Story By Mike Gould / Photos By Elliott Raymond / Engine illustrations courtesy Land Rover Engine Design

The idea of pulling up to the diesel pump at a gas station in a luxury SUV may seem strange to most Americans, but in Europe, it is an everyday occurrence. If the trend spotters are right, a lot more American drivers will be doing it soon, as well.

The European experience is mainly due to the price of diesel, which, in most countries, considerably undercuts that of petrol. Add the improved mileage and it’s no wonder that diesel powered vehicles predominate in all sectors. The one exception to the pricing structure is the United Kingdom, where diesel fuel carries a stinging tax penalty, making it the most expensive fuel in Europe. Even there, however, diesel vehicles are increasing their share of the market, particularly in the SUV sector, so much so that Land Rover has stopped sales of the 4.4-litre V8 gasoline engine derivative of the LR3, known in Europe as the
Discovery 3.

Demand in the US appears equally strong if diesel vehicles were widely available. A recent survey by Autobytel Inc. revealed that 72 percent of Americans would consider buying a diesel car. With low-sulphur diesel on average to be $0.36 per gallon cheaper than regular gasoline according to Energy Information Administration (EIA) as of June 2007, Americans appear ready to look the other way to availability problems in some areas (the Diesel Technology Forum estimates that only 42 percent of stations sell the fuel). The major reason for buying a diesel car is improved mileage. For example, the latest 2007 model year Range Rover fitted with the TDV8 diesel engine reaches 60 mph only 0.3 seconds slower than its naturally aspirated V8 petrol equivalent, but goes 32 percent further on a gallon of fuel on the European combined cycle. Not only does improved economy mean you go further for each dollar spent on fuel, it also means greater range and the convenience of fewer visits to the gas station.

With these advantages, coupled with diesel car manufacturers’ lobbying for the same tax breaks as hybrids, it’s no wonder that JD Power and Associates is forecasting that diesel powered vehicles, currently accounting for 3.4 percent of the U.S. market, will overtake hybrids to claim 15 percent of the market in the next four years. Another weapon in the diesel’s arsenal is that the technology is less complex than that of hybrids. The vehicles are not encumbered by the extra weight of batteries and regenerating equipment, while customers also get a more conventional driving experience—and one they have grown to like. Underlining this, BMW is suggesting that their future vehicle strategy lies with more efficient vehicles, not hybrids.

There are a growing number of diesel vehicles available on the American market. Mercedes offers diesel power on their GL320 CDI, ML 320 CDI and R320 CDI SUVs, and on their E320 BLUETEC® sedan. Daimler-Chrysler’s stable mate, Jeep, offers the same engine in their Grand Cherokee model. VW offers the Touareg in V-10 diesel form, while German rival BMW has announced that models equipped with their six-cylinder diesel engine will be on sale in 2008. The stricter emission standards of California, Massachusetts, Maine, New York and Vermont currently preclude sales in these states, but manufacturers are working on full, 50-state compliance. Fuel-efficient diesels are generally regarded as being less polluting than their gasoline equivalents. They produce less of the green house gas, carbon dioxide (CO2), and most are now capable of also running on biomass-derived fuels, mixed with refined fossil fuels. On the downside, diesel has come under fire for its greater output of nitrogen oxide (NOX) and emission of particulates or soot. But it’s not just about increased mileage and the environment. Modern diesels are actually very satisfying to drive, in some cases more so than their gasoline equivalents. Gone are the clanking, smoky oil burners of the past, replaced by quiet, powerful and torquey power units with a character all their own. This is certainly true of the latest Land Rover diesel engines, the TDV6 and the TDV8. Both are results of a long-standing collaboration between the Ford Motor Company and PSA Peugeot-Citroen. The third phase of this collaboration was Ford led, with the production of the TDV6 engine announced in June 2003.

Code-named “Lion” after the Peugeot trademark, the TDV6 engine is built at Ford’s plant in Dagenham, England and installed in the Discovery 3 for European and other markets. It is now also fitted to the Range Rover Sport and powers the Jaguar S-Type and Jaguar XJ, as well as various Peugeot and Citroen models. The TDV6 was followed by the TDV8 version, intended solely for the Range Rover Sport and the Range Rover and introduced for the 2007 model year vehicle. Land Rover insiders suggest that the Lion family is merely at the start of its life, with exciting developments in the pipeline.

Rumors stemming from an interview with retired Ford executive Dave Szczupak suggested that the TDV8 will be fitted in the US market to the Ford F-150 pickup by 2009 but our findings suggest otherwise. The company is denying that this fitment was ever under consideration. The engine is overly sophisticated for a pickup, and with the current exchange rate, the imported price would give Ford’s cost accountants a few sleepless nights.

The cylinder blocks of both the TDV6 and the TDV8 are cast in Compacted Graphite Iron (CGI), with computer-aided design and modern casting techniques, achieving both a light weight and extraordinary stiffness, which lies at the heart of the engine’s refinement. The engine changes optimize the degree of separation between the cylinder banks, the V6 being at 60o while the V8 is at 90o.

Other factors help improve the engine, too. The engine has a compression ratio of only 17.3:1, much lower than other diesels, to prevent their characteristic clatter. The pistons have a special crown design to optimize combustion, while the lubrication system cools the piston, further reducing noise.”

