blow off valves

[thelycan1121]

my question is can u put a blow off valve on a supercharger, i have a 1992 pontiac bonneville SSEI

[J Wikoff]

In theory, yes. While there is a bypass built into the LIM straight into the intake end of the SC buried in there, you could rig one up off the vacuum tree that comes out of the base of the supercharger right near the bypass actuator. It would be a custom job, and I haven't seen one done. It would be much easier on a centrifigul supercharger, I think.

[00Beast]

You have one built in. Not only would an aftermarket blow-off valve be stupid, but there is no need, especially on these. They are after the TB and only spin as fast as the rest of the engine. There is nothing that you need to protect from boost when you get off the throttle. You wouldn't get that stupid sound either.

[bonneville dan-o]

. You wouldn't get that stupid sound either.

^^^^^ Hater

[J Wikoff]

I kinda like the blowoff sound.

[willwren]

1. There already is one internal to the supercharger.

2. You COULD add one external, but it's a ridiculous idea that would do nothing for you.

[99BonnevilleSE]

I kinda like the blowoff sound.

Me too! I say if your going for the sound then go for it. If your trying to protects something from boost, then don't bother.

[00Beast]

What would you hear? "Pfft"? You wouldn't get that sound that a turbo makes, as there's no boost when you let off the throttle. Don't waste your time or money or mess up your car.

[J Wikoff]

If you shut the bypass off, the BOV becomes your wastegate.

[thelycan1121]

ok thanks for the tips

[douellette88]

If you shut the bypass off, the BOV becomes your wastegate.

how would one go about doing this? i would really like to see if i can get that "blowoff sound"

[00Beast]

You absolutely could not get that sound from a roots-style S/C. The reason a turbo makes it is because there's a lot of pressure from the spinning turbine even after you lift off the gas, and the pressurized air pushes out that valve making noise, especially on the ones with the stupid little reeds for noise-making. Once the belt slows, the S/C rotors slow. There's no need since there's nothing to "protect". The boost is induced after the throttle blade, which is the only thing a BOV is designed to protect. The S/C moves when the valves move and stops moving when the valves stop moving unless you break the belt, which means the S/C doesn't move and the valves do. It's a matter of physics, it won't work.

[00Beast]

Plus, where would you mount it? It would have to be after boost, which eliminates any where before the TB or on the blower housing itself. That leaves the LIM and/or intake runners to be accessed, which leaves very little room to mount these stupid things. At that point when you're off boost, the boost currently has 7 places to go. 1-6 are the intake runners which lead to the valves and cylinders, and #7 is the BBV, which recycles air through the impellers. You'd be adding an 8th, so your total amount of flow through the BBV would be very low, in fact, the engine would probably try sucking through the BBV into the valves, since when you're off boost the engine is sucking air, not receiving pressurized air.

Plain and simple? It's not gonna work.

[01bonneSC]

LMAO its ok Ed, chill out. Need a shot?

[willwren]

I can't believe we're even discussing this.

There's one built-in, it's called the boost bypass.
An external blow-off valve will do nothing for performance or sound.

End of story.

[douellette88]

lol...ok guys. was just a question

[GonneVille]

It's cool, douellette. Just one of those subjects that pushes the debate button, like cross-drilled brakes...

The biggest issue, if the BOV worked at all, is that it would screw up the air-fuel metering. With the internal bypass, the air is returned to the intake behind the throttle blade and MAF. This means the MAF only sees as much air as the engine actually uses. If you used a BOV, the air would escape out of the intake, and the MAF would read an increase in air-flow, and upset the air-fuel mixture in response.

[99BonnevilleSE]

lol...ok guys. was just a question

I think you guys are scaring him hahahhaa

[thelycan1121]

it was just an idea didnt mean to piss anybody off lol it was stupid to even ask sorry

[willwren]

We may give you *poop*, but we'd rather you ask a stupid question than not ask in the first place. Your topic here will serve as a good bit of info for new members.