aww only two pages in? No fun, isn't it suppose to get to 10 or 11 pages before something like this? No one is suppose to actually take this type of thread seriously any more because people are more entrenched on this topic than they were in WW1 and WW2 combined...

but anyways, I disagree of course. I think there is a noticeable benefit, but it really becomes noticeable when you add in a lightweight flywheel and a carbon driveshaft.

For me, the full pulley set from NST seems to allow me to play in the extreme lower part of the rev range without the car freaking out about it as much. I know when I can afford a carbon driveshaft and a lightweight flywheel it will be even more noticeable. You could really notice this on my old Yaris. Of course having wheels that weigh only 6.5 lbs really helps. But having a lightweight flywheel and pulleys helped noticeably as well. I get a little over 40 mpg not even caring about it, and my best was 50 mpg.

but for your #1, a small displacement engine doesn't need it. It is internally balanced. I think Subaru even mentions that somewhere, but that might be me daydreaming too.

#2, well duh. The stock pulley has to last the life of the car. Aftermarket ones don't, or there would be no weight benefit.

#3, 100% disagree. Removing weight from the drive train makes a more noticeable difference. Whether it be lighter weight wheels, tires, driveshaft, flywheel or pulleys, anything that spins will make more of a difference than anything that is static. Now pulley's have a tiny diameter compared to wheels, so there is obvious better places to start modding if you want to remove weight from the drive train.

#4, maybe, but I doubt anyone will ever have the cash to make an honest repeatable test of it.

#5 completely misses the point. It does not add horsepower, but it frees it up. Lighter components need less power to spin. Plus when you add a few of them together you can really see the car rev faster.

#6, and every other time the car is actually on.

People who repeatedly state things as facts that are demonstrably false get yelled at. If lighter was not better f1 cars would not be made of insanely overpriced exotic materials. If we were talking old school big block v8's, that would be a totally different story, as a lot of those were externally balanced and screwing with pulley's without knowing what you were doing could wreck everything.

But I would agree a pulley set probably isn't the best place to start when it comes to bang for you dollar. And if you are ever going to go FI you might not want to do it at all, depending on your power goals. And they do look awesome compared to those ugly stock blah boring ones.

So you're disputing his knowledge with absolutely anecdotal evidence? Gfg bro.

Oh god. Thank you. Thank you. Thank you.

Claims he knows "X" mods will make it better.

Doesn't actually have "X" mods on his car.


You sir, are a Rhodes Scholar, whose use of demonstrable, objective testing to prove your hypothesis is beyond reproach.

I bet we can get everyone to throw in to send you on a trip to the Champagne room.

This is false and one of those misleading statements that gets parroted over & over.
A balanced rotating assembly DOES NOT mean that there are no harmonic vibrations. How can you "balance an engine" to negate rotational (torsional) harmonics? You cant.
Balancing the rotating mass only means that the reciprocating masses are the same. It does nothing to stop the crank from twisting on every combustion cycle and sending a shock to all of the other components.

Then that argument would be a good one FOR using the billet pulley as there is no rubber part that can wear out. Negative points for that one.

"makes a more noticeable difference" - That's scientific.
I can counter that with "I dont think so" and we are at an impasse.
Try using science instead of hyperbole.

There was a calculation on another thread where removing an entire 30lbs driveshaft and replacing it with an imaginary one that weighs ZERO (leaving the total mass of the vehicle the same) made a whopping 10 millisecond difference in a 1/4 mile. How much difference do you think 4 lbs will make? Noticeable? I think not.

There is no maybe, I could calculate it for you. The bolts are so much further from the center of crank rotation than the pulley that it certainly makes bigger difference. You dont need to test it.

"It does not add horsepower, but it frees it up." That one's a hoot.
Could you please explain how something that "frees up" something is different than "adding" that same something.

Then answer this question:
If horsepower can be measured at constant RPM, then how does the rotational inertia factor into the calculation? Since additional rotational inertia can only make a difference in ACCELERATION?
How many dyno plots tell you how long the pull took?

