Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Catalytic Converter and Cracked Secondaries

Cracking secondaries:

There are two intake ports for each cylender that bring air into the engine. The primary ports are always open and air flow is controlled by the throttle body. The secondary ports (the secondaries) are closed below ~3750 RPM by using a butterfly valve. Once you reach 3750RPM, the butterflies open allowing air to flow through the secondaries (after the throttle body). The air coming in through the primaries and secondaries combined produces the power to reach redline. Cracking the secondaries is what we call it when we turn a "stop screw" so that the secondaries intake valves cannot fully close. This allows more air to enter the engine at any given point. Also, it's said to keep gunk from building up since they're always open just a bit and air is always flowing. Supposedly helps lower end torque just before 3700RPM's without comprimising any performance.