The APR Air-to-Water Intercooler System for the B9 RS4 / RS5 2.9T EA839 offers a substantial leap in performance that directly translates to more horsepower and torque, and consistent performance that’s unmatched by the factory cooler. The factory cooler struggles to cool the charged air resulting in excessive intake air temperature due to its small size. This struggle results in ECU protecting the engine by pulling power during a single quarter mile pass, lap around a track, or even during a spirited drive. Simply bolting on the APR System relieves this issue, resulting in an instant boost in power and consistency. The APR system has no trouble remaining consistent thanks to its ability to resist power-robbing heatsoak!

It is easy to see why the APR Air-to-Water Intercooler System outperforms the factory system. The upgraded cooler is 194% larger than stock, coming in at 5,500cm³ vs the undersized 1,870cm³ factory unit. The system features cast end tanks that were computationally flow optimized for a smooth airflow path and connect to all new silicone hoses with ez-flow stepped lips for a perfect connection without disruption. Likewise, all coolant hoses were upgraded with application specific routing for a clean install. With optimized flow through the intake air path with minimal pressure drop, post-cooler boost figures are higher, resulting increased horsepower on top of the lower intake air temperature.

The proprietary intercooler core was designed to not only cool exceptionally well, but limit head pressure on the coolant system, and promote higher airflow with lower pressure drop through the charged air path. There’s no need for costly modifications to your coolant pump or radiator with this setup as it’s able to maintain constant intake air temperature even during 28 back-to-back 60-130 MPH pulls on the track! Simply put, we call it Performance Without Compromise!

APR’s engineers conducted multiple back to back 60-130 MPH acceleration testes to illustrate how well the APR system was at maintaining consistent intake air temperature compared to the factory system. This was conducted on a closed track using an APR Stage 1 (93) equipped Audi RS5 with ambient conditions hovering around 33°C (91°F).

The factory ECU has a range in which it will derate power based on intake air temperature. In doing so, the tests can be skewed because when the ECU derates power, intake air temperature stabilizes. As illustrated below, this only comes into play when using the stock cooler.

During a single acceleration pull the factory cooler was already reducing power to control intake air temperature, meaning if it didn’t pull power, intake air temperature would be even higher. By the second pull it was hitting 75°C and aggressively pulling power to maintain that temperature to protect the engine. The engineers continued conducting the test and after 14 pulls showed the system consistently averaged 73°C across the 14 pulls. Further testing was aborted to protect the engine.

When switching to the APR cooler in the same hot and humid conditions the tests results were dramatically better. Intake air temperature leveled off quickly, and even after 28 back-to-back 60-130 MPH pulls were only at an average of 49C! Unlike the stock cooler, the system had no help from the ECU trying to control intake air temperature as it was not reducing horsepower in an effort to reduce IAT.

On average the intake air temperature with the stock system was +38°C or (+111%) over ambient whereas the APR system was only +16°C (+51%) over ambient. This dramatic difference means the ECU was not aggressively pulling power to protect the engine when using the APR Cooler as it was when using the stock cooler. With the APR Cooler power was higher pull after pull, making the car consistently quicker!