To sum up the project so far, a functional electric supercharger system has been developed in line with the original project concept. With the current setup the maximum boost pressure attainable at maximum engine load and speed is 8psi measured at the intake manifold (this equates to around 10psi at the outlet of the compressor). This is short of the 11psi goal. The main reason for this is the Rotrex C30-84 supercharger is operating too far outside of its efficiency island to increase boost pressure further. With the originally sizing the compressor, a few mistakes were made:
- Underestimated volumetric efficiency of the engine which was exacerbated by upgraded cams, extractors, and 3” exhaust system
- Used compressor sizing logic based on a centrifugal supercharger being driven of engine crank which is an exercise in compromise
- Did not adequately allow for pressure drop across intercooler and charge pipe
Below is compressor map for the current C30-84 supercharger at the maximum operating point.
The performance, and drivability of the system at only 8psi boost have exceeded expectations so investing more time and resources into optimizing the system is justified. The major upgrade will include:
- Larger compressor and new electric motors to suit
- Battery and power cabling upgrade