Would you drive your car off the edge of a cliff, just to reach the bottom faster?

What I am really try to say is would you risk the life of your motor just to gain a couple of HP? Most people never take the time to research the importance of the OEM crank damper when removing it and replacing it with a “power pulley”. I am writing this article in order to educate and disperse misconceptions that exist about after-market motor sport technology. After experiencing many problems with customer’s cars, due to the installation of a power pulley, I am eager to address the potential dangers of this product.

The whole concept behind the power pulley is that they may add a few HP by slowing down the speed of the accessory drive( all your accessories), but end up reducing the life span of your motor and rob power at certain RPM ranges. Yes, the power pulley will minimize the parasitic losses that rob power from the motor, which most companies claim to increase power by replacing the OEM harmonic damper with a lightweight pulley, but there is a significant amount of problems that can be related to this pulley that can be damaging. The harmonic damper is essential to the longevity of your motor.
It is also key to understand that Mitsubishi forms a team of qualified engineers to design these engines in your car, while these power pulleys are manufactured, sold to you and installed on your car by people who don’t understand the important principle of physics that go into designing these motors.

First I would like to give a brief description of how a crankshaft is designed and an explanation of the principles, which are vital to the correct operation of an engine. If you look at both sides of your crankshaft, on one side you have your flywheel and clutch, and on the other end you have the timing chain/gear drive and a small nose to which the damper bolts directly to. In the middle of the two ends of the crankshaft you have the bearing and main caps that bolt up to the block, which keeps the crank in its proper position. Last you have all your other components, this is your main source of crank twist and vicious harmonics, such as the rings, pistons, rods, and pins. In order to create power your pistons have to travel up and down the cylinder. Every time the cylinder fires, force is transformed through the piston and rod to the crank journal, this causes the rotation of the shaft. The sequences of forces that the crank is subjected to is ordered into tangential torque curves which can be either determined as a constant mean curve or INFINTE number of sine wave torque curves. These curves are known as harmonics, which follow an order that is dependent on the number of vibrations per revolution. The crank torque is made up of many harmonics of varying amplitudes and frequencies, which the name harmonic damper originates from. As the crankshaft revolves at an RPM such that the harmonic sine wave frequency coincides with the natural frequency of the shaft, resonance occurs. The RPM to which this resonance occurs is called a critical speed. As your engine rev’s through its possible RPM range it will pass through multiple critical speeds which can be classified into two categories, major or minor.

Major and minor critical RPM’s are quite opposite, of course, due to the fact that some harmonics cancel each other out or actually help one another in the production of larger vibrations. The important ones are the ones that build harmonics together, which are the major critical RPM’s. So this leaves us with the minor criticals, which cancel out the oscillations of the crank. If the rpm of the motor stays at or near one of the major criticals for an elongated period of time this can cause a fatigue failure to the crank. The major’s are very dangerous, which they must be dampened. Major and minor problems can result from an undampened shaft. If this problem is not resolved this can lead to damaged crankshafts, gearbox replacement, sheered crank pulleys and flywheels from the crankshaft.

With in the motion of a motor something is always off centerline, so it allows the revolution of the crankshaft. This is why the crank will tend to twist as the assembly is forced to revolve. When a cylinder fires, the piston is being forced downward, this is a power stroke. Now imagine this going at a rate of 7,500 rpm’s, this force causes the shaft to twist in one direction, away from its original position, and then when the cylinder stops firing it tries to settle on its original location, its momentum causes it to pass that original position and beyond, this is what is called crank twist. This action is what robs your engine of HP and begins to break parts when there is nothing to dampen or eliminate the twist. The amplitude of the vibration varies along the shaft, placing the worst torsional vibrations, farthest from the load or flywheel.

At the point when these vibrations reach the front section of the motor, crankshaft failure can occur. This can be prevented by mounting some form of vibration damper at the front of the crankshaft that is capable of counteracting that motion. This is where you need your damper. The dampers purpose is to absorb and dissipate as much twist and vibration as possible. With the right damper it will absorb almost all of your twist, but with the wrong damper, such as a power pulley replacement, virtually all of the twist will remain. Keep in mind that your Evo motor is design with a tuned rubber damper straight from the factory.

Now you may be asking yourself, what does this have to do with HP? To answer your question, remember from what I stated earlier, that the crankshaft drive is located at the front of your motor. If the front of the crank is twisting then so is the drive, and if the position is changed then your motor cannot accurately induce, combust and eliminate the fuel, which in the long run with cause a loss of power. To help solve this issue you must have a damper that you can rely on. The stock damper that comes from the factory is a piece of metal with a rubber ring inside that has been melted between another piece of metal. The only problem with this design is keeping the concentricity of the inertia during manufacturing. This has to be solved by machining and balancing the damper after the rubber has been molded, but if the ring slips you lose your timing marks and balance. Needless to say the stock damper will work fine as long as you don’t make any changes to your motor. If you do decide to make changes then your stock damper can no longer be relied on.

