Just to clear up the obvious confusion I'm seeing. The accessory pulleys are the same diameter as the original stock accessory pulley but they are significantly lighter. All the diameter change is done from the crank pulley, this makes it smaller so it is lighter. So buying the full set will improve total performance by another 15-20% more over just the crank pulley. So the additional cost is well worth the increase in performance. The FAQ on our web-site lays out all the facts. The accessorys maintain all factory specified output levels (a/c efficiency, p/s feel and charging) even up to a 600 watt stereo.

Respectfully,
Shawn

 

Let's keep this honest....

1- The change in diameter of the pulleys is where almost ALL of the power gains (even if it is a small gain) comes from. The weight of the pulleys doesn't mean much at all. Think about it-- once the engine is started, the pulleys are always moving, so the weight doesn't matter nearly as much as it would with something that is always stopping/starting.

In other words, the pulley weight isn't going to give you another 15-20 percent gains. It is the UNDERDRIVING of the accessories that gives the extra few horsepower.

2- Any time you install a set of underdrive pulleys, the accessories (A/C compressor, alternator etc...) WILL in fact turn slower than they did with the stock pulleys.

What does this mean? Simple- the alternator, under some condtions, will have to work harder to maintain a certain voltage output. And when an alternator has to work harder, it creates additional drag on the engine.

The A/C compressor is similar-- under certain conditions, it will have to cycle on and off more often, or even cycle on for longer periods of time to meet the demand of the climate control settings.

I'm not saying that underdrive pulleys are not a good idea..... You can indeed gain a few HP from them. But just lay out the facts properly......

 

You know, after reading the FAQ on your website, I think it's a damn shame that you people have to spread false information in order to sell your product.

You stress over and over that the pulley weight is where the HP gains come from. The underdriving is secondary, you say....

Let's examine this-

When it comes to rotational weight, like wheels or pulleys, what is most important? Having lower weight on something that is always stopping and starting (like a wheel, for example), or having lower weight on something that continues to turn (like pullys, for example)?

Of course the correct answer would be the starting/stopping object (wheels).

Once your pulleys are spinning, right after engine start-up, it takes very little power to keep them spinning. As a matter of fact, the actual DRAG that the accessories produce robs 1000 times more power than the actual weight of the pulleys themselves.

Furthermore, I see you measure the weights of the pulleys in OUNCES to compare differences in weight between your pulleys and the OEM pulleys. Now, even if weight DID make a difference, how can you possibly expect anyone to believe that a few ounces could even make a difference?

The fact of the matter is that ALL undrive pulley sets make power the same way-- that is, they underdrive the accessories, which in turn slows them down, which "frees up" more of the HP that the engine is already making for actual propulsion, instead of turning the accessories.

 

Boy, lots of missunderstanding on this subject! What has to be remembered is that there are two methods of measuring horsepower - a brake dyno and a chassis dyno. The former loads the engine to a set rpm and then measures the torque at that static rpm. The chassis dyno measures torque while accelerating the dyno drum.

Reducing rotational mass by the use of lighter pulleys will have zero effect on a brake dyno, as the posters above stated. However, on a chassis dyno the reduced mass will show a modest torque increase. This is because it takes power to accelerate the pulleys - lighter pullies = less power lost = more torque measured on the dyno.

Now, which dyno measures power the way we actually use it - the static rpm brake dyno, or the chassis dyno? Hint: acceleration matters.

 

Well he just stated that all the ACC pullies are the same diameter, but the crank one is not. I am with you on the fact that the weight savings isn't going to make a night and day difference. The crank pully; however, is smaller in diameter which would over all be underdriving all accessories at once, therefore freeing up more power.

04' G35 / 6MT / Tein Basic Coilovers
Volk 19" GT-7 Gunmetal

 

"Think" whatever you want, but the physics is real. Example: your alternator. At normal charge it puts out ca. 25 amps and 15 volts. That's 375 watts total drag on the engine. Let's double value that to allow for poor efficiency, so we are at 750 watts of drag on the engine. Guess what, one horsepower equals 746 watts, so disconnecting the alternator completely will only gain one horsepower. But all we are doing is underdriving it by 20%, so the gain from underdriving alone is just 2/10s horsepower. Similar losses are seen from the other accessories.

The thinking man can see that underdriving alone gives only a small power gain, just like Unorthodox states on their site. I am not endorsing their products at all, just validating their physics. But regardless of how it works, for most G owners, what matters is the fact that gains do occur - which they do. Just don't expect too much: 3-5 hp is probably normal based on the dyno sheets I've seen.

