Chevrolet Beretta GTZ performance coupe with a high output Quad 4 & FE7 sport suspension & 5-Speed Transmission

4 cyl 2.3 L Quad 4 (180hp/160tq)

 New for 1990, the GTZ is the hottest version of the Beretta, a two-door sporty coupe. Its heat comes from one of General Motors' newest engines - the Quad 4, which was developed by Oldsmobile division and first offered in the Olds Calais in 1987.

Its impressive 180 hp results from having four valves per cylinder - two intake, two exhaust - rather than the usual two. By comparison, the V-6 also available in the Beretta produces only 135 hp, even though it is larger, displacing 3.1 liters. The standard 2.2-liter four-cylinder, with only eight valves, produces only 95 hp. Pushed hard, the Quad 4 will propel the GTZ from 0 to 60 miles per hour in 7.5 seconds.

But, here's the lesson: Like all engines of this type, the Quad 4 produces its peak horsepower at a relatively high engine speed - in this case, 6,200 revolutions per minute. The additional valves enable the engine to reach that speed.

GM produces two versions of the Quad 4: this one and another that produces only 160 hp. One or the other is available in what is now called the Cutlass Calais, as well as the Olds Cutlass Supreme, the Buick Skylark and Pontiac Grand Am and Grand Prix and Chevrolet Corsica, a mechanical sister to the Beretta.

GM offers just one other engine with four valves per cylinder, the V-8 in the Corvette ZR-1. Ford offers one, Chrysler offers two. Japanese automakers, however, offer many models with this type of engine.