Mr.Jadkowski

It seems like a lot of people on here just have a crank pulley as opposed to a whole set (for underdrive). Is it worth it to get a whole set? How much power are you gaining over just a crank pulley?

Vamos_Rafael

iTrader: (18)

set = bling + go
crank = go

Z BOY

iTrader: (41)

use search function. much has been written.

Vamos_Rafael

iTrader: (18)

3-5 hp
gain
from crank
but good for the money

Mr.Jadkowski

So looking at it from a price vs performance perspective, I'd be better off with just a crank pulley?

steakpinoy

You'll be just fine with the crank pulley (assuming you're referring to the Unorthodox Racing, or UR brand). If you get the 3 piece set, you won't get that much difference except the bling factor. This is mainly because the extra 2 pulleys are basically identical in weight and size when compared to stock. Don't forget to buy another belt when you buy your underdrive crank pulley!!!

Another option that I've heard of is the KJR pulley. It's the same SIZE as the stock crank pulley, but it's alot lighter. But I believe the UR crank pulley is a tad lighter than the KJR (by .2-3 lbs or something). Hope this helps.

steakpinoy

Oh yah I forgot to add, if you plan on going FI, you might want to consider the KJR over the UR. I heard that underdrive pulleys don't fare well with forced induction applications

Eldy

salamat pare!

KRJ is about two pounds and the UR is about one pound. Stock is about six pounds.

HarvesterUT

iTrader: (10)

having the whole set doesnt add any power over just the crank. the "math" states that for every 1lb of rotating drivetrain mass you take off yeilds 2.7hp. the stock pulley weighs around 6.xx lbs. The UR and KJR weigh approx. 1.9xlbs and 2.xx lbs respectively. The difference is about .2-.3lbs.

So assume the difference between the stock pulley and a light one is approx. 4lbs. Thats:

4.00lbs X 2.7hp = 10.8hp
10.8hp X 80% (drivetrain loss) = 8.64hp

It's safe to say a lightweight crank pulley will conservatively add 6-8whp.


====================

On the flip side, some people get a lightweight flywheel. I have read some threads where people "claim" flywheels dont add power, but I assume they follow the same rule of 1lb = 2.7hp.

Stock = 28-30 lbs (have seen conflicting reports)
Lightweight = 8 - 23lbs (depending on model)

Assume a 14lb flywheel (many of them are 13-14lbs)

29lbs - 14 lbs = 15lbs savings

15lbs X 2.7hp = 40.5hp
40.5hp X 80% = 32.4hp

This train of thought seems to add about 32.4whp. However, I think most tuners will agree that flywheel gains are not as much as 32.4hp. I would say conservative estimates are around 15-20whp for lightweight flywheels.

southern_info

iTrader: (3)

Let me get this right! The after market crank pulley is lighter than the stock crank pulley. Is there any difference in diameter or is it the same size as the stock crank pulley in that it is just lighter?

HarvesterUT

iTrader: (10)

2 companies make aftermarket crank pulleys for the Z. UR and KJR. UR offers one that is "underdrive" or smaller in diameter than stock. The KJR is stock diameter.

UR claims they make extra HP (approx 1hp) simply by the pulley being under-driven. I think it's simply due to the fact it weighs a bit less than the KJR. The downside to having an underdrive pulley is that you will need new belts to run the pulleys since the distance travelled is less you'll need a smaller belt. Gates makes a belt designed for the UR pulley.

IMHO it's a waste to get an underdrive pulley when a stock size one will provide 95% of the benefits and will save you $$ on the belts.

southern_info

iTrader: (3)

Thanks! KJR is the way to go then.