Why Diesel Motorcycles Have Stood Still in the Face of Innovation
The Diesel Engine's Advantage
The primary benefit of a diesel engine is its ability to use approximately 30% less fuel compared to a petrol engine to produce a given amount of horsepower. However, this advantage is not as significant for motorcycles as it is for larger vehicles like SUVs. In fact, the idea of a diesel motorcycle is often met with skepticism due to various practical considerations.
Does Fuel Consumption Even Matter?
Motorcycles are not primarily about fuel consumption. A typical 1200 cc bike, even when used as a recreational toy, consumes around 4.5 liters per 100 kilometers on highways and is driven for approximately 5000 kilometers annually. For such applications, the fuel consumption is a trivial part of the overall cost of ownership. Conversely, in vehicles like SUVs, fuel efficiency can make a significant difference in both cost and environmental impact. My 1200 cc diesel SUV, which is used for towing and covers about 20000 kilometers annually, saves a substantial amount of fuel compared to a petrol equivalent.
Designing for Performance
Diesel engines are known for their large size, weight, and low RPM operation, producing high torque. These characteristics make them unsuitable for motorcycles, which require compact, lightweight, high RPM, and high power engines. The need for compactness and lightness is crucial in motorcycle design for rapid acceleration and a high power-to-weight ratio, essential for the thrilling riding experience that motorcycles often provide.
Performance vs. Practicality
Motorcycles stopped being primarily a mode of transport by the end of the 1950s in the UK. Instead, they became leisure toys, cherished for their excitement and performance. These motorcycles are designed to be nimble, agile, and responsive, providing the thrill of speed and control that is hard to replicate with a diesel engine. Diesel engines don't use spark plugs and rely on compression to ignite the fuel, creating a heavier, bulkier engine suited for larger vehicles where weight is less of a critical factor.
The Impact of Diesel on Weight and Vibration
Putting a diesel engine in a motorcycle would significantly increase its weight, adding to the vibration and noise. The added weight and increased size would contradict the very essence of a motorcycle, which is meant to deliver a lightweight, nimble, and responsive riding experience. Additionally, the low RPM, low rev, and high torque characteristics of diesel engines would detract from the dynamic performance that motorcycle enthusiasts seek.
Conclusion
The success of diesel motorcycles is hindered by their design characteristics. While diesel engines offer significant fuel efficiency, this benefit is often outweighed by the drawbacks in the context of motorcycle design. The need for a compact, lightweight, high RPM engine is central to the motorcycle experience, and diesel engines simply do not align with these requirements. As technology and design continue to evolve, it may be worth revisiting this concept, but for now, the challenges of integrating diesel engines into motorcycles remain substantial.