Ward's 10 Best Engines 2007

The 13th year of the Ward's 10 Best Engines competition finds the auto industry and its powertrain sector in acute transition entering 2007.

The U.S. domestic auto industry is undergoing a transformation to align its manufacturing capacity with new market realities. Likewise, consumers are indicating they, too, are shifting their tastes and questioning their vehicular needs in the wake of a protracted period of higher fuel prices.

All of this affects powertrain development, of course, and 2007's 10 Best Engines award winners already reflect a changing environment.

Past 10 Best Engines lists have been dominated by large-displacement engines. Half of this year's winners displace 3L or less, and only two are larger than 3.5L. Four of the 10 winners use forced induction.

In accordance with the average lower displacement of winning engines comes a broad trend toward increased fitment of efficiency-enhancing technology in addition to forced induction, such as direct-injection gasoline (DIG) fueling, cylinder deactivation and more sophisticated variants of variable valve timing.

The landscape of powertrain development may be transforming, but rules governing the competition have not changed.

Nominated engines — 31 this year — must be available in series-production, U.S.-specification vehicles that go on sale no later than the first quarter of 2007.

To ensure the 10 Best Engines winners reflect mainstream sensibilities and relevance to the broad industry, eligible engines must be available in vehicles with a base price of no more than $54,000. Ward's believes engines in more expensive and exotic vehicles should, by nature, be superior examples of powertrain engineering.

This year's price ceiling reflects a slight increase over the competition's $52,500 price limit that had been in effect for several years. The amount is indexed to the average price of a new vehicle.

Winning engines from 2006 are automatically nominated for this year's competition unless the engine no longer is available in a vehicle costing less than $54,000.

The head-to-head format generates a list of true winners, with no artificially constructed segments or sub-categories to diminish the results. All nominated engines must compete against all others.

During an approximately 2-month period in fall 2006, a panel of six Ward's editors evaluated each engine using a variety of objective and subjective measures. There is no instrumented testing. Editors evaluate each engine during their daily driving routines.

There is a variety of engine layouts, sizes and power ranges represented by 2007's 10 Best Engines winners.

Heavily influencing judges' voting are an engine's fuel economy; noise, vibration and harshness (NVH) attributes; technical innovation; and power and performance — particularly specific output, or the power generated in relation to the engine's size.

Audi AG: FSI 2L TURBOCHARGED DOHC I-4

Seems like there suddenly is a lot of small-displacement 4-cyls. pushing silly horsepower. Audi AG's turbocharged, direct-injection gasoline (DIG) 2L DOHC I-4 isn't even the most powerful among them.

But in taking its second consecutive 10 Best Engines award, the Audi powerplant demonstrates that in the new class of power-dense, forced-induction fours, all-around versatility and refinement is at least as important as big numbers.

Engineers used to look at 100 hp per liter as a moonshot number, but these new-generation boosted 4-cyls. blow right past that benchmark.

General Motors Corp.'s DIG, turbocharged Ecotec 2L churns out 130 hp/L. Mazda Motor Corp.'s 2.3L — also employing the killer-ap combo of DIG and turbocharging — makes 114 hp/L and seems laughably unstressed in doing so.

At “just” 100 hp/L, Audi's FSI 2L is the comparative anchor of the bunch.

Audi wins the day with superb drivability and wicked-fun throttle response that leaves its competition, not to mention a lot of larger V-6s, feeling flat. The full whack of its 207-lb.-ft. (281-Nm) torque peak being on hand from 1,800 rpm all the way to 5,000 rpm certainly helps.

The sharp throttle response is enhanced by the feeling of virtually no flywheel inertia. Your right foot whips the tachometer needle like a flyswatter.

Testers universally were enamored of this engine's ability to deliver sparkling power and satisfying economy. No matter how hard it was driven, it seemed impossible to get less than 25 mpg (9.4 L/100 km), and a light throttle is rewarded with economy-car fuel consumption.

And typical of Audi, the 2L turbocharged DOHC I-4 pegs the technology meter. In addition to the auto maker's pioneering FSI (fuel straight injection) DIG technology, there are more variables here than in calculus class: a turbo lag-reducing variable-nozzle turbocharger; variable valve timing; and a variable-length intake manifold that incorporates charge-motion flaps to optimize intake-air swirl.

Refinement is abetted by a pair of counter-rotating balance shafts and a long-stroke layout (long a Volkswagen Group preference). Engineers must have spent extra time on this free-spinning engine's rev-limiting software, certain in the knowledge it would get a workout.

