Thanks for the physics lesson; unfortunately, my graduate degree is in computational physics so I wasn't really impressed. Show me working knowledge of Schrödinger's equation and I might be a little more impressed. I suppose I could change my screen name to something like "Physics Guru" or some such other tripe as that...

Now, back to the subject at hand.

Lightened pulleys work on the same theory as lightening the wheels. Any rotating object object makes something more of a difference than it's mere weight would cause, due to the rotation. Now, as you have pointed out, the relatively small diameter of a crank pulley makes the difference much smaller than a lightweight wheel would make, but it makes a difference none-the-less.

Now, if I remember correctly, the stock pulley weighs on the order of 6 kg's. The UR UD pulley weighs about 1-2 kg's. This is a bit more of a difference than your 2.5 kg constant used in your equation, AND, the overall HP of theVQ35 on the G is a bit more, I would say on the order of 220 whp as opposed to the 16 whp you used. Thus, a paper napkin calculation would be on the order of 2-3 whp in 1st gear. By the way, your math looks correct at a quick glance, though I didn't go over it diligently.

The lightened part is merely one aspect of it, however. The other half of the equation (well, more than half, really) is the the underdrive. Many underpowered cars have a cutoff switch for the A/C when the throttle is depressed past a certain point. This is because the A/C, like everything else driven off the engine crank (water pump, alternator, etc...) takes some of the force that could be used for acceleration and puts it towards some other use (necessary uses, admittedly) So, logically, if you underdrive these accessories, you use less force to run them, and then have more force for the aceeleration in the whole accleration equals force over mass thing you were so kind to mention.

Oh, and one other point: the underdriving of the pulley also brings the mass closer to the center, thus decreasing the moment of inertia even more so over the stock pulley, thus pushing the gains from the reduction of the moment of inertia to about 3-4 whp (in first gear, of course)

Finally, I should mention, in explanation of the above, that I have NEVER been talking about a solely lightened pulley, but rather a lightened AND underdriven pulley. If that misconception has happened, then accept my apoligies.

Of course, since you are a mechanical/electrical engineer, you allready knew the above, and it is merely for the benefit of others who don't.

Dave

 

Wonderful! You so quickly dismissed the use of theory that I never would have guessed. I apologize for my rudimentary physics speak. My BS in ME had GE requirements of 5 terms of physics, two of which are quantum mechanics, though I admit that I haven't used Schrodinger's equation since.

Ah, I was under the impression that it was lightened only. Underdrive is obviously a whole different ballgame, and depending on the underdrive ratio there is room to free up a bit of power, and it is nearly impossible to quantify in theory (unless you have accurate numbers for the parasitic losses stock). What's the Unorthodox underdrive ratio? Let's say it's 80% of stock. Even picking reasonable numbers (say, 30 hp of accessory drag), that's still just ~6 hp, but at least it's something, and is independent of the gear.

I personally wouldn't underdrive my water pump / alternator / power steering just for a couple hp, but that's a personal choice. Don't mind me or take offense, I just like to argue! (It helps get to the bottom of things)

 

People need to understand that the VQ isn't a Ford 5.0. The accessory belt doesn't drive the water pump. The timing chain does that. Many of these "underdrive" claims for the VQ UDP stem from the old 5.0 Mustand days where underdriving the highly parasitic water pump did make some gains.....at the cost of overheating your 5.0 if driven hard.

Also, the stock pulley does not weigh 13lbs+. It weighs in around 7lbs or 2.5 kgs.

 

Interesting! I need to take some closer looks at the engine layout. As soon as the 2006 service manuals become available I'll be all over 'em.

 

Hmm, it felt heavier when I did mine. Either way, the point has been made that the underdriving is more important than the lightening, although they both play a part.

As far as I know, the belt drive the alternator and the A/C.

Between the underdriving and the lightening, it frees up some horsepower, incontrovertably. I think what is up for discussion is how much it frees up, and whether that is worth any POSSIBLE 9note that I didn't say certain) risk to the engine, through POSSIBLE loss of damping characteristics.

My opinion: it's worth it, as evidenced by the UR pulley on my G.

Dave

 

I think the underdrive is somewhere around 15%. On paper, it should produce more power, but I think it's pretty minimal.

Yep, plus the powersteering pump plus a couple tensioner pullies and a pulley, that depending on year, runs the mechanical fan or the same pulley, but with no mechanical fan attached.

 

So what's the Final Word on the Unorthodox Crank Pulley? It seems like we all agree that there is a chance the pulley could damage your engine if it's installed incorrectly. We also agree that the crank pulley is the only one that produces power and the others are for looks, right?

Performance mods are suppose to make your car faster. It doesn't matter if you increased your peak HP or your car feels lighter. What's important is that your gets faster. Regardless of the cost of this pulley, do we agree that this Pulley would make your car faster? Or would it make your car a 100th of a second faster and just be a waste of our time?

 

i havn't posted in this thread since september. but it looks like it hasn't gone anywhere. the only dyno i've seen in this post (dsskyline, a few pages back) shows that the pully adds 12 hp, at least on a 5at. (and even more torque - and i'm not looking at his spikes early in the rpm). I've read everything you guys said, but i don't understand how you can refute the dyno. I've seen no dynos from the people saying it doesn't do anything.

 

Wow someone actually read this and didn't get lost in the forest for the sake of a tree! You are right and you win the prize! You'll typically notice the hottest debate in most other reasonable circles would never get this far as the folks who say it does nothing usually have never tried it and preach thier hogwash from atop the shaky ground of, "never tried it but if you can't prove it works then it doesn't". You won't see any proof it doesn't work mister!

 

You're probably not going to see any dynos where an underdrive set loses power, because there are actually some gains there. What you will find however are many dynos of purely lightened crank pulley setups that don't show any gains (within run to run variance) because the amount of power gained is incredibly small.

 

What do you think of the Unorthodox Pulley? Do you believe that there will be some reasonable gains?

 

Personally I wouldn't underdrive accessories on my car for such small gains. But there are definitely gains from doing so. How much? Depends on the car and the underdrive ratio. But any of the measured gains are definitely not coming from the lightened part. What I find funny is that Unorthodox's marketing chumps claim that a majority of the power gains come from the lightening, not the underdrive.

 

Seems like 11hp from the dyno in this thread is not a small gain. But maybe if people posted dynos to refute that i would agree that the gains are small.

 

11 hp sounds like some decent gains to me, but I didn't think that was the norm. A few more datapoints would be helpful.