A decade ago, a normally aspirated 6-cyl. engine developing 300 hp would have stopped the industry in its tracks. Suddenly, that genus is flourishing, and Honda Motor Co. Ltd.’s new Acura 3.5L DOHC V-6 is at the top of the food chain.

For its all-new ’05 RL flagship, Acura threw out the longitudinal 90-degree 3.5L V-6 from the old 3.5RL and replaced it with this first-time 10 Best Engines winner, which now is based on the 60-degree architecture Acura uses for the MDX cross/utility vehicle. Apart from the obvious noise, vibration and harshness impact of moving from a 90-degree vee angle to the inherently balanced 60-degree layout, Acura’s thrown in everything but the technical equivalent of the kitchen sink to create the most powerful production V-6 in company history.

The new 3.5L V-6’s 300 horsepower equals the Ford Mustang GT’s 4.6L V-8, and represents a whopping 75-hp jump over the same-size V-6 it replaces. This luxury/sport sedan engine has more power and torque than the high-revving 3.2L DOHC V-6 in Acura’s NSX supercar, for heaven’s sake.

Acura’s 3.5L V-6 one of industry’s most powerful normally aspirated V-6s.

On top, engineers fitted a dual-stage intake manifold (worth 15 hp), and of course there’s Honda’s well-known VTEC (Variable Timing and lift Electronic Control) 2-stage variable valve timing. Acura says a host of internal improvements generated 40 horsepower, while the variable exhaust system netted 20 extra horses.

In addition to the newfound horsepower and torque – which improves 12% over the old V-6’s 231 lb.-ft. (313 Nm) – the new 60-degree 3.5L V-6 is 1.4 ins. (3.6 cm) narrower and 2.4 ins. (6.1 cm) shorter.

Reactions like “cranking” and “brutal” were highlights of 10 Best Engines judges’ comments, and few 6-cyl. engines we’ve tried – some turbocharged, even – can generate the startling midrange thrust that seems to flow effortlessly from Acura’s latest and greatest V-6. Throttle action is quick and micrometer-precise, too, imparting a light and responsive feel through the entire rev range.

Despite the monstrous horsepower increase, Acura’s 3.5L V-6 manages the same city fuel economy as its predecessor, and achieves a couple of mpg better in the highway cycle. Acura also says the engine complies with the California Air Resources Board’s LEV II Ultra-Low Emissions Vehicle (ULEV) emissions standard.

Honda upholds its reputation for environmental consciousness with the new Acura 3.5L DOHC V-6: The engine is both clean and economical in relation to its output. But the prodigious specific output – 86 hp/L – is the engine’s predominant character trait. Acura has crafted a technically advanced V-6 that shouts “performance” – the facet of Honda’s engine-development reputation that continues to win customers’ hearts and minds.

Acura 3.5L SOHC V-6
Engine type 3.5L SOHC 60° V-6
Displacement (cc) 3,471
Block/head material aluminum/aluminum
Bore x stroke (mm) 89 x 93
Horsepower (SAE net) 300 @ 6,200 rpm
Torque 260 lb.-ft. (353 Nm) @ 5,000 rpm
Specific output 86 hp/L
Compression ratio 11:1
Application tested Acura RL
Fuel economy for tested vehicle (EPA city/highway mpg) 18/26