I have used the term “imperceptible” to describe the Atkinson/Otto cycle switch a roo in our F cars. But when exactly does the RC F activate the Atkinson cycle and when does it switch to the Otto cycle?



I was playing around in NORMAL mode and mashed the throttle (actually, there is not much to mash because it is quite tamed down in this mode), and when I let go of the throttle the dash flashes the small ECO icon. I take this to mean that the car has switched to the Atkinson cycle. In S and S+ modes, the small ECO icon never flashes in any situation, so I take this to mean the car is on Otto cycle 100% of the time in S and S+ drive modes.



So I surmise the Atkinson cycle is 100% active in ECO drive mode, and will turn on in NORMAL mode when you let go of throttle and in cruising driving.



I have said this before but it is one of my greatest likes with this car, technology from a Prius and engineered to work in a bestial V8…Bravo, Toyota/Lexus.

 

Should be pretty seamless, and it works the same way that pretty much every other modern engine does - it can just close the intake valves way later in low load conditions. Wider range variable valve timing systems allow for essentially both modes. You won't get the same efficiency as a hybrid atkinson, since those have a way higher comp ratio to compensate for the fact that they don't really operate without the intake valves closing... later than usual.