Many are adding turbochargers to smaller-displacement engines to pull more power out of them. But a few are taking it a step further with twin-charging — adding a supercharger along with the turbo.

This engine, the only commercially available twin-charged unit in Japan at the time, ran on 10 psi of supercharger boost up to about 4,000 rpm. From there, the turbocharger kicked in with 14 psi ...