 

I do agree with you Hitman - the underdriving is what produces the vast majority of gains (~4-5whp) on the dyno, not the weight savings. I am interested in buying their crank pulley and it looks like a quality piece, but that doesn't mean I disagree with some information on their site.

Without going into the physics and equations, just look at a flywheel. Not only is it much heavier, but it is a much larger diameter rotational mass (weight that is farther from the center) so it soaks up alot more horsepower. Weight savings here should be much more dramatic for gains. Yet dynos I've seen show even a 10+ lb lighter flywheel only nets you a few HP gained. So compare this scenario to a significantly smaller diameter rotational mass (the crank pulley) where weight reduction has less effect, and now take off a much smaller amount of weight, and you now end up with something with a fairly negligible effect.

Of course what also matters is what gear you are in - in higher gears the engine needs to accelerate the pulley much slower (it is turning at closer to a constant speed) so effects of less weight are again negligible. In say 1st gear I bet it helps a bit more (as does a lightened flywheel) since it has to spin that weight up very quickly.

2004 Black 6MT

 

Fluid,

Do you really think that pulleys of a few ounces less in weight could gain, say, 5 horsepower?

Do you understand that something ALREADY in motion (such as pulleys) are much easier to accelerate than something static?

 

Fluid,

I'll agree that I HP equals 746 watts, at least that's what I remember from my school days.

But to say that disconnecting an alternator that is producing 746 watts of power will equal a 1 HP gain is wrong. Sorry, but it doesn't work that way. It's just not that simple.

Also, to say that your average alternator puts out .25A and 15V is wrong. The voltage varies due to demand.... demand of accesories, demand from the battery (after start-up) etc.....

The more "demand" that is required of an alternator, the more "drag" is created to turn the alternator. The very fact that the alternator will be underdriven (yes, even by 20%) means that the alternator will, under certain circumstances, have to work harder.... And we all know what that means....

 

G35MadMan,

Yeah, I'd say you'll get 99% of the gains with just the crank pulley alone.

Personally, I wouldn't buy the other pulleys, since they are the same diameter as the OEM pulleys.

 

Our own testing has shown without a doubt that wieght reduction is the key to "acceleration" HP as measured by a chassis dyno. This translates into seat of the pants improvements. We tested changes in the amount of underdrive and time after time the weight was the determining factor in HP development. Its called moment of inertia which occurs at any point when you change speed from any steady state. examples are from idle to WOT, from cruise RPM of 2000 RPM in 5th gear to a two gear downshift, etc. These transitions all require power/energy and the reduction in weight dramaitcally aids in the quicker acceleration from any steady state. As for the dyno numbers we have seen they have ranged from 5-9 on the crank pulley and 9-13 HP at the wheels on the pulley sets to date. The 3.5L has a long break in period which adversly effects dyno outputs until the break in is complete. Our prototype car, 350Z from Smithtown Nissan, saw a little over 10 at the wheels with the 3 piece kit. The results are impressive I can assure you.

Respectfully,
Shawn

 

Shawn,

If what you say is true, then it would be apparent that a set of your lighter weight pulleys would give HP gains even if they were the same exact diameter as OEM.

Do you have any dyno graphs to prove that?

I realize that even the same car on the same dyno on the same day will have different results, but I'm just interested to know if you guys have any type of dyno results to back your claims (claims on weight, not underdriving)

 

My concern is the A/C. Summer here in Phoenix requires you to have the A/C cranked for almost 6 months straight. So essentially anytime you start the car, the A/C will be on and running until you turn the thing off. Could having aftermarket pullies cause any problems there?



BS 6MT/Premium/Navi/%5 Tint/Escort 8500/12' Rockford Fosgate Sub/Borla Exhaust

 

Hmm, I do find it interesting though that nissanperformancemag.com got more HP (6.5hp) from the crank pulley alone on their altima (with the VQ35DE engine), than they did from the whole set (5hp gain) on their 350z with VQ35DE engine.

http://www.nissanperformancemag.com/...r02/altima_ur/
http://www.nissanperformancemag.com/august03/350pulley/

2004 Black 6MT

 

Good point, Sinurgy...I lived in Phoenix and Scottsdale and the air HAS to be on...Long term use of pulleys in that environment might be an issue...I'm in LV now, but I wonder...

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