Toyota Opa

Toyota says its Opa sedan/wagon/compact MPV hybrid is named for the Originality in its concept, packaging, and styling; the car-like performance it provides, and its versatile MPV amenities. These are indeed attributes a large majority of Japanese new vehicle buyers are seeking, at the cost of an alarming decline in ordinary three-box sedan types, except in the Toyota-dominated luxury segment and the premium import (largely German) market. These nonsedan and coupe types are unofficially and collectively called RVs-though they have nothing to do with Winnebagos-a class that consists of minivans, SUVs, and car-derived station wagons.

The Japanese automakers are now fervently working on crossover vehicles that combine attributes of sedan, wagon, and small MPV-and, in many cases, some slippery and off-road capabilities with all-wheel-drive variants. Toyota and Honda have been particularly successful, the former with Civic-derived models and the latter with a couple of interesting permutations based on the NBC (Yaris/Echo) platform.

Toyota is now extending the crossover theme to its mid-size (a size larger than the Corolla) platform, which has served the Vista/Ardeo sedan/wagon range.

The Opa is a cab-forward two-box vehicle with as windshield pushed 120 mm (4.7 in) further forward than that of the Vista sedan, shortening the hood. The windshield is sharply raked, and its pane less prominently curved in plan view. It is flanked by minivan-like triangular quarter windows with thin pillars. All pillars are painted black, giving the impression of a larger greenhouse and making the front fenders look longer, an interesting visual effect somehow contradictory to the raked and pushed-forward windshield. All windows are also more upright and have less pronounced curvature than normal.

The Opa shares its same 2700-mm (106-in) wheelbase with the Vista sedan; however, its overall length is held to 4250 mm (167 in), which is shorter than the Corolla sedan by 65 mm (2.5 in). Overall width is held under 1700 mm (67 in), Japan's small car limit (any wider and it would have been classified as an "ordinary" size vehicle, at a slight increase in annual tax). At 1525 mm (60 in), its height is between a normal sedan's and an MPV tall box's, allowing it to fit into mechanized, multi-layer, pallet-type parking facilities found in Japan's overcrowded large cities.

For its short overall length, the Opa's coupling distance of 988 mm (38.9 in) between the front and rear hip points matches that of the Lexus LS400, though the new LS430 has added 50 mm (2 in) to this dimension. The rear seat split is 40/60, with each seat able to be individually folded; each has a fore-aft adjustment range of 120 mm (4.7 in). The front-seat hip-point height is between a tall sedan's and an MPV's at 600 mm (23.6 in), facilitating easy entry and exit. The instrument panel's column-mounted automatic selector lever enables each front-seat occupant to move sideways to enter/exit from the opposite door in a tight parking situation. The IP also features a high-mounted central instrument cluster with digital and graphic display. The interior has a number of useful storage bins and pockets, befitting a typical MPV.

The designers pursued styling uniqueness in the interior, as well as the exterior. The Opa's two-tone upholstery scheme extends to the seats, of which the front pair is in light gray and the rear in a darker hue, except in the sporty version, which features an all dark-gray treatment. The vehicle's already adequate cargo space can be enlarged by folding the rear seat fully flat, extending its length to 1800 m (71 in).

Two powertrain combinations are available in the Opa. The 1ZZ-FE inline four-cylinder unit displaces displaces 1794-cm3 and has dual overhead camshafts, 16 valves, and VVT-i (electronically controlled, continuously variable intake valve timing). The unit is Toyota's mainstream engine, powering various small- and mid-size vehicle series, including the Corolla. The transversely placed engine has a forward-facing intake and rearward exhaust. It is rated at 100 kW (136 hp) at 6000 rpm and has 171 Nom (126 lboft) of torque at 4300 rpm for front-wheel-drive models. For the all-wheel-drive version, it is slightly detuned to 92 kW (125 hp) 6000 rpm and 161 Nom (112 lboft) at the same engine speeds, respectively, for the sake of a flatter low- and mid-speed range torque curve. The 1ZZ-FE is mated to an electronically controlled four-speed automatic transmission. The all-wheel-drive system employs a viscous coupling integrated in the rear final-drive unit.

