Showcasing The Intake

Name: Peter Cochran
Subteam: Powertrain
Part: Engine Intake Manifold System

The maximum power that can be produced by a Formula Student vehicle is limited by imposing the use of an intake restrictor in the intake system.  This restrictor then forces teams to design and manufacture a custom, purpose-built intake manifold.

UGR-19 features a Honda CBR600RR engine, the main aim of the intake system designed for a spark ignition engine like our own is to optimise the delivery of air from the atmosphere to the engine’s inlet ports.  The mass of air entering the combustion chamber should be maximised, and the delivery of air must occur in a predictable manner, to give the driver confidence in the car and the throttle response.

The driving force in the system is the internal pressure generated by the suction stroke of the four stroke cycle.  This negative pressure causes high repetitive loading on the component, and so the manifold must be strong enough to withstand this loading over large periods of time.  The manifold can also become quite hot and will experience some exposure to fuel, therefore any chosen material must have excellent resistance to both heat and petrol. As with all parts of UGR19, the total weight of the system must be minimised with a defined factor of safety.

UGR-19 features a 3D printed intake system made with carbon filled nylon, this is the team’s first intake manifold to be 3D printed, and replaces the previous aluminium system. This switch results in an impressive weight reduction of 1.2kg in the intake system alone.  This weight saving was helped by the ability to print the runners and plenum as one part, reducing the need for fasteners and seals.
The design was first evaluated using CFD so as to analyse the air flow through the plenum and into the runners, from this the design can be changed to optimise the flow rate. Many configurations were tested this way before the final design was settled on.  The final design features a plenum of volume 1.5 litres with raised bellmouths and a domed base.  The bellmouths are arranged in a square profile so as to help with the even distribution of air between cylinders.  When the four bellmouths are arranged linearly, as in UGR18, it is often found that the outer two cylinders experience reduced air low relative to the inside two.
After the design was finalised in CFD, the structural aspects of the component can be considered using FEA, the component must be strong enough to hold a vacuum, but also be able to withstand the high pressures due to any engine backfires.

With the addition of this new intake manifold, and various other powertrain improvements, we have been able to boost the power output of the car, to a maximum of 72bhp at the wheels!