Atkinson cycle

[janvos39]

I am interested in looking into the possibility of making a variable inlet valve timing to run the Atkinson cycle as used in the Toyota Prius.
Who has details of the timing variation that Toyota is using for the Prius with their VVT-i valve control system? Is the workshop manual more detailed than the commercial leaflets?

[janvos39]

I found what I was looking for. A friendly Toyota dealer made this copy of the manual.
It shows that the Prius inlet timing is shifted over an angle of 41 degree from maximum torque to best FE.




Now it is time to make a mechanism for the Suzuki Burgman to realise this kind of inlet cam change . At 70 MPH I only use 1/4 turn on the throttle so it must be possible to do the same as the Toyota Prius.

[Daox]

You probably know, but to take full advantage of the atkinson cycle you'll need to increase the compression a fair amount too.

[janvos39]

My plan is to change the engine capacity of my Burgman from 385 cc to 300 cc by putting a cylinder and piston in of the Burgman 250. They almost fit. Only need to do some bushing in the connecting rod. By making the bore smaller I get some more compression with the 250 cc(bore 73 mm) head. Not sure if I go to the full 13:1 of the Prius. Other users of Atkinson cycle report lower compression ratio.