The Saab H engine is a redesign of the Saab B engine. Despite the name it is not an H engine, but a slanted inline-4.
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. Instead, the distributor was directly driven by the overhead camshaft and the water pump was a separate unit, driven by a fan belt off the crankshaft pulley.
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 this boosted performance from 145 hp (108 kW) to 155 hp (116 kW). This system also produced 20% better fuel efficiency and allowed the use of low-octane gasoline without causing engine damage.
B202
In 1984, Saab added a 16 valve head, creating the world's first multi-valve 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 were hydraulic valve lifters.
B204
A new, shorter B204 version was introduced in 1994 for the transverse Opel-derived Saab 900. Engine displacement is officially 2.0 litre (1984 cc) from a 90 mm bore and 78 mm stroke.
Although the B204 was replaced in the Saab 9-3 with new parent General Motors' Ecotec, the Saab 9-5 continued with the Saab 2.0 through 2001.
In 2005, it was announced that certain 2000-2003 B204 engines suffered from oil sludge-related failures. These problems will be repaired under a special extended warranty.
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 has an intercooler, 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 350 Nm of torque at 1900-4000 RPM.
In 2005, it was announced that certain 1998-2003 B234 engines suffered from oil sludge-related failures. These problems will be repaired under a special extended warranty.
