After introducing the astonishingly good 4.6L Tau V-8 two years ago, Hyundai Motor Co. Ltd. could be forgiven if it chose to sit back and recoup some of its investment for at least a 4-year product cycle.

After all, the Tau easily bests most naturally aspirated V-8s found in much more expensive German and Japanese luxury cars in both specific output and fuel economy.

This achievement did not go unnoticed. At almost the same time the Tau was first named one of Ward’s 10 Best Engines in 2009, the Genesis luxury sedan it powers was named North American Car of Year.

But the word “relax” must not be in the vocabulary of the hard-charging South Korean auto maker. For the ’10 model Genesis, engineers added another 10 hp, bringing total output to 385 hp, and winning another 10 Best Engines award.

For the ’11 model year, Hyundai seduced Ward’s judges by adding direct injection to a larger-bore rendering of the Tau architecture. The compression ratio also is hiked from 10.4:1 to 11.5:1 for greater thermal efficiency.

The engine also features a tuned induction system and dual continuous variable-valve timing that optimizes both intake and exhaust valve timing; low-friction coatings on pistons and numerous other features normally found only on top-line premium engines.

The new version pounds out 429 hp and 376 lb.-ft. (510 Nm) of torque and outperforms by 1 mpg its smaller-displacement sibling in both city and highway driving: 18/26 mpg (13-9 L/100 km).

We’re still infatuated with the standard 4.6L, but the new 5.0L offers even more to love: 44 hp and 43 lb.-ft. (58 Nm) more than the base engine, to be exact.

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“If BMW, Audi and Mercedes were nervous last year, they are soiling themselves this year,” says Ward’s AutoWorld Executive Editor Tom Murphy.

While this new powertrain is designed to replace the 4.6L in the Genesis-derived Equus later in 2011, the Equus has a base sticker above our price cap of $55,000.

However, Hyundai is offering the 5.0L Tau in a new Genesis model that debuts in the first quarter of 2011 that fits under our cap.

It was in this new, still-secret version of the Genesis that we tested the 5.0L. Because it will be introduced in the first quarter, the new model still meets the competition’s long-standing rules. But this is the first time in 17 years of judging we tested a vehicle adorned in full camouflage.

Even so, the disguised exterior allowed us to focus even more intently on this utterly outstanding V-8.

The experience left some editors almost speechless. “Delicious,” was all Ward’s Automotive Reports Editor Eric Mayne could mutter.

dwinter@wardsauto.com

Ward's 10 Best Engines is a copyright of Penton Media Inc. Commercial references to the program and/or awards are prohibited without prior permission of Ward's Automotive Group.