IceY2K1

iTrader: (3)

How are you SC guys doing this?

What BOV? How do you adjust the amount?

Is there problems? Leaking at idle?

Vortech 350/G guys are ADDing a wastegate to the charge piping and NOW they're considering a boost controller because it dumps too much.

Anyone care to go explain how simple it is to run a smaller pulley for more low/mid range boost, but leak off excess max boost using a BOV? Go here: http://www.my350z.com/forum/showthre...99#post1063699

slimer

iTrader: (13)

this is an interesting concept. I would use my 2" pulley and leak the boost with a b/c

slimer

iTrader: (13)

oh wait, that whole impellar speed thing.

anyway, what size is a udp? would it be beneficial to make both the crank and the s/c pulley smaller?

IceY2K1

iTrader: (3)

If you want to keep the impeller speed the same and you run an UDP for the light weight/less wear on accessories, then just compensate with a larger SC pulley.

Use Vortechs website calc for SC pulley that keeps the impeller speed under 50-53K limit using whatever diameter UDP.

IceY2K1

iTrader: (3)

Okay.....

Looking into Stephen Max posts, he uses the Blitz DD BOV. He loosened the preload screw to allow it to bleed off excess boost.

Anyone ELSE do this with other BOVs successfully? If yes, which BOV did you use?

Prodeje79

I have been very curious about this myself.

So do I need a special UDP, or can I use my UR UDP? I thought people said it would not work?

IceY2K1

iTrader: (3)

An UDP will work, you'll just lose boost unless you can compensate with a smaller SC pulley.

For example....

1)Using a stock 6.25", SC 3.125", impeller speed is 46080rpm.

2)Using a UDP 6"(guess), SC 3.125", impeller speed is 44237rpm.<~~less boost.

3)However, using UDP 6", SC 3", impeller speed is 46080rpm, but lighter and easier on accessories if pushing 7000+erpm.

Requin6

iTrader: (36)

what exactly is the point of bleeding off boost? is it only to get a smaller pulley to get it to hit boost quicker and then only top off at a certain psi level?

just seems silly to drop to a smaller pulley when you just want to bleed off the extra boost with the BOV.

maybe i am just not seeing the point.

IceY2K1

iTrader: (3)

Yes, you see more boost in the low/mid range, but peak limit is still the same.

Your peak boost is limited by engine strength/fuel or max impeller speed, so this is a trick to get boost sooner in the power band without exceeding those.

Prodeje79

I have a 2.87 pulley. What do you think? Use it with my UDP?

IceY2K1

iTrader: (3)

What pulley size are you running now?

I think you should make sure your fuel system can support that and measure your UDP main pulley *GROOVE* diameter(where belt rides) and get back here and ask people what they needed to support fuel/timing with that boost.

Stephen Max

iTrader: (59)

Keep in mind that smaller pulleys have less circumference (duh!) so less traction area for the belt to transmit power from the crank to the blower. So you have an increased propensity for belt slip as you go to smaller pulleys. You can make up for it by increasing belt tension, but that decreases bearing life.

JAY25

iTrader: (38)

With a smaller you are going to leak air thru your BOV. Thats normal. All this air coming into the engine all of it is not going to be used. If you want to leak air at peak boost with the supercharger is simple, its all on belt tension. Proper belt tension is going to give you peak boost. Loosen the belt a bit and you wont hit peak boost. With the smaller pulley and proper belt tension your going to peak up pretty quick. A loose belt is not going to let you pick up boost soon and is also not going to hit peak boost.

slimer

iTrader: (13)

i originally had a 2" on my s/c when i bought my kit because ferhan was using it with a udp.

MyownNismo

iTrader: (13)

That's why UR makes the Sc pulley. All it is is a lighter pulley and not a underdrive. Used for SC and large stereo apps. Maybe you could ask UR to make a custom pulley to run with the sized SC pulley.

IceY2K1

iTrader: (3)

Good points guys, I'd say sell the UDP and buy the SC lightweight pulley, so you don't have the belt tension/slipping headaches.

Again, this is where I put my foot in mouth for speaking about something I have no ACTUAL hands on experience with.

Luckily, Jay/Stephen Max are around, because SC guys seem to be getting rarer and rarer.