VW has a monumental task ahead of it: convincing the American public that diesel vehicles, and higher-priced diesel fuel, are a smart, efficient, and enjoyable way to drive. To that end, VW has intelligently equipped each of its North American dealers with one demo-only vehicle to promote its new high-tech, 2.0-liter TDI CleanDiesel (Turbo Direct Injection with 50-state legal emissions, and indeed a cleaner emissions profile than many new gasoline engines). These demo vehicles, white Volkswagen Jetta TDI Clean Diesel sedans, are playfully splattered with artsy green decals representing nature, leaves, and environmentalism in general. On the back of the sedans, VW's personable sans-serif lettering urges, "Take me for a test drive" on the trunk lid. On the bumper the, in green, is the URL: goodcleandieselfun.com.
I confess I've been waiting for this moment...with perhaps an abnormal amount of excitement. A childhood hater of diesel, thanks in no small part to my father's painfully poky and noxiously smoky 1980 Peugeot 505 NON-turbo Diesel with all of 76 horsepower, I've pulled an unthinkable 180 in the last two years. The purchase and continual restoration of a 1982 Mercedes-Benz 300TD (the turbo, thank God), and the realization that diesel engines will run on mildly processed waste vegetable oil (otherwise known as biodiesel) convinced me. I'm now a diesel fanatic, I confess, and recent advances in critical diesel areas such as injection technology, exhaust scrubbing capabilities, and variable-vane turbocharging have eliminated the compromises one had to make back in 1982 when deciding to purchase a diesel. And those same technologies have made the efficiency gains of a diesel even more dramatic.
2009 Volkswagen Jetta TDI
As a passenger, from the comfortable backseat of the Jetta (comfortable except for my head brushing the rearmost portion of the headliner), the experience was remarkable in its normalcy. There simply is zero diesel clatter to be heard, no strained revving for acceleration, and no untoward vibration or harmonic resonance from an engine with higher reciprocating mass, a heavy-duty valvetrain, and a seriously high compression ratio (as is the case for all diesels). The sounds were muted and smooth, and the shifting from VW's trick DSG transmission was utterly transparent. The Jetta's taut suspension and good bump absorption remain intact. The only oddity I noticed was a mild, low-rpm thrum, as the DSG seemed to keep the engine operating at extremely low rpms (just above 1,000) with my father's admittedly conservative right foot.
Yawn. When Rocky commented that "it has a tiptronic" (quite possibly the most overused transmission term of late) and proceeded to click up and down the gears in lightning-quick fashion as only a dual-clutch automated manual can do, I rolled my eyes inwardly. Apparently he thought we were being motivated by a conventional torque converter. Noticing that the only indication of gearshift in this Jetta was a sudden, rapid change in RPM, my father commented that the transmission seemed uncommonly smooth. My impatience reached the tipping point on this flat, boring test route around the dealership, and I suddenly asked to drive.
2009 Volkswagen Jetta TDI
Formerly a pussycat, Rocky now turned into a bit of a watchdog, trying to keep me on the same flat, boring "test" ring a couple of miles around the dealership. I would have none of it, and found a steep loading ramp in what looked like an abandoned warehouse. "Watch this," I said, ignoring Rocky's terse requests for me to please "proceed along the test route." I wanted to demonstrate the DSG transmission's trick clutch actuation. Yes, it is a fully automatic transmission, but it has the internals of a manual (more like two manual transmissions, and placed side-by-side, so that gear changes are handed off with the grace and speed of a baton from hand to hand) and a real, honest-to-goodness clutch and pressure plate, just like that in a row-it-yourself, three-pedal affair. But with only a gas and a brake pedal, the Jetta TDI's drivetrain management microprocessors do the work of your left foot. And they do a seamless job.
With the VW's nose pointed up the ramp, I demonstrated how brilliantly VW's DSG rests the weight of the car on the pressure plate. Just feather the go pedal, and the massive torque of the turbo four provides more than enough oomph to hold the car still while barely above idle. Or, flexing the foot further, the DSG releases the clutch fully breaking static friction and propelling the Jetta forward on a wave of torque. A true stickshift driver can feel the dance going on underhood, with the Jetta magically finding the sweet spot of the clutch every time, never bogging the engine, nor engaging too late and letting the engine rev too high. But it's done so well, and so consistently, regardless of the situation, that an automatic driver never knows the magic happening underneath and simply thinks it's a regular old automatic. But without a heat-emitting (and power-sapping) torque converter, the DSG box yields the full efficiency of a manual transmission. And with two sets of gears - 1,3, and 5 on the one side, 2,4, and 6 on the other - gear changes are startlingly quick and seamless, far better than any traditional automatic could muster. No need to de-clutch, change ratios, and engage the clutch again. The power flows seamlessly back and forth from side-to-side in the gearbox, with literally no interruption in forward progress, and none of the pushing or lurching accompanying such interruptions. The gearchanges are almost digital in nature, as witnessed by a tach needle that does not glide downward to a new RPM upon a gearchange, but rather flicks down instantly. Or flicks up instantly with a downshift. And that's the only indication, along with a change in engine note, that you're exploring a new ratio.
