I m starting to suspect that I have a 5 psi pulley on my used head unit. I just barley see 6 psi at max rpm. The belt that I got for the seven psi is a real bear to get on if it is a 5 psi. Does anybody know what the size of these are and where they are measuring? Mine measures 4 3/8" OD max size of pulley. I need a reference someone please help there is very little info out there.

 

Is this on a D1 or a P1? If your pulley is around 4.60 - 4.75, I would expect to see about 6psi @ 6000RPM on a stock LS1 with headers, cats, and exhaust. Note that my only point of reference is my original blower setup with my original motor where I made about 6psi with a 4.63".

The problem is, you won't find a chart out there that says that a certain size pulley equals a certain amount of boost -- not from ATI anyway. You might make 7psi with a certain size pulley, then make 6psi if you add headers, exhaust, and no cats to the same car. Boost will vary from setup to setup even with the same pulley.

If you want to verify the size for sure check the pulley for inscriptions. I think ATI stamps the pulley size on the side of the pulley. It might be on the side closest to your blower, so you might have to pull it to verify (if you think that's worthwhile).

 

P1SC I believe that you are on to something I do have headers and ported heads. I will probably have to go to a smaller pulley to make up for better flowing abilitys. So I would say that I do have the "standard" ATI pulley. Thanks for the info!

 

I have a 3.7 pulley that I will sell you cheap... That would give you lots of boost for your engine...

VR

 

How much boost do it run for you.

 

that pulley could run 9 or 10 lbs of boost at top rpm.. or more boost at a lower RPM than the pulley you have now.. it will depend on how you want to drive it.

VR

 

Interesting. I actually made 6psi with the 4.63" on a D1 (headers and exhaust were the only "flow" mods besides the blower). I'm surprised you're not making less boost, a 4.60ish pulley is pretty big for a P1.

 

Not necessarily. If you can make the power you want by making your motor more efficient I would stick with your current pulley. I would rather make 500 rwhp on 6 lbs of boost as opposed to 9 lbs of boost for example.

Mark

 

So what is your set up?

 

I believe the standard pulley that comes with the kit is a 4.1" and the 5lbs pulley is a 4.38". At least thats how it worked for me. I started with the 5lb and a year later went to the 7lb.

 

I have a 4.63 pulley making 10 psi at redline with the D1SC. Details in sig. Of course ATI said it shouldnt be making that much and cant explain why it is, but whatever.