What is the percentage by which DI is better in fuel efficiency compared to IDI?

Direct Injection (DI) engines are generally recognized for their improved fuel efficiency compared to Indirect Injection (IDI) engines. This efficiency gain is primarily attributed to the more precise control of the fuel-air mixture in DI engines, allowing for better combustion. The fuel is injected directly into the combustion chamber, which enhances fuel atomization and combustion efficiency, leading to less fuel waste and more power generated from the same volume of fuel.

In the comparison to IDI engines, which have a less efficient injection process and often rely on a pre-chamber for fuel atomization, the gains in thermal efficiency for DI engines are typically within the range of 10% to 15%. This level of improvement reflects advancements in fuel injection technology and engine management systems that optimize performance and efficiency.

Choosing the correct range helps in understanding the fundamental differences in engine designs and their implications on fuel economy, making it a vital concept for anyone studying heavy-duty diesel engines.