Toyota JZ series inline six-cylinder engines
The straight-six JZ engines were a replacement for the old M series, and were themselves replaced by the GR V6. These motors used sequential fuel injection (direct injection on the FSE models), with 24 valves managed by twin belt-driven cams. Spark plugs were mounted on top, Hemi-style.
The engine block was closed, for greater strength, with a girdle bolted on underneath; bearings were a wide design, and the engines had forged cranks. Blocks were cast-iron, while heads were aluminum; triple-layer head gaskets helped deal with the different expansion rates of the two metals.
The 1JZ, made from 1990 to 2007, displaced just 2.5 liters (152 cubic inches), with an oversquare design (3.39 x 2.81 bore and stroke). It was accompanied by a GE version (1JZ-GE), producing 168 horsepower and 173 pound-feet, right from the start; in 1995, this engine gained variable valve timing, increasing power to 197 hp and 185 lb-ft.
The 1JZ-GE had the same bore and stroke; compression was 10.1:1.
The 1JZ-FSE added direct injection; it used the same head as the 1JZ-GE (not GTE), with special heads that increased swirl for efficiency. The engine was designed for extremely lean burn, for much better gas mileage, even with regular unleaded fuel (impressive given the 11:1 compression ratio). Power was rated at 197 hp and 184 lb-ft; it, too, was always coupled to an automatic. A similar 2JZ-FSE 3-liter ran at 11.3:1, and produced 217 hp with 217 lb-ft of torque.
The 1JZ-GTE, which used two turbochargers (CT12A) in parallel (as well as an air-to-air charge air cooler), produced an impressive 276 hp and 268 pound-feet of torque, despite having the same 2.5 liter size. Noted engine tuner Yamaha, which also made Ford Taurus SHO engines, was responsible for the tuning and some production of this engine, which had an 8.5:1 compression ratio. The GTE started production with 1991 Toyota cars. There were some issues, including problems with the ceramic turbine wheels and probelmatic one-way valves on the head which could push blow-by gases into the intake manifold; oil vapor tended to get into the exhaust, wearing the seals. These issues were largely fixed in later years.
The 1996 models included a modified head, better cooling (new water jackets), variable valve timing, and coated shims which reduced cam friction; the twin turbo desing was replaced by a single turbocharger, but smaller head exhausts allowed the turbo to spool faster and at lower engine speeds. The compression ratio went up to 9:1, helping the power rating to actually increase—to 276 hp and 280 lb-ft, with torque at lower engine speeds improving more than it would seem. The engine was used in quite a few cars, most of which were not sold in the United States, though the Supra Mk III was most associated with it.
The 2JZ engine was very similar to the 1JZ, starting production for the 1991 cars, but it had a 3.39 x 3.39 bore and stroke, and displaced 2997 cc (3 liters, or 183 cubic inches). As such, it had more torque than the smaller 1JZ. While it may seem to be a stroked 1JZ, it also had a taller block deck.
The 2JZ-GE started out without variable cam timing, but gained it on the intake side in the 1998 cars; it was accompanied by direct ignition, using one coil for every two cylinders. Bucket-type lifters reduced friction by cutting back on moving parts.
The 2JZ-GTE was similar to its 1JZ-GTE counterpart, and was sold with either a Toyota automatic or a Getrag-designed, Toyota-made six-speed manual. This engine, made from 1991 to 2002, powered touring car championship winners; it was used in the Aristo V, Altezza, Mark II, and Supra RZ. Unlike the 1JZ-GTE, it used sequential turbos; nozzles beneath the pistons sprayed oil to cool the pistons. Different versions of this engine had different connecting rods, with the early ones being stronger. The turbochargers were developed by Toyota and Hitachi.
Power was rated at 276 hp, the same as the 1JZ-GTE, but torque was a stunning 320 pound-feet. In the 1998 cars, variable valve timing was brought in, and horsepower was rated at 321. Export versions had higher output by using stainless steel turbochargers, vs the ceramic ones in Japanese engines; they also had larger injectors and updated cams.