TURBO DIESEL REGISTER ISSUE 73 - AUGUST/SEPTEMBER/OCTOBER 2011
TURBO DIESEL REGISTER ISSUE 73 - AUGUST/SEPTEMBER/OCTOBER 2011
by David Magnoli, TDR Contributor
Replacement Choices
When faced with the replacement of the harmonic damper you have several choices. You can use an OEM unit from the dealer, for which my local Dodge dealer quoted me $420 before tax. It was only $201.47 before tax directly from Cummins. You also have a couple of aftermarket choices.
There are a few companies making what are essentially the stock-style dampers, but if you want an improvement over stock, there are really only two choices that offer a high-performance model. Both of the following aftermarket dampers have what I feel is a definite advantage over the stock damper besides just better performance. The serpentine belt pulley is machined as part of the hub, and as such is driven directly by the engine, not by the transfer of power through rubber as in the stock design. This means that the pulley cannot become misaligned, even if the damping function were to fail or lessen in effectiveness. Nothing will ever be thrown off the crank from deterioration of a rubber part. Keep in mind that the prices I used below are list prices, street pricing is considerably less. Also, prices shown are for my 2001; other year models may vary slightly.
The ATI Super Damper is supplied in three parts:
the damper itself, the vehicle-specific hub, and the aluminum pulley.
All necessary bolts and screws are supplied to assemble this damper, but it
cannot be assembled before installation on the engine, due to the fact that the installation bolts
do not fit through the crankshaft flange holes after it is assembled.
It requires that the pulley and hub be bolted to the crank flange first, and then the damper ring is installed
with the six Torx-Plus screws and six, 12-point cap bolts. Loctite 242 must be used and the torque values
(printed on the damper label) must be followed.
ATI Super Damper
The first option is the made-in-USA, ATI Super Damper at $475 list, which uses eight elastomer O-rings on a grooved, floating inertia ring housed inside an inner and outer shell that are pressed together and then bolted onto a vehicle-specific steel hub. There are three O-rings on the inside radius of the inertia ring as well as three on the outside. These contact the inner and outer surfaces of the two shells. The other two O-rings on the inertia ring contact the inside faces of the two shells. Each of these rings is made of varying density (durometer) designed to come into play at different RPM to manage variable harmonic vibrations. These dampers can be tuned for a specific application by varying the density of each of the elastomer O-rings. The Cummins version is larger and heavier than other applications, with the larger number of elastomer rings tuned to our engines. There is an important difference between this damper and the stock rubber-mounted one in that the O-rings offer a sliding surface rather than a bonded connection that is dependent upon the flex and rebound of the material. The inertia ring in the ATI is free-floating within the housing, allowing it to move and better absorb variable harmonics. When used in applications up to 800hp, they are rated to last 10 years and can be rebuilt by ATI, or by the user if you buy their kit, simply by taking the unit apart and replacing the rings.
They also exceed SFI 18.1 specifications. The hub directly drives the pulley, eliminating any chance of belt alignment issues.
The ATI arrives unassembled in three parts: the inertia ring, the vehicle-specific hub, and the aluminum pulley, each of which is zero-balanced to two-tenths of a gram. There is a dimple on the hub and ring which must be aligned. This damper must be installed on the engine in the following order, the pulley and hub first, and then the damper ring itself with the 12 supplied bolts and screws. This is because the washer-head crank flange bolts will not fit through the mounting holes after the damper ring is placed on the hub. New, longer crank-flange installation bolts are also supplied with the ATI because of the thicker hub. The stock bolts will not work with the Super Damper.
Fluidampr
The second option is a Fluidampr at $436. This USA-made, all-steel product is supplied completely assembled and ready to install. This damper is made in six Cummins models, with the size, weight and characteristics designed specifically for each model/year of Cummins engines; it is not a one-size-fits-all. Dodge/Cummins changed to this type of viscous damper with the introduction of the 6.7L engine.
The Fluidampr is a one-piece laser-welded assembly that is ready to install on your engine crankshaft. It is sealed and requires no maintenance. It is all steel and after coating the center-bore with anti-seize, installs in one piece. You will need to reuse your stock installation bolts or buy new ones, as none are supplied with this damper. The bolts are torqued to 92 ft-lbs.
It uses a steel inertia ring fitted inside a steel housing with a clearance gap that is filled with a thick silicone fluid, allowing it to float and mask vibrations over a much larger range of RPM than the stock, bonded type. Because it is insensitive to any specific frequency, it is able to self-tune to whatever vibration input it is exposed to. It is sealed and cannot be opened, and is maintenance-free for the life of the damper, which by design should never wear out. The machined, nylon-coated inertia ring is precision-balanced both before and after the coating process, and the balanced housing is laser-welded. The machined-steel serpentine-belt pulley is part of the hub and housing. The Fluidampr is also available for the 6.7L engines and includes the tone ring as part of the damper.
The Fluidampr viscous design has been around since 1946 and also meets SFI 18.1 specifications. On any year truck, Fluidampr recommends the use of their available Cummins pinning kit to pin the damper to the crank flange if RPM are to exceed 3500. The kit is supplied with a drilling fixture, bit, and two hardened roll pins.
On the left is the Fluidampr, larger in diameter and thicker than stock, and the heaviest of the three at 24 pounds.
Next is the stock damper weighing in at 14 pounds, followed by the ATI Super Damper at 18 pounds.
The ATI is smaller in diameter than the other two and also uses an aluminum pulley, unlike the steel used on the Fluidampr and the stock damper.
The pulley diameter remains the same on all three units, keeping accessories spinning at designed speeds.
The 6.7L Damper
Another possible choice for replacing the tuned rubber style 5.9L damper is by using the 6.7L damper on a 5.9L engine. There has been talk of this on the TDR forums as well as other diesel forums, but I have not seen anyone actually do it yet. The fluid-type damper on the 6.7L engines is a dramatic improvement over the 5.9L design but it is not a direct bolt-on replacement. At the time of writing this article, I called Cummins West and my local Dodge dealer to see if they had one of the 6.7L dampers in stock and was told that neither they, nor the factory, had any available at that time. Being rather new, they are not at the point of failing yet, and there does not seem to be much call for them. There seems to be a clearance issue with the newer design on a 5.9L between the damper and the fan pulley, but I have not been able to get my hands on one to verify this. If these issues can be easily resolved, this may be another option for better performance.
The 2011 6.7L Cummins engine uses a harmonic damper that is of the viscous-fluid type.
This change from the tuned-rubber was made with the introduction of the 6.7L engine in 2007.5.
The tone ring is part of the pulley on this damper.
Enough Talk Already, Do They Really Work?
So far the claims of the aftermarket manufacturers sound great, but I wanted to see for myself if they were valid. I put the Fluidampr and the ATI Super Damper through their paces by installing them on my 2001 Cummins to see how they would perform under various driving conditions in comparison to the stock damper.
The first thing you will notice about these dampers is the weight. Mass is critical to being effective. A small, lightweight damper will not do much regardless of what method it uses to quell the vibrations, which work against this mass. You need the weight to counter the input energy. My stock damper weighs 14 pounds. The ATI tipped the scales at 18 pounds, a 4 pound increase over stock. The Fluidampr weighed-in at 24 pounds, a full 10 pounds heavier than the stock unit. Aftermarket dampers for First, Third, and Fourth-generation trucks vary slightly in weight from these, but all are substantially heavier than stock.
Originally published in TDR Issue 73, Aug/Sept/Oct 2011.
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