When Volkswagen AG and Audi replaced the highly regarded 1.8T turbocharged 4-cyl. (an engine that took home five 10 Best Engines trophies) with this new, direct-injected architecture, fans of that 5-valve-per-cylinder fun-motor feared nothing could replace it.

But the VW Group's powertrain engineers upped the ante, adopting FSI direct injection (this was the first production engine to combine DIG with turbocharging, Audi claims), an aluminum block and a little more displacement.

Best of all, Audi and VW make this engine available at several price points in both brands' model range, meaning nobody has to be rich to enjoy what is one of the most affordable performance engines in the U.S. market.

Engine Specs:

Engine type: 2L Turbocharged DOHC I-4

Displacement (cc): 1,984

Block/head material: iron/aluminum

Bore × stroke (mm): 82.5 × 92.8

Horsepower (SAE net): 200 @ 5,100-6,000 rpm

Torque: 207 lb.-ft. (281 Nm) @ 1,800-5,000 rpm

Specific output: 100 hp/L

Compression ratio: 10.3:1

Assembly site: Gyor, Hungary

Application tested: Audi A3

EPA fuel economy, city/highway (mpg): 24/32

BMW AG: 3L DOHC I-6

BMW AG has been scrambling lately to maintain its prime position atop the sport-sedan pecking order, as new and revitalized Japanese and U.S. competitors chip away at its Ultimate Driving Machine brand equity.

The cornerstone of that brand image is BMW's famous — and famously smooth — inline 6-cyl. engine.

Shackled somewhat by the sensibilities of a European-market base that demands mainstream engines remain snugly sized, BMW watched in recent years as larger-displacement V-6s worked walloping horsepower advantages of as much as 70 hp over its 3L straight-six in sport sedans. Something had to be done.

The answer, launching last year in the U.S. market, is the magnificent N52 3L DOHC I-6, the 12th generation of the hallowed inline 6-cyl.

Using a raft of new power- and efficiency-enhancing tweaks, BMW narrowed the power gap with the half-liter-larger premium V-6s to the point where the engine's intrinsic design advantages aren't overshadowed by horsepower comparisons, alone.

Winning a 10 Best Engines award for the second time in as many chances, the N52 returns BMW's “standard” inline 6-cyl. to its rightful place as the exemplar of what a sport-sedan engine should be.

Engineers baked in some materials intrigue, evidenced by the 3L straight-six's high-tech magnesium-aluminum block — said to save about 22 lbs. (10 kg).

Equally important, BMW engineers fitted the trick Valvetronic variable valve-lift mechanism to augment the VANOS variable valve-timing arrangement that already had been used in the previous-generation 3L inline 6-cyl.

The new fettling of the basic layout also delivered a key byproduct: an extra 500 rpm of engine operation. The redline now is a satisfying 7,000 rpm, and the new N52 feels robust and willing enough to run to 9,000.

Yanking the N52 up to 255 hp and 220 lb.-ft. (280 Nm) of torque — and unleashing the redline — makes for a mid-displacement performance engine without parallel. BMW's new, ultra-tight valve control takes an engine that already was not short on excitement and adds a magnificent new level of throttle response and exhaust sound.

“This engine totally rips,” says one 10 Best Engines judge. “It's ready to go at any rpm.”

More telling, perhaps, is what that hallmark inline 6-cyl. smoothness does for perceived performance: “255 hp?” says another editor. “It feels like more.”

And the new-generation inline 6-cyl.'s ability to deliver mid-20 mpg in the real world drives home the serious efficiency achievement gained with Valvetronic's elimination of conventional throttle. It is an innovation other auto makers are preparing to emulate.

The sparkling performance and spectacular refinement at all engine speeds make BMW's 3L DOHC I-6 a special experience, no matter how jaded the driver.

Engine Specs:

Engine type: 3L DOHC I-6

Displacement (cc): 2,996

Block/head material: magnesium-aluminum/aluminum

Bore × stroke (mm): 85 × 88

Horsepower (SAE net): 255 @ 6,600 rpm

Torque: 220 lb.-ft. (298 Nm) @ 2,750 rpm

Specific output: 85 hp/L

Compression ratio: 10.7:1

Assembly site: Munich, Germany; Steyr, Austria

Application tested: Z4 3.0si

EPA fuel economy, city/highway (mpg): 20/30

BMW AG: 3L TURBOCHARGED DOHC I-6

Yeah, auto makers and their powertrain engineers have claimed for years some latest pairings of engines and turbochargers have “eliminated” turbo lag, the wait-to-accelerate feeling that forever has been the bane of turbocharged automotive powerplants.

