As any performance enthusiasts who have seen the variable lift assembly firsthand know, Honda's VTEC motion assembly is held in place by two rocker shafts (one on the intake side and one for exhaust side), which run the complete length of the head. When conditions are ideal, an oil control valve (VTEC solenoid) on the distributor side opens and allows oil fluid to fill the rocker shaft. The rocker shaft provides the necessary oil fluid pressure needed to lock the third rocker arm in place-and voila! VTEC is achieved.

In a manner similar to the VTEC system activation, the VVTL-i also utilizes two-rocker shafts to supply oil to the lift mechanism. Since the VVTL-i system only utilizes one lobe for every two valves, a rocker arm pin is locked in place with oil pressure under the high-speed cam (see figure C). When the rocker arm pin is locked in place, higher lift and duration is achieved from the high-speed cam.

Intake Manifold
As stated earlier, the B18C engine incorporates a dual-stage intake. The dual-stage manifold on the B18C engine features two intake runners for each cylinder, one longer than the other. When engine speeds are under 5800 rpm, only the longer runners on the intake are being utilized. When engine speeds pass 5800 rpm, a secondary butterfly valve within the intake opens allowing passage through a set of shorter runners (see figure D).

On the other side, the 2ZZ-GE intake is constructed from a combination of aluminum pipe runners with an aluminum die-cast intake plenum welded together for weight reduction. The reverse plenum design and equal length runners ensure all cylinders are receiving the same amount of air, increasing volumetric efficiency among all four cylinders (see figure E).

Head Design
Both the B18C head and 2ZZ-GE head are constructed from cast aluminum. The DOHC design of the B18C and 2ZZ-GE head also incorporates a high intake port angle, increasing airflow into the combustion chamber. The B18C head is considerably larger and heavier than the 2ZZ-GE, partly because of the large three-rocker motion assembly. Although the head casting of the 2ZZ-GE is rather narrow in width, a cross section of the head (see figure F) shows a steep 43-degree valve angle for improved intake and exhaust flow efficiency.

Block Design
Since the early '80s, Honda has been notorious for using a floating sleeve (open deck) design for its engine blocks. The floating sleeve design promotes heat dissipation to the cooling jackets surrounding the cylinder walls, decreasing chances of detonation caused from extreme heat saturation. The cast aluminum block features cast-iron cylinder sleeves, preventing cylinder distortion and is outfitted with an oil jet cooling system, ensuring long-term durability and reliability. An oil jet under each piston sends pressurized engine oil to the underside of the piston to help dissipate the heat caused by sustained high-rpm operation.

Toyota's 2ZZ-GE block also features an open deck design, which is a new concept for Toyota. Unlike the company's traditional cast-iron, closed-deck blocks, the 2ZZ-GE block is constructed from cast aluminum, which enhances weight reduction on the weight-conscious Celica GT-S. The cylinder walls are made of a metal matrix composite to ensure wear resistance.