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2 turbos and an electric supercharger make this 1 rapidly diesel.
Are diesel engines and sports automobiles mutually exclusive? Most enthusiasts may possibly say so. Compression ignition operates well for lengthy-distance cruisers, pack-mule pickups, and SUVs, and in Europe, there are even a couple of diesel-powered coupes and convertibles for the patient and the parsimonious. Sports vehicles, on the other hand, are all about aggressive response, charging to the redline, and emotional acoustics. Like oil and water, the 2 just don’t mix.
But a new sort of homogenization is underway. The Audi RS5 TDI prototype that we just flogged at the brand’s handling track at Neuburg an der Donau has managed to reset our notions of diesel engines. This 385-hp 3.-liter V-6 TDI—still a prototype, but close to series production—has closed gaps with gasoline engines in areas exactly where diesels used to be hopelessly outclassed.
As you may well count on with 553 lb-ft arriving at just 1250 rpm, response at tip-in is brisk. From rest, the RS5 TDI charges forward with out delay. In a drag race with a gasoline-fueled 553-hp RS6 Avant turbo V-8, the RS5 V-6 TDI held off the far more strong V-8 car for many car lengths. The TDI’s midrange response is also quick, feeling like a high-efficiency, naturally aspirated gasoline engine, with none of the laziness and delay standard of turbo-diesels. This RS5 is surprisingly rev-happy, twisting the tach needle all the way to a comparatively un-diesel-like 5500 rpm. We estimate the RS5 TDI’s sprint from zero to 60 mph will take about 4 seconds, with 100 mph arriving in around 8. Leading speed is 174 mph, Audi claims. Despite these impressive numbers, the RS5’s 385-hp oil-burner is projected to use significantly less fuel than the 313-hp version of the V-6 TDI it is primarily based on.
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Electric Supercharger
The important to the RS5 TDI’s efficiency and efficiency gains is a Valeo-supplied electric supercharger. It is positioned at the “cold side” of the intercooler and, thanks to a low-inertia rotor, capable of reacting within 100 milliseconds and revving to 70,000 rpm. It can blow at full blast independent of engine load and revs. This allows the engine’s twin turbos to be calibrated for maximum boost—up to 49.3 psi—and energy. The leap to 385 horsepower at 4200 rpm is solely accomplished by the turbos, not by the supercharger. And the TDI’s ample 553 lb-ft of maximum torque is accessible from 1250 to 2000 rpm. These figures mirror those of BMW’;s 381-hp, tri-turbo inline-6 diesel, which is an impressive engine, but falls far quick of this Audi mill in terms of responsiveness.
The electric supercharger calls for a separate 48-volt power supply, and the conversion from the 12-volt technique adds cost and complexity. Down the road, expense is anticipated to diminish as much more electrical functions are integrated into a typical 48-volt method.
Audi’;s own, 6-speed dual-clutch transmission would be the ideal companion for this ultrasporty diesel engine, but it lacks enough strength to deal with the RS5 TDI’s torque. And so the RS5 TDI is fitted with the ZF 8HP 8-speed automatic, a fast-shifting and efficient unit that has grow to be a benchmark amongst these kinds of gearboxes.
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Speakers With Benefits
Although we are no fans of artificial sound engineering, Audi is forgiven for squashing this diesel’s clatter with—we’re not generating this up—a pair of speakers situated near the dual tailpipes. The auditory rewards are considerable. They emit a dark rumble at idle and provide a subdued roar as you race up the rev scale.
The initial series-production application for this engine will be in the next-gen Q7 crossover, soon after which it will migrate into the A6 and A7. But the RS5 is the perfect vessel in which to demonstrate its sporting capabilities. Here, the enhanced sound and the explosive energy delivery are backed up by very agile handling. The vehicle turns in with precision, and thanks to a Quattro sport rear differential, it can be coaxed into an simply controllable slide. Audi says the RS5 TDI prototype weighs no more than the traditional RS5 with its naturally aspirated V-7
2 years ago, Audi launched an SQ5 with a 313-hp TDI engine for the European market place, and it fostered discussion about the compatibility of “S” badging with a diesel engine. The question has been settled by the sales accomplishment of that version. Is it time to do an RS diesel? “We are contemplating the options,” is all that Audi powertrain chief Stefan Knirsch will reveal. Our take: The technical barriers have disappeared and electric supercharging has the potential to transform the diesel. Although the fuel efficiency of diesels is effectively established, the newfound energy and responsiveness of the RS5 TDI are on par with that of high-functionality gasoline engines. In our book, the “RS” and “TDI” look pretty good collectively.
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