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AUTOMOTIVE DESIGN


the floor, poor airflow would result in nonlinear power delivery and cause a delay that made it difficult to drive smoothly and consistently. Te team’s prior challenges, combined with the Formula SAE throttle body competition restrictions, set the stage for Hornet Racing to take a fresh approach when designing the intake manifold for its 2017 race car. Carbon’s Digital Light Synthesis technology enabled unique design advantages and production capabilities, enabling Hornet Racing to overcome previous challenges rooted in design restrictions associated with conventional manufacturing.


IDENTIFYING REDESIGN OPPORTUNITIES Hornet Racing’s legacy intake manifold had been used for several years prior to the team’s 2017 redesign effort. Te majority of its components were aluminium and needed to be welded together after machining steps. Additional components were made separately using carbon fibre moulds. Tese conventional manufacturing methods imposed numerous design limitations. Te team was restricted to using basic part geometries and could not quickly iterate on designs. Such limitations contributed to substantial engine performance problems, including considerable boundary layer formation and uneven air distribution across the four cylinders. Additionally, assembling the legacy intake manifold involved many small components and intricate steps, creating considerable room for error. Setting its sights on simplifying the intake manifold design, Hornet Racing identified the following goals


half-gallon in volume). Inspired


by supersonic jet engine shock cones, which regulate air intake based on shape, the team combined the functionalities of the diffuser and plenum by designing a spike-like flow split within the bulb structure. Te spike feature enables airflow optimisation in a diffuser that is only 30% of the length of a traditional diverging nozzle diffuser. As a result, the team was able to eliminate the traditional plenum entirely. Moreover, taking design inspiration


The legacy intake manifold had a large number of moulded and machined parts, necessitating significant welding and complicated assembly steps


for redesigning the part: optimise the airflow for better engine performance; create components that promote minimal boundary layer formation to allow for smooth airflow; integrate the fuel injector ports into the base of the intake runners (tubes that connect the plenum with the cylinder heads) to achieve minimal flow turbulence; and reduce overall manifold weight to promote improved handling characteristics. As the team moved forward to perfect its legacy manifold, it became clear that with traditional manufacturing methods, the desired improvements would be impossible to manufacture or prohibitively expensive. To overcome the design constraints and high costs associated with traditional manufacturing approaches, Hornet Racing turned to Carbon’s Digital Light Synthesis technology and Carbon’s RPU 70 material to execute its vision for an improved intake manifold.


The 2017 race car had its best competitive finish in the history of CSU Sacramento Hornet Racing


OPTIMISING DESIGN THROUGH TO PRODUCTION With Carbon’s technology, the team was able to access previously impossible geometries, reimagining an entirely new manifold design unconstrained by conventional manufacturability. Te part could be produced rapidly, with no lead- time constraints and tooling costs. Te result was an isotropic, durable, engine- ready intake manifold manufactured to optimise vehicle performance. Central to the new design is a ‘bulb’ only 7in in length that replaced the 2ft long diffuser and the large plenum (over a


from the dimples on golf balls, the shock cone-inspired spike structure contained a dimpled pattern on its main body, which helps air flow directly into the intake runners without losing velocity. With this design, the team exceeded its own expectations and achieved an intake that allows the engine to rev to the original redline of 14,000rpm. Tis 33% increase in performance was impossible with the team’s legacy manifold intake, which at best enabled the engine to reach 10,500rpm. Beyond the spike structure that allows for optimised airflow between the diffuser and upper intake, the new intake manifold also possesses the following advantages enabled by Carbon’s technology: seamless integration of fuel-injector ports into the base of the intake runners; customised intake runner tubes with a precisely tapered diameter that minimise boundary- layer formation for smooth airflow; and major weight savings due to a simplified, more compact design and the use of Carbon’s RPU material. Te new intake weighs approximately 50% less than the legacy intake. Since the intake is positioned high in the vehicle, a heavier intake can destabilise the car’s roll centre and vehicle dynamics. Te lighter intake contributes to improved vehicle handling and a better overall driving experience.


ADDITIONAL APPLICATIONS Ultimately, Hornet Racing optimised its intake manifold design in ways that were either physically impossible or prohibitively expensive using traditional manufacturing methods. Te vehicle performance results were astounding. Te 2017 race car - the HR2017 - had its best competitive finish in the history of CSU Sacramento Hornet Racing. Te team placed 16th overall out of 80 university teams from all over the world.


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