Wagner Tuning Competition Water to Air Intercooler Audi RS4 B9 RS5 F5 | AustraliaWagner Tuning Water to Air Audi RS4 Intercooler (Also Suits RS5 B9 Series) The 2. 9L V6 biturbo engine (VW EA839) of RS4 models is equipped with an indirect charge air cooling system. So the cooling of the charged air is not cooled by the ambient air as like the conventional intercooler set ups. Charge air cooling is courtesy of water to air cooling set up. The Wagner Tuning high performance Audi RS4 intercooler has got a new performance core with the