Volvo's "flagship" luxury sedan traded its rear-drive layout for front-wheel drive in 1999, as the old S90 gave way to a new S80. Two distinct, transverse-mounted 6-cylinder engines were used. In the base sedan, a 2.9-liter engine produced 201 horsepower. A twin-turbocharged 2.8-liter, making 268 horsepower, went into the sporty T6 model. Both cars used 4-speed automatic transmission, but a Geartronic feature with a separate shift in the T6 permitted manually selected gear changes. Safety equipment included Volvo's inflatable curtain airbags, which dropped down from above the side windows in a side impact. Volvo's WHIPS system was designed to move the front seatbacks and headrests rearward to minimize whiplash during a rear-end collision. Standard equipment included dual-zone automatic air conditioning, a tilt/telescoping leather-wrapped steering wheel, cruise control, eight-way power front bucket seats (with driver memory), and a split folding rear seat. Heated power mirrors, power locks and windows, remote keyless entry, a cassette/CD player, and 16-inch alloy wheels also were standard. The T6 sedan added heated front seats and mirrors, along with wood interior trim. Rivals included the Acura RL, BMW 5-Series, Lexus GS 300/400, Mercedes-Benz E-Class, and Saab 9-5.