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  • Road Test Comparison: 2007 BMW X5 and 2007 Land Rover Discovery 3

Road Test Comparison: 2007 BMW X5 and 2007 Land Rover Discovery 3

Diesel Duo: 510 Miles on a Tank of Fuel!

G.R. WhaleDec 21, 2006
With a few formally announced diesel-powered SUVs that are due in the U.S. by 2008 and a Grand Cherokee diesel shown at Detroit, it appears the diesel is gaining ground. To see what Europe may have to offer in the growing diesel battle, we went to Germany to drive a diesel BMW X5 and Land Rover Discovery3 (aka LR3), neither of which have been announced for sale in the U.S., but you never know what may be coming.
BMW and Land Rover have had diesel power in North America before, BMW with the 524td sedan and Land Rover with Defenders for the military. We expect a BMW diesel here by 2008, probably a thirsty premium vehicle. In the meantime, the best we can do is to head to Europe to drive the X5 and Discovery3.
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Our examples were automatics; market research suggests they'd sell better than those equipped with manuals. Apart from slight changes to lights and bumpers, instruments, snow tires (the same size and speed rating as standard), perhaps slightly stiffer spring rates, intercoolers behind the grilles, and exhaust systems, the X5 pipes come out below the rear valance, not through it--they're similar to North American units.
Quieter Than Gas
When we first turned the key on the Discovery3, our eyes focused on the instruments, looking for a glow plug or wait-to-start indication. What stood out instead was a gauge indicating a whopping 820 kilometers' range on the tank. This equals just under 510 miles. Even using fingers for the math this was way more than any benzene-burning LR3 ever gave us.
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The TDV6, the diesel version of the Discovery3, uses a PSA/Ford-developed 2.7-liter V-6. An iron-block, aluminum-head twin-cam with four valves per cylinder and common-rail injection, the Land Rover variant uses a single variable nozzle turbo and, as would be expected, the oiling system and seals are modified for extreme-angle off-road use.
It's rated at 188-190 horsepower at 4000 rpm, depending on which rating system you use, and approximately 325 pound-feet of torque at 1900 rpm. The 2.7 diesel makes more peak torque than the 4.4-liter gas engine, but, far more importantly, it delivers close to 300 pound-feet from 1500-3000 rpm where it's most frequently operated. The comparable 4.4-liter needs close to 3200 rpm to approach 300 pound-feet.
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Manufacturer figures show diesel fuel consumption (with the automatic) as roughly 50 percent better than the 4.4-liter V-8's, the biggest gain in the city cycle, and the manual gearbox enjoys an even larger advantage (no manual is offered with the V-8). This is a primary reason diesel has market penetration near 80 percent for SUVs over the pond. The diesel also has significantly lower CO2 emissions.
Unless it sat overnight in subfreezing temperatures (when it needed four seconds for preheat), the D3 diesel started up immediately and idled smoothly. At idle with fans and radio off, you can tell it's a diesel, or perhaps a gas engine with noisy injectors or tappets, but once accessories are on and you're moving it's comfortably quiet. According to Land Rover literature, drive-by noise is 70.8 dB on a diesel auto and the V-8 is louder (72.7).
Drop the TDV6 in Drive and as soon as the torque converter goes to work, low-end urge is apparent. Plenty of throttle travel means you hardly need revised mapping in low-range or specific Terrain Response modes, and even if you floor it from a stop, the turbo spools up to take out any hard hit. That initial delay might cost half a second in all-out blasts, but it's not noticed underway, and using Sport mode doesn't make it faster at wide-open throttle. At full throttle the engine goes past horsepower peak and off boost slightly, resulting in luxo-smooth shifts rather than blunt and harsh.
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The D3 goes like any diesel and most previous Land Rovers: it gathers momentum rather than accelerating. Our hand-timed jaunts to 62 mph (100 kph) averaged 11.6 seconds, a tenth better than factory claims and about 3.0 seconds behind a gas V-8. Top speed is listed as 112 mph (180 kph, in fifth or sixth gear) though we had no trouble making the needle climb to 188, nearly keeping up with air traffic approaching the adjacent airport.
For perspective, that acceleration puts the D3 diesel soundly in H3 territory and a fraction to one second slower than an Escape V-6, Liberty CRD, H2, and Prius. None of those weighs 5500 pounds and none carries seven people; we're not convinced they can all do 112 mph, either, and shorter gearing would likely make a TDV6 brisker with next to no penalty in fuel economy.
