SOMbitch

iTrader: (8)

Anybody know what a March weighs? I shoulda weighed mine before it went on

regency

iTrader: (15)

i would like to have some actual time and or HP comparisons but i dont have a dyno close or the time to do it. What have you guys gained in the 1/4 by adding the pulley, i didnt gain a thing, and im thinking its the weight of it.

89Formulaws6

iTrader: (52)

i was curious average whp gains

SIC LSX

iTrader: (10)

9-12whp is what i have seen! My car picked up 19whp with ported TB and pulley at same time

SIC LSX

iTrader: (10)

everything ive found
ASP - 8 lbs.
Stock truck - 10 lbs.
Powerbond - 12 lbs
Summit - 12lbs
March - 11lbs
ASP old non SFI - 6lbs
stock f-body - 10.5lbs

nemss1

i have heard many good things on ASP and it is lighter (not saying lighter is always better)

with an ASP, i like how an underdrive alt pulley is an option too

vjo90rs8

iTrader: (9)

You could use the ASP overdrive or underdrive pulleys with any crank pulley. And remember, rotation weight is more important than static weight. The crank is more worried about how hard it is the spin the pulley not how hard it is to keep it up.

nemss1

does the ASP crank pulley have enough rotational weight to where it wouldnt be making less power than the other brands of pulleys?

vjo90rs8

iTrader: (9)

The moment of inertia of each pulley will depend largely on where the mass of the pulley is located. A pulley that weighs 12lb but has a majority of its weight at the outer most edge like the stock crank will have a higher moment of inertia than a pulley the same size with its weight evenly distributed throughout the pulley. When someone says, "damn, my SLP/Powerbond/Summit pulley weighs more than the stock pulley, I think that offsets any gains" that doesn't mean much because you can see that the UD pulleys are 25% smaller in diameter and have more of their mass towards the center of the pulley. Just think, a pulley that weigh 100lbs but is only 1" in diameter is probably easier to rotate than a 1lb pulley that is 100" in diameter. Don't feel like doing the math but you get my point.

nemss1

ya that makes sense. it would be interesting to know which one has better rotational mass transferred away from the center on all underdrives, like a comparison

Chhh Chhh

iTrader: (2)

all the sameeeee

SOMbitch

iTrader: (8)

Thanks good info!

vjo90rs8

iTrader: (9)

just for fun.....
R (stock pulley) = 1
R (UD pulley) = .75
Rc = radius of center of mass for stock pulley

Assume UD pulley has its mass distributed evenly which I'm sure isn't true but it kind of looks like it is and it allows us to use the disk MofI equation.

Assume the stock pulley is like a hoop with its center of mass at about 60-70% of its total radius (assumed because it looks like it is a hoop with the addition of the 3 structure pieces in the middle, without those structural pieces I would say its center of mass is probably 75% of its radius but those help move the center of mass in towards the center, lets pick 60%), so Rc = .60 (best case for stock pulley, not sure)

I (disk, UD pulley)=1/2MR^2
I (hoop, stock pulley)=MRc^2

I (UD pulley, summit) = 1/2(12)(.75^2) = 3.38 (don't care about units)
I (UD pulley, ASP) = 1/2(8)(.75^2) = 2.25
I (stock pulley) = 10.5(.60)^2 = 3.78

Probably very inaccurate but more of an idea. I'm sure 90% of the gain is from underdriving the accessories.