The resource named EVO6 is the further development of our previous, EVO5 engine, during whose development we put the emphasis on thermodynamics.
The new crankshaft did not only become lighter with the help of the optimized placement of swinging masses, tungsten rods but also its stroke became greater by exactly 4 mm compared to the previous generations. The electric supply is provided by a Kawasaki generator, whose space requirement is less than that of the previously used generator. Instead of the piston, we used so far, we used a new Wiseco piston, thanks to which we managed to significantly increase the compression ratio together with the longer swept volume so that combustion is as quick as possible and has the greatest energy possible.
In compliance with the competition rules and in order to reach the optimized volume according to the simulations, an intake system different from a sphere and equipped with an airbox with a volume of 5 litres has been created so that we can increase the amount of air mass available for the intake stroke. Besides the length and geometry of the intake manifold has been optimized so that the second charge movements become ideal. Thanks to these in the competition season of 2018 the SZEngine EVO6 resource can burn E85, the fuel used by the team for the first time, cleaner. The reason why E85 was chosen was to increase efficiency. In compliance with Formula Student rules for this fuel, there was a need to create a restrictor with a diameter of 19 mm to replace the previously used restrictor located in the front of the 20 mm intake system.
For an enhanced driveability and faster race car based on track simulations we optimized the number of shift gears, the transmission and we utilized the quick-shift and start electronics function while applying the Bosch MS4 Sport engine control unit, just like in previous years, thus helping to carry out shifts without releasing the gas pedal and using the clutch as well as helping to put the most torque of the engine on the asphalt. Besides these, the self-developed shift drum played an important role too.
The cylinder itself is a KTM 500 EXC cylinder, for which we chose a KTM 450 SXF cylinder head, whose intake ports were enlarged in order to reach a greater flow of air mass. The more aggressive opening and closing of valves are enabled by a sliding rocker arm on the intake side. We had to modify the timing of the valves because they were not optimized for the gas exchange of the limited systems caused by the restrictor. By modifying the intake port of the cylinder head and with the help of a tumble ramp created with a two-component metal adhesive we were able to correct the flow rate reaching the combustion chamber, which provides a steadier mixing of fuel-air particles, thus increasing performance.
Thanks to the support of sponsors related to 3D printing we had the opportunity to use a printed intake manifold and chain leader when assembling our engine. Both the chain tensioner and the intake manifold were made of PA2200 polyamide powder and with a layer thickness of 100 microns. The intake manifold was designed for two types of intake systems, for a laminated and for a printed one. During the tests, we used the whole printed intake system, while during the competitions we used the laminated one. We needed the printed chain guide because none of the commercially available timing chains were appropriate for the greater stroke owing to their length, so we needed a custom made one which is appropriate for the factory timing chain.