4) "Is my crank pulley a harmonic/torsional/vibration damper or a harmonic balancer?"

People are getting the pulleys confused with the harmonic dampers found on some V6 / V8 engines. "Harmonic Balancer" is a term that is used loosely in the automotive industry. Technically, this type of device does not exist. The "balancer" part comes from engines that are externally balanced and have a counterweight cast into the damper, hence the merging of the two terms. None of the applications that we offer utilize a counterweight as part of the pulley as these engines are internally balanced.

The pulleys on most of the new import and smaller domestic engines have an elastomer (rubber ring) incorporated into the pulley that looks similar to a harmonic damper. The elastomer in the OEM pulley serves as an isolator, which is there to suppress natural vibration and noise from the engine itself, the A/C compressor, P/S pump, and alternator. This is what the manufacturers call NVH (Noise Vibration & Harshness) when referring to noticeable noise and vibration in the passenger compartment. It is important to note that in these applications, this elastomer is somewhat inadequate in size, as well as life span, to act as an effective torsional damper. If you look at the pulleys on some of the imports there is no rubber to be found at all. We have samples of these, mostly from Acura/Honda, the Nissan Altima, 1.8L Eclipse, 2.3L Fords, Chrysler 2.2L's, and 1.8L VW's, to mention a few. This is not to say that with our pulleys you will hear a ton of noise or feel more vibration from your engine compartment. Most who have installed and driven a vehicle with our pulleys will notice the engine actually feels smoother. This is a natural result of replacing the heavy steel crank pulley with a CNC-machined aluminum pulley. NVH is variable and unique to every car. NVH will increase with the installation of an aftermarket intake and/or exhaust, for example. Think of OEM intake systems in newer cars, they use baffles and resonators in the intake to quiet all the intake noise. Aftermarket intakes eliminate these resonators and create dramatic increases in engine noise from the throttle opening and closing. So to most tuners, certain types of NVH can make the driving experience more enjoyable.

The purpose of a traditional harmonic damper is to protect against crank failure from torsional movement. This is not necessary in most modern engines because of the many advances in engine design and materials. Factors such as stroke, displacement, inline, V configurations, power output, etc., do determine when and how these harmonics and torsional movements occur.

Again, there is a lot of internet hearsay about the pulleys. When motor failures occur, too often people are quick to blame the pulley first, rather than taking the time to look logically into why there was a problem. We hope that after reading this you will understand the crank pulleys better.

Originally posted by drumsy
After reading that, I'd say that you can get buy with an aftermarket crank pulley.

Everything You Ever Wanted To Know About
Underdrive Pulleys (but were afraid to ask)
By Dennis Grant
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Dennis Grant is a Canadian member of the SCCA and a very active member of the online autocross community. He is an automotive engineer by day, and in his spare time he autocrosses a highly modified Eagle Talon. His name may be familiar to some of you as he was a driving force behind the creation of the SCCA ‘s new Solo II Street Mod fled category. This article was posted to the Street Touring email list in response to questions of why there is a limitation on replacement of crankshaft dampeners in the STS class. It is reprinted with permission. Direct any questions or comments to Dennis at trog@wincom.net
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The theory behind underdrive pulleys is sane enough: various engine accessories are driven off a belt system taken off the nose of the crankshaft. It takes power to drive these accessories, and the amount of power consumed by each accessory is usually proportional to the speed at which it is driven. Slowing down an accessory thus reduces the amount of power it consumes. Note, however, that is not ‘‘free power’’ but rather “robbing Peter to pay Paul”. The output of an accessory is proportional to the amount of power it consumes, so if you reduce the amount of power a given thingie is consuming by underdriving it, then you are also reducing its output. Go too slow, and you can cause more harm than good.

For example, if your car draws 20 Amps of current at idle, and you underdrive the alternator to the point where it is only producing 15 Amps, then that 5 Amps will come out of the battery so a running car will discharge a battery, not charge it.

Anyway, depending on the design of an individual engine and its accessories, some power may be found by underdriving the accessories.

To do that, you have a choice: just like on a 10 speed bicycle, you can change the diameter of either the driven pulley (gear in the case if the bike) or the driving (crank) pulley.

Reducing the diameter of the crank pulley underdrives all accessories. Increasing the diameter of a given accessory’s
pulley underdrives just that accessory.

So far, so good. This is all just plain Jane high school mechanics here. If you’ve ever had a multi speed bike with a tire driven light generator on it, you’ve experienced everything that’s going on here. But now it gets complicated: Crankshafts flex. One end of the crankshaft (the transmission end) is for all intents and purposes held solid, and the other end is free floating. The crank is then subjected to a series of pulses tangental to the axis of rotation, both in the direction of rotation, and opposite to it (not just power pulses, but compression pulses, inertial loads as the pistons come over the top of their strokes, and so on and so forth)

The crankshaft is being wrung like the neck of a chicken, constantly back and forth, with each crank throw acting like an
additional hand on its neck. No Crankshaft Design Is Immune To This. ALL crank shafts flex. There is no way around it.

