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 Post subject: Re: Engines
PostPosted: Thu Mar 26, 2015 5:04 pm 
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1.2 engine uses double belt running in oil supposed to have a guaranteed life of 220,000 miles iirc.
It was done to reduce noise, weight and friction.


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 Post subject: Re: Engines
PostPosted: Sun May 10, 2015 10:20 am 
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As a point of pickiness the Toyota isn't a true Atkinson Cycle motor. It's still Otto cycle, but used valve timing trucks to mimic the beneficial effects of the Atkinson Cycle, Mao my a much longer ignition stroke than intake stroke.

On a real AC motor there's a linkage between the big end and the crank to physically make the intake stroke shorter than the exhaust stroke,

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 Post subject: Re: Engines
PostPosted: Mon May 11, 2015 7:42 pm 
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Well, I think you're kind of right, but it depends how picky you want to be.

From mechanical standpoit you're right. The displacement of the engine is constant as well as the "geometric" compression ratio, so that's not an atkinson cycle.

However, from a thermodynamic standpoint you can say it's an aktinson cycle. By keeping the intake valve opened during the compression stroke you get a shorter compression stroke than the power one.
Since some of the air is only moved from the intake to the exhaust without contributing to the compression and power strokes you can also consider it as a variable displacement engine. Not a perfect one though.


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 Post subject: Re: Engines
PostPosted: Mon May 11, 2015 9:05 pm 
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The defining characteristic of the Atkinson Cycle motor is the linkage that alters the stroke length, not the gas flow characteristics. Atkinson wasn't trying to make a thermally efficient motor - although my accident he did - but rather was trying to invent a petrol engine he could sell without infringing Otto's parents, hence the big eng linkage.

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 Post subject: Re: Engines
PostPosted: Mon May 11, 2015 9:51 pm 
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I think it dependes what you consider determinant for an engine. You say it's the mechanics (for good reasons). I say it's the thermodynamics (not only the gas flow but also the enegy flow, and also for other good reasons, mainly that the thermodynamics sets the biggest limitations of the efficiency).
However, at least in Europe you can have a patent on a design but not on a cycle (or a theory, theorem, etc), so if you invent a cycle that is perfect you can't have a patent on it. You have to invent an engine that uses that cycle if you want to get any royalties.

Coming back to Atkinson, we have the Atkinson cycle which is one thing (that ugly diagram) while the Atkinson engine is another thing (that engine with that ugly kinematics and with the patent). You can have an Atkinson cycle in an engine that doesn't look like the atkinson engine (for instance using a rotary design). The new Toyota 1.0L engine is other option.

Same about the Otto cycle/engine, the cycle is one thing, and the design (that he patented) is another. Wankel engines use the Otto cycle even if the design has nothing to do with the Otto engine, while the Toyota engine even if it looks like an Otto one actually it uses an Atkison cycle.

I need a drink :D


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