No. When the car is in gear it is attached to the GROUND and the resistance to acceleration is the ENTIRE MASS OF THE VEHICLE.
Hence the M in F=MA

Thats why I got the Subaru instead of the Scion "brah" :thumbup:

I summand you because you are an engineer and of the multitude of threads I have read on this topic you explained the realities the best.

Welp. My buddy I went to high school with is a mechanic at Subaru dealer and found out today he is actually taking the Subaru classes his job sent him off for.... I asked him about it and he sends me this article
http://www.motoiq.com/MagazineArticl...velopment.aspx

Guess it's not going on there...

Excellent find!

Their data shows lower hp numbers on the LWCP.

I particularly like this statement:
"Comparative gains between 4,000rpm – 7,000rpm at only 150rwhp peak on a boxer engine is impressive. One can only conclude how much of an improvement the Fluidampr performance damper would make at much higher horsepower. Why did the Fluidampr, at 4.6lbs heavier than the 1.195lbs lightweight crank pulley, come out on top? “Excessive crankshaft torsional vibration robs power and accelerates component wear. You need proper mass with broad range damping to control it."

Which says that the better damper (the HEAVIER one) actually showed gains in HP.
This is likely what @why was alluding to above.

High vibration can cause excessive forces in bearing surfaces which leads to increased friction and higher parasitic loss.

The Perrin claims seem to be explained simply..However,

The Raceseng claims seem pretty scientific care to chime in on this>?

http://www.raceseng.com/revo-crank-t...z-2013#answer1

From the link ^

CAN I REPLACE THE CRANK PULLEY HARMONIC BALANCER?

The harmonic balancer has the sole responsibility to retard or lessen the resonant frequencies that occur during the normal operation of any internal combustion motor. The crank is like a tuning fork for musicians; when the firing cycle hits each cylinder, its like a flick to the tuning fork. So when you see the term "harmonic", it is a literal description of what is occurring to your crank. Your crank is actually flexible, believe it or not, if it wasn't, your engine wouldn't last more then 10,000 miles. It flexes on a microscopic level to absorb the explosion from each cylinder, this flex is precisely what creates an engine's natural frequency. Some vehicle's frequencies are more violent then others due to the architectural layout of the cylinders. For example, a V6 or V8 will have higher resonance because the downward thrust of each cylinder travels through the center-line of the crank in a non-linear pattern; this actually has the ability to amplify the frequency, depending on your RPM. Compare this to an I6 or I4 and you reduce the harmonics due to the linear pulse of the cylinders approach the crank from a single direction. Finally the Flat-4, with force traveling through the crank to opposing cylinders, the frequency is reduced by its own operation. We're not saying that the frequency is completely eliminated! We're saying that of all the engine formats available, a flat-4 is the best candidate for a lightened crank pulley.

We can have a lot of discussions about the lightweight crankshaft pulleys. I don't question of any engineering knowledge or logical reasoning. However, practical evidence tell us that they don't cause issues in Boxer engines. There are many happy users using them in Subarus for years and years. If there were issues, they would appear till now.

Are there any performance gains? Answer is YES. Please check a dyno from a respectful company (Toda Racing) where the gains are +8 whp:

http://i63.tinypic.com/2isfgqg.jpg

However, the specific pullies are very light and the alternator is underdriven. I don't suggest this set for daily driven cars.

I suppose the performance gain for other brands would be in the range of 5-6 whp.

"and the alternator is underdriven."


There is absolutely no question that under-driving the pulley driven components WILL result in a net HP gain.
That just means that the Alternator is getting 8hp LESS than before.
(And I don't believe that #, 2-3hp is more like it)


1hp = 745 watts.
To drive the Alternator by 8hp LESS means the car is somehow consuming 6000 watts LESS than it was before.
Sound wonky? - Yes.

You get approximately 2-3whp from the underdriven alternator and 5-6whp from the light pulleys. Overall +8whp.

While interesting, I can tell that the paragraph above was not written by a technically knowledgeable person (or even reviewed by one). It is filled with buzzwords and technical sounding jargon, but misuse of key terms tells me it is mostly bullshit.