There is a big difference between rising rate-fuel pressure and the unit (SX) that is pictured there....... A rising rate adds fuel pressure in a ratio greater than 1 to 1 as boost increases. This helps add more fuel on budget turbo setups... most are 4 to 1. 1 psi boost adds 4 psi to base fuel pressure, etc. While this works to some extent, the fuel rail pressure can get crazy high very fast. Raising the pressure will add some fuel, but pressure does not equal volume, so double the pressure does not equal double the fuel.
The pressure regulator pictured is just a 1 to 1 pressure regulator, so as boost increases, it will add fuel pressure to maintain a steady fuel pressure as referenced to manifold pressure. The boost in the manifold will work against the pressure in the rail, effectively lowering your fuel pressure as boost increases.
Some factory regulators can boost compensate, most do not. Some merely reference fuel pressure to atmosphere. So at 15psi boost, your 43 psi rail pressure is effectively 43-15=28psi. Also, since these are all bypass systems, small stock regulators cannot cope with the added flow from high-performace fuel pumps. This causes a bottleneck at the regulator, and can make the rail pressure very high at idle, light cruise etc.
The SX regulator is very nice, and has 2 inlets, one for each bank of cylinders. I believe it also has a 1/8 pressure port to run a gauge from....
Cheers!
Carl Crawford
