[Christ]

Originally Posted by KJSatz

Lean burn is different. Civic HX and VX of old, and the current hybrid's ICE, have lean burn. That actually changes the ratio of fuel to air in the mixture. What our R18 does is partially retract some of the charge so that less of the mixture is used. I think it's pretty clear in the second link in my first reply here. Also, calling it VTEC would be incorrect. If you are in a lower load situation from 1000 to 3500RPM, you will probably be in VTEC, but you won't be in this weird thing unless you're in especially low load. At least that is the way I understand it; if they are activated only with each other, I am mistaken.

VTEC - change in the cam's profile. (Variable Timing Electronic Control)

You're in Vtec anytime the Cam changes profiles, i.e. when the engine is using a different airflow profile while running.

The lean burn characteristic, (as far as I know) comes from running in Vtec mode. The point of lean burn is the same as CVCC was, just doing it in a more efficient way (supposedly). It's supposed to inject a very rich mixture into the cylinder before adding air/fuel at a very very lean mixture... the rich mixture ignites, and will still burn the rest of the mixture with max efficiency.

When you change the profiles of the cam in the R18 iVtec engine, all you're doing is changing the intake cam's profile to allow the intake valve to remain open longer so the cylinder will lose some of it's air. This is an example of a variable atkinson cycle.