Honda Is Still The Specific Output King

Automotive Industries, March, 1999

Just five years ago, it took a turbocharger to give a production car engine the prodigious specific output of 120 horsepower per liter (hp/L). AI's 6th Annual Engine Trends issue listed that engine, the Lotus 2.2L dohc 16-valve 4-cylinder, as the highest specific-output passenger car engine. For a number of years in the early to mid-1990s, the Lotus twin-cam Turbo remained at the top of the heap.

Progress marches on. Next year, Honda's new S2000 roadster will be powered by a naturally aspirated 2.0L dohc 16-valve four with VTEC variable valve timing that produces a claimed 240 hp at a stratospheric 8,900 rpm. Those numbers will, once again, give the limited-production Honda the highest specific output of any naturally aspirated passenger car engine.

During the mid-1990s when the turbo Lotus was the king, the only unblown engine listed on AI's 10 hottest production engines chart was also a Honda. The 1.6L Acura Integra 4-cylinder, also with VTEC, made exactly 100 hp/L.

To compare the state of the art between the production and racing engine worlds, we decided to see how the S2000's numbers stack up against two small-displacement 1998 racing engines -- a Ducati 996cc V-twin, which won the World Superbike Championship, and a typical Indy car 2.65L turbocharged V-8. Besides specific output, we also calculated each engine's brake mean effective pressure (BMEP) -- the theoretical average pressure in the cylinder during the expansion, or power stroke.

BMEP particularly reflects an engine's volumetric efficiency and internal friction levels, which is one reason the turbocharged Indy engine's number is drastically higher than the two unblown engines. The higher the BMEP, the more power an engine makes for its size and rpm.

Perhaps the remarkable thing about the S2000 engine's output is not obvious in horsepower or BMEP numbers. It's the fact that anybody can drive it, everyday, knowing that it meets California LEVI] tailpipe emissions regs. Not bad for an 8,900 rpm zinger.