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Toyota creates all-new diesel V-8 for 2008 Land Cruiser
by Editorial Staff
At the Sydney Motor Show in October Toyota unveiled a redesigned version of its
venerable Land Cruiser full-size SUV.
Like the previous generation model, the new one shares a platform with the latest
Lexus luxury SUV, the LX570. Prior to the mid-nineties, Toyota did offer diesel engines in the US market
Land Cruiser but in recent years they have only offered gasoline V-8s.
At the US launch event for the new Land Cruiser Brian Smith, Toyota's truck and
SUV marketing manager said that diesels are the dominant choice for buyers outside
of North America. Smith indicated that at some point this new diesel could turn
up at US dealers as well. In the US market the Land Cruiser has never been one of the top sellers among
large SUVs with fewer than 3,400 sales in 2006. Nonetheless Toyota is projected that to more than double to 8,000 anually with
the new model.
For overseas markets, Toyota is offering an all-new 4.5L diesel V-8 in the new
Land Cruiser. The D-4D engine as it has been dubbed features a common rail injection system,
the first time that Toyota has used this setup on a V-8 engine. In combination
with a pair of variable nozzle turbochargers the new engine generates 286hp at
3,600 rpm and 479lb-ft from 1600 to 2800rpm.
Each bank of the V-8 gets its own independent common rail injection setup which
has 33 percent higher pressure than the older 4.2L inline six cylinder diesel
from the last generation model. The 1,800 bar injection pressure helps facilitate finer more precise metering
of the fuel. The use of this new injection system enables a pair of 1 mm^3 pilot injection
strokes before the main pulse which helps reduce the noise from the combustion
process by 3.5 dB compared to the old six.
The twin turbochargers have electrically actuated variable intake nozzles. The DC motors can make faster more precise adjustments to the turbo inlets than
the more typical vacuum actuator. The combination of the new turbochargers and fuel system means the engine can
respond better to inputs from the driver. With the engine following the driver's request more precisely, the driver is
less likely to overshoot what's really needed contributing to improved efficiency.
The turbochargers are also equipped with the equivalent of a dry sump lubrication
system. A scavenging system pulls out excess oil in the turbocharger housings, reducing
the consumption and emissions. Emissions are further reduced through the use of an exhaust gas recirculation
system to lower combustion temperatures and NOx production. The EGR passages have been integrated into the cylinder head castings. This reduces the part count for assembly, while the potential for leaks as well
eliminating another source of noise from the connections that are eliminated. The manufacturing costs are also reduced.
In spite of the larger displacement and increased power, the new engine is significantly
lighter than the old diesel. The combination of the V-8 block configuration and casting it from compacted
graphite cast iron provides for a block that is 75 percent stiffer and 30 percent
lighter than the inline six cylinder block. The stronger material and the stiffer configuration reduces the vibration and
the noise produced by the new engine.
Compared to the previous diesel engine, the D-4D produces 40 percent more power
and 50 percent more torque. The new engine pushes the nearly 5,800lb Land Cruiser to 62mph from a standing
start in 8.2 seconds, one second faster than the 4.7L gasoline V-8. The D-4D is compliant with current EURO IV emissions standards but not with
US Tier 2 Bin 5 standards. On the European Union combined mileage cycle the 4.5L diesel is rated at 23
mpg compared to 16.3 for the 4.7L gasoline engine.
For the time being Toyota is only offering this new diesel V-8 outside of North
America. Toyota spokesman Curt McAllister confirmed that although Toyota is looking at
alternative fuels the company has no immediate plans to offer the new diesel to
American consumers. At the Los Angeles Auto Show introduction of the 2008 Sequoia, Toyota did announce
plans to offer a flex-fuel version of the 4.7L V-8 in that vehicle. According to McAllister there are currently no plans to offer the flex-fuel
engine in the Land Cruiser either. If the new fuel economy regulations do get enacted by the US Congress, these
plans may change. |
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