APR 08-12 Audi S5 4.2L V8 (Pre Nov 2008) High Pressure Fuel Pumps

The HPFP internals must be machined to extreme tolerances and installed in a clean environment or the pump can easily fail. Dimensional tolerances on the APR HPFP are as tight as .00004" and geometric tolerances are as tight as .00005". The plunger and barrel are created from certified and heat-treated bearing-grade stainless steel and the plunger undergoes a special diamond like coating process for exceptional surfaces hardness and ultra-reliable operation. To prevent float associated with altering the plunger's mass, APR supplies each unit with a properly specified spring. All internal seals are replaced, including the spring seal, and the tip of the pump retains the factory pivoting head to reduce cam follower wear and piston side loading.