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The Volvo B21 was a slant straight-4 engine first used in the Volvo 200 series, meant to replace the B20. The B21 and all derived engines are often referred to as ''red block'' engines for the red paint applied to the block. The primary differences when compared to the B20 was the switch to a SOHC in place of the older pushrod configuration, and an aluminum crossflow cylinder head versus the iron head of the B20. ==History== Initially the overhead camshaft versions were offered as optional equipment on the 240, becoming standard in all markets by the 1976 model year. The overhead camshaft motors were available in displacements of 2.0 (B19 and B200), 2.1 (B21), and eventually 2.3 (B23 and B230) litres. The B21 featured an stroke, and bore. In the US, the B21's power output ranged anywhere between and 107 hp (73 to 80 kW), based on variations in the compression ratio and was typically supplied with a B or M camshaft. The engines are tilted approx 15 degrees to left (exhaust side) to make room for the more complicated injection systems. B19 and B21 blocks can be identified by water plugs on one side of the block. The B23 blocks have them on both sides. The camshaft is driven by a toothed belt that is driven off the front of the crankshaft. The belt turns the intermediate shaft as well, which in turn drives the oil pump, distributor (on 240 engines and BXX 700/900 series engines) and the fuel pump of carburetor models. In 1981 the B21FT, a B21F with a turbo, was introduced with a compression ratio of 7.5:1 mated with a Garrett T3 turbocharger and a T camshaft. Additional turbo variants, not offered in the US market, were the B19ET and the B21ET, based on the B19E and B21E respectively. The turbocharger increased power output to 127 hp (91 kW) for the B21FT, and 157 hp (115 kW) for the B21ET. Also new for the 1981 model year was the B23, with a displacement of 2.3 litres (80 mm stroke and bore). Aside from the increased bore size, the engine is identical to the B21. Volvo used a slightly different mold for the turbo engines to cast a boss for the turbo oil return line. Because a turbocharged engine has a higher operating temperature they used sodium filled exhaust valves and a thermostat controlled oil cooler (air/oil model). In 1983 the B23 was introduced to the American market. Also introduced in 1983, the "intercooler boost system" (IBS) was introduced for the B21FT motors. The IBS kit consisted of an intercooler, appropriate ducting, a new fan shroud, new oil cooler lines and mounting brackets, and optionally an automatic transmission kit. IBS raised the output of the B21FT to , slightly more than the non intercooled European market B21ET's . Midway through the 1984 model year, the "intercooler boost system" became standard on American 240 Turbos. Additionally a bigger clutch and a stepped flywheel were included. In 1985 a revised, "low friction" design was introduced, dubbed the B200 and B230 (depending on displacement). Several components had design changes, longer rods (152 mm c-c, longer), pistons with a lower compression height, lower friction bearings (smaller in size), a crankshaft with 8 counterweights (instead of 4 on the older Bxx engines) and a heavy harmonic balancer (aka damper) in the crank pulley. 1989 saw an upgrade to the crankshaft, with a relocated axial thrust bearing back to the number 5 journal, bigger main bearings, rods were enlarged to from in 1990. Also introduced in 1989 were 16 valve, twin-cam variants of the B200 and B230, dubbed the B204 and B234 respectively. The B204 was also available in turbo form in some markets (such as Italy) where large displacement motors were taxed heavily. It came in two versions: The B204GT turbo motor operates with a lead resistant lambda probe and generates approximately . The B204FT has a catalytic converter and generates . Both were the first redblocks standard equipped with oil squirters for piston cooling. Crankshaft, conrods and pistons all forged. Exhaust valves were sodium filled for cooler operation. It has smaller valves and stiffer valve springs than n/a 16V. Crank torque is at 2950 rpm for the GT, and for the FT. Other differences from the normal 16V redblock engine are that it uses a remote mounted oil filter (Away from block on exhaust side engine mount) and a windage tray. For the B230 engines 1993, piston cooling, oil squirting jets were added to help alleviate piston slap problems on the turbo motors. Another modification was to go from a square toothed timing belt set up to a round toothed timing belt setup which made for quieter belt running. The last redblocks were made in 1998, when the 940 model was discontinued in Europe, although the 940 was discontinued in 1995 in North America. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Volvo Redblock Engine」の詳細全文を読む スポンサード リンク
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