Bretton Woods
Well-Known Member
With the R18A2 (AFAIK) engine the (i) VTEC is more of a marketing word. The engine has SOHC configuration and doesn't have the high and low cam profiles found in proper performance oriented VTEC-systems (B-series, K-series etc). If I remember correctly the i-VTEC only refers to the way engine can close another intake valve at low rpms to increase the breathing a bit, as speed of the air going into the engine is naturally higher through one valve than through two valves. I guess it also has variable timing on the camshaft. Anyway, it has rather good combination of economy and horsepower considering specs it has.
Anyway, good color and surprisingly fresh looking car for it's age. Definitely much better looking than the current model!
It's actually quite smart, even with SOHC. At low RPM on partial throttle, the butterfly valve is normally open a very small amount, and that creates pumping losses and inefficiencies. What i-VTEC does is delay the closing of the intake valve in conjunction with opening the throttle valve way open. Way open, on partial throttle, you say?
Yup. Delaying the closing of the intake valve means it spits back out some of the charge mixture, so you get your low power output and reducing your pumping losses.