[Tom Vaught]

I decided to start from the beginning and discuss a simple "Draw Thru Boost System" first.
The most simple one is the Roots Blower with the Holley carb on top of the Blower and the Blower attached to the Intake Manifold.

But, this is the street section and we are talking about Boosted Engines so we will do simple first.

A street car is different from a Race Vehicle in that the Race Vehicle does not care a bit about Fuel Economy and Air/Fuel Ratios higher than 12.7 to 1. But a Street Guy would like to have the Big Blower with the carb(s) on top and still be able to pass the gas station occasionally without stopping.

The way to do that is to have the carb(s) Air/Fuel Ratio a bit leaner under light load just cruising down the road. More like 13.5 to 1 Air/Fuel Ratio.

You are not going to get those Air/Fuel Ratios with Power Valve Plugs in the Carb(s) and Big Jetting in the Carb(s).

So you need to dial in the engine to run under light load (with smaller Jetting and with a Power Valve) that enriches the Air/Fuel Ratio when higher loads and more fuel demand is required.

The way that a Street carb (without a blower works) is there is a passage in the base of the carb that is connected to the Power Valve Vacuum Cavity that releases the vacuum applied to the Power Valve Diaphragm and lets the Power Valve open.
It gets that Vacuum Signal from the intake Manifold. No need to explain the different Power Valve Numbers or the point where the spring over-powers the vacuum and opens the valve. We already know that deal with Holley carbs.

Problem is Now we have a Supercharger stuck right in the middle between the carb and the intake manifold. So the vacuum signal to the carb is not the correct one.

So the fix for that is to change where we get the signal from. Not in the normal location but BELOW the SUPERCHARGER (back at the intake manifold point again). Will post "the fix" in the next post.

Tom Vaught