The i-VTEC K
In Japan, the K-series engine first came out in 2000, and later in 2001 with Honda's newly developed "intelligent" or i-VTEC technology that uses Variable Timing Control. But that wasn't the only thing unique about the power plant. As most tuners know by now, it is a positive rotation engine, which is a rarity for a Honda-designed mill. The K20 ultimately became the OE's de facto 2-litre engine; the only other is the F20C, native to the '00 to '03 S2000.
Production of the K20A Type R motor officially ceased with the discontinuation of the DC5 chassis Integra Type R in 2006. Of course the K20A is still used for other Honda models, such as the JDM Accord and the Edix minivan. The DOHC i-VTEC engine that carried the Type R distinction, however, remains in a league of its own, as Honda made several important developments in engineering the K to be something akin to a race engine.
First, the definitive race mill needed to be able withstand high revs. In the holes compression was a relatively high 11.5:1, so individual bottom end parts were strengthened using different materials and all fine tuned one by one. For example, the connecting rods use high resistance metals similar to ones found in Formula 1 applications. This was how 220 horsepower at 8,400rpm was finally achieved, while saving 10kgs of weight over other K20 bottom ends. Honda got creative in casting its R cylinder heads by using finer sand in the portions of the mold that corresponded to the ports. The smoother mold resulted in less liquid resistance once the aluminum was poured, which ultimately created much smoother port surfaces than in other versions of the K20 head. Only Type R plants got this treatment.
On the cold side, throttle bore diameter was increased and a single lumen isometric short intake manifold is used. This technology was originally used in racecars. The valve seat on the intake port was also modified with a special 20-degree tapered cutter for optimum intake flow. For the exhaust, a dual manifold with a bigger diameter than other Ks was selected. A variable valve silencer that opens and closes based on pressure is used to decrease exhaust resistance.