: P valve / boost control explained.



wait4me
07-31-09, 04:39 PM
OK guys, This is pretty simple.

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The boost control system is done in a 3 part system.


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The Boost bypass valve on the side of the blower has a P and a V port.

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P = protection. It is there to bleed off access boost.

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When the pressure exceeds 10-12psi, the pressure on that port PUSHES the bypass valve shut to recirculate boost back into the intake and relieve pressure. "We dont want this protection when we are trying to ADD boost via pulleys as it will dump it out"


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You just unplug the port, and CAP off the vacume line on the Boost SOLINOID. That way the p port is unobstructed and will allow the V Valve to still function properly..

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Now the V valve is simple. It makes the supercharger bypass its boost while regular driving and while boost is not needed, so then you only have 1/4 hp of drivetrain loss instead of 60hp.. As Vacume goes down, the Valve will slowly shut to create more and more boost. At wot, the V valve sees 0 vacume so then it will stay closed and make full boost... This same Valve is on EVERY roots eaton blower and aftermarket roots style supercharger....

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There is a Stopper that makes the internal bypass valve shut at a certain point at wot. You sometimes have to "Adjust" that set screw to allow the internal bypass valve to shut all the way. Sometimes, just doing that will get rid of any wide open throttle boost loss and you will gain boost.

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Now, on to the Computer controlled boost bypass soloniod. It too is a 3 part system.

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When the engine is running, it can BYPASS BOOST by the valve that has the sponge foam on it. As you are driving, it can pull boost while in reverse, park/neutral, which is just fine, BUT THERE COMPUTER limits that can and will try to cut back boost also. "Which is bad when you try to make more boost via pulleys"

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So, the system goes by what is called Boost duty cycle.

At 0 duty cycle, the SOLINIOD is full 12Volts and it is fully open. on BOTH THE P PORT ON THE SYSTEM AND the foam part on the solinoid itself. Both WILL AND HAVE THE ABILITY TO 100% recycle boost into the intake.

At 50% it will be pulsing the foam port to relieve boost.

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At 100% means that All systems are good, Boost is allowed, and the computer is not trying to pull boost. HOWEVER!!!! the P port is / has access to the boost being applied so WITHOUT COMPUTER intervention, the p port WILL CUT BOOST if it goes higher than its designed limit of 11psi.

EVEN THOUGH THE COMPUTER says it is allowing 100% boost.


So, really to get rid of all boost protections, one would have to just CAP off the port going to the supercharger lid and unplugging/ removing the soloniod completely. BUT doing this is not recommended, as then you loose the ability for the computer to dump off boost if it needs to while in traction control or reverse, ect...

musclesbmf
07-31-09, 07:11 PM
Any chance of throwing up some pics or a vid on youtube to "idiot proof" this process. Which line to pull, wheich end to plug, what screw to adjust, etc. I believe I know what you are referring to, but I would mind you dumbing it down for me :-)

thanks,
Mark

jwa999
08-01-09, 01:16 AM
Sorry, i don't see a third way in controlling boost or bleeding of boost.

The V/P valve controls the Boost. The solenoid will connect X to O, which controls P. I don't see how the solenoid bleeds off boost if P is no longer connected? Are you saying that the tube coming out of the upper supercharger going to X can some how bleed off boost? How? By releasing air through the tube that has foam on it? It's a tiny tube compared to the 4 inch air intake. If any forced air would come out it'd blow the foam off the tube?

Fubar75207
08-01-09, 09:18 AM
Don't you want the computer to dump boost for the transmission to shift? or when you close the throttle body?

wait4me
08-01-09, 10:14 AM
Don't you want the computer to dump boost for the transmission to shift? or when you close the throttle body?

It is still doing that with the V port. It works just as it should.

Gotham CTS-V
08-01-09, 01:11 PM
Can you just take a quick pic of the P-valve and how you capped it?

Thanks.