Pulleys
 

Where are you guys sourcing your pulleys?

The 9lb pulley on Z1's website is ~$155, ConceptZ ~$220, I couldn't find a 7-rib pulley on Vortech...

I saw some discussion about picking up a smaller 8-rib pulley for the SC side...

I know there was some talk on Topgunz A2A thread about the pulley ratios and such but in an effort to break down the monster thread into more manageable pieces, maybe we could talk about pulley setups here :tup:.

Thanks!

I second the pulley info...I almost ready to go A2A but I am only on page 79 of 115ish of the thread...and am having trouble keeping things straight with pulleys, sizes, belts.

/Z/

The slip comes mostly from the serpentine side around the stillen pulley. The 8psi pulley is 3.2" and shotpeened for grip (not sure how effective it is) and obviously has a larger diameter than the 9psi (2.8") pulley, hence will have more traction. There is minimal wrap around that pulley. This is the reason Tbatt sells his extra pulley mod that places a pulley in front of the stillen one to create twice the amount of wrap on it.

Now on the supercharger side we have a 3.2" driving a 3.2" or 1:1 ratio. Here we do not see slip but can change these out to accomplish more boost instead of swapping serp side pulleys. The problem is that the idler pulley on that side has little room to keep tension on the belt when the pulley size drops. Pending you drop the pulley that comes directly off the shaft of the SC. The jackshaft pulley could go bigger but then you cant get the belt on. So, to remedy that you can buy a smaller SC pulley, directly off the SC, and then buy a larger idler pulley (3") so you still get the throw distance you need to keep tension on the belt. j

Another method is to get a smaller supercharger pulley but a larger jackshaft pulley so you keep the same amount of tension on the belt without needing a larger idler. This is what I did. 3.4 jackshaft and a 3.0 supercharger. This keeps the belt tension the exact same but will spin the supercharger about 10K faster than the 1:1.

Those pulleys from vortech are $99 each. So the cheaper method is the get the smaller supercharger pulley in a 3.0 or 2.8, depending how fast you want to spin, and the idler pulley that is $30. This method saves about $70 overall.

At least this is what I recall from everything I did almost 2 years ago. Is everyone confused yet?

Tbatt can you confirm this?

You are dead on!

Just to be sure I am understanding the names of the different pulleys, attached is my guess at them. Can someone confirm I understand correctly?

Thanks
/Z/

That is correct!

Except I would remove the 8psi from the SC and move it to the serp jackshaft pulley as that is the pulley that is swapped out from stillens definition of 8psi pulley or 9psi pulley. The SC pulley that comes off the shaft really doesnt have a "psi" denoted to it.

Ok, thanks for the clarification. So up 4 posts you did a great explanation, however I just want to be sure of something...you mentioned "This is what I did. 3.4 jackshaft and a 3.0 supercharger"...so that means in my picture with the way I happened to label it, you changed the jackshaft on SC side pulley and the jackshaft on serp side pulley, correct?. Aka...both pulleys on opposite sides of the mounting bracket.

I think my previous post has the wrong understanding...i think you replaced the pulley off the shaft of the SC and the jackshaft pulley...so you changed the two pulleys that are both on the SC side. Am I correct here?

Close but not quite there. The only drive pulley that changes is the one on the SC. When you go to a smaller diameter SC pulley you need a larger SC idler pulley to take up the slack.

I changed the Jackshaft on the supercharger side and the supercharger pulley. Those come stock at 3.2 and 3.2. By going to a 3.4 and 3.0 it is the exact same tension on the belt as stock. It also spins it the same ratio as going from the stillen 8psi pulley (3.2") to the stillen 9psi pulley (2.8")

Here play with this. Our crank diameter is 5.75 and redline is 7500.

https://vortechsuperchargers.com/pag...eed-calculator

Even with your kit? Could you install the old sc pulley as the idler pulley or is it not compatible and/or big enough?

Not compatible, you have to use a larger idler pulley if you go to a smaller SC pulley.

There are several ways to get to a 9psi drive system. You can either spin the jackshaft faster and leave the SC drive belt system as is (this is how Stillen does it) or you can keep the serpentine drive belt side stock and go to a smaller SC diameter pulley. Either way you spin the SC faster which increases boost.

When you spin the SC faster, it takes more power to do so which leads to belt slip on the serpentine drive belt at the jackshaft pulley. My kit gives the belt more wrap (contact area) on the jackshaft pulley and eliminates the belt slip.

When you increase boost, you increase the amount of power that is needed to drive the SC. At 9psi it takes around 60hp to drive the SC. That is a lot of power running through the serpentine belt. That is why my kit includes the HD belt. It can handle the load and the additional pulley insures that the jackshaft is getting all of the power to the SC. With a SC, it takes power to make power where a turbo is kind of "free" power.

I like the linear power curve of the SC. I can look at my tach and tell you how much power the engine is making. It is purely a function of throttle position and RPM. I love it!

I purchased a 9lb jackshaft pulley and I also purchased a (if I'm not making the power that I want) 2.87 suoercharger pulley. Of course I have your kit. Supercharger is being installed this week and goes to Seb on Tuesday for tune.

So, what you're saying is that I can install the 9lb jackshaft pulley without changing the idler pulley but if I want to use the 2.87 pulley then I'll need to install a larger idler pulley? You're tensioner kit wouldn't take up the slack of using the stock idler pulley?

I'm hoping to not have to use either of the pulleys as I'm installing an si supercharger and Seb thinks he can hit my numbers with the stock pulleys but I just wanted to have back up pulleys just in case.

Sorry but you are confused by the two drive belts.

My kit goes on the serpentine belt that is driven by the crankshaft pulley. That is why I include a longer belt. The other belt that connects to the SC also has an idler that is used to adjust the belt tension. If you switch to a smaller than stock SC pulley you won't have enough adjustment with the stock idler so you need to go to a 64mm idler pulley to take up the slack (Gates #36225).