Well, ah, BMW AG's actually done it.

So sweet, so smooth, so willing, so immediate is BMW's all-new turbocharged 3L DOHC I-6 that we're convinced car enthusiasts will not know the auto maker's hallmark inline 6-cyl. engine has forced induction.

The only way they'd really know, perhaps, is from the epic torque rush that signals turbo, rather than from the presence of turbo lag.

BMW, in fact, had quickly tired of its “standard” 3L DOHC I-6 taking a back seat to larger V-6s dealing out in excess of 300 hp. It called in forced-induction boffins from turbocharger expert Mitsubishi Heavy Industries Ltd., which helped engineer the new N54 twin-turbo setup, making the first BMW turbocharged gasoline engine since 1981.

With just three of the BMW straight-six's cylinders dedicated to huffing exhaust past each turbine, the turbochargers can be sized for rapid response rather than to handle large exhaust volume.

The other turbo lag-reducing factor is BMW's fitment of its second generation of direct-injection gasoline fueling. DIG naturally plumps low-speed torque, which also helps rouse engine rpm while the turbos wind up.

The effect is electric: Apart from adding a substantial 45 hp to the standard 3L inline-six's 255 hp, torque surges to a V-8-like 300 lb.-ft. (407 Nm) that effectively is available for just about the entire useful engine-speed range.

One of the few criticisms that can be leveled at BMW's inline 6-cyl. layout is that, at 3L of displacement, torque output is relatively meager. Well, the turbos have solved that problem, thanks very much.

The thrust from this new turbocharged I-6 is captivating. With a much broader torque peak than any V-8 can deliver, the acceleration surge seems endless. The driver never tires of calling the torque out to play, thanks in large part to the deliciously precise throttle, a hallmark of all BMW inline sixes that only seems magnified with the twin-turbocharged variant.

The low-inertia dual turbochargers and direct injection — along with variable valve timing — seem to have been fated to join with the always-special straight six in a systems-approach design that, to our right feet and pants seats, have no appreciable shortcomings.

OK, it's a shame the Valvetronic variable valve-lift system isn't there to increase what already is startlingly good fuel economy, even when extracting the most from both turbos. And this variant of the standard N52 I-6 foregoes that engine's exotic magnesium-aluminum block for just plain aluminum with iron cylinder liners.

But those are inconsequential nits. With its new turbocharged inline-six, BMW has developed what may be the perfect performance engine for this age. It's that good.

Engine Specs:

Engine type: 3L Turbocharged DOHC I-6

Displacement (cc): 2,979

Block/head material: aluminum/aluminum

Bore × stroke (mm): 84 × 89

Horsepower (SAE net): 300 @ 5,800 rpm

Torque: 300 lb.-ft. (407 Nm) @ 1,400-5,000 rpm

Specific output: 100 hp/L

Compression ratio: 10.2:1

Assembly site: Steyr, Austria

Application tested: 335i

EPA fuel economy, city/highway (mpg): 19/29

DaimlerChrysler AG: 3L DOHC V-6 TURBODIESEL

Two identical cars. One has a gasoline 3.5L V-6, the other, a 3.2L V-6 diesel.

The gasoline car runs from 0-60 mph (97 km/h) in 6.5 seconds. The diesel car takes a tenth of a second longer to get there but makes up for it with 35% better fuel economy.

With $3.50-per-gallon gasoline anything but a distant memory, you'd take that diesel, wouldn't you? We sure would.

“A game changer” says one 10 Best Engines judge of the DaimlerChrysler AG 3L DOHC V-6 turbodiesel, developed by DC's Mercedes-Benz unit to replace its inline 6-cyl. turbodiesel.

If it were just a fuel-economy play, it would be convincing, achieving 27 mpg (8.7 L/100 km) city and 37 mpg (6.4 L/100 km) highway.

But this mill comes with noise, vibration and harshness quality levels comparable to gasoline engines. Just as important, the new V-6 wields a hefty performance hammer.

At 208 hp and a thumping 400 lb.-ft. (542 Nm) of torque in the '07 Mercedes E320 Bluetec application, the new V-6 turbodiesel is stronger than the 3.2L inline unit it supplants. And it has more torque than the auto maker's 5.7L Hemi V-8. Need we say more?

Incidentally, the same engine, with slightly different specs, is in the '07 Jeep Grand Cherokee CRD, which we also tested — and found to be slightly less refined.

Mercedes ladled on technology to assure the mill lives up to the fuel-economy promise while attaining new levels of NVH and cleanliness.

