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The Triumph Slant-4 is an engine developed by the UK engineering company, Ricardo, for Triumph and Saab. Initially offered at 1.7 L (1709 cc) for the Saab 99, the company continued development into the 1990s. The engine is a straight-4 with the cylinders tilted at 45 degrees (actually a half Triumph V8).
Variants of the design were also used in the Triumph Dolomite 1850 and Sprint, Panther Rio (1975-1977) and Maserati Merak 2000/3000 (1972-1983).
Triumph Sprint
Triumph Motor Company added unique SOHC 4-valve cylinder heads to the Slant-4 for 1973's Dolomite Sprint. This is regarded as the first mass-produced multi-valve engine.
Saab B engine
Saab later increased the engine size to 1.85 L and in 1972 the company brought production in-house (to Scania) for the 2.0 L B version. This engine shared much with the original Ricardo design, including bore centers and bearings, but was substantially redesigned.
In 1977, Saab added a turbocharger, creating one of the earliest production turbocharged engines.
Saab H engine
B201
In 1981, Saab began lightening and redesigning the engine. The most-significant change was the elimination of a central shaft which powered the distributor and oil and water pumps.
In 1982, Saab added Automatic Performance Control (APC), a knock-sensing system which allowed a much higher compression ratio (9:1 as opposed to 7.2:1) and boosted performance from 145 hp (108 kW) to 155 hp (116 kW). This system also produced 20% better fuel economy and allowed the use of low-octane fuel without causing engine damage.
B202
In 1984, Saab added a 16 valve head, creating the world's first multivalve turbo engine. They retroactively renamed the 8-valve version the B201 and used B202 as the name of the new multivalve unit. Another notable addition to the B202 was hydraulic lifters.
B204
A new shorter B204 version was introduced in 1994 for the transverse Opel-derived 900. Displacement is officially 2.0 L (1984 cc) from a 90 mm bore and 78 mm stroke.
Although the B204 was replaced in the 9-3 with new parent General Motors' Ecotec, the 9-5 continued with the Saab 2.0 through 2001.
B234
The B234 was a new 2.3 L (2290 cc) version with many changes. It was stroked by 12 mm to a square 90 mm bore and stroke. Also notable are the added balance shafts to smooth the large four's vibrations. The B234 was selected as one of Ward's 10 Best Engines for 1995 and 1996.
1996 saw the Ecopower variant added. It had a pre-heated catalytic converter for reduced emissions.
The B234 uses a cast iron block and aluminum DOHC 4-valve cylinder heads. It uses MFI fuel injection, is turbocharged and intercooled, and features fracture-split forged steel connecting rods.
The turbo B234 continues in use in the Saab 9-5 as the last Saab-produced engine in the marque's lineup. Output stands at 250 hp (186 kW) at 5300 RPM with 258 ft.lbf (350 Nm) of torque at 1900-4000 RPM.
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