Do I need a Fluidampr for my stroker?

[tfoti]

I noticed my harmonic balancer was starting to deteriorate so I started doing some research and learned that the stock balancer dampens only certain frequencies with the stock 2.0. The theory is: if a different engine configuration is used, such as a stroker with forged pistons in my case, these vibrations occur at different frequencies. As a result, accelerated main bearing failure occurs.

In the next couple weeks my stroker is going in and I am leaning towards buying one 2 days from now. I was hoping I could get some more info and personal experience with this situation. Most likely I will get one, but I would like to see some talk on it and see if there is any reason NOT to get it

 

[fourreGsixty3]

If your driving it on the streets then get it. Why? I thought you would NEVER ask.

1) The vibration of the engine, and its rigid components caused by the imbalance of the rotating assembly. 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. Balancing the rotating assemly, and matching reciprocating masses together is very important.

2) The vibration of the engine components is partially due to their individual elastic deformations( the different rates at which they change, and reform shape). These deformations are a result of the 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.

Torsional Vibration (Natural Frequency)
Every time a cylinder fires, the force twists the crankshaft. When the cylinder stops firing the force ceases to act, and the crankshaft starts to return to the untwisted position. However, the crankshaft will overshoot and begin to twist in the opposite direction, and then back again. Though this back-and-forth twisting motion decays over a number of repetitions due to internal friction, the frequency of vibration remains unique to the particular crankshaft. This motion is complicated in the case of a crankshaft because the amplitude(intensity) of the vibration varies along the shaft. The crankshaft will experience torsional vibrations of the greatest amplitude at the point furthest from the flywheel or load.

Harmonic (sine wave) Torque Curves
Each time a cylinder fires, force is translated through the piston, and the connecting rod to the crankshaft. This force is then applied tangentially to, and causes the rotation of the crankshaft. The sequence of forces that the crankshaft is subjected to is commonly organized into variable tangential torque curves that in turn can be resolved into either a constant mean torque curve or an infinite number of sine wave torque curves. These curves, known as harmonics, follow orders that depend on the number of complete vibrations (cylinder pulses) per revolution. Accordingly, the tangential crankshaft torque is comprised of many harmonics of varying amplitudes and frequencies. This is where the name "harmonic damper" originates.

Critical RPM's
When the crankshaft is revolving at an RPM such that the torque frequency, or one of the harmonic sine wave frequencies coincides with the natural frequency of the shaft, resonance occurs. Thus, the crankshaft RPM at which this resonance occurs is known a critical speed. A modern automobile engine will commonly pass through multiple critical speeds over the range of its possible RPM's. These speeds are categorized into either major or minor critical RPM's.

Major and Minor Critical RPMs
Major and minor critical RPM's are different due to the fact that some harmonics assist one another in producing large vibrations, whereas other harmonics cancel each other out. Hence, the important critical RPM’s have harmonics that build on one another to amplify the torsional motion of the crankshaft. These critical RPM’s are know as the "major criticals". Conversely, the "minor criticals" exist at RPM's that tend to cancel and damp the oscillations of the crankshaft.

If the RPM remains at or near one of the major criticals for any length of time, fatigue failure of the crankshaft is probable. Major critical RPMs are dangerous, and either must be avoided or properly damped. Additionally, smaller but still serious problems can result from an undamped crankshaft. The oscillation of the crankshaft at a major critical speed will commonly sheer the front crank pulley and the flywheel from the crankshaft. These failures have often required crankshaft and/or gearbox replacement.

Harmonic Dampers
Crankshaft failure can be prevented by mounting some form of vibration damper at the front end of the crankshaft that is capable of absorbing and dissipating the majority of the vibratory energy. Once absorbed by the damper the energy is released in the form of heat, making adequate cooling a necessity. This heat dissipation is visibly essential in some racing applications which channel air from the brake ducts to the harmonic damper, in order to keep the damper at optimal operating temperatures.

 

[project_tsi]

I would definitely get it. I have one with my stroker.

 

[tfoti]

Great info!! Such a change in the most critical engine parts, as with a stroker, definitely warrants a better damper. I think this may be one of the more overlooked parts in a stroker build.

