One of our primary goals and objectives is to level the playing field for clean diesel vehicles. Our challenge, well, President Obama in one policy statement after another has advocated for an all of the above strategy when it comes to sustainable mobility. And yet clean diesel, one of the cleanest choices for putting the US on the road to energy independence, hasn’t see any sort of incentive since the Energy Independence and Security Act (EISA) of 2007.

TDI clean diesel represents almost 25% of Audi and Volkswagen US sales. Are these sales incentivized? No. Do they receive HOV access for their improved fuel economy and ultra low emissions? No. Do they get state or federal tax breaks? No. In fact in 6 of the states, diesel fuel is penalized with additional state taxes. So diesel fuel gets taxed twice or penalized twice at the federal and state level. The only incentive that TDI vehicles receive—and it isn’t doled out by the US government—is almost consistently best-in-class fuel economy, reduced CO₂ emissions and clean diesel drivers knowing that they are doing their part to reduce the impact on the environment.

—Anna Schneider, VP Industry and Government Relations, Volkswagen Group of America

(Schneider leads all advocacy efforts for the Group at the federal and state level. Previously she was vice president over government relations at Toyota Motor North America and executive director, government relations at Mitsubishi Motors North America.)

Market. During his presentation at the TDI Efficiency Rally, UMTRI researcher Bruce Belzowski first presented a summary of his analysis of the total cost of ownership of diesels with a comparison to that of their gas vehicle counterparts. Essentially, Belzowski and his colleague Paul Green found that drivers of diesel vehicles can save thousands of dollars in total ownership costs compared to similar gasoline vehicles. (Earlier post.)

In that study, they developed three- and five-year cost estimates of depreciation by modeling used-vehicle auction data and fuel costs by modeling government data. They then combined these estimates with three- and five-year estimates for repairs, maintenance, insurance, fees and taxes from an outside data source.

Belzowski also presented preliminary results from a survey of powertrain experts—from automotive manufacturers, suppliers, government, NGOs, academia and consulting—asking for their predictions of powertrain penetrations for 2016, 2020, and 2025. The survey is similar to surveys run by UMTRI on the same topic in 2006 and 2007. The results so far suggest that:

• The penetration of spark-ignited engines in passenger cars is projected to drop to 51% in 2025 from 74% in 2016. At the same time “advanced diesel—which doesn’t have a specific technology definition, Belzowski said, but instead is whatever a given expert considers will constitute “advanced diesel”—will increase to 12% in 2025 from 8% in 2016.

  For passenger cars, hybrids will continue to claim a larger share of the market than diesel, rising to 28% in 2025 from 15% in 2016. Fuel cells are seen as hitting 1% by 2025; extended range electric vehicles, 3%; and battery-electric vehicles, 4%.

• The penetration of spark-ignited powertrains in light trucks is projected to drop to 55% in 2025 from 74% in 2016. Advanced diesel will increase to 23% in 2025 from 17% in 2016.

  The 2025 diesel share is higher than the projected share for hybrids (17%); both hybrids and diesels are far beyond the share of the other types of powerplant listed (HCCI, fuel cell, extended range electric vehicle, and electric): 1% apiece.

A separate forecast from LMC Automotive, shared by Audi at the event, projects diesel volume in the US growing from 445,376 units and 3.2% marketshare in 2012 to 1.25 million units and 7.4% marketshare by 2018—i.e., share and volume are expected to more than double from 2013 to 2018.

LMC’s forecast suggests that pickup trucks will represent a shrinking percentage of total diesel sales in the US, dropping from 66% of diesel sales in 2012 to 35% in 2018. That drop, however,is offset by significant growth in sales into the SUV segment—an increase from 8% of total diesel sales in 2012 to 26% in 2018.

The company sees the percentage of diesel sales into the compact car segment growing from 4% in 2012 to 11% in 2018. Van share grows from 5% in 2012 to 12% in 2018; and the midsize car share of total diesel sales drops from 17% in 2013 to 10% in 2018.

The 3.0 TDI. Audi is only applying the new second-generation 3.0-liter TDI in the models currently on sale in the US: the Q5, Q7, A6, A7 and A8. The engines are paired with 8-speed Tiptronic transmissions.

The first generation 3.0L TDI delivered 225 hp (168 kW) and 406 lb-ft (550 N·m) of torque; the current second-generation engine is 55 lbs (25 kg) lighter (from 458 lbs to 425 lbs), and delivers 240 hp (179 kW) and 428 lb-ft (580 N·m) of torque. (The Gen 2 engine is also a bit shorter than its predecessor.)

The company had set a number of development objectives for Gen2 of the engine, said Axel Macher, head of Thermodynamics/Application V6 TDI at Audi in Neckarsulm, Germany. These included:

• Higher power and torque;
• Lower fuel consumption;
• Meeting ULEV2 emissions;
• A start-stop system;
• Minimized weight;
• Compact design;
• Acoustic refinement;
• Modular construction;
• Optimized driving dynamics; and
• Optimized production time.