The upper-grade powertrain combination marks a Toyota second and first, the former referring to the second-generation direct-injection gasoline engine, and the latter a new continuously variable automatic transmission employing a push-type steel belt and variable-diameter pulleys.

The Opa is the second new car powered by the second-generation D4 engine (the first was the Japanese RAV4 compact SUV). As its designation indicates, the 1AZ-FSE is based on the new aluminum-block AZ family, which is currently available in 2.0- and 2.4-L displacements (see AEI July 2000 Tech Briefs). The 1AZ-FSE unit (and the port-injected FE version) dispenses with the twin contra-rotating balance shafts of the bigger 2AZ 2.4-L unit. The engine is shorter and narrower than the previous D4 3 unit, measuring 628 mm (24.7 in) long and 660 mm (26.0 in) wide, versus its predecessor 3S-FSE's 659 and 696 mm (25.9 and 27.4 in), respectively. However, it is taller at 678 versus 655 mm (26.7 versus 25.8 in). It has a mass of 117 versus the 3S-FSE's 128 kg (258 versus 282 lb). The bore pitch (the distance between the adjoining bore centers) is 97 mm (3.82 in), 3.5 mm (0.14 in) larger than the 3S to accommodate the enlargement to the 2AZ's 2.4-L displacement. Bore and stroke are a square 86 x 86 mm (3.39 x 3.39 in), for a total displacement of 1998 cm3.

Dual overhead camshafts are driven by a single-stage roller chain of 8.0-mm (0.31-in) pitch and act on four valves per cylinder via shimless bucket-type tappets. The intake camshaft is fitted with a four-vane VVT-i device, which continuously alters intake valve timing up to 43°. The intake camshaft also drives the single-plunger, high-pressure fuel-injection pump. Valves are inclined at 27.5° in a shallow pentroof-shaped combustion chamber.

The second-generation D4 engine employs a revised charge-forming strategy with several new components. Toyota's direct-injection gasoline engine operates in three mixture modes: 1) homogeneous charge combustion with an air/fuel ratio (AFR) ranging between 12: and 15:1 during cold temperature, starting, high load, or NOx reduction operation; 2) weak stratified charge combustion with an AFR between 15: and 30:1 during medium-load operation; and 3) stratified charge lean-to-ultra-lean operation employing an AFR ranging from 17: to 50:1 for low-load duties. (The "air" of the AFR includes recirculated exhaust gas.) Fuel is injected during the compression stroke for stratified charge operation, during the induction stroke for homogeneous operation, and split-injected during the induction and compression strokes during weak stratified-charge operation.

The original D4 in the 3S-FSE relies on the incoming air's powerful swirl motion to create charge stratification, gathering a fuel-rich portion around the spark plug to ignite and burn lean-to-ultra-lean mixtures. Swirl is generated with one of the two separate intake ports closed by an electronically controlled, stepping-motor-actuated swirl-control valve (SVC), letting air enter through the open "helical" port. The SVC and helical port are combined with a deep, asymmetrical heart-shaped bowl in the piston to obtain charge stratification. The bent intake port and deep bowl designs impede efficient filling of the combustion chamber in the engine's high-load, homogeneous-charge operation, thus limiting high-end power output.

The new D4 strategy uses the mixture's inertial dynamics versus the original version's swirl flow. The key to the system is the new "slit" injector design. The injector has a very thin-0.72 x 0.15 mm (0.03 x 0.006 in)-curved slit, from which fuel is injected in a solid, fan-like pattern versus the previous type's hollow cone "casting net" (as used in fishing) pattern. Injection pressure is unchanged, ranging between 8 and 13 MPa (1160 and 1890 psi). The injector is affixed by a clamp, one O-ring and three backup rings to ensure sealing tightness, and secured by a clamp. The original D4 injector was encased in a brass receptacle, which was screwed into the cylinder head-a fail-safe arrangement that was both expensive and cumbersome.

