Quote:
Originally Posted by danwat1234
Wait wait, I have never heard of the Prius engine (whether the 2nd gen 1.5L or the 3rd gen 1.8L) having an OTTO cycle mode! That is why the 1.5L is only rated at a peak of 76HP and the 1.8L 3rd gen Prius engine only has a peak of 98HP. Maybe it's because it does OTTO sometimes at low RPMs for power, but always Atkinson at high RPM (see post #43), hence the low peak HP.
Are you saying that it has an OTTO cycle mode? I have never heard of this, I thought it was strictly Atkinson cycle, hence why it needs an electric motor for assistance, especially at low RPMs.
I thought some of the new Honda/Acura "Earth Dreams" engines that are 2L and smaller will have on demand Atkinson/OTTO cycle behavior so it'll work well in a car that doesn't have an electric motor to help out at lower speeds and could get hybrid like economy on the highway.
If the Prius engine does have an OTTO cycle mode, then why isn't/wasn't it made for some Toyota cars that weren't hybrid, such as a Yaris?
Great innovative project
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They don't. There is no clear distinction between Atkinson cycle and Otto cycle when used in modern engines. Atkinson cycle simply refers to a larger intake cam than usual that results in lower torque but increased efficiency. Guess what else has this kind of setup? A race engine, except the exhaust cam is typically way too big and destroys the efficiency at low rpm by allowing way too much hot exhaust into the mix and ruining combustion.
The VVTi range on the 1NZ will not allow you to advance the long intake cam enough to recover the full torque of the 1NZ-FE. The reason VVTi is continuous is so that the ECU can adjust it based on torque demand and rpm together. The OP IIRC has a Megasquirt running the engine; since it's a cable throttle setup you can't fine tune the VVTi as well for maximum efficiency since the VVTi can only follow the throttle rather than move independently, but I think he would still benefit from a proper VVTi map.