Tau V-8 Continues to Improve

IT'S HARD TO MAKE IT ONTO WARD'S 10 BEST ENGINES LIST, AND with powertrain technology advancing at a breakneck pace, it is harder still to maintain a spot multiple years in a row.

But Hyundai Motor Co. Ltd.'s Tau V-8 has managed to stay on the list for a third year thanks to major technological advancements and improvements in specific output.

For the '11 model year, Hyundai won over the judges by adding gasoline direct injection to a slightly larger displacement version of the Tau, making an impressive 429 hp and 376 lb.-ft. (510 Nm) of torque, 44 more horsepower than the already power-dense 4.6L Tau V-8 that won 10-Best honors in 2009 and 2010.

The 5.0L 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.

Mated to a new 8-speed automatic transmission in a new version of the Genesis sedan that debuts by the end of the first quarter, the 5.0L V-8 provides 0-60 (97 km/h) acceleration in 5.3 seconds.

It also offers 18/26 mpg (13-9 L/100 km) city/highway fuel economy. That beats the 17/24 mpg (13.8-9.8 L/100 km) offered by competitors such as the Lexus GS460.

In addition to the Lexus V-8, the Tau 5.0L blows away the rest of its naturally aspirated competitors in both power and fuel economy. That includes its 4.6L 385-hp little brother. Equipped only with a 6-speed automatic transmission, the smaller engine gets 17/25 mpg (13.8-9.4 L/100 km).

That makes the 5.0L Hyundai's new top-dog in the U.S. It is slated to replace the 4.6L in the newest versions of the flagship Equus luxury sedan, expected to go on sale later in the first quarter. (The Equus starts at $58,000 in the U.S., above the current Ward's 10 Best Engines $55,000 price cap, so it was not included in our official evaluation.)

Does the premier status make it the favorite engine of Hyundai Vice Chairman H.S. Lee? He flew in from South Korea to accept a Ward's 10 Best Engines award for the V-8 for the third time.

The question is a serious one, because Lee has an especially close personal connection with the Tau. As a young engine designer, he dreamed of creating a world-class V-8 to replace the dated engine in the auto maker's Equus sedan, an old 4.5L Mitsubishi Motors Corp. design that made only 270 hp.

Later in his career, when he headed powertrain development, Lee fought to have such an engine built. He thought it was important for Hyundai to have a prestigious flagship V-8. But, he says, “not everyone agreed.”

However, Lee is diplomatic about naming favorites. “Every engine is very dear to me. Every child is dear to its parents,” he says.

GDI now is the icing on the cake for this engineering dream come true.

When the engine originally was being designed eight or nine years ago, GDI, cylinder deactivation and several other technologies were not yet mature.

But Lee says the engine architecture was based on a modular concept that would allow the base engine to be easily upgraded when such new technologies were ready.

The modular design made the basic changes relatively easy, but while GDI is great for increasing power, torque and fuel economy, it also has a distinct downside: noise, vibration and harshness issues.

Unfortunately, gasoline being pumped through fuel-delivery systems at very high pressures can create a lot of racket under the hood, even during idle.

High-pressure fuel pumps make clacking and ticking noises, and fuel rails and injectors can create vibrations that are transmitted and amplified as they resonate through the engine block. To the typical automotive consumer, and to our judges, this is not the sound of advanced technology at work. It is just a turnoff.

During our testing over the years, noise from GDI systems has significantly hurt the scores of some otherwise superb engines. However, we noticed no such problems in the Tau 5.0L, which delivers its increased power as quietly and smoothly as ever.

Lee says great pains were taken to ensure the noise and vibration that is a normal part of all GDI systems was kept in check.

“To control idle noise, we use a single high-pressure pump at low rpm to minimize NVH (issues), and we also developed a special O-ring to isolate the injector vibration and noise to prevent transmission to the engine body,” he says.

The fuel rail is insulated to prevent it from transmitting vibration to the engine main body and the fuel system's high-pressure pump is covered to seal in noise.

Some of these NVH-improving features will be migrated to the auto maker's less-expensive GDI engines in the future, but Lee says there will be cost limitations.

GDI is an expensive technology by itself, without adding additional refinement features, and migrating it to smaller, higher-volume engines such as the 198-hp 2.4L I-4 in the high-volume Sonata family sedan is no small task.

But Lee says increasing the volume of GDI systems should bring down the cost. “Sooner or later, it will pay off,” he says. “I have confidence in GDI technology and turbo GDI.”

The auto maker recently decided to offer GDI engines in China. The fuel quality in major cities is fine, but there still are some concerns about the fuel in more remote areas, he says. The biggest limitation to introducing the technology worldwide is fuel quality.

Meanwhile, Hyundai continues onward at a breathtaking pace. Now that GDI has been added to the Tau, displacement has been increased and an 8-speed transmission has been added, what is left to do?

Lee is not specific, but says there is plenty of room for more improvements to the young engine. He mentions the possibility of further valvetrain enhancements and cylinder deactivation, but does not say when they will arrive.

Would Hyundai ever consider holding off on changes for a model year or two, rest on its laurels and save money? “That's not our style,” Lee says.