The bowl-in-piston combustion chamber shape was revised and is now a shallow symmetrical oval, a part of which is machine-finished. The recessed geometry directs a richer portion of the mixture towards the spark plug in stratified charge, lean-to-ultra-lean mixture operation.

One of the intake ports is still fitted with a butterfly valve, now called a "flow control valve." The valve closes during cold, homogeneous combustion operation when fuel is injected in the induction stroke. Turbulence generated by airflow coming in from the single port improves combustion during this operating mode. An engine-vacuum-actuated diaphragm now closes and opens the control valve, a much simpler device than the previous electronically controlled, electrically actuated SCV.

The new charge-forming strategy has resulted in a 5 to 10 Nom (4 to 7 lboft) increase of torque throughout the engine's operating range. The 1AZ-FSE D4 engine is rated at 113 kW (152 hp) at 6000 rpm and 200 Nom (148 lboft) at 4000 rpm on a moderate 9.8:1 compression ratio and regular-grade, unleaded gasoline. The engine's lean- and ultra-lean combustion envelope has been extended, resulting in superior fuel economy-so much so that a new exhaust cleansing strategy called "rich-spark control" is employed so that NOx may be reduced by periodically reverting to stoichiometric combustion to enable the catalytic converter to cleanse stored NOx. For example, at steady 60-km/h (37-mph) cruising, this occurs for 1-2 s every two minutes.

The emissions control system employs two catalytic converters-one three-way unit immediately aft of the exhaust manifold and a NOx storing and cleansing unit located under the floor. The storage and cleanse catalyst now has 1.5 times the storing capacity of the previous type, and its sulfur resistance has been increased. A large dose of EGR is introduced during stratified-charge combustion. An aluminum chamber is attached to the plastic intake manifold, and a nozzle injects exhaust gas to the individual tract to each cylinder. EGR is electronically controlled, and the chamber is cooled by engine coolant.

Toyota has no plan to install the second-generation D4 engine in models destined for the U.S. or Europe. A senior engineer concedes that the engine system has not yet met America's stringent cold-start emissions requirements. Neither the NOx storing-and-cleansing catalyst could stand up to the relatively high sulfur content of European fuel.

The 1525-kg (3360-lb) Opa with D4 power and Super CVT satisfies Japan's J-LEV emissions standards, reducing three major pollutants by 25% from current requirements. The Opa is certified, using the Japanese 10/15-mode urban driving cycle, with consumption of 17.8 km/L (about 42 mpg). The Opa's engine computer and automatic air-conditioning amplifier are coordinated to save fuel. The compressor kicks in at peak efficiency whenever the throttle is closed, as on deceleration and braking, which cuts the fuel supply to the engine, or when the engine is accelerating hard, at which time the engine is producing more than enough power to spare to drive the compressor.

The Super CVT is Toyota's first steel push-belt and pulley continuously variable transmission, manufactured inhouse and using a Dutch Van Doorne Transmissie belt. Seven Japanese OEMs now offer CVTs in their car and light-truck products. Two nonconformers are Mazda and Isuzu; however, the former is expected to join the fray soon. The latter specializes in light trucks, SUVs, and commercial trucks and vans, whose transmissions are predominantly manual types.

The electronically controlled Super CVT employs a torque converter with lockup clutch for the start-up unit. The transmission may operate in a manual selection range with steering-wheel-mounted push buttons, allowing selection of six virtual ratios ranging from 2.396: through 0.428:1. The CVT is combined with a final drive ratio of 5.182:1. The transmission can, of course, be left alone to select ratios automatically. It features hill-grade logic to provide ample engine braking downhill.

The Opa shares its running gear with the Vista sedan and features front MacPherson strut and rear twist-beam suspensions. A short- and long-arm suspension replaces the rear beam axle in all-wheel-drive models. Steering is by hydraulically assisted rack and pinion, and a front-disc/rear-drum brake combination with ABS and electronic brake distribution system (EBD) is standard. EBD has two functions: adjusting braking forces between the front and rear and left and right brakes.