Toyota to use Atkinson cycle in non-hybrids: 10% efficiency boost, "no power loss"

[cRiPpLe_rOoStEr]

Originally Posted by Old Tele man

Yes, the higher CR helps, but at what cost to FUEL "knock" sensitivities?

One could expect them to make direct-injection available to reduce the pre-ignition sensitivity. Anyway, in my country the gasoline quality is below average, and we still have many non-Atkinson engines running around 12:1 compression without direct-injection...

[Daox]

I'm wondering if direct injection hasn't been used on the Toyota atkinson engines for a reason. They've been using direct injection on the Yaris since before the 3rd gen Prius came out. My theory on this is that the port injection allows more time for the fuel to vaporize and the benefits of that outweigh the benefits and costs of direct injection. Due to the way Toyota does their atkinson cycle, part of the intake charge is pumped back out of the intake valve during the compression stroke. This allows more time for the fuel to vaporize and to cool the intake charge thus producing an anti-knock benefit. If they went to direct injection, they would loose some of this effect. Anyway, thats just my theory on it.

[cRiPpLe_rOoStEr]

Originally Posted by Daox

My theory on this is that the port injection allows more time for the fuel to vaporize and the benefits of that outweigh the benefits and costs of direct injection. Due to the way Toyota does their atkinson cycle, part of the intake charge is pumped back out of the intake valve during the compression stroke. This allows more time for the fuel to vaporize and to cool the intake charge thus producing an anti-knock benefit. If they went to direct injection, they would loose some of this effect.

Makes sense.

[aerohead]

Toyota also has engines with up to 42% thermal efficiency,which rivals that of a diesel,minus the extra energy of the diesel fuel itself of course.