While there are currently no mass-produced production cars with motorcycle engine powertrains, there are a few reasons why motorcycle engines are not commonly used in (super) cars:
Power and torque limitations: Motorcycle engines are typically designed to be lightweight and compact, optimized for high rpm performance. While they can deliver impressive power-to-weight ratios in motorcycles, they generally lack the torque and low-end power required for larger and heavier cars. Super cars often demand significant horsepower and torque figures to provide the desired acceleration and top speed, which is challenging for most motorcycle engines to achieve.
Thermal and durability challenges: Car engines, especially high-performance ones, operate under more demanding conditions compared to motorcycle engines. Cars have larger engine bays that allow for more extensive cooling systems, whereas motorcycles have limited space for cooling components. Car engines need to handle sustained high speeds, heavy loads, and extended periods of operation, which would pose thermal and durability challenges for many motorcycle engines.
Safety and crash requirements: Cars are subject to extensive safety regulations and crash standards, which include engine design and placement considerations. Motorcycle engines, due to their compact size and construction, may not meet these safety requirements or provide the necessary crash protection in car applications.
Comfort and refinement: Motorcycle engines tend to produce more noise, vibration, and harshness (NVH) compared to car engines. Cars, especially luxury and high-performance models, require a refined and smooth power delivery with minimal NVH levels to ensure a comfortable and enjoyable driving experience. Achieving such refinement with motorcycle engines in a car chassis could be challenging.
These examples often cater to specific enthusiasts seeking lightweight and high-revving performance, rather than aiming for the performance levels and requirements of mainstream super cars.
Overall, the unique characteristics and limitations of motorcycle engines make them less suitable for powering (super) cars, which require a different set of performance, safety, and refinement standards. Car manufacturers tend to develop and utilize engines specifically designed for automotive applications, considering factors like power, torque, durability, safety, and overall vehicle performance.