3-stage VTEC
Examine the SOHC VTEC and SOHC VTEC-E implementations. The clever Honda engineers saw that it is a logical step to merge the two implementations into one. This is in essence the 3-stage VTEC implementation. 3-stage VTEC is implemented on the D15B 1.5l SOHC engine in which the VTEC-E mechanism is combined with the power VTEC mechanism.
Many of us probably has laughed at the poor ignorant layman who said "I want power AND economy from my Honda". We know of course that power and economy are mutually exclusive implementations. Honda decided not to abide by this rule. Now, with 3-stage VTEC, we get BOTH power and economy !.
The diagram below illustrates the 3-stage VTEC implementation. The intake rocker arms have two VTEC pin actuation mechanisms. The VTEC-E actuation assembly is located above the camshaft while the VTEC (power) actuation assembly is the standard wild-cam lobe and rocker assembly.
Below 2500rpm and with gentle accelerator pressure, neither pin gets actuated. The engine operates in 12V mode with very good fuel combustion efficiency. When the right foot gets more urgent and/or above 2500rpm, the upper pin gets actuated. This is the VTEC-E mechanism at work and the engine effectively enters into the '2nd stage'. Now D15B 3-stage works in 16V mode (both intake valves works from the same mild cam-lobe).
Stage 2 operates from around 2500rpm to 6000rpm. When the rpm exceeds 6000rpm, the VTEC mechanism activates the wild cam-lobe pushing the engine into the '3rd stage', the power stage. Now the engine gives us the full benefit of its 130ps potential !
The 3-stage VTEC D15B engine is used on the current EK-series JDM Civic/Civic Ferio VTi/Vi together with Honda's new Multimatic CVT transmission. Stage-1 12V or "lean-burn" operation mode is indicated to the driver by an LED on the dashboard. The 2500rpm cutover from lean-burn to normal 16V operation in fact varies according to load and driver requirements. With gentle driving, lean-burn can operate up to 3000rpm or higher. Stage-3 may not always be activated. The Multimatic transmission has a selector for Economy, Drive, and Sports mode. In Economy mode for eg, the ECU operates with a max rpm of around 4800rpm even at Wide-Open-Throttle positions.
The essence of 3-stage VTEC is power AND economy implemented on a 1.5l SOHC PGM-Fi engine. Many people mistakes 3-stage VTEC as a "superior" evolution of the power oriented DOHC VTEC implementation, describing DOHC VTEC as "the older 2-stage VTEC" and implying an inferior relationship. This is totally wrong because DOHC VTEC is tuned purely for high specific output and sports/racing requirements. 3-stage VTEC is in truth an evolution of SOHC VTEC and VTEC-E, merging the two implementations into one
achor said:
got v tec with 3 stage ar? why never know one? =)
