs up when shifting.

 

[Boosted98gsx]

On the one without a damper, put a timing belt pulled tight to something else and see if it still rings.

A timing belt will dampen to some extent, but the crank will still be severely underdamped.

Well there is no timing belt on the crank pulleys..... There is a wobbling alternator belt on it.

Why do you think the stock dampeners fail so much.. I thought that rubber is pretty durable.. Maybe the constant vibrations it sees at very high rpms has something to do with it. I don't know..

I am a guy that believes in making more power than trying to save weight. My car has been down to bare body from the engine bay back and I went to the track last week and weighed in at 3420lbs. I will take my full weight 2g into the 11s with a OEM dampener and OEM flywheel. The rotating mass helps launching the car and keeping the revs up when shifting.

I bet if you looked at a SUPER slow mo camera monitoring the OEM damper under OEM engines loads, you would see very minute wobbling of the damper around the crank as the pistons fired. Amplify this by 2 or 3 times (people using the OEM damper in high HP setups) and you will probably see large displacements of the outer ring with respect to the inner ring. Then you run the risk of separating the damping medium from the crank sprocket. At this point, you should be running a viscous damper, instead of the OEM solid rubber damper.

Especially if you have a stroker motor on a large frame turbo.

 

[viperlp01]

Engineering major I take it .. Me too.

 

[ramsack]

This is just like when mythbusters put that 5 Lb. (is that right?) weight on a bridge that they had hooked to a cylinder that they could precisely control the oscillation of by .1 Hz. When they got it tuned to the bridge's natural frequency they could hear the tone anywhere on the bridge. They could also see the waveform in a bottle of water anywhere on the bridge. Granted that weight wasn't enough to bring down that bridge, but I'm sure if they would have had a whole crapload of those going, they would have been able to destroy it.

The same thing happens in a crank. There are rpm ranges where each firing happens in such a sequence that it can create a resonance in the crank. It's not about bearing failure, it's about the material of the crank literally breaking down. I don't care what kind of high dollar crank you run, it will break! It's not a question of if, it's a question of when!\

Also to end with...The accessories that run off the belts are "geared" that way for a reason. Underdriving them will do exactly that, and make them function less than what they are intended. In the case of an alternator, that would be very bad for it! If the car is requiring a lot of current and the alternator is spinning slower, you are putting unnecessary load on the brushes inside of it.