Audi brings its electric turbocharger closer to production with RS 5 TDI concept
Audi has been developing an electric turbocharger for several years and seems close to launching it on a production car. The new RS 5 TDI concept adds an e-turbo to its biturbo V6 to provide an immediate boost in power that doesn't wait around for exhaust gas.
"Twenty-five years ago, Audi launched the first TDI on the market, writing the first chapter of an enduring success story," says Prof. Dr. Ulrich Hackenberg, Audi board member for technical development. "Our latest innovation is the electric turbocharger, which further improves not just sprint times and pulling power, but also efficiency. This technology illustrates the possibilities harbored by 48-volt electrical systems, which we are currently developing for use in production vehicles."
Electric turbocharging is a bit of a misnomer since turbos rely on exhaust gas-powered turbines by definition, but Audi's been in the habit of calling it that since revealing it several years ago. Since then, it's been applied to the R18 e-tron quattro LMP1 car and now the new RS 5 TDI concept, which shows what it could do in a more road-friendly application.
The RS 5 TDI concept loses the 4.2-liter V8 engine of the production RS 5 Coupe for a 3.0-liter V6 TDI with triple turbos – the e-turbocharger supplements the two traditional turbos. Replacing the typical exhaust-powered turbine wheel, the electric turbo's motor spins the compressor wheel to over 70,000 rpm in a few hundredths of a second. This action essentially eliminates turbo lag and provides a powerful boost right off the line.
"What all turbocharged engines have in common is that the turbocharger is driven by energy from the exhaust," Audi explained when it discussed its electric turbo technology in 2012. "This means that starting from very low revs, the rise in boost pressure and therefore torque becomes gradually greater only as the exhaust energy increases.
A new development stage is the electric biturbo. This makes it possible – independently of the exhaust energy available – to build up charge pressure quickly and achieve high levels of torque even at very low revs."
The RS 5 TDI Concept has a dedicated 48-volt power system providing the large quantities of energy needed to feed the electric turbo. The system is energized by brake recuperation, storing electricity in a lithium-ion battery.
The tri-turbo set-up gives the RS 5 TDI a bank of 385 hp (287 kW) and 553 lb-ft (750 Nm) of torque, firing it to 62 mph (100 km/h) in four seconds (more than half a second faster than the 450-hp production RS 5) and 124 mph (200 km/h) in under 16 seconds. The car's top speed is listed at 174 mph (280 km/h). Meanwhile, it rolls for more than 44 miles for every gallon of diesel (5.3cL/100 km), another large improvement over its production sibling, which combines for 18 mpg (13 L/100 km).
Audi doesn't make any hints at RS 5 TDI production, but the e-turbo seems likely to find its way into dealerships. A report in Drive this week suggests that the Q7 SUV will be the first production model with the technology when it debuts at this year's Paris Motor Show.
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I wouldn't be surprised to see more companies looking to replace the standard 12v 40lb lead acid battery with something more suited to work with regenerative braking (like 48v Li-Ion).
One thing I'm not sure of though, aren't regenerative braking systems in hybrids just using the motor itself to recoup energy in braking? If so the only thing preventing the motor from also helping to power the car is essentially just a larger battery right? Is there anything else that separates non-hybrid regenerative braking systems from the ones in hybrids or are the costs to build it about the same?
I cannot wait until this hits the market!
i like Audi too...but the cash for it? In my neck of the woods Audi means you have cash and no brains... (Toronto..Yonge/Finch...you know the deal). R8's with automatic shifters where the drivers bounce the car up and down the street anyway with absolutely no clue what they are doing.
had a few Audis (6).... i'll stick to vw diesel and let the others spend spend.
There's a lot of interesting side effects and benefits that can be gained purely through software. For example, if the batteries are low, the engine can burn a little more fuel to generate more electricity by some slight dragging of the generators, and vice-versa, without the driver noticing any change.
There's also some old designs being resurrected to remove a lot of the moving parts in these hybrids, like making the pistons be magnets and the cylinder containing a generative coil, eliminating all the rotational components.
(I'll admit I'm not a true-mechanic type gearhead - I love cars, love to drive them, but not so handy at taking apart an engine to do a valve job. In 12th grade I replaced brakes in Auto-tech class, and I've replaced a radiator and alternator on my own!)