Perrin light wieght pulley
 

I have read a lot of 2 sided posts everywhere about the pulleys. Most are old and on here around 2012/13 post. I'm just curious as of now what everyone's opinion on them and now that these cars have some miles have anyone had any problems. What exactly are people saying when they say they're acting as a damper and causing barring problems?

@justatroll you wantta field this one?

Guess I'm catching and he pitching?

Holy eff this is a topic that has been, and will be beaten to death on every Subaru model. Do some research and come to your own conclusion here. Hardline benefit results? You will find almost nothing but subjective results.

Oh he will pitch on this subject!
He will also get called all sorts of things but he is right. I will let him explain the facts to you though since he is much more knowledgeable on the subject than I am.


My opinion on it is save your money for something that actually makes an impact.


Oh great, now I will get called names as well.

Butt dyno yooooooooo

You do know the difference between objective and subjective right?

I guess dyno testing is subjective though, brah.

That's what I'm trying to do here is build my own opinions and conclusion. I agree they beat the snot out of this topic especially on the Wrx forums and everyone is 2 sided and that's fine. My goal here is to see how people who have ran it over the years are holding up now. Also I would really like to understand exactly what is occurring on the opposing argument that it damages the car with the whole damper bearing deal.

Yes, I know the difference. 99.9% of "dyno" results for the lightweight pullies either show minimal gains within tolerance of a dyno or they're inconclusive, or better yet done by people who want to sell their product. The biggest benefit people see from this are the "feels like it revs faster" benefit.

Lol did you copy and paste this post because I think I have read this exact post on 4 different threads LOL

That's the general consensus.

Ya it is not coincidence that you keep reading it.
I personally will never, ever, for any reason, even consider a dyno reading within 5HP one way or another as accurate when measuring mods. These places that throw a pretty graph up and say "look our xxx gives you 3 more HP" are only proving that there can be a 3HP variance in the dyno reading between pulls.

The Dyno is not that big a deal to me with this part. Everyone says the rpm hits up faster and Perrin claims it to be like shedding 100lbs off your car. That's directly in the product description. Now if they have proof of this claim idk. I am excited though for the chance to pop my gas and have a little more response for rev matching .

have them on my car atm no issues to report, have had them for 15k kilometers

Thanks you. Are you running just the crank or all 3 ?

Well it sounds like you have researched but I am afraid you are just going to get the same split decision here that you have everyplace else. Those that like them will say they do wonderful things. Those that don't will say they are crap. I have never tried them but based upon the objective evidence I have seen (remember I rule out the questionable dynos) I don't think they do what people claim.
There is something to be said about the psychological aspect of the placebo effect though so if people think it makes the car better then the car is indeed better to them.

That's funny because I was just thinking about the placebo affect on that last response when I wrote it. I ordered it last night because I got a hell of a deal. Guess I'll be just another test dummy. The absolute only argument I can understand for not doing it on this car would be because it's a high revving engine. Most all arguments include that the problems are from shifting a rev limiter for instance in the Wrx. High miles with high revs over time seem to be the only valid explanation for failures with them. With this car being high revving engine it's almost like a catch 22 lol.

I'm well aware chief. That's my point. A lightweight crank pulley is almost a "bro" mod as shifter knobs and interior wraps.

http://www.ft86club.com/forums/showthread.php?p=2379089

:cheers: Well played..... well played.

I'd have to recheck to make 100 sure (so many things everywhere on that car lol) but I believe all 3. I mean they shave a bit of weight that's all one could objectively say lol (can't speak to the revving as im sc'd)

I like to be 10lbs lighter sue me :P don't know how many weight they do shed but wtv they are on so they are staying lol

3.7 lbs wieght loss on the crank pulley if it's Perrin

I know I read on one of the super charger kits you can't run the light wieght pulleys.... No clue which one it was

If you want to drop money on it, then go for it. But it'll be 100% placebo. And, if something does happen to your engine and you're under warranty, good luck getting covered if you have a LWCP

I got a stack of parts ordered and on back order.... 17k miles and I don't think I could ask for warranty work if I was the dang service manager lol

Since Tcoat would be disappointed if I didn't check in,
Some simple facts:

1 - The stock crank pulley IS a torsional damper. It is a textbook example of one and testing by a member on this forum shows that it absorbs engine harmonics better than a billet crank pulley. Whether or not the engineers put it on the engine because the engine NEEDS it or not is up for debate.

2 - The stock pulley cost more to install as OEM than a Billet Al. pulley.

3 - Shedding weight from anywhere else on the car will give the same advantage as shedding the weight from the pulley (as far as a human can FEEL). Removing the weight from the spare tire or taking 1/2 gallon of gas out of the tank will make just as much of a difference. (can you FEEL the difference between 12 and 12-1/2 gallons of gas? No, then you wont feel the difference of your LWCP except in elevated engine NVH)

4 - If you feel the need to shed rotational inertia from the rotating assembly (for whatever reason you feel is beneficial) the pulley makes the LEAST difference of any component. Shedding GRAMS from the drive belt would make as much of a difference. Changing the pressure plate bolts from steel to titanium would make a BIGGER difference)
Finally my favorite:

5 - Shedding rotational mass from the rotating assembly will NOT give the engine more horsepower. It is simple physics.

6 - a lightened rotating assembly WILL be noticeable in rev rates when the engine is out of gear.


There now - Flame ON!
Disclaimer - I AM an engineer, so lets just get that out of the way so that everyone can tell me that I don't know what the fuck I am talking about. Engineers seem to get told that more than anyone else on these forums. If a fireman tells you how to put-out a fire they get thanks. If a member of the armed forces talks about anything, they get a "thank you for your service". If an engineer states that they are an engineer they immediately get shit on even if they are regurgitating facts.

Déjà vu

Deja Stu?

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.