APR - T4100001 - Fits Audi S4 18-24, S5 18-24, S5 Sportback 18-24, SQ5 18-24, SQ5 Sportback 21-24

APR Stage 3 software was designed with reliability in mind. It's designed to not spike the turbo hard in the lower RPM band or run on the edge of what the factory rods and pistons have been known to handle. Particular attention was paid toward component protections, for exhaust gas temperature (EGT), back pressure safety (EMAP), turbocharger discharge temperatures, and fueling system capabilities. This was done through accurately adjusting the factory modeling during the development phase. As the need for more fuel increases through rising exhaust gas temperature, the system will lower lambda to cool EGT, but will not excessively tax the injection system with excessive on-times. Secondary protections will limit output for safety. By using our HPFP software headroom is increased significantly, but does so without overdriving the pressure to the injection system. The need for limiting power under extreme prolonged use (Tracking the vehicle for example), is greatly reduced. Lastly, with the upgraded HPFP, output on ethanol is dramatically increased whereas on the stock HPFP Ethanol makes similar power to pump fuel.