Forced Induction Supercharger/Turbocharger

A way to reduce boost without pulley change?

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Old 03-18-2005, 09:58 PM
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A way to reduce boost without pulley change?

I have 2 pullies and the biggest one still gives me around 9psi at 59xx rpm. Is there a way to bleed some boost off without changing pullies?

Would it work if I adjusted the bov to not fully close?
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Old 03-20-2005, 08:55 PM
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Re: A way to reduce boost without pulley change?

good question ttt for ya
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Old 03-20-2005, 10:31 PM
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Re: A way to reduce boost without pulley change?

something called a pop-off valve. I know Greddy makes one but that's the only company I've seen. It bleeds boost at an adjusted level with an adjusting screw.
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Old 03-20-2005, 11:36 PM
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Re: A way to reduce boost without pulley change?

Ahh, something I have to buy, lol.
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Old 03-24-2005, 11:53 AM
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Re: A way to reduce boost without pulley change?

long tubes and a highflowing catback will bleed some of the boost off.
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Old 03-24-2005, 01:24 PM
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Re: A way to reduce boost without pulley change?

Originally Posted by Kredz28
long tubes and a highflowing catback will bleed some of the boost off.
How does belt driven boost lower with better flowing exhaust?
I can see that simply with a Turbo.
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Old 03-24-2005, 09:34 PM
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Re: A way to reduce boost without pulley change?

Boost is simply resistance to flow. If you increase the engine flow & the charger supplies the same amount of air, it will make less boost. This still increases efficiency & power. I have seen LS1 cars lose 2# boost with headers, exhaust & no cats, while still running substantially better.
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Old 03-25-2005, 12:12 AM
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Re: A way to reduce boost without pulley change?

a cheaper method would be to replace your bov with a plastic elbow(no valve). im sure youll loose quite a bit of boost this way.

but unlike less restrictive exhaust, you will loose power instead of gain it.
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Old 03-25-2005, 01:07 PM
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Re: A way to reduce boost without pulley change?

Pulley down if you have to. A BOV will lose boost, but you still have the same parasitic drag on the motor. Keep the boost, keep the boost .

Ryan
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Old 03-25-2005, 06:21 PM
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Re: A way to reduce boost without pulley change?

I already have a good exhaust but it wouldn't have made a difference anyway. Unless I change cams, boost will stay the same. The exhaust valve closes at the same time regardless of exhaust.

I am not going to totally throw away the bov so that is out. I would probably lose alot that way.

And 96speed, I would love to, but I want to keep the motor alive for at least a year.
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Old 03-29-2005, 09:09 PM
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Re: A way to reduce boost without pulley change?

Ooohhh, vaseline! I don't think so
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Old 03-30-2005, 08:32 PM
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Re: A way to reduce boost without pulley change?

Originally Posted by slimdawson
And 96speed, I would love to, but I want to keep the motor alive for at least a year.
um.. keep the 9psi.. dont get on it as much? Then it will last.. No matter how much boost your running.. you beat it, it will die..
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Old 03-31-2005, 03:49 AM
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Re: A way to reduce boost without pulley change?

What constitutes "beating". I have maybe made 4 full 1/4 mile passes since I got the blower on 8 months ago.
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Old 03-31-2005, 07:36 AM
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Re: A way to reduce boost without pulley change?

Restrict the inlet side of the blower....less air going into it=less air for it to compress=less boost.
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Old 03-31-2005, 10:07 PM
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Re: A way to reduce boost without pulley change?

do you have a boost gauge? if you do, you can experiment and see whats working and whats not.

the restriction on the inlet side of the blower sounds like a good idea.

i actually tried what i mentioned to you today. i replaced the BOV with a simple 1" elbow. its cheap so i thought id give it a try.

i dont have a boost gauge so i cant tell you how much boost it scrubbed off. i know its still boosting cause the ignition retard light comes on when i put my foot down so there is boost being sensed by the secondary MAP that came with the crane ignition/retard kit.

and also, the "but-O-meter" says im only loosing maybe 10 to 20ponies. but you know the but-O-meter isnt very accurate. but my point is, the car is still really friggin fast.

i think if your seeing 9psi right now, and you do replace the BOV with a regular elbow, i think you will still be satisfied with your power.

if you try it, let me know how much boost you lose.
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