The amount of flex does vary in degree though. Cranks that see more torque flex more. Cranks that see higher RPM (and thus higher piston inertial loads) flex more. Longer cranks flex more. (There is an aircraft engine in the Chrysler museum that has a crankshaft about 6 feet long. Crank flex was so bad in this motor that they moved the power take off to the center of the crank, effectively halving the length of the crank) Crank flex is also dependant some what on crank metallurgy.

Thus, a short, slow, low power motor wont see much crank flex, where a long, high revving, powerful motor will see more. But that’s not all...

Each crank has a “natural frequency” that it wants to vibrate at (and higher order frequencies called “harmonics” that are integer multiples of its natural frequency). If a crank sees pulses at its natural frequency, each pulse will re enforce the one proceeding it (like sloshing back and forth in the bathtub, or rocking a car to get unstuck from a snow bank) If this happens, the crank will eventually tear itself apart. Not only that, but due to a law of physics that I can’t explain very well, because one end of the crank is supported and the other not, you get a sort of crack the whip’’ effect that causes the crank nose to move at 90 degrees to the axis of rotation, turning the crank nose into a hammer.

Needless to say, all these effects are bad for motor life.

You cannot get rid of them they are an intrinsic part of the nature of the crankshaft. It is the nature of crankshafts to flex, to have harmonics, and to try and pound out their bearings. But you can control these effects. Enter the “harmonic damper”. The harmonic damper consists of an inertial ring bonded to the crankshaft via some elastic sub stance, usually a rubber of some sort.

The inertial ring is just a circular weight that, thanks to inertia, wants to keep turning in the direction of crank rotation. As the crank flexes back and forth, the inertial ring stays pretty much steady, and the rubber that joins the two together damps out the crank pulses. It is this flexible rubber joint that makes the damper work. Without it, the inertial ring be comes a solid part of the crank shaft, and will flex back and forth with the crank (possibly even magnifying the effects!) No rubber ring no damper. Further complicating the issue, not all engines were internally neutrally balanced; they needed offset counterweights external to the engine to bring the engine into balance. Often, the counterweight was added to the hub section of the harmonic damper (you already had to have the bloody thing, why not put the counterweight onto it?) and so the damper got called a “harmonic balancer”, often shortened to “balancer”.

So the terms “balancer”, “harmonic balancer”, “torsional damper” and “harmonic damper” are all basically interchangeable. They are not all the same thing (depending on if there is a balancing counterweight in there or not) but they all perform the essential function of controlling crank flex.

Now, on most domestic V8s, the balancer and the crank pulley were two separate parts, bolted together. One could thus change the diameter of the crank pulley without disturbing the damping function. But on most modem engines, the crank pulley and the damper assembly are the same unit. What’s more, it seems that the size of the inertial ring has dropped, and the thickness of the elastomer ring has shrunk, so it is often difficult to see at first inspection that a given pulley/damper assembly is in fact an assembly and not just a plain-jane pulley.

If a pulley/damper assembly is replaced with a solid pulley, engine damage WILL eventually occur. The likelihood and se- verity varies from engine to engine, but the physics behind the damage is immutable.
Now there ARE engine builders who will remove damper assemblies. It was common in my drag race days to replace 151b dampers with solid aluminum hubs (in order to reduce rotational inertia) but this was done on engines that were tom down and rebuilt after every event.

If you have the type of operation that has a couple of spare engines, and every week the engines are rotated, and the past week- end’s engine is tom down and inspected, then yeah, you can get away with deleting the damper.

If you have a short-crank, low-torque, low-rpm motor, or your motor rarely sees full-throttle use, then you too can probably get away with a solid pulley. And once and a while, someone will just get lucky. I’ve heard of guys who smokes 5 cigars a day from the time they were 12 dying at the age of 104, but that doesn’t mean smoking is safe.

The manufacturers of underdrive pulleys COULD, if they wanted to, build under-drive combo damper/pulley assemblies, but they have chosen not to. Instead, they will make claims about OEM engineering incompetence, dispute the function and effectiveness of dampers, and generally deny that there is any problem - after all, designing a proper part would take research, and it would cut into their profit margin. I am singularly unimpressed with the underdrive pulley people. They are not people with whom I would do business.
The bottom line is this:

1. Replacing a pulley/damper assembly with a solid pulley as a minimum greatly increases the risk of engine damage.

2. Assuming you are set on underdriving your accessories, the same thing can be achieved with replacement accessory pullies.