BoostCooler Dual Düsen Upgrade Ladeluftsystem Wassereinspritzung Dual Nozzle Upgrade The DNU allows an additional Hyper-Sonic nozzle to be mounted in any of our Boost Cooler kits. It includes a Tee junction piece with our quick-connect fittings, a nozzle holder and a section of hose. We recommend: Bi-Turbo engines (e.g. Audi S4/RS4, Porsche) Engines with 2 separate throttle valves (e.g. V8) Powerful engines (>500 hp), where one nozzle alone is not sufficient. 2-nozzle installation for combined charge air and combustion chamber cooling (one Boost Cooler nozzle directly downstream of IC-output, another one right in front of the throttle valve resp. intake manifold). .