youngrigo

I have a ATI Stage II kit, P1SC making 8lbs with a 4.63 pulley. I have a 4.25 pulley and wondering how much boost i should make with the new pulley??

regorih

Not sure from who I read this but it's from one of the blower gods,

For every .1 you decrease the pulley, it will equat to 1lb. Of boost increase.

I would say you would be in the neighborhood of 12 lb.

joshtownsend

Its a good estimate...but that seems high for a 4.63 pulley... Our you running dual intercoolers or something?

1redz06

Does sound high for the 4.63 pulley does the car have any other mods other than the blower kit.

youngrigo

It has LTs no cats a small blower cam and yes on the twin intercoolers.. it's making 585rwhp and 493tq. The boost does seem high for the size pulley but the boost # seems about right for the HP # imo

youngrigo

I would think I would loose boost with the twins and pick up boost if I went with a less restricted front mount if... btw the cam is a 219/227 115lsa 600+ lift

youngrigo

One thing I forgot to mention was that I chenged out the inlet tube to the blower from the little plastic one procharger provided to a 4in inlet with a 4in filter... which I'm sure I picked up like 2lbs with just this mod... I was making 520 @ 7lbs then I removed the cats added the cam and inlet and now I'm at 585 with 8lbs

joshtownsend

you got it backwards.. boost is a measure of restriction.. You would loose boost with a front mount but make the same HP... easier on the motor

youngrigo

I thought anything you do before the motor would gain you more boost and anything you do to the motor and after will loose boost... maybe I'm wrong... either way it looks like 4lbs increase with this other pulley... hope my stock block can hold it

95wht6spd

The twins are more restrictive hence more boost V's front mount. But your cam and LTs will reduce boost.

Z06supercharged

Cmon now throw some E85 in that and boost that sucker up..You know you want to.
I agree just that pulley change will get you about 12 psi. What size injectors do you have though right now?

youngrigo

I have 60lb injecters at the moment... Thinking of going with meth if i throw this pulley on! Just kinda scared as it will probably be close to 700hp on the stock block

bullitt4110

You'll need meth at those boost levels. On my old car I ran a 3.85" pulley which netted me around 12-13psi and 605rwhp on a mustang style dyno, never had a chance to run it on anyother dyno but another supercharged C5 that dynoed 525rwhp on a dynojet made 465 on the dyno I ran mine on.

youngrigo

added meth to the car now I have to decide if i want to go to the 4.25 pulley or just go down one notch to the 4.5 pulley before i get re tuned... What would you guys do?? Run the 4.25 or 4.5 from what i have now (4.63)?

02402ramair

If the twins are more restrictive then you will see less boost because you are taking the measurement after the restriction.

youngrigo

FWIW - I went with the 4.5 pulley (Regret it now) and went from 8lbs to 8.5lbs.

So switching from 4.63 to 4.5 netted me .5 lbs of boost.

My HP level did jump from 585hp to 626hp and 493tw to 525tq.... This was with Meth as well... Looks like I'll be going to the 4.25 pulley pretty soon

MVP'S ZO6

^^^^ this

reactor2

Weird that you're making 8psi with a 4.63 pulley. I'm running a 4.25 (A&A) on my P1SC and making about 5psi. I do have heads/cam/intake/exhaust though (228/232 .571/.573 112...so its not really a blower friendly cam).

youngrigo

I picked up around 2psi when i did my custom blower inlet pipe... 4in exhaust pipe with a 4in A&A filter...

mikebq

Where did you get the 4" inlet pipe and filter ?