Since 1977, beginning with the pace-setting 320i, two generations of BMW 3-Series have brought the pleasures of BMW driving and ownership to more people than any other BMW series.

Over the model years since the second-generation 3-Series made its debut in 1983, this most compact of BMW lines has been expanded and refined far beyond the pace-setting original concept of a four-cylinder two-door sports sedan.Today, this Series includes two- and four-door sports sedans and a convertible, powered by four- and six-cylinder engines. In 1988, the line received numerous improvements, including a larger fuel tank, a revised front-end structure for improved impact-energy absorption, glare-reducing ellipsoid low-beam headlights and foglights, improved high-speed windshield wiping, and a discreet styling update.

For 1989, the evolution takes another step as the most affordable 3-Series models get the powerful 2.5 liter engine that has been reserved for the more upscale models since 1987. Formerly called simply 325, these 3-Series two- and four-door sedans were powered by a 2.7 liter eta-concept engine whose design emphasized fuel efficiency and low-end power more than top-end performance.

The revised 1989 versions now take on the 325i designation. Their powerplant is the same engine found in the new 525i - and in this lighter, more compact BMW it takes on the role of a small powerhouse.

This is an especially important step, adding substantially to the value inherent in two models that already offered outstanding quality, durability, engineering sophistication and driving pleasure in their prime class.

Compared to the previous 325 engine, the new engine actually has slightly less piston replacement - 2494 versus 2693 cc. But its shorter stroke, higher compression ratio and different valve timing make it a higher-output, higher-revving engine. In fact, it delivers 41 horsepower more than its predecessor.

Along with the more powerful engine, the new 325i sedans also have sportier 195/65VR-14 tires, replacing 195/65HR-14s. Thus these 3-Series models are now mechanically identical with the car that carried the 325i name last year, which was a leather-upholstered, luxury-equipped four-door sedan.

The 325is, a sportier and more luxurious version of the two-door 325i, continues for 1989 with its own special equipment: limited-slip differential, sports suspension, wider 14 x 6.5 J cross-spoke wheels, front and rear spoilers, leather seating, and sports front seats.

Introduced last year in two-door form with manual transmission only, the all-wheel-drive 325iX plays a greatly expanded role for 1989. There's a new four-door model; automatic transmission is now available, and standard equipment has been simplified to make all-wheel traction available in a BMW at a lower price.