Mitsubishi’s “Silent Shaft” engine was the first modern mass-produced engine to introduce the significant benefits of balance shafts, a feature that has become quite common since. Four cylinder engines were becoming very popular in the 70s, after the energy crisis, and as they got larger, the four cylinder’s inherent harmonics became increasingly problematic. The droning and buzzing was a big detriment, especially in more upscale models. The Silent Shaft put those nasty issues to bed, once and for all. Too bad it wasn’t adopted more uniformly and quickly.
The Arrow had the 2.0 liter version. But it was the larger 2.6 L that really revolutionized the market. Almost nobody (except GM, with their various large-displacement fours) would have thought of building a modern four that large. 2.0 liters was considered the limit for a relatively smooth four; 2.3 liters if one really worked at it, like Mercedes with their 2.3 four. But the Mitsubishi 2.6 became very popular, and bailed out Chrysler until it had its own balance-shafted 2.5 (as well as a V6).
The Arrow was quite conventional in every other respect, with rear wheel drive, good handling, a slick 5 speed manual, and a mediocre ride due to the firm suspension and limited wheel travel of the crude rear axle suspension. The 2.6 L version eventually found its way into the Arrow’s body, and became the legendary Fire Arrow.