Road Test Review: 2006 BMW 330d - Road Tests
Here’s the diesel of your dreams — too bad it’s not sold here.
BY TONY QUIROGA, PHOTOGRAPHY BY NICK SAY
With the fear that $3 gas is here to stay, American drivers may soon find themselves groping in a panic for more fuel-efficient cars that aren’t penalty boxes.
A natural alternative is a diesel car. Unfortunately, just as the public is positioned to warm up to the idea of diesel, the government is coming down hard, emissions-wise, on the oil burners.
For an explanation of why diesel cars have a tough row to hoe on their way to the American market, see the sidebar, “The Diesel Dilemma.”
Meanwhile, we borrowed a not-sold-here BMW 330d from Honeywell Turbo Technologies to examine the state of the modern European diesel engine. The 330d is of the latest generation of diesels that boast the performance of a gasoline engine with the parsimonious fuel-sipping characteristic of a diesel. With the potential of fuel economy in the mid-40-MPG range and no significant loss in performance, we wanted to see if the 330d could deliver on its seemingly incongruous promises.
It’s no secret that the gas-powered 3-series sedans are perennial favorites around here. Witness their 15 10Best trophies since 1992 and a comparison test victory last year [“$35,000 Sports Sedans,” C/D, October 2005] as evidence. How would a diesel engine affect our long-term love affair with the 3-series?
Equipped with a 228-hp, 3.0-liter inline-six turbo-diesel engine, the 330d makes less horsepower than the 255-hp, 3.0-liter naturally aspirated gas engine in the 330i. On the other hand, the turbo-diesel engine twists out a massive 369 pound-feet of torque
, 149 more than the 3.0-liter gas engine
and nine more than the 4.8-liter gas-powered V-8 in the 750i. All that torque is primarily due to the turbo-diesel’s high combustion pressures. With that much torque and an easily accessible power curve, the 330d actually felt faster in day-to-day driving.
To test the acceleration of the 330d against its gas-fed counterpart, we headed to the track. In acceleration, the 330d proved to be a near match for the 330i despite its slight power-to-weight-ratio deficit — 13.6 pounds per horse versus the diesel’s 15.3. The 228-hp diesel took six seconds to go from 0 to 60, and the quarter-mile fell in 14.5 seconds at 97 mph. A few pounds lighter and packing more horsepower, a 255-hp 330i we tested took 5.6 seconds in the 0-to-60 run and posted a 14.4-second quarter-mile time at 98 mph. It might feel faster, but the 330d is actually a bit slower.
Aside from giving up a few 10ths in the 0-to-60 run, one of the things you’d miss if you opted for the diesel would be the gas engine’s terrific sound throughout the rev range, particularly the snarl that is released as the engine crests 5000 rpm. Although the 330d is the best-sounding diesel we’ve ever heard, that’s like saying it’s the best American Idol reject.
Another endearing aspect of the gas-fed mill is the way it delivers power in a constant and linear manner all the way to its 7000-rpm redline. In contrast, the diesel has a low 4800-rpm redline, with peak horsepower arriving at 4000 rpm and torque at 1750 rpm. Power comes in abruptly. Below about 1700 rpm, the diesel suffers from a brief moment of turbo lag: Witness the 13.1-second 30-to-50 top-gear acceleration, 3.1 seconds slower than the 330i’s. After the lull, all 369 pound-feet hit you like an angry Bill Romanowski. The V-8–like midrange power continues until the peak at 4000 rpm. Rev beyond 4000, and the power tapers off precipitously. From idle to redline, the power delivery is nowhere near as smooth as the 330i’s, but keep the revs between 2000 and 4000 rpm, and the punch of the diesel engine will keep you pressed firmly into the seatback.
So the 330d lacks some of the spirit of the gas-engined car, but it also doesn’t require as much work, as you can always rely on its midrange punch. Running at the same speed on the same road takes less effort in the 330d. Granted, enthusiastic drivers enjoy working the gearbox, running it up to the redline and generally flogging a willing car, but the diesel’s laid-back nature is exactly what increases fuel economy, which soars if the driver keeps the engine revs low, selects higher gears, and rides the 330d’s massive torque curve. If you’re getting the idea that the diesel engine allows the driver to be a bit less wrapped up in driving the car, you’re right.
