RE: Can you install a Blowoff without a Turbo??
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RE: Can you install a Blowoff without a Turbo?? - 12/29/2004 12:44:17 AM
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Super Mario
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I don't understand how does vaccum actuate a "blow off" valve. it seems that it would activate when the pressure from the turbo has no where to go when you shift from high rpms, to low rpms the pressure is still there. therefore the bov allows pressure to escape without ruining the engine or any of the turbo components.
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RE: Can you install a Blowoff without a Turbo?? - 12/29/2004 12:48:09 AM
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Kappa22
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I think you're right, sacicons. I too find myself waiting for someone to actually do it. But about the whole BOV situation, I wanted to clear up the clear ups (Forced Induction 110, if you will).
Obviously, the turbo itself is a free spinning device. When you are under boost, then suddenly let off the accelerator (i.e. to shift or just to slow down), the throttle plate closes rather abruptly. Logically, the turbine continues to spin of its own accord, which builds up boost pressure in the charge pipe that has nowhere to go. Because of this, the turbo is essentially compressing air against its own speed, which causes turbulence as the air tries to exit around the spinning impeller blades, more commonly referred to as compressor surge. Not only does this cause unnecessary wear (and possibly damage) to the turbo cartridge and bearing, as well as slowing it down, but it kills your recovery time when reapplying boost.
The BOV itself is basically a pressure-activated piston valve that opens when a certain amount of pressure is applied to it from the inside. What the vacuum line does is help assist the opening of the blow off valve, since the vacuum applied from the top will help open the piston. Once you begin boosting again, however, the negative pressure (vacuum) becomes positive again, and this positive pressure is applied through the vacuum line to the top of the piston, helping to keep it sealed under acceleration. For example, if you are boosting at 10 psi, your blow off valve will have 10 psi pressing down on the top of the piston (via the vacuum line) along with a stiff spring to keep it sealed.
Hope that all makes sense... And I hope I didn't repeat too many things that were already said (sorry)
To answer your question, Super Mario, a BOV is activated by built up boost pressure, but it is assisted by vacuum.
< Message edited by Kappa22 -- 12/29/2004 12:51:28 AM >
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RE: Can you install a Blowoff without a Turbo?? - 12/29/2004 6:48:14 PM
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sacicons
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yeah, ill go along with that. but it also kinda depends on how hard you have it set. (on adjustable ones)
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RE: Can you install a Blowoff without a Turbo?? - 12/29/2004 7:55:47 PM
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Kappa22
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Very true
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RE: Can you install a Blowoff without a Turbo?? - 12/29/2004 8:15:03 PM
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sacicons
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and if it relyed on boost alone, it would still slow the turbo alot, cause it would have to be hard enough to hold 20+psi. but yeah, the boost pressure definately pushes on it too.
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Yes, there's a "Replacement for Displacement". Its called Volumetric Efficiency.
quote:
ORIGINAL: Forty04
I choose the rear ending
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RE: Can you install a Blowoff without a Turbo?? - 12/30/2004 12:19:08 AM
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Super Mario
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The reason why i asked this, is because I thought that you could possibly stick one on your exhaust manifold (or anywhere along the exaust line that pressure can be applied to it). The thinking that pressure building up on the bov would be provided by exhaust. therefore the pressure could be released when ther is enought pressure built up, or perhaps by a switch or something. but I see now how it works and that it couldn't. Just thinking about it thats all....
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RE: Can you install a Blowoff without a Turbo?? - 12/30/2004 12:40:37 AM
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sacicons
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well, that could work, but BOVs arent made for that much heat (it can hit well over 1500*) and then when it opened, instead of a PPSSSHHHH, it would be a BRAP BRAP BRAP. it would be an exhaust leak, not a pressure relief.
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Yes, there's a "Replacement for Displacement". Its called Volumetric Efficiency.
quote:
ORIGINAL: Forty04
I choose the rear ending
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