jmc007
10-14-2005, 07:57 PM
For any of you who had installed (or plans to install) a CAI (or even a drop-in filter) , I strongly suggest you to do the supercharger bypass selenoid mod (see the posts #28, 34 and 36 on the first link below).
Here is the main reason : With a less restrictive filter, I noticed (and others too) that the maximum boost came sooner and max boost increased a few (depending of some conditions like the weather).
For example, those who usually saw a max boost of 10,5 PSI stock saw it went up to 12 PSI, but those who already boosted a max of 12 PSI stock saw it went up to 12,5 PSI, but not more (like mine).
About the stock Electrical Autometer gauge, there is a misconception about it. NO the stock gauge itself isn't max out to 12,5 PSI !!! The pressure (physical air) is read mechanically from a sensor and then the data is being transferred electronically to the stock electrical gauge, which shows EXACTLY the boost in the intake manifold. For those who always see a max boost lower than 12 PSI, it can be caused by several factors. Like the weather and / or the by-pass valve (butterfly) itself who isn't properly sitten (closed), because of the Allen screw on the by-pass valve actuator (little motor on the side of the supercharger) who isn't set properly.
Today I understood the TRUE reason why I got a dyno LOSS with a replaced drop-in filter. With the less restrictive filter, the boost came up quicker, but mainly tried to goes past 12,5 PSI, exactly the point that the PCM "says" to the by-pass valve selenoid to open (to vent the extra boost) (it happens somewhere around 5700 to 6000 RPM's). The dyno loss I saw for myself is clearly visible (see my first dyno graph on the post #4 of the second link below); there is a hollow at 5700 RPM.
I think that a dyno loss (at very high RPM's) is only possible for those who are already close to 12 PSI ...
About the Fujita dyno graph ... We can see on the stock baseline pull there is a hollow at 5700 RPM. But on the CAI pull, there isn't any hollow. Even if I couldn't be 100 % sure, I think Fujita disable the by-pass valve selenoid to produce a max increase of 14 HP. I think K&N didn't disable it for the 8HP gain on the Cobalt SS CAI, and I think K&N disable it on the 14 HP gain on the Ion Redline.
Those who already installed a CAI (or even a replacement filter) said that the butt dyno indicate it pulls harder between 2000 and 6000 RPM's. It's definitly true, but maximum gains will only be achieved by disabling the by-pass valve selenoid.
http://www.*************/forums/showthread.php?t=4369&page=2&pp=20
http://www.cobaltss.com/forums/showthread.php?t=1933
Have a nice day !!!
Here is the main reason : With a less restrictive filter, I noticed (and others too) that the maximum boost came sooner and max boost increased a few (depending of some conditions like the weather).
For example, those who usually saw a max boost of 10,5 PSI stock saw it went up to 12 PSI, but those who already boosted a max of 12 PSI stock saw it went up to 12,5 PSI, but not more (like mine).
About the stock Electrical Autometer gauge, there is a misconception about it. NO the stock gauge itself isn't max out to 12,5 PSI !!! The pressure (physical air) is read mechanically from a sensor and then the data is being transferred electronically to the stock electrical gauge, which shows EXACTLY the boost in the intake manifold. For those who always see a max boost lower than 12 PSI, it can be caused by several factors. Like the weather and / or the by-pass valve (butterfly) itself who isn't properly sitten (closed), because of the Allen screw on the by-pass valve actuator (little motor on the side of the supercharger) who isn't set properly.
Today I understood the TRUE reason why I got a dyno LOSS with a replaced drop-in filter. With the less restrictive filter, the boost came up quicker, but mainly tried to goes past 12,5 PSI, exactly the point that the PCM "says" to the by-pass valve selenoid to open (to vent the extra boost) (it happens somewhere around 5700 to 6000 RPM's). The dyno loss I saw for myself is clearly visible (see my first dyno graph on the post #4 of the second link below); there is a hollow at 5700 RPM.
I think that a dyno loss (at very high RPM's) is only possible for those who are already close to 12 PSI ...
About the Fujita dyno graph ... We can see on the stock baseline pull there is a hollow at 5700 RPM. But on the CAI pull, there isn't any hollow. Even if I couldn't be 100 % sure, I think Fujita disable the by-pass valve selenoid to produce a max increase of 14 HP. I think K&N didn't disable it for the 8HP gain on the Cobalt SS CAI, and I think K&N disable it on the 14 HP gain on the Ion Redline.
Those who already installed a CAI (or even a replacement filter) said that the butt dyno indicate it pulls harder between 2000 and 6000 RPM's. It's definitly true, but maximum gains will only be achieved by disabling the by-pass valve selenoid.
http://www.*************/forums/showthread.php?t=4369&page=2&pp=20
http://www.cobaltss.com/forums/showthread.php?t=1933
Have a nice day !!!