Lightweight Crank Pulleys. Good? Bad? Depends!

ON THE TOPIC OF LIGHTWEIGHT CRANK PULLEY VIBRATIONS, HARMONICS, AND SAFETY

Q. Do lightweight aluminum crank pulleys lead to premature engine failure?
Most American V8 engines of the muscle car era (50s-60s) were externally balanced.  An external (harmonic/vibration) balancer was attached to the outside of the engine, on the crank snout. The crank pulley in such engines was a separate piece attached to this balancer and the removal of this balancer was a bad idea. External balancers were most often used on large displacement V8 engines and the majority of today’s internet forums and social media discussions regarding harmonics stem from this principle.

Modern (1980s and up) Honda, Toyota, Nissan, or other Japanese engines are NOT equipped with external balancers. These engines are internally balanced and this process has improved even further since the 90s. So the topic of a BALANCER does not apply here.
The crank pulley found on many modern engines is often called a harmonic damper. This damper is a thin rubber band, less than (1/8 inch) 2mm, built into the crank pulley. This rubber is used to absorb something called NVH, noise/vibration/harshness. Suffice it to say, this rubber is actually not very good at performing its intended purpose after as little as a few thousand miles. What happens to rubber after exposure to weather conditions such as humidity, snow, rain, etc? It often becomes brittle, hard, and crunchy. Can something with these properties actually absorb vibrations very well?
Many NST customers have reported smoother running engines with NST pulleys, especially at idle. How is this possible if the rubber is such a vital important piece? As it turns out, the rubber is not as important as it is cracked up to be.

On a well maintained engine with bolt-ons or low amounts of boost like what most owners probably run, a lightweight aluminum crank pulley will not have any life threatening consequences. The engineering reasons are that most modern engines have a short (increasingly strong) crankshaft operating under 8,000 RPM. The dangerous second harmonic that can cause damage occurs at an RPM that this sort of engine will never see, in the area around 10,000 RPM. Even the OEM damper is not tuned for attenuation above 10,000 RPM, so the argument is somewhat of a moot point.  The great majority of our customers do not fall into the latter category. How many 500+ HP, 10,000+ RPM engines do we have on the street?

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Q.  Does NST have cars/customers in professional motorsports using its products?
There are a large number of Honda, Toyota, and Nissan guys who use underdrive crank pulleys in road racing series like NASA or SCCA. Road racing is much more punishing on an engine than other motorsports. The engine is subjected to run times lasting roughly 30 minutes with the engine always in the upper ranges of its RPM limit. One race weekend is the equivlent of hundreds of 1/4 mile passes. These guys would not use NST pulleys if they were not reliable.
NST sponsored the first ever wheel to wheel Scion tC NASA Road Race car. The same car was very competitive in the Grand Am series and had factory backing from Toyota, Scion, and TRD. This car used pulleys from NST with great results since day one.
NST has sponsored several drift cars participating in the professional US drift series, Fromula Drift. Several of our cars have also competed in D1 GP USA, Xtreme Drift Circuit, and NOPI Drift series. To make things better, NST products are also used in autocross, time attack, and drag cars.

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SUMMARY ON VIBRATIONS, HARMONICS, SAFETY
Older American V8 engines are externally balanced and require pulleys designed specifically for these applications, or damage to the engine could result. You will not find solid aluminum NST pulleys on our website for such engines.
High RPM engines, when modified well beyond the simple bolt-on stages, may have issues with solid aluminum pulleys. Such engines reach critical harmonics above 10,000 RPM, a range in which the dangerous wave of harmonics can come into play.  For such RACE engines, OEM dampers are also not sufficient.
90% of our customers’ engines do not fall into the above categories, and as a result, will benefit from the lightweight pulleys NST offers. Rest assured, your engines will not suffer damage nor will they have a reduced life in street and/or track use when NST products are installed properly.
We would bet that every “expert” preaching otherwise has little personal, practical, real world experience with the subject; as it applies in your case.

NST - NonStopTuning
​www.NonStopTuning.com