Hi ! See the thread #5 of this post for a picture.
http://www.redlineforums.com/forums...read.php?t=5512
As you can see on the picture and on your own car, there is two hoses on the by-pass valve actuator (little black device attached to the supercharger). This by-pass valve actuator include a spring and a diaphragm and controlls the by-pass (butterfly) inside the supercharger. It is normally closed.
The top hose on the actuator isn't connected to a sensor. It is only a vacuum hose who "reads" the before supercharger pressure (uncompressed air) and controls the diaphragm inside the actuator. At idle and lower RPM's, the vaccuum is greater than the spring force, which force the by-pass valve to open. When hitting gas pedal hard, the vaccuum itself became lower and the actuator's spring overcome this force and close itself.
Most of the supercharged car doesn't have any other hose (like the lower one on our cars). On our cars, this hose is connected to the electrical selenoid which is activated only in specific conditions (like abusing conditions). The way it works : There is a pressure hose (which is connected to the intake manifold (after the compressed air) which is connected to the selenoid. This electrical selenoid is normally close. When the PCM tells the selenoid to open (a good example is when the PCM reads more than 12 PSI from a MAP sensor), the positive air coming from the manifold pass through this selenoid and goes to the bottom of the actuator. This pressure (higher than the actuator spring), forces the by-pass valve to open, which bleed the extra boost.
The way to avoid it is to unplug the bottom hose (on the actuator side) and plug the hose with a screw. The lower actuator nipple MUST stay opened to air. If it's closed, than the diaphragm won't work properly. You can installer a miniature filter on it. The other side of the same hose MUST stay connected to the selenoid. If the selenoid isn't plugged properly, you could lose some intake manifold pressure under the specific (abusing) conditions listed.
We should'nt name this mod the "By-pass mod", but instead we can name it the "Selenoid disabling". This way is totally safe and ensure the by-pass valve (the butterfly inside the supercharger) to work the same way like in stock form.
Two other important things :
The first one is that the little Allen screw on the by-pass actuator is handset and isn't set equal for one car to another. The best is to unscrew it since you feel that the by-pass butterfly (inside the supercharger) is properly closed (sitten), then you screw a little bit the screw to sit with the swivelling arm. Be sure that the swivelling arm continue to work porperly.
The second one is : There is 2 nuts holding the by-pass actuator, you can unscrew it and push down the actuator the most possible, the tighten them. Make sure that you not push down too much, because it will open the butterfly (you'll see it when ajusting). This way you will not achieve higher maximum boost, but if you successfully push down the actuator a little bit, his inside spring will be compress with a little higher pretension, which will cause the boost to come a little bit sooner. Be sure to keep the actuator in the same axis of his plunger, to ensure it works properly. For me it works, and i saw on Pontiac Grand Prix forums that most have done it with success.
Have a nice day !
10-15-2005, 07:22 AM
Similar Threads
Linear Mode