While the two engines have a lot in common, there are some fundamental differences; the V8 is not just the V6 with two extra cylinders. The cylinder heads are cast in aluminium and house four valves per cylinder driven through twin camshafts for each bank. For the V6 they are belt driven, while the extra power and torque of the V8 demands a simplex bush chain for the intake valve gear and gearwheels for the exhaust camshaft. Both engines have intercoolers to increase the density of the incoming air, and while the V6 has a single, top-mounted turbocharger, the V8 employs twin units slung underneath the cylinder banks. The turbochargers use variable nozzle technology with vanes in the turbine intake that move to optimize its response according to engine rpm. Use of variable nozzles also eliminates the need for a wastegate. The position of the turbo chargers on the V8 diesel is dictated by a steeper bank angle and requires a unique oil scavenge system to ensure lubrication at the angles likely to be encountered during off-road use. The inlet manifold on both engines incorporates valves for the port deactivation system, which, in certain conditions, closes one of the ports feeding fuel into the engine, optimizing the combustion characteristics to reduce noise and emissions.

Ford's Technology Lab

The engines use the latest, high-pressure, common rail injection technology with piezo-electric controlled injectors for micro-control over the fuel charge. There can be up to five bursts of fuel into the cylinders per combustion cycle, improving fuel consumption and refinement and reducing emissions.

The quest for ultimate refinement continues with the use of computer simulated “modal separation” techniques. With each component and ancillary having its own fundamental frequency, it’s important that they don’t combine to produce undesirable resonances. The compact size of the V configuration engines means that there’s plenty of room in the engine bay for noise damping acoustic covers.

In a typical European installation, the Lion TDV6 produces 190 bhp at 4,000 rpm and develops 325 pounds-feet of torque, peaking at 1,900 rpm. Its bigger brother, the TDV8, produces 268 bhp at 4,000 rpm, while torque is an impressive 472 pounds-feet at 2,000 rpm. For the Discovery 3 TDV6 automatic, Land Rover quotes 27.2 miles per Imperial gallon (26.4 miles per US gallon) on the European combined cycle. The Range Rover TDV8 achieves 25.1 miles per Imperial gallon (24.3 miles per US gallon) on the same basis. So with all this technology providing impressive power and muscle car torque while returning good mileage, what’s stopping Land Rover from launching it in the American market? The first issue for Land Rover is one of perception. Land Rover is a premium brand, and the Range Rover is its premium name plate. The company is obviously concerned that diesel fueled vehicles are still considered dirty and smelly by many US consumers. Customers may also think that it’s hard to find filling stations with diesel pumps. The next issue is emission compliance.

Manufacturers, including Land Rover, have to contend with a wide variety of emission standards for diesel engines. Differing regulations apply in the European Union (EU) and Japan, while the U.S. has two sets of standards. The strictest applies to the states of California, Maine, Massachusetts, New Jersey, New York and Vermont, states that follow regulations set by the California Air Resources Board (CARB). The other 45 states of the Union apply more lenient standards. All concentrate on what they regard as the major pollutants, have different test cycles and categorize vehicles in different ways. Faced with the costs involved in producing a wide range of compliant vehicles, manufacturers are lobbying for harmonization, but this seems a long way off.

In Europe, regulations target emissions of carbon monoxide (CO), a gas produced by incomplete fuel combustion which oxidizes in the atmosphere to produce CO2. In the U.S., NOX, which leads, among other things, to acid rain and the photochemical smog that affects cities like Los Angeles, is the main target. The greater fuel efficiency of diesel engines produces less CO, meeting European regulations, but their higher operating temperatures produce more NOX, so complying with U.S. regulations is problematic. U.S. regulations, especially those instituted by CARB, are also much stricter with regard to particulate emissions.

However, the recent advent of low-sulfur diesel fuel in the US made the fitting of Diesel Particulate Filters and NOX-reducing cataysts practical in sedans and SUVs, and European manufacturers were quick to take advantage. The ultimate aim is full, 50-state compliance. This requires the injection of urea, an ammonia-like fluid, into a Selective Catalyst Reduction (SCR) system. This reducing agent can be carried in a tank that is easily filled up, but if it runs dry, the vehicle’s emissions will be non-compliant.

The Environmental Protection Agency (EPA) has recently advised manufacturers of its approach to SCR systems, specifying the distance required between fill-ups and the methods to be put in place to prevent the reducing agent running dry or being replaced by an inappropriate fluid. These include driver warnings, and ultimately, ways to prevent the vehicle from being driven without urea. The size of the tank for the reducing agent, enough to last between scheduled service intervals as required by the EPA, has been estimated to be up to 10 gallons, a significant packaging problem for engineers, but meeting these requirements will open the door to 50-state diesel sales.

Land Rover’s official position is that it is right now looking at all alternative fuels for the future and is exploring the feasibility of bringing diesel engines into North America. However, they cite packaging and engine-related issues that need to be resolved before their introduction is possible. With 20 percent of Land Rover sales concentrated in California alone, they will need to come up with a full, 50-state compliant solution to make the sales of diesel-powered vehicles viable.

Market forces may yet force Land Rover’s hand. There is a growing lobby arguing that efficient diesel power, rather than complex hybrids, is the way forward in the search for a cleaner environment. With the advent of modern, low-sulfur fuels and sophisticated engines, diesel power is losing its old stigma. Mercedes is reporting a “very strong” take-up rate on their ML 320 CDI model, and with BMW waiting in the wings with a range of diesel powered cars, it may not be long before the Lion’s roar is heard across North America.

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