Audi took 26 lbs (11.8 kg) out of the crankcase, crankshaft, main bearing frame and upper oil pan—the last by switching from aluminum to magnesium. Macher noted that Audi has a new machining process that allows them to make a cylinder bore that will be perfectly round when the engine is operating. “If you have a perfect round bore in engine operation mode, you can reduce the pretension of piston weight, and that reduces friction,” Macher said. Laser smoothing of the bores also reduces friction.

Further contributing to a reduction in friction was going from four chain drive chains to two, as well as a reduction in weight of 8.8 lbs (4 kg).

For the second-generation, Audi further optimized the turbo with integral insulation and by moving away from flange-based mounting to the exhaust manifolds to an integrated component. Reducing thermal mass, it enables the turbo to reach operating temperature more quickly in the heat up phase. Audi also specifically optimized the turbocharger for the North American market to deliver very quick performance off the line. (A design target that appears definitely to have been met, at least subjectively, based on our experience in the TDI vehicles.) In Germany, Macher noted, the turbo is optimized for longer stretches of high-speed autobahn driving.

Changes in the exhaust manifolds and turbo from Gen 1 to Gen 2. Click to enlarge.

Injection pressure in the Gen 2 3.0 TDI is raised to 2000 bar, helping increase the power output and reduce emissions. The piezo injectors also use a multi injection strategy—two small pilot injections, followed by the main injection, followed by a post-injection. This strategy contributes to the quietness of the engine.

You need high EGR rates so you can reduce 70-90 % of the NO_xemissions. With the second generation of the diesels, we have a bigger EGR cooler, we have tubes with a bigger diameter, so we have less gas flow resistance. This helps us to make better fuel economy and good emissions.

—Alex Macher

Cooled EGR system. Click to enlarge.

Exhaust gas aftertreatment system, shown in an A7. Click to enlarge.

Driving the cars. For the rally, journalists paired up first to drive the Q5 TDI, then the A7 TDI, then the A6 TDI. All cars followed the same courses for each vehicle set, and the objective was to come back with the lowest fuel consumption.

The TDI Efficiency Rally fleet. Click to enlarge.

The course was primarily in the Virginia countryside—not a challenging terrain, but with rolling hills, some winding curves, and a few small towns. Exposure to Washington DC beltway-type traffic jams was minimal, and city driving was also minimal.

In other roads, the route was selected to showcase one of diesel’s strengths—efficiently cruising down the highway.

Audi collected fuel economy data from each car for each team at the vehicle changeover, then collated and analyzed it all at the end of each day for four different waves. (The last wave is concluding today, Friday.)

Subjectively, while each of the three models has its own special attributes, whether in terms of appearance, road hugging, handling, etc., uniformly the diesel powerplants proved exceptionally quiet, responsive, quick and powerful.

Assisted by selecting “Dynamic” driving mode, the diesel on more than occasion could shove us back in our seats—during a quick acceleration maneuver to make a left turn onto a highway with relatively high speed oncoming traffic, for example. There was no discernible lag on kickdown.

While outside the vehicle, they are audibly diesels (but not obtrusively so), inside the cabin it’s difficult to tell. Audi did a superb job of acoustic management with this generation of its US diesels—much more so than on the earlier 2009 A3 TDI, which, for all its pluses, had a distinctive diesel sound. (When that model was in the sales mix, Audi said, it also accounted for 55% of A3s sold.) Under the range of speed and traffic conditions on the rally, the inside of car was extremely quiet.

The stop-start function works flawlessly, without any untoward shaking or rumbling as it shuts the engine down or restarts.

And definitely one of the pleasures of cruising around the countryside in comfort and quiet was glancing at the fuel indicator and seeing how much was left.

Ideally, Audi team members suggested, the TDIs wouldn’t necessarily be targeted to diesel enthusiasts per se, but rather to buyers who simply want that combination of performance (not necessarily upper-end sport-class performance), low emissions and fuel economy—especially on the highway.

And, back on the policy front, Audi would also like Jacuzzi’s “fair shot”.

One of the challenges I see [facing diesel] is the way EPA weights city and highway driving when it comes to the label values for fuel economy. Currently, city is weighted at 55% whereas highway is at 45%—which obviously is going to favor your hybrids. I would argue that that’s not typical of the average person’s driving. In fact, the numbers I have seen are that people do 55% highway driving and 45% city driving. So right away we are penalized when in fact I think the fuel economy numbers would be much higher if they reflected real world driving.

As we know, and as you all are experiencing in your test drives, our label values... we exceed them consistently. You go to fueleconomy.gov, and you’ll see that time and again people are experiencing much higher fuel economy than the Monroney label [the required window sticker on new cars].

—Anna Schneider

(GCC will post results from the TDI Efficiency Rally when Audi has collected all the data. Audi hosted GCC at the TDI Efficiency Rally.)

Update: Fuel economy results from Wave 2 of TDI Efficiency Rally.

A6 TDI results. Click to enlarge.

A7 TDI results. Click to enlarge.

Q5 TDI results. Click to enlarge.