When using series turbocharging in a diesel engine, how are the twin turbos arranged?

In series turbocharging, twin turbos are specifically arranged in a sequential manner, meaning that one turbocharger drives the other. This arrangement allows for enhanced performance and efficiency across a broader range of engine speeds and loads. In this setup, the first turbo typically handles lower engine speeds and can spool up quickly, ensuring there is reduced turbo lag. As engine speeds increase, the second turbo kicks in to provide additional boost, thereby improving power output without sacrificing efficiency.

This configuration is particularly beneficial in diesel engines, where a wide torque band is crucial for performance. It allows for better exhaust gas flow and optimized air intake, particularly at different RPM ranges, leading to improved performance characteristics. Thus, the correct answer accurately reflects the operational principle of series turbocharging in diesel engines.