Modification of the 2.0T FSI engine far beyond OEM power levels requires an additional volume of high-pressure fuel especially in the midrange(3000-5000rpm) of the powerband. To understand why this fuel is neededfor the midrange, one must first understand how the fuel delivery system works in the 2.0T FSI.

APR High Pressure Fuel Pump Internal Parts

A low pressure fuel pump, which varies from ~40-95psi, delivers fuelfrom the gas tank to the high pressure fuel pump. Then the highpressure, camshaft driven pump pressurizes the fuel to upwards of 130bar (almost 1900psi!) in order to spray fuel directly into the combustionchamber. Unfortunately on cars that have many modifications, the stockfuel pump cannot flow enough volume of fuel to maintain the systempressure and the car suffers from the familiar "fuel cut" that so manymodified customers experience.

The limitation of how much volume of fuel the high pressurepump can flow is dependent upon the volume displaced by the pressurizing cylinder inside the pump and the number of times the pistonreciprocates inside that cylinder. Since the high pressure pump isdriven off of the engine camshaft by a three lobe cam the piston of thepump cycles at 1.5 times the engine rpm. (Engine camshaft turns atone-half engine rpm multiplied by three for the number of lobes on thehigh pressure cam lobe).

Due to this dependency on engine rpm for the high pressure fuel pump output volume, the FSI pump is capable of flowing almost 370hp at7000 rpm but only 158hp at 3000rpm. The graph below illustrates themaximum 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 insufficientfor the output generated by this upgraded kit. The only way to addressthis issue while maintaining a pump that fits in the stock location isto change the volume of the pump's internal pressurization chamber.

Fuel Pump Potential

In order to address the lack of fuel in the midrange, the APR FSI fuel pump increases the volume of fuel from the high pressure pumpby over 40%. Simplified, this is achieved by modifying some key internal parts within the pump. Changing these components requires precisionmachining of the new components with special surface treatments as wellas enlarged, redesigned seals. Using inferior components on thiscritical part can lead to many problems from gasoline in the engine oil(from a bad seal) to complete engine failure (from a seized piston inthe high pressure pump).

To give an idea of the tolerances involved, the final surfacefinish on the piston inside the fuel pump is so critical that it can bedamaged by touching them with bare hands. The tolerances between thepiston and the new barrel the piston rides in can only be measured by amulti-million dollar machine which uses air volumes to measure the partclearances to within microscopic levels.

Fuel Pump Components

The components used in the APR pumpare also of a high caliber. The piston and barrel of the new pump aremade of a certified and heat-treated bearing-grade stainless steel andhave a special diamond like coating. The seals used in the pump are made of a high performance, filled polymer with a high modulus spring toretain the seal forces throughout the life of the product. The crosssection of the seal is also of a proprietary design to maintainintegrity over many years of use.

APR FSI pumps have been track tested since 2006 with several hundreds ofthousands of miles of combined usage. Each APR pump starts out as abrand new OEM pump and is then modified with the new components by APR and undergoes a rigorous testing process on our high pressure fuel pump tester. Once a pump passes our standards it is serialized and shippedto the customer.

Motorsport Development

When it comes to a critical component that can mean the differencebetween winning a race and not finishing at all, motorsport teams mustuse the best components available. Motorsport teams around the worldhave put the APR High Pressure Fuel Pumpthough brutal and demanding testing and have proven again and again thereliability and performance you can expect from each and every APR High PressureFuel Pump. The initial success of the R-GTI and APR's own motorsportteam have lead other noteworthy teams around the world to rely on APR.

Your fuel pump is fragile! Please make sure the fuel pump is packeged properly!