Yes nothing times 2 is nothing! But if the gains can't be measured then the math is pointless - as is trying to be right in the UDP argument. If you don't have a UDP, then you really can't comment on the power or lack of it now can you? When you lighten the crank by 10+ pounds, the car revs much faster and it's noticable beyond what you can surmise never having tried one!

Sometimes living life by the dyno is a limited and shallow place to safely live your life. Obviously the 350 Z race teams can look beyond the shallow shallow world of mag racing where people who've never tried a mod promulgate what the pioneers of the mod should be doing with thier time and money. If you don't have one and you don't have any charts of you own...pipe down and let the debate run it's course without the childishness.

 

This thread is about a lightweight pulley only, not underdrive, and "math" can 100% tell you the maximum theoretical gains from such a mod. That is, unless you claim the power is coming from something other than the reduction in rotating mass.

 

Well in this case the math can't as the values that you would protract from a dyno run don't show gains as the gains were made while getting the rotational mass moving BEFORE they could be measured. What good is an equation you have no variables for? The power does come from reduced intertial or mass, but, you'll never see these gains on the chart.

Again - the nayayers (all but one I can think of) have never tried the pulley, but they have more half baked opinions than a bunny fucs.

 

"Gains" from reducing rotating mass only show up when the masses are being accelerated. This is precisely why the calculated gains that I show are a percentage of the power or torque output, because the output varies with acceleration, and acceleration to first order is proportional to engine output at that instant. On most all of the dynos out there, the car is put in to a higher gear and accelerated on the dyno. Now the acceleration seen on the dyno will surely be different than that on the street (since they're not accurately simulating vehicle weight and drag, though some attempt it), so dyno gains in general are not an accurate measurement of lightened component "gains".

BUT what IS 100% accurate is the mathematical calculations of these gains as a function of your assumptions. The minimum "gains" from a lightened crank pulley or flywheel are described by:



where nfd is the final drive ratio, ngear is the gear ratio, ro is the lightened component radius, rtire is the tire radius, dm is the change in mass of the component, and Mv is the vehicle mass. The maximum gains are twice that. This is very simple physics (read the page). Once you add drag on the street in to the equation, gains decrease even further at high speed (beacuse engine acceleration is reduced). Now if you want to speak intelligently about the gains from lightened components, I'd be happy to discuss any issues you see with my assumptions or math, because that's the only place where you're going to be able to disupte these conclusions.

I've driven friends' cars before and after crank pulley installs that just couldn't resist the hype, and they admittedly couldn't feel a difference afterwards other than in neutral, where the engine will rev faster. Unfortunately the engine revving faster in neutral gives you this impression that there is all this freed power and will rev faster in gear too, which is the mostly likely cause of the placebo that makes you think your car feels faster in gear too.

You don't always have to try something to know if it will work or what it's effects will be. That's why they have these things called math, physics, engineering, etc. A good engineer knows where theory and reality diverge, but in the case of accelerating a mass, I'm sorry, but it's really that simple.

But from your comment:

it is clear that you either don't understand how most all dynos measure your engine output, or you aren't familiar with the physics responsible for the gains from lightweight components. In either case I don't understand why you would attempt to argue a point. Either get educated on the topic and make an intelligent argument, or admit that you've learned something new.

 

Dude - save your fingers....you are still missing it. The fancy formulae only work if you have variables to plug into them. At <3000 rpm where the gains are, most dynometers are not reading accurately.

There are those who wax theory covered up with facny formulas and then there are those who live in reality and while there may not be a hard fast textbook answer to why a gain is made, it is still made and while not measureable, mostly indisputable for those who have tried them. If your engine goes faster, so does your car. Now go read up on that formula, but please don't paste it here until you can speak from experience. I've seen more lectures on this topic in three years than a phd student.

 

Who cares what the dynamometers read? For gains of this order the error and run variability dominate. And what does the dyno not being able to read properly below 3000 rpm have to do with numbers I'm plugging in to my formula? Whatever the true engine outpout is below 3000 rpm, regardless of how accurately I know it, I can very accurately tell you what precentage of that will be gained from the lightened component.

You've admitted ignorance on the topic, which is fine. I was just expecting more out of you from just the few posts I've seen of yours in the off-topic forums. You request intelligent political discussions there, but can't hack it here.

Again if anybody would like to make an intelligent argument as to why a lightened pulley can violate basic physics, I'm all ears. And "I can feel it, I really can! I believe, I believe!" does not count. It may count in your belief structure, but not in mine.

 

................nothing like bench racing.........

 

Right. If the Nissan engineers didn't bench race, you wouldn't have a car.

I machined my own vortech pulley, I built my own custom turbo kit on my last car, I swapped out the bottom end on my own in my garage, I hacked my own ECU and decoded the checksum algorithms and modified the maps, I do it all. And with graduate degrees in mechanical and electrical engineering, I know where reality meets theory, and when I spot a hater.

I'm just trying to save some of you the headache and the money of a lightened crank pulley. Some can't handle the truth, and will fight it to the death even though they have no clue what they're talking about.

 

MechEE, I'm glad to see there's a bit of sanity in this thread.

