Boost Reference Fuel Pressure System
The ZZPerformance Boost Reference Fuel Pressure System (BRFPS) easily installs into your Cobalt or Redline allowing fuel pressure adjustment above the PCMs range of adjustment. We prefer the "manifold regulated pressure" way of installing it, this lowers fuel pressure at idle to cure large injector idle issues and raises fuel pressure under boost to help fuel high HP applications. Required for LSJ's running over 17psi of boost or LE5's over 12psi.
Manifold regulated fuel pressure:
For this installation method, the factory in canister regulator is bypassed. This requires dropping the tank and bypassing the factory 60psi regulator. When the canister is removed, open the canister and clip off zip ties holding the clips on the regulator. Now open the regulator to expose ball and spring tab, next remove ball and spring tab, then clip fuel diverter back on and re-install canister.
This will have two different ways to get a boost/vacuum signal to the rear mounted ZZP regulator. You can either use the factory EVAP line for a boost/vac line, or it can come with a reel of flexible steel tubing that you can run from the engine, all the way to the back where the regulator is located.
When everything is installed set your fuel pressure to ~42psi at idle under full vacuum, and rise 1:1 under boost. This requires PCM reprogramming.
Full return system:
This installation option is the same as above, but includes an adapter piece up front to change your system to a full return style fuel system using the EVAP line for fuel return. There are no benefits performance wise to doing this, but some customers have requested it, so we are offering it as an option.
So how and why does this kit work? What is it actually doing?
The PCM doesn't compensate for boost over 17.5psi (12psi on LE5), so the car begins to go lean after that because the PCM file does not see more boost above the 17.5psi. This is unless you raise fuel pressure the same amount as boost, which is exactly what our BRFPS does. You can try and tune around the 17.5+psi but it's guess work and a very poor solution.
On the 2.4L kit, we adjust the regulator to kick in at 12psi instead of 17, but the function is still the same.