At a steady 65 mph, the TDV6 computer displayed an average fuel use of 29.8 mpg, and despite our repeated top-speed verification, acceleration runs, generally driving exactly the opposite you should in a three-ton 4WD, and less-then-ideal conditions, typically in 30-degree wet weather, fully loaded, we still averaged more than 20 mpg. In city stop-and-go or less aggressive use, we'd expect close to 25 overall.
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The Ultimate Diesel Machine?
One might argue that BMW knows as much about diesels as Mercedes, having brought one to the U.S. market, offering them in every sedan (even the long-wheelbase 7 Series), and entering a twin-turbo diesel in the Paris-Dakar rally.
BMW makes more than one 3.0-liter turbodiesel and multiple ratings. This second-generation unit has an aluminum block and head with a single turbo, EGR, and diesel catalyst. Ratings are about 214 U.S. horsepower at 4000 rpm and 368 pound-feet of torque from 2000 through 2750 rpm, again comparable torque at lower rpm than the 4.4-liter gasoline V-8 choice.
A handheld stopwatch recorded 0-to-62 mph in 8.74 seconds while the trip computer's stopwatch gave us the same 8.8 that BMW quotes for the automatic. This is about one second slower than an X5 3.0 gas engine we tested in 2002, but that X5 benefited from a manual gearbox (with 5.09:1 first and direct-drive fifth) and 4.10:1 gears; the diesel tested had 3.91:1 gears that, like the D3, might sensibly be swapped for something a bit shorter for the North American market. Top speed is given as 210 kph (close to 130 mph), an indication that proved easy to reach unless the snow dictated slowing down. A certain amusement comes from driving at top speed with a trip computer showing mileage in the teens, whether or not it's precise.
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BMW's gas 3.0-liter carries EPA ratings of 15/21, and we were able to record 19.8 on one highway cruise. The 3.0-liter diesel, routinely tested in city traffic or close to its top speed, roughly twice as fast as the gas tester, averaged better than 21 mpg. Official figures give the diesel a 50-percent economy advantage in the urban cycle and a smaller gain in the city; CO2 values are similarly lower.
Although the opportunity to test at less than 20 degrees F didn't happen the X5 always started immediately, and it warmed to the point of supplying occupant heat noticeably faster than the iron-block TDV6. Despite its inline layout, it sounded similar outside, while inside it made a deeper thrumming sound than a BMW gas six. The BMW did, however, have a much more detectable turbo whistle.
With nearly the same ponies, a chunk more torque, and the same gearbox ratios, the X5 diesel feels faster than it is. You need to load the converter to make it snap your neck, and you get the impression that if the gearbox shifted faster it would significantly cut performance times. However, that same torque might render the gearbox recycling material, so the X5 goes near the 4600-rpm mark where the "yellow" line starts at wide-open shifts, falls off boost, and ramps it back as soon as the next gear's locked in. The sport mode feels more aggressive than in the TDV6, even factoring in the X5's added power and lighter weight.
An X5 diesel could go anywhere it needed to keep up with traffic, never reaching past 2200 rpm until exceeding U.S. speeds. It's no high-performance car (if BMW installs the two-stage turbo 3.0-liter, at about 270 horsepower/420 pound-feet, you'll never want a V-8), but it rarely needed a downshift to return to its chosen maximum speed. And at well past 25 mpg in everyday use, it might better a CRD and make an SUV hybrid seem rather boring.
Without import plans, prices are conjecture at best. In Land Rover's home market (England), an X5 3.0-liter diesel starts at about $700 more than the 3.0-liter gas engine, but that doesn't account for currency fluctuations and taxation clauses. Were they to make it to the U.S. we'd expect an LR3 diesel to be contented like the gas V-6 and priced just below a V-8 HSE, and the X5 to come in a bit below a 4.4i. We can only hope.
 BMW X5 3.0DLand Rover Discovery3 TDV6
Engine type TD inline-six, alum block/head TD V-6, iron block, alum heads
Bore x stroke, in3.54 x 3.31 3.19 x 3.46
Displacement, ci/L183/3.0166/2.7
Compression ratio 18.0:1 18.0:1
SAE horsepower, hp @ rpm188 @ 4000214 @ 4000
SAE torque, lb-ft @ rpm325 @ 1900 368 @ 2000-2750
Transmission type 6-speed automatic 6-speed automatic
1st 4.17:1 4.17:1
2nd2.34:12.34:1
3rd1.52:11.52:1
4th 1.14:11.14:1
5th 0.87:10.87:1
6th 0.69:10.69:1
Reverse 3.40:1 3.40:1
Axle ratio 3.91:13.54:1
Final-drive ratio 2.70:1 2.44:1
Base curb weight, lb 4796 5508
Max payload capacity, lb 11441598
Max GVWR, lb 59407106
Max towing capacity, lb 6500 (est) 7700
Fuel capacity, gal 24.5 23.2
Fuel econ (urban/extra urban/combined), converted to mpg19.6/29.4/25.0 17.8/27.0/22.6

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