In addition to any crankshaft issue, there are all sorts of problems that may arise from the use of a power pulley. Slowing down the accessories assembly below their designed speeds can result to inadequate charging of the battery, dimmed lights, and electronic malfunctions. Also a major issue would be the slowing down of your water pump which can lead to over heating of the engine, nobody needs that. Though it would be possible to implement these corrections either with design or software but I think it is easier to avoid these scenarios in general. We at Infinite Speed and Performance feel that our customers deserve the highest of standards when it comes to development of a product and this is why we put more effort into products that ensure the safety as well as performance of your vehicle than our competitors. As a result we, long with ATI, have developed the harmonic damper for the Mitsubishi EVO VIII.

Pics are here: damperhttp://forums.dcevoclub.com/showthre...0019#post30019

 

I ran this by my cousin, he is an engineer in Mitsubishi Motors. "Mitsubishi forms a team of qualified engineers to design these engines in your car" that what he does lol. He said that you hit the nail right on the head! He said the smaller, thin, & lighter so called upgrade power pulley is a waste and can cause trouble for you down the road. Hopefully people will think twice about this. Then he went on to talk about harmonics and I was lost fast, haha.

 

good write up, but your link requires you to be a member of that board, and are you saying that if you had basic upgrades like turboback and reflash and things like that, the damper can't be relied on?

 

Very good info! This thread should be made sticky.

There are some parts of our cars that are there for good reason. The crank pulley is one of them. The mere fact that these lightened solid crank pulleys are associated w/ broken cranks isn't enough to deter some people from putting them on their cars.

 

marksae: That is not the main issue with the "power pulley", the main issue is the constant vibration resulting to the deterioration of your bearings. Especially if you are raising your stock rev limit, you are in need of a damper. I'm not saying you will break your crank, highly unlikely, but you will do serious damage if those bearings go bad.

 

how much???

 

Your post is long so im not going to bother reading it...however, I've got crank pulleys on both of my eclipses with over 100k miles on them between the two cars with zero problems... My information is not speculation, it is fact.

 

Case closed.

 

Just read the last paragraph for sh*ts and giggles...Most cars have waterpumps driven by the timing belt, and for obvious reasons, this pulley is not "underdriven" so therefor, pulleys dont really effect the waterpump.

 

2GDSM: If you read the whole article then you would understand that it is very important, especially when making alot more power than stock. I am not saying everyone is going to have problems who has a power pulley, but as you increase power in your motor you are increasing your risk of damage. Our car is the perfect candidate, we were spinning bearings until we were introduced to this concept. The length of my article if neccessary to explain this concept to an "average joe".

AMSTuning: So I guess ATI, the most credible damper manufacturer, is wasting their time supply dampers to Nascar teams, pro drag teams, roadracers, and street driven cars around the world. You wouldn't understand!

Case re-opened!

 

That's what I am saying - your car is one of the only candiates simply because its one of a kind motor. Any other Evo will not get ANY benefit from the ATI pulley. The stock pulley is balanced to the shaft perfectly from factory, even when making immense power you are still well balanced with a stock pulley. Especially an Evo that's on the street - that Evo is not even coming close to any stress because of an underdrive pulley. If you have a dyno queen - with C16 and etc pushing major power than the pulley may benefit you somewhat. Other than that you are copying and pasting generic info from the ATI press release.

Mike @ AMS

 

By the way, 365AWHP and 305FWHP between the two and 100k miles, no problems. Maybe with 500AWHP problems might arise, but not many people have 500hp motors that last 100k miles anyway.

 

I take back the 365AWHP, its actually a little over 300 on the stree trim I use 99% of the time. It was not my intention to come post on here to be a dick or anything, but this damper discussion has been argued hundreds of times, and while the theory you stated certainly is viable, I felt it neccessary to show that people have had the pulleys for long periods of time with lots of miles without showing and ill effects.

 

beer.

 

Mike @ AMS: So I take it you have an EVO with immense power using a stock pulley with no harmonic problems? You are right about the stock damper it is perfectly balanced with the shaft from the factory, with the stock damper don't forget. So when you remove the stock damper you are at risk, unless you are saying Mitsubishi put in on there for no reason and all the major damper companies out there. So I agree, with a STOCK pulley not a power pulley your are balanced. If you have ever built a motor and balanced a stock crank then you would know it is in need of a damper. If you can't take my word for it, contact the REAL AMS (who also builds motors and has an EVO) and they will educate you on this matter. I wouldn't know about dyno queen evo's since we haven't been able to get the car to stay on the dyno to get a true read out. But since we actually have an EVO so I can speak from experience. Last, we meet with ATI to develop all of this and the write-up . Sorry we are taking the time to R&D performance products for the EVO, to which we can pass on to EVO owners. It's ok you don't have to agree with our article, b/c after all body kits and stickers don't cause that much vibration in your shaft. Once again, you wouldn't understand!

I would like to apologize to every for the outcome of this post, it was originally meant to help educate others on this matter of the importance of a stock damper and for those you plan to make "immense" power, the option of a race damper.