Words and Photos by Mike Levine, Dyno Chart Courtesy of K&N Filters
Eight-cylinder engines are slowly being snuffed out, as manufacturers shift their focus to fuel-sipping cars and smaller, more powerful motors, but they’re still a popular and necessary choice in full-size pickups. There’s nothing -- yet -- that can tow and haul as capably as a V-8.
With the writing on the wall, though -- in the guise of CAFE standards and inevitable hikes in gas prices -- truckmakers are having to work some serious technical magic to wring more efficiency out of V-8 engines to keep them viable and competitive.
The old axiom that “there’s no replacement for displacement” is no longer as relevant as it once was. We’re entering the age of smaller, lighter, more powerful eight-cylinder motors, where the spotlight will shift from quasi-big-block mills with 6.0-liter-plus displacements to V-8 engines in the 4.0- to 5.0-liter range.
That’s where Toyota’s all-new 4.6-liter i-Force V-8 comes in, in the marginally freshened 2010 Tundra. It’s smaller than the 276-horsepower, 4.7-liter V-8 (313 pounds-feet of torque) it replaces, but stronger, lighter and more efficient. The new engine is paired with a new six-speed automatic transmission, and together they’re expected to get up to 20 mpg on the highway.
Part of the engine’s appeal is its 310 hp and 327 pounds-feet of torque. Those are the best power ratings per liter of any midlevel half-ton V-8. Toyota is hitting those numbers by applying many of the same technologies found in the Tundra’s 381-hp, 5.7-liter i-Force V-8, which makes 401 pounds-feet of torque. The dual-overhead-cam 4.6-liter V-8 uses dual Variable Valve Timing to precisely control the intake and exhaust valves for better engine performance across all rpm. The old 4.7-liter only had single VVT, for the intake side of the cam.
We got our hands on a preproduction 2010 Tundra Double Cab 4x4 SR5 with the 4.6-liter V-8 and put it through a range of tests suitable for a mid-range half-ton pickup.
Toyota says the 2010 Tundra refresh is a face-lift, but you have to look very carefully to spot the exterior changes. The three-bar grille has been replaced by a beefier two-bar grille, the lower front bumper is different and there are updated taillamps in back. There are interior changes too, but you’ve got us if you can tell what they are. The big-for-bigness’-sake climate and audio controls remain, and the materials are still very plasticky and dark. This is one Toyota product that could learn some best practices on interior design from Chrysler (never thought we’d say that).
The Tundra’s a heavy beast, weighing in at about 5,400 pounds. The old 4.7-liter got the job done moving it, but it never generated excitement or high levels of confidence while driving around town or on the freeway, especially compared to the monster 5.7-liter powertrain, which begged for a load from the moment you blipped the throttle.
The 4.6-liter reminds us a lot of the 5.7-liter, but it’s more casual in going about its duties. Sure, less power has a lot to do with that feeling, but Toyota has also geared the 4.6-liter Tundra’s rear differential completely differently. The 4.6-liter Tundra has a final drive ratio choice of either a fuel-efficient 3.90 or a mixed-use 4.10, whereas the 5.7-liter only comes with a launch-optimized 4.30 rear ring and pinion that’s perfect for heavy towing. Our truck had the 3.90 rear axle.
We took the 4.6-liter Tundra to Irwindale Speedway’s eighth-mile drag strip to measure how its zero to 60 mph times compared to our gut feel. To check out its work ethic, we loaded it up with 1,000 pounds of salt (25 40-pound bags) in the cargo box.
The Tundra is known for computerized intrusioneering, so we manually disabled vehicle stability control, traction control and the virtual limited-slip differential (it's actually precise application of the ABS system to reduce wheel slippage instead of a mechanical locker or clutch pack) before our runs so the truck wouldn’t automatically cut throttle or apply the brakes. All the runs were conducted in two-wheel drive.
Using zero rollout, but brake torquing for launch, our VBOX-instrumented testing at Irwindale yielded a zero to 60 mph run of 9.16 seconds, with an eighth of a mile clicked off in 11.14 seconds at 66 mph in third gear. With the driver, a full tank of fuel and a true half-ton load in the bed, we were within a couple hundred pounds of the max 1,255-pound load rating indicated in the door jamb for the Tundra’s Bridgestone Dueler H/T P275/65R18 tires.
Even with the electronic nannies turned off, the Tundra exhibited noticeable lag at launch until about 3,200 rpm, or about a second, at which point the power really kicked in. Still, that pause limited performance for the first few feet rolling down the strip. Once it found its groove and hooked up, the Tundra felt very confident down the track with the heavy cargo, finishing the eighth-of-a-mile run in third gear. Shifts points were around 5,400 rpm, falling back to 3,800 rpm with tow/haul mode off.
We unloaded the salt from the bed and repeated the same tests, with noticeable improvements in performance. The Tundra hit 60 mph in only 7.97 seconds and ran 660 feet in 10.56 seconds at 69.37 mph. For comparison, during unloaded tests in our 2008 Light-Duty Shootout, the 5.7-liter Tundra yielded a zero to 60 mph time of 7.16 seconds. At Irwindale, the unloaded 4.6-liter Tundra finished the eighth-mile in third gear, with the same launch lag we experienced when the truck was loaded. The shift points, however, moved slightly higher, shifting at 5,800 and dropping back to 4,100 rpm. Without all the salt in back, the ride was a bit wilder, though still confident and true down the track.
