Research and Development
Uncommon to most in the market today, APR spared no expenses during the research and development period. For the better part of a year, APR’s Mechanical Engineers created several prototype intake designs utilizing our in house Sterolithography 3D printer and other rapid prototyping techniques. Various filter mediums were tested in conjunction with the new intake designs through simulated models, flow bench analysis, dyno data collection and in real world applications all in an effort to derive the best possible solution. To increase performance over the factory intake system, the intake system’s ability to flow a higher mass of air is critical. In order to achieve this, APR’s Mechanical Engineers focused on improving the pressure ratio between the inlet and outlet of the intake system, reducing turbulence, maximizing filter efficiency and keeping IAT as low as possible.
Improving the Pressure Ratio
In an effort to strive for an ideal pressure ratio (1:1) between the intake’s inlet and outlet, the intake features several key characteristics. Through CFD optimization and flow-bench validation, the intake’s filter housing was shaped into a reducing spiral, or volute, which uses the inertia of the air entering the system to increase pressure on the outside of the filter. This creates an even pressure distribution across the entire face of the filter, rather than only a few key spots, and as such, maximizes utilization of the filtration element. Compared to many other popular intake styles, the APR intake system allows for the use of a small, compact filter with better filter utilization as systems often twice its size. Unlike traditional open element filters, the APR intake design only pulls air from the grille area near the leading edge of the vehicle’s hood. In doing so, it draws air from an area of relatively high pressure. As the vehicle increases in speed, pressure continues to build and ultimately aids in the intake’s effectiveness. By sealing the intake system, pressure created during the ram air effect and volute design is not simply lost within the engine bay. This is contrary to open element filters that pull air from a relatively low pressure region formed within the engine bay.
Flow disruptions and turbulence ultimately impede airflow to and from the intake filter, resulting in a performance loss. The APR Intake system takes a two-step approach to improving mass airflow in this region. As air enters the intake entrance, directional vanes ensure airflow is properly directed towards the entire length of the intake filter rather than only a small portion. This results in a reduction of air turbulence and creates an even pressure distribution over the entire filter surface for maximum filter efficiency. As the filter becomes dirty with age, performance drop happens less dramatically as particles form evenly over a larger portion of the intake rather than localizing to one location or another. When air flows through a smooth pipe, the speed at which the air flows is slower along the pipe’s smooth walls than is in the center of the pipe. Ultimately this results in a boundary layer that effectively reduces the cross-sectional area of the free flowing portion of the pipe, and creates drag. To minimize this effect as much as possible, the intake’s inner surface is kept mildly rough during the manufacturing process. As such, a thinner turbulent boundary layer forms, which ultimately prevents the boundary layer from growing larger as flow increases.
Intake Air Temperature Management
Intake air temperature (IAT) plays a critical role in engine performance, especially on turbocharged engines where the ambient air temperature is raised twice through both compression via the turbocharger, and then again during the engine’s compression stroke. In an effort to maintain the lowest possible starting IAT, the APR Intake system begins by drawing air from the coldest possible location, which is the front end of the vehicle before the radiator. Air travels a short path through the intake system, past the filter and on its way to the turbocharger through a sealed intake design that prevents ingestion of hot, under-hood air. Finally, the intake’s carbon composite design features a thin fiberglass backing, which improves thermal insulative properties. NOTE: Unlike many intake designs with a full frontal scoop, the APR system does NOT block the factory engine cooling duct found on the opposite side of the factory intake system.
APR’s design requirements called for an intake filter medium that exhibited high flow capabilities, long service life and adequate filtration properties. While traditional paper filters and even some foam filters can achieve one or more of these requirements, only a pleated cotton filter was able to achieve all three. This is due in part to the intake housing’s volute design and turning vanes. With even pressure flow distribution across the entire filter element, the filter is loaded more evenly, retaining performance over time, increasing the length of the maintenance intervals, and increasing the filter’s effectiveness.
Upon opening the hood, it’s clear to see why the APR Carbon Fiber Intake System is so highly sought after. Featuring a carbon fiber 2×2 weave common to the engine bays of Audi’s high end of Quattro GMBH vehicles, the intake demands attention and delivers form that matches the intake’s function despite playing a secondary role in the design requirements.
The intake system comes preassembled from APR ready to be installed in minutes with minimal tools. With the factory unit removed, the intake slips into place and connects to the factory turbo inlet pipe using the OEM hardware without filling the engine bay with additional couplers and hose clamps. Because the system fits in the OEM location, it’s fully compatible with future upgrades from APR, including our larger Stage 3 Turbocharger Systems.