On the highway, the diesel’s superior midrange power and torque make it the clear favorite for passing maneuvers. Our 50-to-70 top-gear passing test bore out our seat-of-the-pants evaluation as the 330d, despite 26-percent-taller gearing, posted a 7.5-second time, 1.9 seconds quicker than our long-term 330i’s. It may not seem like much, but in the cut and thrust of highway traffic, the diesel car never calls for a shift out of sixth gear. To get comparable torque and passing power from the gasoline engine calls for a downshift into fifth or fourth.
To measure the fuel economy of both cars, we designed two driving loops. The first covered 136 miles of twisty back roads at an extra-legal clip, and the second covered a 220-mile highway run at 75 to 85 mph.
After each loop we filled the tanks of both cars and calculated the mileage. The back-road loop yielded an average of 24.3 MPG for the gas car; the diesel consumed at the rate of 33.6 MPG . On the highway loop, the gas car put up a respectable 27.8 MPG , while the diesel scored a truly impressive 40.4 mpg.
Total the loops, and the averages come to 26.3 MPG for the 330i and 37.8 MPG for the diesel — that’s a 44-percent increase in fuel economy.
Assuming that the price of gas and diesel is more or less equal at roughly three bucks a gallon, then it would take about 37,000 miles to recoup the extra $1264 that the 330d commands over the 330i in Germany.
So which would we choose? Fact is, we remain purists, and what we love is listening to a high-revving engine, working a gearbox, and digging the spurs into a car that loves to run. The 330d’s torque and 44-percent-better fuel economy are compelling, but the overall experience isn’t as involving. Having said that, we do recognize that the 330d is better suited for nearly everyone else. We just wish BMW would give us the opportunity to decide.
There’s no question the 330d is the least compromised diesel I’ve ever driven. Almost no driving joy was lost in the 3-series’ transformation to diesel-fuel sipper. Forget about that extended waiting period between throttle-pedal nudge and forward thrust. Okay, there’s still some turbo lag, and enthusiasts will likely prefer the linear power delivery of the gas engine to the varying shove of the diesel. But unlike most fuel-efficient cars, this one doesn’t skimp on performance. And the fact that we experienced a 44-percent fuel-economy bump — making more economic sense than most hybrids — in a car you’d enjoy driving every day is simply amazing.
It’s undeniable that the 330d offers an amazing package — 3-series driving pleasure and diesel fuel economy — but I can’t bring myself to like it. Mostly, it’s because of my strong affection toward BMW’s new 3.0-liter magnesium-and-aluminum gasoline engine. It’s simply too good to pass up. The gas engine delivers strong, linear power anywhere between 1000 and 7000 revs. It’s smoother than a Lexus V-8 and makes great serene sounds. Although the diesel does a brilliant utilitarian job of pushing the superb 3-series chassis around, the gas engine sings and completes the experience of driving a BMW.
For an extra $1264 (in Germany), the 330d offers the great chassis balance and nearly identical performance of its gasoline brother. Sure, the 330d idles slightly louder and lacks the thrust to the redline of the 330i, but with 369 pound-feet, you never have to downshift while passing, and the savings at the pump add up quickly. I even find the four-speaker stereo and lack of cup holders or sunroof charming. The d has all the characteristics that make the 3-series a 10Best winner, plus a 44-percent increase in fuel economy. Where do I sign? Now, if BMW could just get serious about selling its diesels in the States like Mercedes-Benz and Volkswagen are doing…
VARIABLE-GEOMETRY TURBO: What Is It Good For?