One interesting thing we picked up on while running the Tundra at Irwindale was how well Toyota has insulated the Tundra’s cabin from engine noise. Sound levels remained low during all the runs, so motor thrash wasn’t a distraction. The subdued sound levels worked well with the engine’s constant application of torque to provide extra driving confidence in the powertrain. Standing outside and watching the truck run down the track was a different experience. The 4.6-liter exhaust note is strong and smooth to observers.
Of course, zero to 60 runs can only tell so much, so we took the Tundra to the performance-obsessed staff at K&N headquarters in Riverside, Calif., to see what the torque curve looked like across the rev range. Essentially, it’s flat from 3,500 rpm to 5,900 rpm, with a slight peak at about 4,500 rpm. Toyota says peak torque is expected at 3,400 rpm, so that result is a bit unusual. With the transmission in third gear, max rear-wheel torque was measured at 266 pounds-feet. In second gear, it was virtually identical: 265 pounds-feet. Rear-wheel horsepower builds steadily until about 5,600 rpm, as Toyota says it should, and peaks at 262 hp (both measured at the rear wheels instead of the crank that’s used in the Tundra’s advertised 310-hp, 327-pounds-feet rating). The engine continues to pull with only a slight drop until 5,950 rpm, when it bumps into the rev limiter.
Toyota expects the 4.6-liter V-8 to provide the 2010 Tundra with a 15/20 mpg city/highway fuel economy rating from the EPA. That’s up from 14/17 mpg for the 4.7-liter and only 1 mpg less than special fuel-efficient pickups from Ford and GM. Much of that improvement can be chalked up to the fact that the new six-speed transmission keeps the same first-to-fifth gear ratios as the old five-speed, but adds a new second overdrive gear with a .59:1 ratio for optimal highway fuel economy, as well as the 3.90 rear axle.
In our experience, driving a 211-mile loop unloaded through West Los Angeles to the Pacific Coast Highway, up to Ventura, Calif., and back to West L.A. on the 101 freeway, we were able to achieve 16 mpg combined with the 4.6-liter -- a tolerable number considering LA's stop-and-go surface streets and we were keeping up with late night traffic traveling at more than 70 mph on the return portion of the trip.
The rest of the Tundra remains the same. Ride quality still suffers greatly when the truck is unloaded, making it very uncomfortable at times on some of L.A.’s notorious freeways. We like the Tundra when there’s payload in the bed or a trailer hanging off the back. In those cases, it’s a completely different pickup suitable to just about any task the other half-tons can do, if not more.
The 4.6-liter has a lot of ground to make up for Toyota. When the 2007 Tundra debuted with a choice of two V-8 powertrains, Toyota expected its then-new 5.7-liter V-8 to make up about 50 to 60 percent of the mix. Today, it makes up 80 percent of sales. That’s because the power-challenged legacy 4.7-liter V-8 drove buyers to the bigger engine. Only 13 percent of Tundra buyers opt for that engine; the remaining 7 percent choose the 236-hp, 4.0-liter V-6 with 266-pounds-feet of torque.
“We’ve been underrepresented,” said Bob Carter, Toyota Motor Sales USA vice president and general manager. “If you look at the full-size truck segment, about 20 percent is small V-8. We feel very confident that with the new 4.6-liter V-8, you’re going to see us become slightly overrepresented in the mix.”
The 4.6-liter Tundra is the first Toyota to offer water-cooled, computer-controlled exhaust gas recirculation, which allows for more accurate control of combustion temperatures through more of the power band for a wider, flatter torque curve, as verified in our dyno run at K&N.
The new 4.6-liter V-8 can tow up to 500 pounds more than its predecessor, depending on cab configuration. A 2009 4.7-liter V-8, regular cab, two-wheel-drive Tundra was rated to tow up to 8,500 pounds. A 2010 4.6-liter V-8, regular cab, two-wheel drive Tundra is rated to tow up to a healthy 9,000 pounds. That’s capable enough to handle most half-ton towing needs, and only 100 pounds less than the maximum tow rating of a 2009 Dodge Ram 1500 with a premium 5.7-liter Hemi V-8.
Overall, the 2010 4.6-liter V-8 Tundra’s biggest challenges will come from the Ford 4.6-liter three-valve V-8 (9,500-pound maximum towing with 3.55 rear axle, 4x2 crew cab) and GM’s 5.3-liter two-valve V-8 (9,700-pound maximum towing with 3.42 rear axle, 4x2 extended cab). Both of those engines come equipped with six-speed transmissions, like the 4.6-liter. Having driven all three powertrains, the 4.6-liter Tundra stacks up well with them in terms of power, refinement and efficiency. Depending on pricing, which hasn’t been announced yet, the 4.6-liter could turn out to be a very good deal for half-ton truck buyers looking to save money but retain lots of capability.
The 2010 Toyota Tundra with all-new 4.6-liter V-8 goes on sale later this month.
Drivetrain layout: Front-engine, RWD or 4WD
Engine type: 1UR V-8, aluminum block/heads
Valvetrain: DOHC, four valves/cyl., chain drive (dual VVTi)
Displacement: ci/cm 3:281.2/4608
Bore & stroke: 3.70 x 3.27
Compression ratio: 10.2:1
Horsepower: 310 hp @ 5,600 rpm
Torque: 327 pounds-feet @ 3,400 rpm
Transmission: A760E six-speed auto
- 1st 3.52:1
- 2nd 2.04:1
- 3rd 1.40:1
- 4th 1.00:1
- 5th 0.72:1
- 6th 0.59:1
- Rev. 3.22:1
Ring and pinion: 3.90:1, 4.10:1
Fuel efficiency: 15/20 mpg city/highway (preliminary numbers)
Emissions cert.: ULEV II