Volvo Car Group is testing a 2.0-liter four-cylinder engine that uses three turbochargers to crank out at least 450 hp.
Volvo calls its "triple boost" engine a concept and has not said if the powerplant will go into production. But if it does, its rating of 225 hp per liter would be one of the highest ever for a regular production vehicle's engine.
The 450-hp engine far eclipses the power output per liter of such supercars as the Bugatti Veyron, whose 8.0-liter engine makes 1,200 hp, or 150 per liter.
The concept engine is part of Volvo's new Drive-E engine family, the first new engines designed and built by Volvo since the company's split from Ford Motor Co. in 2010.