What a perfect match the DSG is for this new turbo. In moderate driving, it keeps the engine around 2,000 rpm and below. While driving modestly, a lot of the acceleration occurs right around the 2,000-rpm mark, making this motor seem extremely relaxed and far bigger than its 2.0 liters. in operation, it feels like a big, torquey six. I did notice that the DSG rushed to high gears so quickly at times that the engine hovered just above 1,000 rpm for extended periods, at which point there is a little bit of rumble and resonance that almost felt like lugging, and yet the engine still pulled happily with no complaint. Perhaps just a sonic kink the VW engineers haven't yet worked out, or perhaps the one concession to all of the explosive force and torque going on in each one of those half-liter chambers underhood.
2009 Volkswagen Jetta TDI
But even though the TDI will rev up to 4,500, there's no point in it. The torque fun is over pretty much at 4,000 rpm, that nice shove in the back tapering off gradually and pretty much gone at by that point. But faster than you can say "boost," the DSG has swapped to the next ratio and you ride the torque wave all over again. Compared to the gasoline powerplants most of us are used to, it's counterintuitive acceleration. In this engine, less is more; less rpms equal more thrust. Wonderfully, less rpms also equals greater economy. Drive most modern gasoline engines for max thrust, and you’ll be reaching for that redline in each gear, burning copious amounts of the black gold we’ve taken for granted for years. Stomp the TDI's gas pedal (diesel pedal?), and you’ll instantaneously leave twin rubber marks wherever it was you were idling quietly. Try that in any other four-cylinder economy sedan. Without brake-torquing. Or, in a manual, without revving high and then dumping the clutch; 236 pound-feet of easily-accessible torque is fun indeed, and it’s your ally for tire squealing shenanigans or 50 mpg cruising (so swears VW, despite EPA numbers that are not so generous).
If diesel again takes off in America as it did in the early '80s, a generation of drivers sick of paying out the nose for the American Birthright, driving, will have to make a couple of adjustments in how they are used to cars responding to their right feet. But they won't have to deal with noise. Or smoke. Or slothful acceleration. And I think plenty of drivers will be more than willing to trade high-rpm scream for enthusiastic low-rpm torque. Most especially for commuters, who rarely venture much above 3,000 rpm in their daily journeys on the clogged arteries of our major metropolitan areas, an engine that is operating at its most efficient and most powerful down low makes all the sense in the world.
We'll have to save our own impressions of the Jetta TDI's thriftiness until we can get a model to test. Volkswagen was throwing around a highway number of 50 mpg until the EPA rained on their parade, slapping the Jetta TDI with a highway rating of 40 mpg. So adamant was VW that it got an independent agency to do its own testing, and that organization arrived at a number of 44 mpg on the highway. I've noticed that all of Mercedes' new BlueTEC diesels consistently get higher mpg ratings than the EPA grants them, such as the ML 320 BlueTEC, which rates an EPA highway mileage of 24. In most real-world tests I've read, notoriously lead-footed journalists record numbers of 27 or 28 mpg highway. So perhaps VW's claims of higher mileage aren't without merit.
Of note, VW is introducing its Jetta SportWagen bodystyle along with the TDI engine option. I think the styling is a success, coming off as sexier and tidier than the slab-sided Passat Wagon. It's also more attractive than the Jetta sedan, which I find has an awkwardly high beltline and rump. Rocky claims that the wagon will outweigh the sedan by some 100 pounds, and I found that my headroom qualms were more than solved when I sat in the back of a 2.5 gasoline Jetta Sportwagen, as its roofline does not taper over the rear seat as in the sedan. Last but not least, nearly all station wagons have less aerodynamic drag than sedans, due to reduced turbulence at the rear (the late German aerodynamicist Wunibald Kamm, originator of the Kammback design found on AMC Gremlins and Toyota Priuses alike could have explained it more fully than I). So who knows, if you're an obsessed hypermiler looking for that extra 0.5 mpg...-Colin Mathews