Quote:
Originally Posted by Hubert Farnsworth
Controlling the fuel intake effectively throttles the power output of the diesel engine yes, but I was referring to the throttle plate on the intake air charge, which modern diesels typically don't require and are effectively at wot all the time on the air side ie the volumetric efficiency goes up, and the precise amount of fuel required can be injected just prior to the top of the compression stroke. This increase in volumetric efficiency coupled with the higher energy density of the diesel fuel helps lead to higher fuel efficiency/lower fuel consumption
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Historically,a Diesel engines mpg advantage diminishes with speed.As an Otto cycle engine car gets into higher load situations ( faster ) the throttle is moving closer to WOT all the time.Honda 3-barrel carburetors were designed to have both the idle and the #2 barrel throttle plates at WOT at highway cruise speeds for nice volumetric efficiency,something modern EFI fails to do.
The Diesel will still have the chemical energy density advantage over gasoline.You can argue the cost/benefit ratio.
Presently,my gasoline pickup is returning better mpg than the VW Diesel Rabbit at higher speeds.