APR FSI Fuel Pump

While modifying the 2.0T FSI engine beyond factory power levels, it became quickly apparent that an additional volume of high-pressure fuel was needed to make horsepower, especially in the midrange (3000-5000rpm) of the powerband. To understand why this fuel is needed for the midrange, one must first understand how the fuel delivery system works in the 2.0T. A low pressure fuel pump (which varies from ~40-95psi) delivers fuel from the gas tank to the engine. Then, in order to spray fuel directly into the combustion chamber, a high-pressure, camshaft-driven pump pressurizes the fuel to upwards of 130bar (almost 1900psi !). Unfortunately, on cars that have many modifications the stock fuel pump cannot flow enough volume of fuel to maintain the system pressure, and the car gets the familiar “fuel cut” that so many modified customers experience. The limitation of how much volume of fuel the high pressure pump can flow is dependant upon the volume displaced by the pressurizing cylinder inside the pump and the number of times the piston reciprocates inside that cylinder. Since the high pressure pump is driven off of the engine camshaft by a three lobe cam, the piston of the pump cycles at 1.5 times the engine rpm. (Engine camshaft turns at one-half engine rpm multiplied by three for the number of lobes on the high pressure cam lobe). Because of this dependency on engine rpm for the high pressure fuel pump output volume, the FSI pump is capable of flowing almost 370hp at 7000 rpm, but yet only 158hp at 3000rpm. The graph below illustrates the maximum horsepower potential of the stock fuel pump compared to the APR FSI fuel pump. Also on the graph are stock and APR Stage III horsepower numbers. Clearly, the stock pump is insufficient for the output generated by this upgraded kit. The only way to address this issue while maintaining a pump that fits in the stock location is to change the volume of the pump’s internal pressurization chamber. To ensure flawless drivability the APR 2.0T FSI fuel pump requires APR engine management recalibration to allow for the increased size of the APR fuel pump. If you already have APR software installed this recalibration upgrade is included in the fuel pump price, otherwise it needs to be purchased separately. Currently, some APR Stage II and K04 turbocharger clients will be able to take advantage of increased horsepower and torque up to 25hp and 35lb ft with APR fuel pump specific engine management performance recalibrations.