The 22,700-psi (1,600-bar) common-rail fueling system pressurizes the latest piezo-hydraulic-electric fuel injectors that just plain eradicate diesel clatter. Cold starts still are a tad noisy, but once the engine is warmed up, the “dieselness” is in-distinguishable from the mechanical gnashing of a gasoline engine's ancillaries.

And there's the latest in variable-nozzle turbochargers to minimize turbo lag, although there's still a moment of dead-throttle anxiety just off idle and before this powerhouse can start delivering its peak torque at just 1,600 rpm.

Now, about those emissions. This year, the E320 Bluetec uses the first phase of the Bluetec exhaust-aftertreatment system that will, by sometime next year, cleanse oxides of nitrogen (NOx) and particulates to the point where diesels so equipped can be sold nationwide.

That will require a suite of aftertreatment components, including a urea-injection system to reduce NOx to acceptable levels.

For now, the E320 Bluetec uses an oxidizing catalyst, an NOx-scrubbing catalyst, a particulate filter and a basic selective catalytic reduction converter to take one final swipe at NOx. This system makes the diesel compliant with federal Tier II, bin 8, emissions standards.

To get to the diesel Valhalla of Tier II, bin 5 — low enough to make diesels salable even in California — the urea-injection system will be required.

Don't worry — DC will work out the emissions thing. Its 3L turbodiesel is the real deal. Spectacular performance and serious fuel economy now officially co-exist.

Engine Specs:

Engine type: 3L DOHC 72° V-6 Turbodiesel

Displacement (cc): 2,987

Block/head material: aluminum/aluminum

Bore × stroke (mm): 83 × 92

Horsepower (SAE net): 208 @ 3,800 rpm

Torque: 400 lb.-ft. (542 Nm) @ 1,600-2,400 rpm

Specific output: 69 hp/L

Compression ratio: 18:1

Assembly site: Stuttgart, Germany

Application tested: Mercedes E320 Bluetec

EPA fuel economy, city/highway (mpg): 27/37

DaimlerChrysler AG: HEMI MAGNUM 5.7L OHV V-8

Those who thought DaimlerChrysler AG's hulking Hemi 5.7L OHV V-8 this year would be “politically corrected” from the Ward's 10 Best Engines list probably don't know the Hemi very well.

It takes more than $3-per-gallon gasoline to change our minds about the Hemi.

Returning for its fifth consecutive 10 Best Engines win, the Hemi's intrinsic goodness and legitimate effort to improve efficiency transcend this year's fuel-price scare, in the minds of the competition's judges.

After high gasoline prices dented everybody's wallet and definitively shifted consumer tastes, we wondered if anybody would care anymore about the Hemi, for several years nothing more than the hottest brand in the powertrain sector.

But the Hemi waltzed its way on to this year's list, mostly because there's still plenty of need for traditional V-8 power, and right now, nothing's serving that need better than the Hemi.

“After several years in the market, the Hemi still feels fresh and invigorating — and sounds great,” says one editor.

“This engine wouldn't be out of place in an $80,000 car,” insists Ward's AutoWorld Editor Drew Winter, a self-admitted connoisseur of that breed. Indeed, although we typically do not hold up OHV layouts as paragons of refinement, V-8s tend to be the exception, and the Hemi continues to set the refinement benchmark for OHV V-8s.

Power and torque, the Hemi's calling cards, remain its most convincing 1-2 punch. Regardless of the vehicle it's powering, the Hemi always delivers what you want, when you want it.

Our Chrysler 300C test vehicle, sporting a Hemi at its chesty 340 hp and 390 lb.-ft. (529 Nm) torque rating, was the ideal vehicle to reaffirm this mill's assets. The car is plenty good without it, but the Hemi is what takes the 300C from darn good to darn wonderful.

Chrysler also wisely broadened the scope of the Hemi's Multi Displacement System (MDS) cylinder-deactivation setup to almost every vehicle in which the Hemi is offered.

And although critics have questioned the real-world fuel savings attributable to MDS, we're convinced it makes a difference.

MDS definitely has sleep-better-at-night value: The MDS-equipped Hemi in the 300C, according to the Environmental Protection Agency's ratings, at least, is just 2 mpg thirstier than the available 3.5L SOHC V-6 in the same car.

A 2-mpg penalty for the Hemi? C'mon. It would take way more than that (apart from the extra money, obviously) to turn away any sane person from the Hemi.

There's little question the mood of the nation has changed, and nearly everyone now is questioning U.S. buyers' consumptive vehicle and engine preferences of the past decade or more.

