I'm new to this particular forum but I come from HA.com lol.gif

Well anyways, I saw that kspec and shark racing both sell complete pulley sets. However the sharkracing set specifies that it comes with new belts needed because of the diffrent size of the new pulleys. This of course means that the accesories are being underdriven correct? ok then;

But when i asked at the kspec forums if their kit came with new belts, they told me that their pulley set does not need new belts because they dont underdrive the accesories and gain the extra HP through weight reduction alone. and Im like WTF!!

Would a correct conclusion be that the shark racing kit is better cuz it theoretically would gain more HP than the kspec kit?

Course, the flip side to that coin would be that the kspeckit is better cuz since it won't underdrive the alternator and water pump, the cooling efficiency of the car and the electrical system won't be affected?

Would anyone that has bought either kit share their thoughts?
Am i right in my assumptions for both kits?
Any help will be greatly appreciated.

 

No, that conclusion wouldn't be correct.

The JSpeed ones at Kspec.com don't change the diameter, just the wieght. Everything will run like it's supposed to but you just won't be turning as much weight so it'll get you some lost power back.

The SR ones, if they underdrive, are lighter than OEM, and smaller. Smaller is going to make the accessories work faster and harder right? Gonna make those pulleys spin faster.

So, your other conclusions are correct.

I have the JSpeed set from Kspec obviously, they are very light and look great. I haven't put them in yet so I can't tell you too much, I just don't have a garage to do my mods in.

Lastly, I just don't see how you'd get MORE HP back from Underdrive pulleys.

Welcome to the site mang, hope ya like it.

 

I wanted to research the whole underdriving thingie and came upon this nifty FAQ at the UR page:

http://www.unorthodoxracing.com/faq_pulleys.html

And apparently I was right in my assumptions... shock.gif

And also i found the answer to the dilemma that was once debated over at HA.com, about the crank pulley being a harmonic damper. I think you posted in on that also redz; its the 4 statement of the FAQ.

So basing my thoughts of that particular FAQ, i believe that the SR kit would gain more HP than the kspec kit.... If only the service were as good as kspec... *sigh*

BTW, IMO that faq should be made a sticky.
Hope this helps someone else also laugh.gif

 

I still don't see how the underdrive ones will get you more HP mang. It should just be the weight.

Also, most likely we can get you the same ones they sell. David just doesn't like to sell things he thinks aren't good for you.

 

the kspec (jspeed) pulley set is the water and crank pulley, right??

 

Yes.

I belive.

 

well.. that is because you are looking at it wrong Redz.. A pulley set is just not a cheap way to transmit power from one point to another.. but often include a ratio. Take a mountain bike for instance... when in the top gear.. the BIG gear on the crank is turning one of the smallest gears on the wheel. That little tiny gear in the back, probably with about 8 or 9 teeth on it.. is spinning like crazy to keep up with the big 48 toothed ring in the front.. It also take a LOT of power to spin that little gear to quickly.

Ok move down to the middle ring on the crank and the big ring on the rear... they are much closer to equal.. about 38 teeth on the front and 20 on the rear... Get on the bike and take off from a stand still.. you are going to have no trouble at all making the bike move as compared to the top gear from a standstill. At low speeds, this is an efficent gear and you do not have to work as hard...

Now lets get down to the granny gear.. with between 18 and 15 teeth in the front and about 20 in the rear.. you are running almost a 1 to 1 ratio.. this is the EASIEST gear to get the bike rolling in.. it takes almost no pressure on the pedals to get it moving.. the downside, you have to pedal like crazy to ride as fast as a normal person can walk...

Now lets apply this to the crank and accessory pulleys on a car. If you downsize the crank pulley, the engine needs that much less power to turn the accessories.. but, it also turns them slower. At normal road speeds, you will NEVER notice... at an idle you will. Your lights will dim some and there is a greater chance that your waterpump is not working well.. thankfully there is almost no thermal load on the car at idle... At higher speeds, the power that was being used to turn the alternator, water pump, and powersteering is now being used to put the power to the wheels.. The accessories are using less power to be turned because it is easier to spin them with a smaller ratio between their pulleys and the crank pulley.

Being lighter is only the icing on the cake..

 

UR's documentation states that underdriving only makes up for 15-20% of the hp gain. The rest is from lightening the pulley. ~2.7hp/lb removed

 

Hmm...

Cool.

 

I actually was thinking in the same direction as MAd Machine actually, but instead i had to actually go to my mountain bike out in the back and see for myself... LOL. But as Jon GTR put it; according to UR, the underdriving part of the pulley IS the icing on the cake. So I guess it depends on what your tastes are. CUz, well i got a thumping soundsystem; about 2000w total(1200w RMS sub amp+ 400wrms Front stage amp). So i have to take that into account. shock.gif

But, I'm prob goinna order the UR pulley(later next month when i get payed by my summer job; student at college lol) and the JSpeed power pulley set. If my lights dim too much, ill prob add a second battery while i get even more money to have my alternator rebuilt and wound with more magnetic material(cheap way to up the amps of the alt.) and see if it betters. :roll:

Course, the easier way would be to just order the full Jspeed set and not worry about underdriving, but I'm 20 years old... You know the alpha male attitude always gets in the way of making rational choices.. :twisted: