From steering wheels and dashboards to air intakes, 3D printing technology has come into play for many Formula SAE teams looking to improve their race cars. In a new case study recently published by Carbon, we learn how student engineering organization Hornet Racing, affiliated with the Sacramento campus of California State University, worked with the company last year to leverage its 3D printing and end-to-end digital design capabilities to reinvent the intake manifold of its competitive race car and improve the performance of the engine.
The Hornet Racing team designs, builds, tests, and races a Formula-style car, with one seat and an open-wheel design, every year for the international Formula Society of Automotive Engineers (SAE) competition, which, in addition to the final race between university teams, challenges participants to come up with creative solutions to engineering and design problems.
The team’s car uses a 4-cylinder, Honda CBR600RR series engine, which has an individual throttle body for each cylinder. While this many bodies help to maximize engine performance, Formula SAE design challenge guidelines dictate that these must be replaced with a single throttle, complete with a diameter restrictor that limits the engine’s power outputs. While this may seem counterintuitive, the rule was made for a reason – to challenge the student teams to rethink the design and engineering of the engine.
The intake manifold is essential to a car’s performance, as it supplies a mixture of air and fuel to the cylinders. For the last several years, the Hornet Racing legacy engines had been giving teams issues with driving consistently and smoothly. When the throttle was pressed to the floor, poor airflow was causing nonlinear power delivery, which resulted in a delay. Most of its components were aluminum and had to be welded together, while carbon fiber molds were used to make the rest.
Conventional manufacturing offered several design limitations, such as engine performance issues like uneven air distribution, caused by slow design iterations and only being able to use basic part geometries. In addition, because there were many complicated steps and small components involved in putting together the legacy intake manifold, there was a lot of room for error. So the team decided to overhaul the component’s design for the 2017 race car and make it simpler.
Redesign goals included:
- Reducing the overall weight of the manifold to promote improved handling characteristics
- Optimizing the airflow for better engine performance
- Integrating fuel injector ports into the base of the intake runners for minimal flow turbulence
- Creating components that would promote minimal boundary layer formation, for smooth airflow
The Hornet Racing team members quickly realized that traditional manufacturing methods would be too expensive, and may not even be able to complete the improvements, so they instead used Carbon’s proprietary Digital Light Synthesis (DLS) technology and RPU 70 material to overcome the design challenges and complete its new intake manifold.
By taking advantage of DLS, and the complex geometries 3D printing technology is capable of achieving, the team was able to completely reimagine the intake manifold design into a durable component, ready to be placed into the engine and optimize their race car’s performance.
“Central to Hornet Racing’s new design is a ‘bulb’ only 7 inches in length that replaced the two-foot long diffuser and the large plenum (over a half-gallon in volume),” Carbon explained. “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.”
This spike allows for the airflow to be optimized in a diffuser, which is just 30% of the length of a traditional one, allowing the team to get rid of the traditional plenum. Additionally, it has a dimpled pattern, similar to a golf ball, which sends the air right into the intake runners without a loss of velocity. The 3D printed intake manifold was manufactured rapidly, with no tooling costs or time constraints, and helps the race car’s engine rev up to the original redline of 14,000 RPM: a 43% increase in performance from the team’s legacy intake manifold.
The spike structure isn’t the only advantage the team achieved by using Carbon’s DLS technology. By consolidating the fuel-injector ports into the base of the intake runners, the number of weld joints went drastically down, which helped minimize flow turbulence and maximize engine performance.
Customized intake runner tubes with tapered diameters helped with smoother airflow to the cylinder head, which meant a much more consistent power delivery. Finally, by working with Carbon to develop a more compact and simple design, and using its RPU material, the 3D printed intake manifold has achieved a 50% weight reduction, which improves the race car’s handling.
If all of these explanations aren’t enough to convince you of the many ways Hornet Racing’s race car benefited from Carbon’s DLS technology, then maybe its performance results will – out of 80 university teams from all around the world, last year’s HR2017 car placed 16th overall, giving the Hornet Racing team the best competitive finish CSU Sacramento has ever achieved.
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