But to say the Hemi isn't good anymore because of that is specious. There's a place and a need for V-8 power in the U.S., and the Hemi is far and away the best combination of power, affordability and versatility among contemporary V-8s.

Engine Specs:

Engine type: 5.7L 90° OHV V-8

Displacement (cc): 5,654

Block/head material: iron/aluminum

Bore × stroke (mm): 99.5 × 90.9

Horsepower (SAE net): 340 @ 5,000 rpm

Torque: 390 lb.-ft. (529 Nm) @ 4,000 rpm

Specific output: 60 hp/L

Compression ratio: 9.6:1

Assembly site: Saltillo, Mexico

Application tested: Chrysler 300C

EPA fuel economy, city/highway (mpg): 17/25

Ford Motor Co.: DURATEC 35 3.5L DOHC V-6

It wasn't a secret Ford Motor Co. had some catching-up to do in the matter of high-volume V-6s.

It's longstanding Duratec 3L DOHC unit traces its development lineage to the early 1990s, and its 4L SOHC V-6 built in Cologne, Germany, is equally aged and off the pace.

Compounding the problem, the competition has become fierce. There are mainstream and premium DOHC V-6s in more market segments than we care to count, and in the ongoing quest for torque, most have converged at 3.5L of displacement.

Until now, Ford just didn't play there.

With the all-new Duratec 35, Ford sticks with the established Duratec name — the engine was known internally as Cyclone — but it owes nothing else to the previous Duratec architecture, Tom McCarthy, Ford manager-V-6 engine programs, says.

McCarthy and Bob Fascetti, director-powertrain programs, say development goals were premium performance and drivability, improved fuel economy and decreased emissions.

The Duratec 35 wins its first 10 Best Engines award largely for the versatility those goals suggest: The engine is thrusty and refined and demonstrates decent fuel-economy.

The Duratec 35 is particularly delightful in the mid-range, where it revs viciously with even light throttle applications. In fact, revving all over the place is one of this new engine's strong suits.

“I've never seen a tach needle jump from 1,500 to 5,000 rpm quite like this,” says Senior Editor Tom Murphy. Often, larger-displacement V-6s can be slow to rev with gusto, but the Duratec 35 delivers some of the crispest throttle response we can recall.

Our guess: Exceptionally fine control of the variably timed intake valves helps the Duratec 35 seem more powerful than its brawny 265 hp and 250 lb.-ft. (339 Nm) torque rating suggest.

Along with inspired mid-range snap, the Duratec 35 3.5L DOHC V-6 fronts what we believe to be class-leading refinement.

Vibration, in particular, is bewilderingly absent. All sorts of low-friction detail engineering and big-ticket items, such as the deep-skirt block and weight-optimized DOHC valvetrain, make this one of the silkiest sixes you'll find short of one with all the pistons in a row.

The Duratec 35 is a brilliant performer, convincingly developed in all areas, and it's particularly impressive when one considers it's all done with a 10.3:1 compression ratio on regular unleaded gasoline.

Performance and refinement at this level sets a new standard for V-6s; bridging the gap between those with workaday specs and refinement and the big-dollar, big-power premium V-6s that require, or at least recommend, premium unleaded.

Our reservations are meager: We'd like a little more exhaust expressiveness. The new Duratec 35 is too quiet, at least in the MKX and MKZ Lincoln models we've driven so far.

And the new V-6, for now, is available only with an automatic. However, as automatics go, Ford's new 6F 6-speed is rock solid. This may be solved once the Duratec 35 traverses throughout the Ford empire, eventually powering one in five of all the auto maker's vehicles, likely including the Mustang.

Engine Specs:

Engine type: 3.5L DOHC 60° V-6

Displacement (cc): 3,496

Block/head material: aluminum/aluminum

Bore × stroke (mm): 92.5 × 86.7

Horsepower (SAE net): 265 @ 6,250 rpm

Torque: 250 lb.-ft. (339 Nm) @ 4,500 rpm

Specific output: 72 hp/L

Compression ratio: 10.3:1

Assembly site: Lima, Ohio

Application tested: Lincoln MKX (AWD)MKZ Sedan

EPA fuel economy, city/highway (mpg): 17/24

Ford Motor Co.: 4.6L SOHC V-8

A funny thing happened while Ward's 10 Best Engines judges were pondering the expanding list of Mustang variants in search of the best way to sample the auto maker's modular 4.6L SOHC V-8: Ford's on-the-ball press-fleet coordinators hustled over one of the first examples of the Shelby GT.