Small turbos create boost quickly at low rpm but choke the exhaust at high rpm. Larger turbos work well at high rpm but suffer from turbo lag. Modern turbo-diesels, like the 330d’s, employ variable-geometry (or variable-nozzle turbos) to allow a single turbo to be efficient at both high and low rpm. At low rpm, the vanes nearly close which directs and speeds up the relatively small volume of exhaust over the turbocharger turbine — it’s like putting a thumb over the end of a hose. The increased exhaust velocity accelerates the turbine harder, which decreases turbo lag. At high rpm, the vanes open to allow the larger volume of exhaust gas to pass over the turbine nearly unimpeded at the appropriate velocity.
front-engine, rear-wheel-drive, 5-passenger, 4-door sedan
Price as tested (Germany):
$51,958 (includes $7167 value-added tax)
Options on test car:
M Sport package (includes sport suspension, body kit, and 17-inch M Sport wheels and performance tires)
Major standard accessories:
power windows and locks, A/C, tilting and telescoping steering wheel, rear defroster
BMW AM-FM radio/CD player, 4 speakers
Type: turbocharged and intercooled inline-6 diesel, aluminum block and head
Bore x stroke: 3.31 x 3.54 in, 84.0 x 90.0mm
Displacement: 183 cu in, 2993cc
Compression ratio: 17.0:1
Fuel-delivery system: common-rail direct injection
Turbocharger: Garrett GT22 60V
Maximum boost pressure: 22.6 psi
Valve gear: chain-driven double overhead cams, 4 valves per cylinder, hydraulic lifters
Power (SAE net): 228 bhp @ 4000 rpm
Torque (SAE net): 369 lb-ft @ 1750 rpm
Redline: 4800 rpm
Transmission: 6-speed manual
Final-drive ratio: 2.56:1
Mph/1000 rpm Max test speed
I 5.09 5.5 27 mph (4800 rpm)
II 2.80 10.1 48 mph (4800 rpm)
III 1.80 15.7 75 mph (4800 rpm)
IV 1.26 22.4 107 mph (4800 rpm)
V 1.00 28.2 135 mph (4800 rpm)
VI 0.83 33.9 155 mph (4550 rpm)
Wheelbase: 108.7 in
Track, front/rear: 59.1/59.6 in
Length/width/height: 178.0/71.5/55.9 in
Ground clearance: 4.0 in
Drag area, Cd (0.29) x frontal area (22.7 sq ft): 6.6 sq ft
Curb weight: 3492 lb
Weight distribution, F/R: 51.6/48.4%
Curb weight per horsepower: 15.3 lb
Fuel capacity: 16.1 gal
Type: unit construction
Body material: welded steel stampings
SAE volume, front seat: 50 cu ft
rear seat: 41 cu ft
trunk: 12 cu ft
Front-seat adjustments: fore-and-aft, seatback angle, front height, rear height, upper side bolsters, thigh support
Restraint systems, front: manual 3-point belts; driver and passenger front, side, and curtain airbags
rear: manual 3-point belts, curtain airbags
Front: ind, strut located by 1 diagonal link and 1 lateral link, coil springs, anti-roll bar
Rear: ind; 2 diagonal links, 2 lateral links, and 1 toe-control link per side; coil springs; anti-roll bar
Type: rack-and-pinion with variable hydraulic power assist
Steering ratio: 16.0:1
Turns lock-to-lock: 3.0
Turning circle curb-to-curb: 36.1 ft
Type: hydraulic with vacuum power assist and anti-lock control
Front: 11.8 x 0.9-in vented disc
Rear: 11.8 x 0.8-in vented disc
WHEELS AND TIRES
Wheel size: F: 8.0 x 17 in, R: 8.5 x 17 in
Wheel type: cast aluminum
Tires: Pirelli eufori@ run-flat; F: 225/40R-17 91W, R: 255/40R-17 94W
Test inflation pressures, F/R: 33/36 psi
C/D TEST RESULTS
Zero to 30 mph 2.2
40 mph 3.2
50 mph 4.6
60 mph 6.0
70 mph 7.7
80 mph 10.1
90 mph 12.4
100 mph 15.3
110 mph 19.4
120 mph 23.8
130 mph 29.8
Street start, 5–60 mph: 6.7
Top-gear acceleration, 30–50 mph: 13.1
50–70 mph: 7.5
Standing Ľ-mile: 14.5 sec @ 97 mph
Top speed (governor limited): 155 mph
70–0 mph @ impending lockup: 158 ft
Roadholding, 300-ft-dia skidpad: 0.86 g
Understeer: minimal moderate excessive
European urban cycle: 32 mpg
extra-urban cycle: 55 mpg
combined: 44 mpg
C/D-observed: 38 mpg
INTERIOR SOUND LEVEL
Idle: 47 dBA
Full-throttle acceleration: 73 dBA
70-mph cruising: 68 dBA
The Diesel Dilemma
Popular European diesels face a gantlet of tough emissions laws in this country. Starting in 2007, all cars sold in the U.S. must comply with the Tier 2 regulations that began phasing in with the 2004 models. These emissions regulations make no distinction between gasoline and diesel engines and are considerably more demanding than current emissions regulations in Europe, where most of the modern passenger-car diesels originate. As a result, only Mercedes-Benz has committed to selling a diesel car here next year.
