Quote:
Originally Posted by Diesel_Dave
I think what your describing is actually called the Miller cycle rather than the Atikinson Cycle. Both have the same basic goal: expansion ration > compression ratio,
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Modern Atkinson cycle engines
A small engine with Atkinson-style linkages between the piston and flywheel. Modern Atkinson cycle engines do away with this complex energy path.Recently Atkinson cycle has been used to describe a modified Otto cycle engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold. The effective compression ratio is reduced (for a time the air is escaping the cylinder freely rather than being compressed) but the expansion ratio is unchanged. This means the compression ratio is smaller than the expansion ratio. Heat gained from burning fuel increases the pressure, thereby forcing the piston to move, expanding the air volume beyond the volume when compression began. The goal of the modern Atkinson cycle is to allow the pressure in the combustion chamber at the end of the power stroke to be equal to atmospheric pressure; when this occurs, all the available energy has been obtained from the combustion process. For any given portion of air, the greater expansion ratio allows more energy to be converted from heat to useful mechanical energy meaning the engine is more efficient.
The disadvantage of the four-stroke Atkinson cycle engine versus the more common Otto cycle engine is reduced power density. Due to a smaller portion of the compression stroke being devoted to compressing the intake air, an Atkinson cycle engine does not take in as much air as would a similarly designed and sized Otto cycle engine.
Four-stroke engines of this type with this same type of intake valve motion but with a supercharger to make up for the loss of power density are known as Miller cycle engines.
(
Atkinson cycle - Wikipedia, the free encyclopedia)
Quote:
Originally Posted by Diesel_Dave
Changing just the IVC, however, won't give you any benefit. The benefit would come from running a high compression ratio piston that would otherwise knock.
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The compression ratio increase is one of the difficulties I raised but one more that springs to mind is the intake sizing (valves and carb) is gonna be too big on a velocity point of view.
Quote:
Originally Posted by Diesel_Dave
On another note, I've toyed with the idea of finding a motorcycle with a blown engine and putting a small diesel on it. Just a thought...
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Engine swap is very difficult in France (homologation required)