Most of us didn't get out of the parking garage before scrambling for a pen to wax eloquent about this seemingly innocuous tweak to the 4.6L V-8, the brawny and vocal new generation of Ford's excellent modular V-8 family that scorched its way to a 10 Best Engines win when launched two years ago.

That's because the even growlier exhaust note is immediately evident when bouncing off concrete walls. Not that it really needs any augmentation. The 4.6L V-8's exhaust symphony simply is the best on the market, but the new Shelby GT specification of the 4.6L somehow improves on what we were convinced already was V-8 aural perfection.

This comes by way of Ford's Racing components unit, which supplies for the Shelby GT a Ford Racing Power Pack that fits a cold-air intake (an import tuner-market staple), a revised crossover pipe for the dual exhaust and some engine-management software fettling.

The result is an extremely noticeable 25-hp improvement over the standard 4.6L V-8's stout 300 hp and a slight gain in torque, from 320 lb.-ft. (434 Nm) to 330 lb.-ft. (447 Nm). The shorter final-drive ratio, 3.55:1 compared with the Mustang GT's 3.31:1, also is a likely conspirator in notably nastier in-gear acceleration.

The Shelby GT, by the way, is the civilian version of the Shelby GT-H, which only can be sampled by renting one from Hertz.

The Ford Racing Power Pack “really wakes this engine up,” says one Ward's editor, reminding that one of our only reservations regarding Ford's modular V-8s is some low-rpm sleepiness that isn't erased until the engine gets “on the cam.”

But as usual with this V-8, the sounds leave as much impression as the power.

The cold-air intake, for example, isn't shy about making it's presence known. With the Power Pack, the revised 4.6L V-8's intake bark can singlehandedly raise the national terror-threat color. Coordinating with the even more luscious exhaust, the 325-hp 4.6L V-8 is about as subtle as a truck-stop breakfast.

If you don't yearn for all that sturm and drang, go for the 4.6L V-8 in standard 300-hp trim, which is one of the market's unqualified excitement-per-dollar leaders and is more convincing than most engines while just idling in the driveway.

And as one reader reminded just minutes after posting this year's 10 Best Engines winners on WardsAuto.com, you don't need the admittedly limited-purpose Mustang GT to partake of the 4.6L V-8's special character: Ford also offers this engine (in iron-block form) for the Explorer and Explorer Sport Trac.

But really, the Mustang Shelby GT — 325 hp, 330 lb.-ft. and 0-60 mph (97 km/h) in about 5 seconds, all for about $35,000. We see more 10 Best Engines awards in the future with numbers like those.

Engine Specs:

Engine type: 4.6L SOHC 90° V-8

Displacement (cc): 4,604

Block/head material: aluminum/aluminum

Bore × stroke (mm): 90.2 × 90

Horsepower (SAE net): 325 @ 5,750 rpm

Torque: 330 lb.-ft. (447 Nm) @ 4,500 rpm

Specific output: 71 hp/L

Compression ratio: 9.8:1

Assembly site: Romeo, Michigan

Application tested: Ford Mustang Shelby GT

EPA fuel economy, city/highway (mpg): 17/25

Mazda Motor Corp.: DISI 2.3L TURBOCHARGED DOHC I-4

You've seen those percussion grenades thrown in action films: Pull the pin, toss it in the room, there's a big bang and blinding flash, and everyone in the room is rendered senseless.

Imagine the analogue in the engine world, and you've got Mazda Motor Corp.'s DISI 2.3L turbocharged DOHC I-4 all but blasting its way past the competition for its second consecutive 10 Best Engines award.

Total sensory overload is how we'd describe testing Mazda's ultra-power-dense 4-cyl. in the new Mazdaspeed3 application. Turning the key and lighting off this big-boost variant of the Mazda-developed MZR 4-cyl. architecture — also used by part-owner Ford Motor Co. — is the equivalent of pulling the pin.

From there, 114 hp per liter in a car that weighs 3,180 lbs. (1,443 kg) and, well, we'll do the math for you: 12 lbs. (5.4 kg) per horsepower. That's spittin' distance from high-dollar hardware such as Porsche Cayman (11.7 lbs./hp) or even Mazda's own sports-car flagship, the RX-8 (13 lbs./hp).

But this is an engine award. Consider that with its 15.6 psi (1 bar) of boost pressure ramming out 280 lb.-ft. (380 Nm) of torque, this 2.3L 4-cyl. out-torques Porsche's 3.4L H-6 in the $59,000 Cayman S and, really, just about any other normally aspirated 6-cyl. around.

