The Concept:  

Audi endowed the S4 and A6 2.7T with a respectable platform to build upon. The 250 horsepower found in the 2.7L twin-turbo V-6 is just the beginning of this engine's potential. With the addition of several key components and proper tuning, the potential is realized. The selection and development of these components is crucial in maintaining the integrity of the car.

APR has the largest development staff in the Audi aftermarket and we put them to work in choosing the proper components in developing this system. The turbochargers for this kit are larger-than-stock K04 units. These turbochargers have proven to be much more reliable than the stock 2.7T K03 turbochargers (this kit is an excellent choice for anyone needing to replace their stock turbochargers, by the way). The extra flow and pressure capacity of these turbochargers allow boost pressures of approximately 20psi to be run at full throttle all the way up to high engine speeds.

The K04 turbochargers bolt up perfectly to the stock manifold. APR chose to retain the stock manifold design for several reasons. The stock manifold has a small internal volume for quick spool-up and a cleverly designed dual-wall construction. The dual-wall construction keeps heat in the exhaust gases where it is needed. This increases the amount of energy available to the turbocharger turbine to spool the turbo (reduced lag/lower boost onset) and also reduces the heat transmitted to other components (an important consideration given the tight constraints). A conventional cast manifold would transmit too much heat to the surrounding components after shut down. A fabricated manifold would adversely affect lag and would transmit too much heat during operation. The factory decided to use the S4 exhaust manifolds in the RS4 and we chose to do the same for this kit.

For fueling, APR opted for larger fuel injectors and the increased flow capacity fuel pump used in the RS4. With larger turbochargers and the engine running higher boost pressures, these components were necessary to meet the fueling needs of the engine and retain an adequate safety margin. The stock and upgraded fuel components were thoroughly tested on our fuel component test equipment to determine flow capacities. Although the stock components clearly were not up to the task, the components they chose to use fit their requirements perfectly.

In order to accurately measure the quantity of air entering the engine, it is vital that the air metering system be well designed and precisely manufactured. It is also very important that the mass air flow sensor be precisely mounted in a quality sensor housing and that the system be well thought out.  A custom design was not necessary for the 2.7T Stage III kit because they found a quality factory alternative for increased airflow capacity.

The kit is available with or without increased capacity intercoolers. For maximum performance (especially in hotter climates) we recommend replacing the intercoolers with larger units. Although an intercooler will not directly add much peak horsepower, it will allow the engine to operate as it would when the outside temperature is lower. This will give you more usable horsepower while driving the vehicle.

Dynamometer Developed and Proven on the Street/Track

At APR, they have invested in the equipment, facilities, and personnel to do the job right. These investments can be experienced in the overall quality of their product. For this upgrade system, APR made extensive use of their four-wheel drive chassis dynamometer. This vital tool enabled them to put the engine through a very wide assortment of operating conditions. Used in conjunction with their proprietary datalogging tools, APR has optimized the engine control parameters for all conditions. They have also programmed in safety factors for extreme conditions to protect your investment.

Laboratory testing and development go a long way in developing a premium product. However, no development cycle is complete without extensive real life use tests. What better way to test a system than to drive it 3000 miles at high speeds? APR put one of their S4 Stage III vehicles to this very test and entered it into the 2002 Gumball 3000. This event took the car from New York, New York to Los Angeles, California in five days. The car handled the trip without a hiccup, a testament to the performance and reliability of the kit.

If power, drivability, and reliability are what you are looking for, than look no further then APR's S4 K04 Stage III kit.