Up until owning this car, I've never heard of people buying pullies JUST for the lighter weight....what marketing genius came up with this one? For a street car it has absolutely an abysmal price/performance ratio. A 4lb difference in a small diamater pulley? Come on guys...

An underdrive pulley, however, can obviously have more gains assuming all the accessories are belt driven.

 

HUH??? Last I checked, nissan is and has been involved in several forms of motorsports.

 

I could put up pics of me pulling on a coupe right after my pulley mod but I and everyone else would attribute gains to something else. Even real racing ends up a subjective moron fest.


Don't save anyone the headache you never had. You can machine an a$$hole into a cucumber for all I care but unless you own and operate and test your own underweight pulley, get your six eyes out of a text book and step into reality. Your 12th grade physics lesson is worthless if you don't have any inputs from real world data and not frikking textbook blather. How about you take my science lesson? Take a crank - lighten it by 10 pounds the frikking thing goes faster. You don't own one; you haven't put anything up but conjecture.

Save everyone the headache and give us advice about something you know about and have actually tried or even held in your llittle hands.

Oh and please, could you fill in all the variables in that cut and paste equation of yours and show us the actual evidence of no gains. Preach theory - I 'll be winning at at the track with whatever combination of mods work for me while not taking advice from the likes of you.

 

LOL! Hopeless. Beating you over the head with the logic stick only makes your skull thicker.

Enjoy your mod, no skin off my back. Those that understand my argument will appreciate it. Man, did nobody pass high school physics here or what? Pure intuition should let you call bull**** on purely lightened pullies, let alone solid theory to back it up.

By the way, I've got some lightweight lug bolts for sale. They add 10 dyno proven horsepower! And I can REALLY FEEL the difference! Only $100. How many sets can I sign you up for? Man, I'm gonna make a bundle on you suckers!

 

It's my understanding that the OEM pulley weighs 7.5lbs and the aftermarket pullies weigh in at ~1.5lbs or a 6lb loss.

I'll just say that the true 350Z "race" teams wouldn't be caught dead running lightened crank pulleys. I know that Nissan's race teams use much heavier fluid-style crank dampers. The fluid dampers do a far better job a prolonging engine life under high stress and revs plus the crank resonance is dampened so much that the valvetrain actually becomes more effective.


Everything MechEE has stated is true. As you enter each successive gear, the gains disapate dramatically. It's torque multiplication, fellas. The same thing holds true for lightened flywheels. SCC, Grassroots, Motor Trend, Muscle Mustangs & Fast Fords, plus many others have posted the same formulas and calculators plus some interesting torque-in-gear graphs showing how the gains fall dramatically, gear after gear. Only in first gear is there any real "gain". Seeing that you're in 1st for about 2.5 seconds, a 2-3whp gain isn't going to do you much good because that extra 3whp is going to accelerate the car about one hundreth of a second quicker. It's really not rocket science. MechEE is simply giving you all the calculations.

 

So are there gains or are there not . WTF is wrong with saving precious launch time and having a stronger first gear. No one stated there were massive gains once the "mass" was moving along. If nothing else, I can tell that my car launches better as it bogs less thanks to the first gear gains you ascribe to the pulley above. I never said I felt tremendous pull once the car was moving at a good clip now did I???

The combination of mods is what matters and is what I would stress every confused reader here take from this ho-down. One mod may not do much, but the synergy of a couple of mods working together begins to add up. A little here and a little there.

When I pull hard on Z's in my 27 HP less (stock), 200 pound heavier car - there's no doubt in my mind that folks like MeChee do nothing but a dis-service to this forum trying desparately to impress us with thier vast knowledge and credibility that doesn't apply here while never having owned the mod. Again I ask: How can a 6, 7, 10 or half pound decrease in weight at the end of the crank not provide gains in a gear???? Maybe I'll do a handy dandy cut and paste of the pyhsics formula that says if you have less mass, acceleration is positively affected for a given amount of force or thrust. Don't lose sight of the trees for the sake of the forest.

And I wouldn't have called him out in a such a manner but like I've done with some others before him, I try to stop such misinformation based on theory's that work on paper (Still waiting for the numbers to be crunched but have a feeling that variables can't be produced just like real world support for his argument) and try to keep a more prosperous level of information flow for our new readers.

This argument is not settled and for him to make such ridiculous claims while both sides argue with pretty much nothing to support their claims (oh except owning other G's and Z's - but formula's trump ultimate results around here) his omniscience is unwelcome and prickish.

Spread baseless misinformation and suddenly propose to have the answers that aren't there and I'll call it out. Our readers deserve better.

 

It is you who is doing a disservice to the readers. There are likely many who understand as little about the car and dynamics as you, and are equally scared of theory that they can't understand, and may somehow find comfort in your flawed logic that brings them to the answer they wish to find.

It is quite humorous that you compare my argument to a religious faith, yet your argument relies solely on "but other people believe it" and "i can feel it, i really can".

Again, I have some lightened lug nuts for sale. Interested? I mean, they're LIGHTER, they MUST make the car accelerate faster! $100 per wheel. You know you want it.