Is the heat that will be released anything I will have to be overly concerned about? This car will probably never see the track and is going to be a DD for awhile.

Thanks guys, will be ordering one tonight!

 

[fourreGsixty3]

That was speaking in general terms. It really warrents it with any build not only strokers.

No you don't have to put too much thought into the heat released from the dampner, its used in race applications(were they run on the edge all the time) but I wouldn't be too worried about it.

 

[tfoti]

Alright, thanks!

 

[TunaTalon]

Yes, get the harmonic balancer. The vibrations from a stroker motor are at the same frequencies as the base 2.0L engine. If you use light weight pistons and rods the imbalance forces from the stroker will be about the same as the stock engine. See Figure 19 on page 23 of my StrokeOrNot document ( http://www.kidzuku.com/StrokeOrNot.pdf) for more on the forces involved.

FourreGsixty3 made an excellent post on the need for the balancer. If you still feel the need for a more user friendly description, then please see Pro-race.

 

[99gst_racer]

Just for clarification purposes: Our cars do not have harmonic balancers. We have harmonic dampers.

A harmonic damper is designed to help control harmful torsional harmonic vibrations.

A harmonic balancer is a damper with a built-in counterweight. Externally balanced engines do not have enough room in the crankcase for a proper amount of crankshaft counterbalance, so they add the counterbalance to the harmonic balancer.


tfoti - Accelerated main bearing failure is more common with an improperly balanced "externally balanced" engine, rather than basic torsional vibrations of an internally balanced engine. Even if the frequencies are slightly different between a 2.0L and a 2.3L, it shouldn't ever be enough to make any difference.

 

[TunaTalon]

Just for clarification purposes: Our cars do not have harmonic balancers. We have harmonic dampers.

Right on for how it works, but there is no profit in debating what it’s called.

The crankshaft pulley in my Talon with the elastomer material to dampen vibrations is Mitsubishi part number MD377604 and sold on Parts Train (Eagle Harmonic Balancer - Partstrain.com) as a “Harmonic Balancer”.

Parts Train is not particular about what it’s called. On the same page:
“Otherwise known as torsional damper, crank pulley damper, or vibration damper, the harmonic balancer is a mechanism that’s connected to the engine’s crankshaft to significantly trim down torsional vibration.”

Communications is a wonderful illusion.

 

[99gst_racer]

Right on for how it works, but there is no profit in debating what it's called.

The crankshaft pulley in my Talon with the elastomer material to dampen vibrations is Mitsubishi part number MD377604 and sold on Parts Train (Eagle Harmonic Balancer - Partstrain.com) as a "Harmonic Balancer".

Parts Train is not particular about what it's called. On the same page:
"Otherwise known as torsional damper, crank pulley damper, or vibration damper, the harmonic balancer is a mechanism that's connected to the engine's crankshaft to significantly trim down torsional vibration."

Communications is a wonderful illusion.

Right on. Kleenex to tissue.

I only pointed out the difference for one main reason though. Many problems associated with externally balanced engines and balancers, also get carried down to internally balanced engines when you call their dampers "balancers". If the distinction is correctly made and used, then hopefully there will be less misconceptions concerning the two (like in the first post).

 

[fourreGsixty3]

Just for clarification purposes: Our cars do not have harmonic balancers. We have harmonic dampers.

A harmonic damper is designed to help control harmful torsional harmonic vibrations.

A harmonic balancer is a damper with a built-in counterweight. Externally balanced engines do not have enough room in the crankcase for a proper amount of crankshaft counterbalance, so they add the counterbalance to the harmonic balancer.

Sorry bout that Paul. Yes there is a difference. I just didnt thinking about it

Also there IS a difference between Kleenex, and tissue...Kleenex is a brand name...of tissues. That means they are the same things where as dampners, and balancers are different...even though we call them the same.

 

[tfoti]

All good info here guys. It seemed when talking about it I would generally not think about it being a damper or balancer. Whichever I chose to say people always knew what I was talking about.

All the same, I ordered it a few hours ago and hopefully it will be here by the end of the week.