Moreover, this firecracker 4-cyl. rams the Mazdaspeed3, incredibly, to a stated top speed of 155 mph (250 km/h) and runs 0-60 mph (97 km/h) in less than 6 seconds.

But the DISI 2.3L turbocharged DOHC I-4 is more than a bang-for-the-buck, strap-on-a-turbo special. There's serious engineering at play here, the kind of action that elevates this engine above others we've tested that offer a great performance-per-dollar quotient.

For one, there's Mazda's first use of direct-injection gasoline technology. The new-age, higher-pressure fueling naturally bolsters low-rpm torque, making it the perfect technology to counter turbo lag. First seen on high-dollar engines, the technology quickly is sifting into the mainstream to the benefit of us all.

Mazda engineers also have addressed noise, vibration and harshness concerns. The aluminum block has been braced to absorb the higher stresses, and the twin balance shafts certainly seem to be earning their keep.

It would've been enough to generate the giant power numbers and call it a day, but this engine never gives the sensation that refinement got “costed.”

And, under the Mazdaspeed3's hood, it's advisable to hang on when the turbocharger hits its stride, because there's still a not-totally-civilized wallop.

Some 10 Best Engines testers admit to preferring Mazda's mini-dynamo DISI 2.3L turbo I-4 in the CX-7 cross/utility vehicle or the Mazdaspeed6 midsize sedan (both of which calm this brute with all-wheel drive), but all agree this engine is a special example of affordable-engine development.

Engine Specs:

Engine type: 2.3L Turbocharged DOHC I-4

Displacement (cc): 2,260

Block/head material: aluminum/aluminum

Bore × stroke: 87.4 × 94

Horsepower (SAE net): 263 @ 5,500 rpm

Torque: 280 lb.-ft. (380 Nm) @ 3,000 rpm

Specific output: 114 hp/L

Compression ratio: 9.5:1

Assembly site: Hiroshima, Japan

Application tested: Mazdaspeed3

EPA fuel economy, city/highway (mpg): 19/25

Nissan Motor Co. Ltd.: 3.5L DOHC V-6

We wondered where Nissan Motor Co. Ltd. possibly could go with its VQ-series 3.5L DOHC V-6 after winning a 10 Best Engines award for a dozen consecutive years. After all, most contemporary engine families don't last this long, much less last this long at the top.

So where is Nissan going? To the podium for its 13th award.

The company's engineers apparently don't intend to relinquish the VQ's now-legendary status as the definitive V-6 benchmark because this year, the fourth generation of the VQ is 80% new, flaunting revised design features that address the one development aspect in which the VQ had been slipping — refinement — and brewed in a fresh new level of performance, just to be certain everybody knows they're serious.

In recent 10 Best Engines competitions, Ward's editors have been straightforward about the VQ's benchmark role: It's tough to rag on a legend, but ever since the '02 model year, when Nissan bored the sweet original 3L VQ to a brawnier 3.5L, we've noted an erosion of refinement.

Noise, vibration and harshness levels had been sacrificed at the altar of increased horsepower and torque.

The modular DOHC V-6 that launched in 1995 in the U.S. at 3L and 190 hp gradually had grown to 3.5L and as much as 298 hp — a 50%-plus hike in power from just a 17% increase in size.

But for the fourth-gen '07 variant, the VQ35HR, there's a critical new structural ladder frame, an enlarged crankpin and crank journal diameter, a new cylinder-head design, a trick new asymmetric piston skirt and longer connecting rods, in addition to a raft of friction-reducing updates.

The engineers out there easily will assemble the puzzle to see improved NVH was a prime target.

It worked. The VQ has regained much of its hallowed silkiness.

“Once again, it's easy to forget to upshift, it revs so smoothly,” Editor Drew Winter says.

But all that refinement attention bore gifts even better than those best appreciated by the J.D. Power quality fanatics. The “HR” designation for this latest-generation VQ stands for “high revolution,” meaning there are more revs available from an engine that always preferred the high-altitude section of the tach to begin with.

The VQ35HR now offers a luscious 7,500-rpm redline (up from 7,000 rpm with the manual transmission for the old VQ) and revs so passionately that a gearshift feels unnecessary before 6,000 rpm.

A 6,800-rpm power peak would be a warning sign in less religiously detailed engines. But for the new VQ, that region of the tach is fully and invitingly exploitable.

