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Old 03-03-2015, 02:08 PM   #43 (permalink)
redpoint5
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Quote:
Originally Posted by EVmetro View Post
It still takes a certain amount of energy to drive a car of a certain weight and cd, and I don't fully understand how the Atkinson engine coupled to an electric motor benefits this.
It may be helpful to read about BSFC and pumping losses. You are correct that it takes a specific amount of energy to go a specific speed, but different speeds and loads on an engine greatly affect how efficiently it is producing that energy. An gasoline engine can be 5x more efficient when accelerating compared to cruising at a steady 40 mph. That's because large throttle openings minimize pumping losses and larger quantities of fuel maximize thermodynamic efficiency. It's not efficient for all cylinders of an engine to work against a vacuum while producing 20% of their designed power.

Whenever an engine is putting around, barely producing it's peak potential, it's operating in a very inefficient way. It can be more efficient to generate a little extra electricity when the engine is operating at peak efficiency, and later use that electricity to move the car when it would otherwise be using the engine in a very inefficient way (parking lots, low speeds, etc).

Quote:
Originally Posted by vibrating_cake View Post
No, the ICE in a Hybrid is no more or no less efficient than the ICE in a non-hybrid.
This statement is only true sometimes. Sure, some vehicles have the identical ICE in both their hybrid and non-hybrid models, and the electric system exists mostly just to boost acceleration performance. However, some cars, such as the Prius, specifically engineer the engine for efficiency. The Prius engine is 1.8L and produces only 98 HP compared to a VW 1.8L engine that is designed to produce 170 HP. Which engine do you think is more efficient for maintaining a steady 55 mph cruising speed where only 15 HP is needed?
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Last edited by redpoint5; 03-03-2015 at 07:02 PM..
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