The Ward's 10 Best Engines competition celebrates 14 years of recognizing outstanding powertrain development. In this first of our 2008 series, Ward's delves into the design philosophy and manufacturing technology behind Honda's 3.5L V-6.
Honda V-6 Strikes Perfect Balance
New 3.5L perfectly manages the conflicting goals of sportiness and practicality.
If we had to describe Honda Motor Co. Ltd.'s new 3.5L SOHC V-6 with one word, it would be balance.
The word comes to mind whether you are spinning the engine up to the redline with the 6-speed manual in the Accord EX-L Coupe; driving it in any number of Honda's more mundane people movers; or musing about the design philosophy behind the engine's development.
It's all about managing conflicting goals such as horsepower and fuel economy, high rpms and noise, vibration and harshness; sportiness and practicality. And while it does not excel in each specific area, the ultimate result is a marvelous unity of opposites that you can't help but like.
These are the kind of achievements Ward's editors strive to recognize with the 10 Best Engines awards. We constantly try to remind our readers, and the bloggers worldwide who sometimes criticize our choices, that this is not strictly an engineering competition, nor a list of the best high-performance powertrains.
It is about recognizing great engines that are developed on a budget and designed for mainstream consumers who care about fuel economy as well as performance, and price as well as pedigree.
In the Accord coupe, it is the silky trip up and down the rev range that brings the word balance to mind, as we marvel at how smoothly all the engine's moving parts operate. The idea of balance surfaces again as we find this powerplant's normally sedate personality is offset by a wild side: Open the throttle and it lets out a lusty howl as the 2-phase VTEC (variable valve timing and lift electronic control) switches to the high-rpm mode.
The 4-door version of the Accord conjures up the image of equilibrium again when the V-6 is attached to a 5-speed automatic transmission and equipped with Honda's Variable Cylinder Management (VCM) cylinder deactivation system.
Managing vibration during the transitions between 3-, 4- and 6-cyl. operation is much trickier with a V-6 than it is with a V-8, especially during differing conditions and engine loads. But Honda accomplishes the feat with noise-cancellation technology and active engine mounts that silence the odd-firing vibrations emitted during cylinder shutdowns.
The 3.5L represents a significant jump in size for the '08 Accord, which previously has made do with 3.0L. Ironically, engineers say the larger displacement actually enables the fuel-saving VCM technology, because it was determined the smaller cylinders of the 3.0L engine would not be able to generate enough power in 3-cyl. mode to make the system practical.
And we can't help but think of balance again when we look at how well Honda engineers have designed this bread-and-butter, high-volume engine to play so many roles within its product portfolio, whether it be family hauler or just plain hauling in the coupe.
It is tough to be all things to all people, but this V-6 does a good job of coming close, churning out 268 hp and 248 lb.-ft. (336 Nm) of torque while still managing an economical 17/25 city/highway mpg (14 L/100 km/9.4 L/100 km) in the Accord Coupe.
The V-6 also is a showcase for advanced materials and manufacturing technologies, says David Jessen, senior staff engineer-Anna Engine Plant, Honda of America.
Jessen points to the intake manifold, which is made of magnesium instead of aluminum or plastic, and is very light, with excellent sound attenuation properties.
And yet, despite all its sophistication and refinement, this definitely is an engine of the people. It is built at Honda's giant engine plant in Anna, OH, which produced 1.1 million I-4 and V-6 engines last year virtually from scratch for Honda Civics, Accords, Elements, Ridgeline pickups, as well as Acura TLs and MDX cross/utility vehicles.
“It's a highly integrated engine plant. We have a cast-iron foundry at one end where we pour gray iron for brake discs, camshafts; then there is ferrous machining, and in the middle of the plant there are three different assembly lines,” says Dan Smith, vice president and plant manager-Anna Engine Plant, HAM.
“At the other end of the plant we die-cast heads and blocks and then machine them, so we've got raw aluminum coming in one end, pig iron and coke coming in the other and finished engines going out the door of the frame (assembly) plant. It's pretty unique,” Smith adds.
Smith says the new VCM cylinder deactivation system on the V-6 requires hollow camshafts with a lobe pattern so intricate that Honda's in-house engineering division had to develop a new molding process to be able to produce them.
Called “quick casting” the process eliminates the conventional use of sand in the molding process and utilizes instead special water-cooled copper dies that cast the camshafts from molten iron into precise near-net shapes that do not require additional machining.
The process time is very fast, taking only 10 or 15 seconds to mold a tree-like group of six camshafts, Smith says, and its success is one of the reasons the Anna plant has launched another expansion.
Another interesting technology being explored at Anna is the use of aluminum cylinder liners in place of traditional cast iron.
The aluminum liners, made of an especially durable high-silicon content alloy, are lighter and provide beneficial thermodynamic qualities that aid combustion and output. At Anna, the technology only is being used on the 3.7L version of the V-6 that goes into the Acura MDX luxury CUV, but it has the potential to expand to other engines in the future, Jessen says.
But as excited as they are about all the manufacturing and technology aspects, Jessen and Smith say they are most proud of the fact this latest iteration of Honda's venerable SOHC V-6 architecture was able to improve fuel economy and performance at the same time it grows an extra half-liter of displacement.
“The balance of power and fuel economy,” Smith says, mentioning the word that seems inescapable with this engine.
But then Smith briefly takes off his engineer's hat and speaks more like an enthusiast, and says the added displacement of the 3.5L now goes a long way in answering Honda's critics who say its engines simply do not have enough low-end torque.
“We're talking about building high-volume cars, and we have to design to that wide range (of consumer requirements),” he says. “I'll agree it's taken a while to get (more low-end torque) but I think you'll see more of it. You can lay down rubber in three gears in that thing,” he says of the Accord Coupe.
For more details on Ward's 10-Best engines: http://wardsauto.com/reports/2007/tenbest
ENGINE SPECE
Honda Motor Co. Ltd.
3.5L SOHC 60° V-6
Displacement (cc): 3,471
Block/head material: aluminum/aluminum
Bore × stroke (mm): 89.0 × 93.0
Horsepower (SAE net): 268 @ 6,200 rpm
Torque: 248 lb.-ft. (336 Nm) @ 5,000 rpm
Specific output: 77 hp/L
Compression ratio: 10.0:1
Assembly site: Anna, Ohio
Application tested: Honda Accord EX-L Coupe (6-speed manual)
EPA Fuel economy, city/highway (mpg): 17/25
