Auto Manifesto

May 23, 2008

Diesel Engine Notes From SAE (Belated)

Fascinating presentations on diesel engines. About 70% to 75% of an engine's energy input is lost to the atmosphere as waste heat and to the cooling system. Ten percent is lost to idling and auxiliaries, so only about 15% to 20% is effectively used for propulsion.

The projected solution to improve diesel engine efficiency is to use hybrid power to bring about a 15% to 20% improvement, engine stop/start to eliminate idling will save about 6 to 7%, and 10 to 15% optimization and electrification of auxiliaries, as well as another 7% to 10% improvement from downsizing the engine and downspeeding RPM.

Thirty years ago maximum injection pressure was 500 bar. Now it's close to 2,000 bar and direct injection allows for higher compression ratios, more torque and higher knock thresholds.

In addition to consuming less fuel, downspeeding results in lower friction and wear, and also keeps the weight down. Engines need forced induction for torque, and sequential turbos are even better to eliminate the turbo lag of one big turbo.

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