2L DOHC I-4 You just don't ignore an 8,900-rpm redline. You definitely don't ignore it when the tach in Honda Motor Co. Ltd.'s S2000 roadster sweeps past 6,000, your boot's hard on the throttle and the 2L DOHC VTEC 4-cyl. has cleared its pipes to bark the howl of Cerberus at you and every other road user in the parish.

The hellish allusion is apropos. Because Honda's 2L screamer, when opened up in anger, becomes more wild animal than inhuman machinery. More motorcycle engine than passenger-vehicle engine - and, we admit, more eardrum-assaulting than may be healthy on an everyday basis.

Chalk it up once again to VTEC (Variable valve Timing and lift, Electronic Control), Honda's mild-or-wild-and-nothing-in-between variable valve timing system that adjusts both intake and exhaust valve timing to narrow the compromises between efficiency, low emissions and high performance. VTEC can be used to maximize fuel economy and reduce emissions, but for the S2000, Honda engineers say VTEC was specifically tailored for high-performance, high-rpm operation.

Gee, we never would have guessed.

But the S2000's 2L I-4 does more than simply show the net effect of how high-rpm operation pumps more air and subsequently pounds out power. That's apparent in the startling 120 hp per liter, the highest specific output of any production passenger-vehicle engine.

No, there's plenty more, in the details. Carburized forged connecting rods. Hollow camshafts that serve double duty as oil passages to feed the VTEC hardware. A novel, geared camshaft drive system developed to save just a little bit more space.

And our favorite: Cylinder walls with a special, cast-in carbon fiber/ceramic material reinforcement to eliminate the need for heavy iron liners and to facilitate heat transfer. Too sweet!

Yes, this engine's decidedly too high-strung for, say, a high-volume family car. And, as with other howling Honda VTEC engines of the past, caning this engine at every gearshift to its almost preposterous 7,800-rpm power peak could be a short-lived novelty, soon replaced by disdain for its inability to deliver in the lower rpm ranges.

But Honda's taken that into account: The S2000's a performance roadster, dammit, not an Accord. The Honda engineers have saved their best - and the S2000's VTEC 4-cyl. is a genuine technical accomplishment - for those who don't fancy compromise.