Quote:
Originally Posted by mechman600
Almost Atkinson-esque, no? Probably close, but not close to enough to have to say it out loud.
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Well, all cams have their natural peak volumetric efficiency speed, and most engines with 1 cam profile have this peak rather high in the rev range, so basically all engines have some sort of Atkinson-esque stuff going on at low engine speed. With cam phasing I believe what happens is that at lower rpm they advance the intake cam so that it closes earlier if you need more power, although if you have too much overlap then you end up with a lot of fresh, hot exhaust trapped in the cylinder and you have a knock problem.
As an example, I think the new Subaru FA20 (on the BRZ/FRS, and some variant will appear in the new WRX) the intake cam seems to have a volumetric efficiency peak in the 6000s rpm, so it's very possible that the actual cam duration is longer than the cam duration on a Prius for example.