The resource code-named EVO6 is a further development of our previous EVO5 engine, which was developed with an emphasis on thermodynamics.
CRANKSHAFT / CRANKSHAFT MECHANISM
The new crankshaft is not only lighter, with more optimized swing weights, with the help of tungsten rods, but its stroke has also increased by exactly 4 mm compared to the previous generation. The electrical supply is provided by a Kawasaki generator, which requires less space than the previously used generator. Instead of the previously used piston, we used a new Wiseco piston, thanks to which, together with the longer stroke volume, we managed to significantly increase the compression ratio so that the combustion run is as fast and with the highest energy as possible.
In order to achieve an optimized volume in accordance with the competition regulations and based on the simulations, an intake system with a 5-liter airbox, different from the sphere, was designed to increase the amount of air mass available for the intake stroke. In addition, the length and geometry of the intake duct have been optimized so that the second-order charge movements are ideal. Thanks to all of this, the SZEngine EVO6 power source can burn more cleanly the fuel used by the team for the first time in the 2018 racing season, E85, which was chosen to increase efficiency. In accordance with the regulations of Formula Student, instead of the restrictor placed at the beginning of the previously used 20 mm intake system, it was necessary to design a restrictor with a diameter of 19 mm for this fuel.
In order to improve drivability and make the racing car faster, the number of gear ratios and gear ratios of the transmission were optimized based on track simulations, and when applying the Bosch MS4 Sport engine control, the quick shift and start electronics functions were used, as in previous years, thus helping to perform shifts without taking off the gas or using the clutch. and the most complete delivery of the engine’s torque to the asphalt. In addition to these, the self-designed worm shaft also played a major role.
CYLINDER / CYLINDER HEAD
The cylinder itself is a KTM 500 EXC cylinder, for which a KTM 450 SXF cylinder head was selected, the intake ports of which were enlarged to achieve a higher air mass flow. The sliding rocker on the suction side enables more aggressive valve opening and closing. The valve timing had to be modified as they were not optimized for gas exchange in restricted systems caused by the restrictor. By transforming 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 improve the amount of tumble flow entering the combustion chamber, which ensures a more uniform mixing of the fuel-air particles, thus increasing the performance.
3D PRINTED PARTS
Thanks to the sponsor support related to 3D printing, we had the opportunity to use a printed intake pipe and chain guide when assembling our engine. Both the chain tensioner and the intake pipe are made of 100 micron layer thickness and PA2200 polyamide powder. The suction pipe is designed in two types of suction systems, one laminated and one printed. During the tests, we used the entire printed suction system, while during the competitions, we used the laminated one. The printed chain guide was needed because none of the commercially available timing chains could match the increased stroke due to their length, so a custom fabricated piece was needed to match the factory timing chain.