Most of us as North American consumers associate diesel engines with trucks. Volkswagen is hoping to change that perception next year when it will introduce all-new diesel engines in virtually every model they sell. From a 100hp 1.9l engine in the Golf, Jetta and New Beetle to a 133hp 2.0l in the Passat to a full 10-cylinder TDI powerplant with over 550 lb-ft of stump pulling torque in the new Touareg sport utility vehicle, diesel technology is coming and you only need to remember three little letters: TDI.
In the spring of 1976 series production began of VW’s first diesel passenger car – the 1.5-litre, 50-bhp naturally aspirated unit for use in the Golf and Rabbit. This engine with its superior fuel economy and high levels of low-end torque created a market for itself, particularly in Europe where gasoline prices are considerably higher than they are here in America.
In the early eighties Volkswagen introduced turbocharging and bumped displacement to 1.6l bringing the horsepower to 70hp and creating the new designation of "Turbodiesel" for all its diesel models. Later in the early 90's Volkswagen introduced direct fuel injection technology calling it TDI, the initials standing for Turbocharged Direct Injection. TDI enabled engineers to make the engine quieter and more efficient which meant even better fuel economy and more power. Compared to indirect injection engines, the TDI had a fuel savings potential of up to 15 percent.
Further development lead to the adoption of a variable-geometry turbocharger which utilized variable vanes within the turbine wheel to vary the amount of air and effectively reduce turbo "lag" at low RPM's but also allow for a higher volume of air at high RPM's. Volkswagen also added charge-air cooling in the form of an air-to-air intercooler as standard equipment. This boosted the current 1.9l unit to 90hp and 110hp with impressive levels of torque and refinement.
The next major peak in TDI development was high-pressure fuel injection called "pumpe duse" in German. By utilizing upwards of 20,000 psi in certain applications, Volkswagen was able to atomized and meter fuel delivery very precisely using a unit-injector developed by Bosch. This resulted in superior economy, further increases in power and even quieter running engines. Power in the 1.9l TDI is now available in europe in 100hp, 130hp and 150hp variations.
While the 1.9l 4-cylinder TDI powerplant is the bread and butter of Volkswagen's diesel offerings, it is far from being the only unit available - Volkswagen has everything from a 3-cylinder super high-efficiency TDI unit capable of nearly 90 miles per gallon, to inline-5, V6 and V8 models and even a V10 TDI that is available in the Touareg and Phaeton luxury car in Germany with unheard of levels of refinement, power and economy.
Today diesel engines make up over 40% of the Volkswagen models sold in Europe. Here in America, TDI sales represent less than 10 percent of total sales. Volkswagen has only offered us one TDI engine choice, the 90hp 1.9l TDI with a 2-valve head and older low-pressure injection systems. Why? Well two main reasons, one, diesels don't sell well here because gasoline is cheap and two, diesel fuel in North America is far less refined than European equivalents and makes it difficult to apply strict car emission standards to the TDI engines sold here.
Currently the 90hp 1.9l TDI is available in the Golf, Jetta and New Beetle and is rated at 42 mpg city and 49 mpg highway. With a 14.5 gallon tank and a 49 mph highway rating, you could theoretically drive over 710miles on a single tank of fuel. These models are only sold in limited numbers in states that have stricter emission standards such as California, Maine, Massachusetts, Vermont and New York so they don't affect Volkswagen's CAFE fleet standards too adversely but are otherwise available in the 45 remaining states.
While Volkswagen owners tend to be an enthusiastic bunch, TDI owners have elevated themselves to near-cult like status. Owner sites like Fred's TDI Club (www.tdiclub.com) have cropped up as a means for TDI owners and fans alike to communicate, share war stories, help each other with maintenance and other issues and even seek new ways to extract even more power from the existing 90hp 1.9l TDI.
TDI fans have been clamoring for the latest TDI technology available in Europe to find its way over to our shores. So far the new generation of pumpe duse/high pressure TDI engines have not been offered here due to the sub-par diesel fuel we have available. Particulate standards are nearly impossible to meet with the fuel available here, but Volkswagen's engineers have finally devised a way to get some of the new engines to run properly and pass emissions in 45 states. We'll start to see these new TDI engines starting with model year 2004 which we will cover in depth in our fifth installment.
In anticipation of these new TDI offerings coming to North America we set out to Germany last year to drive a number of the latest and greatest TDI models available in that market. We drove everything from the phenomenally economical Lupo 3L TDI to the tire shredding 150hp 1.9l TDI Bora/Jetta (with the same torque as a 3.2l VR6!) to the foundation moving V-10 TDI in the Touareg. Over the next several installments we will be highlighting a number of these TDI equipped vehicles to give you a feel for the different TDI offerings available in Europe and a little preview of what to expect in 2004.
