Ok, I see this question coming up quite a bit. People are getting their SC kits installed, and their boost guage reads a little bit low, they check their belts and everything seems to be fine.

First of all, note that PSI is NOT a measurement of airflow. PSI is the amount of backpressure in a system. The 8 (or 9) psi pulley that ships with your supercharger kit was designed for the car in its stock form, and as such, it should produce 8 (or 9) psi under stock back pressure. Because of the nature of the design, any given rotation speed of the pulley will have a fixed amount of air output. That means for the most part, with a given pulley, the SC will always output the same amount of air regardless of PSI (assuming install is proper, belt not slipping, no leaks etc).

Now as soon as you do any other mods, such as exhaust or headers, your system is more free flowing. That means the air your SC is forcing through has less resistance to make it through the entire system, resulting in less pressure...which is why your PSI reads lower.

Consider an analogy where you put a showerhead on a firehose. The amount of pressure coming through that showerhead is going to be very high. Now take the showerhead off and obviously the pressure will be much lower, but that doesnt mean less water is coming out.

So basically, do not be concerned that your modded G appears to not be reaching full boost, because it probably is.

 

I think most have figured this out a while back . Some just dont want to believe it