Back in college, a teacher in a physics class explained to me and my classmates the models that rule diesel and gasoline engines. This stirred a classic debate: what's better: diesel or gasoline? The concept that explained the better efficiency of diesel engines was "thermal efficiency." This is also the concept that a prototype originally developed at Coventry University uses to claim that a 2.0-liter MUSIC (Merritt Unthrottled Spark Ignition Combustion) gasoline engine achieved more efficiency than a 2.4 liter diesel engine. For those unfamiliar with MUSIC engines, they are un-throttled, with high thermal efficiency, lean-burn, and work with a spark ignition system that uses an indirect combustion chamber to produce charge stratification by means of controlled air management. The tested engine was simply a new cylinder head mounted over a standard Duratec engine.

According to MUSIC performance data, brake thermal efficiency was about 20 percent higher than a diesel engine. However, the comparison used data not from a real engine but from a "reputable" engine R&D company, according to MUSI Engines Ltd. So, there is no information about parasitic loads, the specific diesel technology (what about comparing an old indirect injection diesel with modern common-rail units?) or test conditions were provided. Nevertheless, taken with a pinch of salt, let's hope this leads to a promising solution.

[Source: Green Car Congress]

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