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VTEC (Variable Valve Timing & Lift Electronic Control System)
In order to develop its next generation of engines for the mainstream market, Honda's NCE (New Concept Engine) program
was launched in March 1984. Specific targets identified through the program included high torque in both the low- and high-rpm
ranges and dramatic increases in horsepower per liter. The program was a success, resulting in a series that included the
DOHC engine found in the 1985 Civic and Integra, and the SOHC center-plug engine in the 1987 City.
Ikuo Kajitani, who was employed in the First Design Dept at Honda's Tochigi R&D Center, was involved in the development
of these four-valve engines. Through his experience in engine design, Kajitani had become convinced that Honda's next engine
should offer a mechanism that could alter the timing of the valves.
DOHC VTEC
Honda's VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high
RPM operations. Instead of one cam lobe actuating each valve, there are two - one optimized for low RPM stability & fuel
efficiency, with the other designed to maximize high RPM power output. Switching between the two cam lobes is determined by
engine oil pressure, engine temperature, vehicle speed, and engine speed. As engine RPM increases, a locking pin is pushed
by oil pressure to bind the high RPM cam follower for operation. From this point on, the valve opens and closes according
to the high-speed profile, which opens the valve further and for a longer time. The DOHC VTEC system has high and low RPM
cam lobe profiles on both the intake and exhaust valve camshafts.
The VTEC system was originally introduced as a DOHC system in the 1989 Honda Integra sold in Japan, which used a 160 hp
(119 kW) variant of the B16A engine. The US market saw the first VTEC system with the introduction of the 1990 Acura NSX,
which used a DOHC VTEC V6. DOHC VTEC motors soon appeared in other vehicles, such as the 1992 Acura Integra GS-R.
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