Nissan S20 engine
The Nissan S20 engine is a straight-6 four-valve DOHC internal combustion engine produced by Nissan from 1969 to 1973, originally designed by engineers of the former Prince. It was the first mass-produced Japanese engine with more than two valves per cylinder.
Essentially a revised production variant of the 1966 Prince GR-8 engine from Prince/Nissan's R380 racecar, it produces at 7000 rpm and of torque at 5600 rpm and weighs. The S20 powered Nissan's Skyline GT-R|Skyline GT-R] and Fairlady Z432 models.
While the engine code is similar, the S20 is unrelated to the SR20 engine family, which were straight-4 DOHC petrol engines based on the SR series used in other Nissan models.
History
The S20 was one of the technical carryovers to the Nissan brand from Prince technology. Prince had been producing the Skyline since the model's inception in the 1950s; following the merger of the two companies, Nissan took over production of the Skyline, which received the new engine in the late 1960s.The third generation Skyline was exhibited at the 1968 Tokyo Motor Show in October, which included a special "Skyline 2000GT Racing" model equipped with the S20; it was promoted as being equipped with the same engine as the R380. The production Skyline 2000GT-R was introduced in February 1969, followed by the Skyline Hardtop 2000GT-R coupe in 1970. The two models would later collectively win 49 straight Japan touring car victories between 1969 and 1971.
Aside from its use in the PGC10/KPGC10 Skylines, the S20 also was fitted to the Nissan Fairlady Z432, a sports racing model of the Nissan Fairlady Z line, starting in fall 1969. The Z432 designation was derived from the design of the S20: four valves per cylinder, three carburetors, and two overhead camshafts. In addition to the S20, changes in the Z432 version included a 5-speed manual transmission and a limited-slip differential. A special lightened variant of the Z432 was designated as Z432R, built for homologation purposes. The cost of the Z432 was nearly double the price of a standard Fairlady Z.
In September 1972, Nissan introduced the fourth generation Skyline powered by the L series of engines. A KPGC110 "Skyline 2000GT-R Racing Concept" powered by the S20 was shown at the 1972 Tokyo Motor Show after the commercial models were introduced; although the concept's number hinted at Nissan's racing efforts for 1973, Nissan dropped its factory team that year in favor of developing anti-pollution technology and improving fuel efficiency in response to increasingly stringent emissions laws. In addition, the contemporary oil crisis of that year created a wasteful perception of auto racing and high-performance vehicles by many people, which led to the introduction of smaller and more economical cars from various manufacturers. Less than 200 examples of the KPGC110 GT-R would be built from January through April 1973 as a result of this. Because of its rarity and Nissan's withdrawal from touring car races at the time, the KPGC110 Skyline GT-R has been dubbed as the "Phantom GT-R".
Engine specifications
The S20 is an inline-six with a cast iron block and aluminum head, using a 7-bearing crankshaft. It features a dual overhead cam, cross-flow head with pent-roof combustion chamber and four valves per cylinder. Heads were ported and polished manually, and the motors were bench tested for consistent power production before installation.Compared to the preceding GR-8, the bore was retained but the stroke was reduced from in order to ensure that displacement would not exceed 2 litres if slight errors were made during manufacturing. In addition, the valvetrain was driven by timing chains, rather than gears.
Most engines utilized triple Mikuni-Solex 40PHH dual-choke carburetors; models after 1969 offered optional Lucas mechanical fuel injection. As fitted to Shinohara's No. 39 racing car, the S20 was tuned for higher output, generating at 8000 rpm and at 6000 rpm. In racing trim, the fuel-injected motors reportedly produced over, with for larger tracks like Fuji Speedway; custom tuning yielded race engines with output at 12,000 rpm.
Applications
This engine was used in the following vehicles:- Skyline GT-R (PGC10 type) 4-door sedan 1969–1970.
- Skyline GT-R (KPGC10 type) 2-door coupe 1970–1972. shorter wheelbase than the PGC10.
- Skyline GT-R (KPGC110 type) January–April 1973.
- Fairlady Z432 1969–1972.
- Fairlady Z432R Z432 race car-based for homologation nearly lighter than production Z432.