A diesel’s problems start with exactly what makes them so efficient — high compression ratios and lean air-fuel mixtures. Unfortunately, those features generate high combustion temperatures, which in turn raise the output of oxides of nitrogen (NOx) and tiny particulate matter, better known as smoke. (As in a gasoline car, a catalytic converter works to eradicate other gases such as carbon monoxide and hydrocarbons.) To reduce the smoke, automakers concentrate on precisely controlling the fuel entering the diesel’s combustion chamber with ever-higher injection pressures. Despite their best efforts, some particulates are created by the burning of the fuel. These leftovers are then trapped by a particulate filter in the exhaust system. Until now, particulate filters haven’t been available in the U.S. because our fuel has comparatively high levels of sulfur, which clogs these filters and renders them useless. By 2007, cleaner diesel with 15 parts per million of sulfur per gallon (down from 500 ppm) will be available, and that will allow the use of particulate filters.
Lowering the amount of NOx streaming out the tailpipe is more of a challenge. In the European Union, 0.40 gram per mile of NOx is allowed. But here in the U.S., the Tier 2 regulations limit a company to a fleet average of 0.05 gram per mile of NOx emissions — one-eighth of the European limit. Complicating matters further are even more stringent California regulations, which have also been adopted by New York, Massachusetts, Vermont, and Maine.
In its upcoming ’07-compliant diesel, Mercedes uses two catalytic converters that specifically target NOx. The first takes NOx out of the exhaust, stores it, and eventually releases it to the second catalytic converter, which then converts it to water (H2O) and harmless nitrogen gas (N2). Eventually, and to make its diesel 50-state legal, Mercedes plans to use AdBlue, a water and ammonia-rich fluid that, when injected into the exhaust stream, will aid in changing the NOx gases into N2 and water. Without AdBlue, the Mercedes E320 BlueTec can be sold in only 45 states.
Developing diesel engines that can meet 50-state standards, which is every manufacturers preferred approach, is costly and technologically challenging. That’s why most diesel cars will disappear from the U.S. market in 2007 and will only gradually trickle back as these newer emissions-control technologies come down in cost and enter mass production. — TQ
If that 330D is not strong enough? Try this one out:
BMW 330D M Sport
The overall attributes of the 3-Series are too well known to bear repetition here. The heart of this car is the superb three-litre power unit common to both SE and M Sport models. You can guess ­ just - that it's a diesel on start-up, largely from the idle speed, but the harsh clatter and knock of a cold diesel has been almost completely suppressed. And once on the move I would defy anyone to tell the fuel employed.
That it develops 231bhp is impressive enough - it's the most powerful diesel ever to be fitted to a 3-Series - but it's the stonking torque that defines the car's performance. 500Nm (369lb/ft) in a virtually flat line from 1750rpm to 3000rpm means you can almost feel the car wanting to revolve around its own crankshaft as you open the throttle
; such is the surge of acceleration. Given so much torque a six-speed box (short gear lever in the M Sport) seems superfluous - seamless power is available in any gear at almost any speed. In fact, why is no automatic available?