All those revs mean extra power, too, and the HR variant of the VQ (a fourth-gen VQ35DE with fewer of the high-rev ministrations will be fitted for several models) loads up with 306 hp and 268 lb.-ft. (363 Nm) of torque — power that matches the class-leading Lexus IS 350's 3.5L DOHC V-6, but lags it slightly in torque.

Nissan engineers say they developed the high-rev variant of the 3.5L DOHC V-6 to be a more “emotional” experience, and we're down with that, too.

Anytime you can spin a V-6 to 7,500 rpm, get more power and refinement and bask in magnificent new sounds specifically targeted for the HR, there's nothing to do but once again award the champion its hard-earned belt.

Engine Specs:

Engine type: 3.5L DOHC 60° V-6

Displacement (cc): 3,456

Block/head material: aluminum/aluminum

Bore × stroke (mm): 95.5 × 81.4

Horsepower (SAE net): 306 @ 6,800 rpm

Torque: 268 lb.-ft. (363 Nm) @ 5,200 rpm

Specific output: 87 hp/L

Compression ratio: 10.6:1

Assembly site: Iwaki, Japan

Application tested: Infiniti G35 6MT (6-speed manual)

EPA mileage, city/highway (mpg): 19/27

Toyota Motor Corp.: 3.5L DOHC V-6

Winning its second consecutive 10 Best Engines award with the 3.5L DOHC V-6 used in the Lexus IS 350 sedan, Toyota Motor Corp. scores top marks in the realm of special technical effort.

Direct-injection gasoline technology is not unique in the U.S. DIG systems can be found on numerous engines powering vehicles in a wide range of prices.

But Toyota, with the 2GR-FSE V-6, adds an intriguing layer by blending a conventional port-injection system with DIG to optimize the advantages of both fueling designs.

In low- and part-load conditions, each cylinder's direct- and indirect-injection fuel injectors are used according to the desired performance: emissions reduction, low-speed torque enhancement and reduced fuel consumption.

Variable valve timing and a variable-length intake manifold assist in creating the intake-mixture formation desired from both fueling systems to generate the ideal engine operation according to that moment's engine load.

On the road, the 2GR-FSE delivers superb drivability and eye-opening performance. Its 306 hp ties the output of Nissan's new-generation 3.5L V-6, but the Toyota V-6's 277 lb.-ft. (376 Nm) of torque surpasses even the vivacious Nissan V-6 for outright class leadership.

Toyota's V-6 has sparkling throttle response, using DIG's torque-enhancing traits to pull hard from virtually every engine speed. It all comes with a large dose of Lexus-typical mega-refinement.

“So quiet, the acceleration is deceptive,” says Senior Editor Alisa Priddle. “An excellent example of DIG.”

“This one really checks off all the boxes,” gushes Ward's AutoWorld Editor Drew Winter, noting the only complaint most 10 Best Engines judges can file: The Toyota 3.5L DOHC V-6, like most DIG engines, struggles to generate a satisfying and authoritative exhaust note.

We hear exhaust-component suppliers are hard at work on a fix for DIG engines of all layouts.

Another advantage of the dual-fueling systems is improved fuel economy. Many testers compliment the Toyota V-6 for its thriftiness, highlighted by class-leading 21-mpg (11.2 L/100 km) city and 28-mpg (8.4 L/100 km) highway fuel-economy ratings. One editor saw an overall average of 24 mpg (9.7 L/100 km) on a mixed-driving trip of several days.

While the aural emanations still could be more involving, Toyota and Lexus do indeed check off all the boxes here. The 3.5L DOHC V-6 is a thrilling sport-sedan engine that compromises nothing in terms of refinement and fuel economy. It's a technical achievement worthy of Toyota and Lexus' high-flying reputation.

Engine Specs:

Engine type: 3.5L DOHC 60° V-6

Displacement (cc): 3,456

Block/head material: aluminum/aluminum

Bore × stroke (mm): 94 × 83

Horsepower (SAE net): 306 @ 6,400 rpm

Torque: 277 lb.-ft. (376 Nm) @ 4,800 rpm

Specific output: 87 hp/L

Compression ratio: 11.8:1

Assembly site: Kamiga, Japan

Application tested: Lexus IS 350

EPA fuel economy, city/highway (mpg): 21/28

10 Best Engines Nominees — Our Infamous Three-Line Dossier

AUDI AG

BMW AG

DAIMLERCHRYSLER AG

FORD MOTOR CO.

GENERAL MOTORS CORP.

HONDA MOTOR CO. LTD.

HYUNDAI MOTOR CO. LTD.

MAZDA MOTOR CORP.

NISSAN MOTOR CO. LTD.

TOYOTA MOTOR CORP.