Atkinson cycle engine question

i dont think it would work well. the atkinson engine works well because it is never running in the inefficient mode or running inefficiently as little as possible.

that means reduced cold running, no standing starts, etc.

iow, with out the EV for high torque assists and low speed starts, the atkinson engine would wear out much faster.

just a guess as i dont specifically know.

 

The reason an Atkinson cycle engine works so well in a pri is that it has an electric engine to help it out at low speeds and during moments of peak demand. If you put the ICE all by itself in another car, it would have all the power and responsiveness of a golf cart. People would like it every bit as much as they liked the Yugos.

I think it is quite possible that Toyota will gradually move to put a hybrid system in all its vehicles, and thus you would have your Atkinson cycle Corrollas, but done well, the Toyota way.

 

the Echo and the Prius both use the 1NZ series engine with some differences and the Echo makes 108 hp and 105 Ft Lb's of torque, the Prius on the other hand makes 76 hp and 82 Ft Lb's of torque, -32 HP and 23 Ft Lb's of torque less and the difference is where you need it the most on the bottom end. With a standard transmission it would probably be useable but the torque converter in an automatic transmission would probably sap all the bottom end torque the engine is capable of putting out. With a belt driven supercharger it might work but no one in their right mind would buy such a car. It works in a Prius because the electric motor has most of it's torque output at low rpm's and the Atkinson/Miller cycle engine has it at high rpm's. And Toyota computer controls work to harvest the benefits of both.

 

I think you answered your own question in there: part of the efficiency of the Prius is in running the ICE always closer to its most efficient RPM. That can only happen because of the PSD, which isolates the ICE rpm from the wheel speed. Excess power goes through MG1 to the battery or to MG2, as needed, and the ICE can shut off entirely at low speeds, when it would be inefficient, and let the battery and MG2 do the work, until it needs to charge the battery again, at which point it can again run fast (efrficiently) to do that.

Put the same engine in a non-hybrid car and you lose all that, plus you have insufficient low-end torque. You say that you seldom need all the torque the Corolla is capable of. But if you need it once a year to avoid an accident, then you have to have it.

 

granted you might only push the pedal down a quarter of the way but you have way more bottom end torque in the Corolla than you would get out of a 1NZ from a Prius.

 

i agree, the atkinson by itself would not work efficiently. you may think you arent using much torque by depressing the pedal ¼ of the way down, but you are using much more than you think.

straining the atkinson at low rpms would use up a huge amount of gas. the Prius demostrates the same thing under normal acceleration when the ICE kicks in and the mpg reading drops into the 20's. but after it gets up to speed and is cruising and i mean good speed (65 mph) the mpg's are in the 50's. now that acceleration is with the EV assist. without the EV assist, your mileage will suffer.