Audi power-dense 2.5L TFSI engine with electric biturbo delivers 591 hp from 2,480 cc; 48V subsystem for the turbo
09 May 2015
At the Wörthersee festival, Audi is showcasing the Audi TT clubsport turbo technology concept equipped with a new 2.5 TFSI gasoline engine with an electric biturbo (earlier post) that delivers 441 kW (591 hp) and 650 N·m (479.4 lb-ft), with acceleration from 0 to 100 km/h (62.1 mph) in 3.6 seconds. Peak torque is available from 3,000 to 7,000 rpm. Power is transferred via a manual six-speed transmission.
While production car engines with this level of output are available from a number of mainstream OEMs, the displacement of the Audi engine is about half or less that of the others, resulting in a very power- and torque-dense unit. The five-cylinder, 2,480 cc engine produces 178 kW (239 hp) and 262 N·m (193 lb-ft) per liter of displacement. By comparison:
The new Ford Shelby GT 350 will feature a naturally aspirated 5.2L engine delivering more than 500 hp (373 kW), or approximately 75 kW/L. The 2014 Ford Shelby GT500 is powered by an aluminum 5.8-liter supercharged V8 producing 494 kW (662 hp) and 856 N·m (631 lb-ft) of torque, or 85 kW/L and 148 N·m/L.
The 2016 Corvette Z06’s features an LT4 supercharged 6.2L (6162 cc) V-8 engine, which is SAE-certified at 650 horsepower (485 kW) at 6,400 rpm and 650 lb-ft of torque (881 N·m): 79 kW/L and 143 N·m/L.
The 2015 Dodge Challenger SRT Hellcat’s supercharged 6.2-liter (6,166 cc) HEMI V-8 engine is rated at 707 hp (527 kW) and 650 lb-ft (881 N·m) of torque: 85 kW/L and 143 N·m/L.
The new Mercedes-Benz AMG GT S with 4.0L (3,982 cc) biturbo delivers 375 kW (510 hp) and 650 N·m (479 lb-ft): 94 kW/L and 163 N·m/L.
Audi’s electric biturbo combines a conventional gas-driven turbocharger with a secondary electrically driven compressor; in exterior appearance it is almost identical to that of a conventional turbocharger.
Turbochargers are typically driven by energy from the exhaust—i.e., starting from very low revs, the rise in boost pressure and therefore torque becomes gradually greater only as the exhaust energy increases. The electric biturbo, by contrast, makes it possible to build up charge pressure quickly and achieve high levels of torque even at very low revs.
Thus, an electrically powered compressor can offers significant advantages: It revs up to maximum rpm rapidly and without any perceptible delay, and it continues to boost charge pressure when too little drive energy is left in the exhaust gas for the conventional turbocharger.
This operating principle makes it possible to design the conventional turbocharger more specifically for high charge pressures and consequently for high engine power—the e-turbo assures spontaneous response and powerful sprints from low engine speeds at all times.
In the lower engine speed range, the electrically driven compressor boosts torque by up to 200 N·m (147.5 lb-ft). A dedicated 48‑volt electrical sub-system—another key future technology from Audi (earlier post)—supplies electrical energy to the turbocharger. A compact lithium-ion battery in the luggage compartment stores the energy that is generated by recuperation when coasting. A DC/DC converter provides the connection to the 12‑volt electrical system.
The electrically driven compressor lets the TT show car cover up to 16 meters (52.5 ft) within the first 2.5 seconds—which is six meters (19.7 ft) further than a comparable car without this innovation.
The electric biturbo signifies a new dimension in driving enjoyment; it boosts sprinting ability and torque and enables high peak power. In our TDI engines, we are close to production readiness with this technology. We are now presenting it in a TFSI – here too, we are the first automaker in the world to do this. For our fans at Wörthersee, we have packaged the electric biturbo in a very sporty show car.—Prof. Dr. Ulrich Hackenberg, Audi Board Member for Technical Development
Thanks to systematic lightweight design, the TT clubsport turbo show car has an unladen weight of just 1,396 kg (3,077.7 lb). The car completes the standard sprint from 0 to 100 km/h (62.1 mph) in 3.6 seconds, and its top speed is 310 km/h (192.6 mph).
Amazing power and speed for a 3,000 lbs car?
Posted by: HarveyD | 10 May 2015 at 08:50 AM
F1 levels of output from an engine supposed to be used, nominally, in a road car, suggests F1-type durability as well. Such huge outputs per litre have been possible for many decades, starting with the supercharged Grand-Prix engines of the 1920s and 1930s, but they always have short lives. In other words a bragging-rights exercise only by Audi, unless they have a race series in their sights.How does this promote Green transport?
Posted by: Peterww | 11 May 2015 at 03:06 AM
@peter, I would not believe that at all.
Audi could not afford to destroy their good name with that kind of performance.
I would imagine the engine is designed to last 10-15 years and 200 K miles.
However, it is a very overpowered engine, I would like to see 1.3 and 1.5 litre versions for more "normal" cars.
I suppose the question is how much extra cost does it add?
Also, having a 48V system means they could do stop/start and brake energy regeneration.
Posted by: mahonj | 11 May 2015 at 04:03 AM
The difference between this and a racecar engine is that this engine will only use full power for a few seconds at a time.
10 seconds of full throttle will make the car go faster than any legal speed limit, and even unrestricted top speed on the Autobahn will only require a fraction of the engine's total output: aerodynamic cars can reach 250 km/h using 150 kW or less.
How does it promote green transport? Engine downsizing. You can get supercar performance using an engine that's the same size as that in a 4 cylinder Toyota Camry. There's no need to drag a huge V8 around all day and only use its full capacity for a few seconds while merging onto the freeway.
Posted by: Bernard | 11 May 2015 at 05:50 AM
Mahonj, I'm glad you agree with me that this is very overpowered, which rather negates Benard's argument that it is simply Downsizing in action. Near on 600bhp is not necessary for anything to be driven on the road, and claiming that it will last for years because full power will rarely be used is simply ignoring human nature. If they've got it they will use it, and when they take it back to the main agent with melted pistons the technicians will simply plug in their diagnostics and read off "excessive use of full throttle" Such people are never put off by "any legal Speed Limit". To echo your own Argument Bernard, there is no need to drag around anything with this kind of output and only use it for a few seconds. You've totally failed to understand why the American industry always favoured large capacity engines, they could run at speed all day on the interstate and last for years and years, compared to smaller units of the day, back in the 1950's when they were introduced. That the Speed-Freaks then proceded to hot them up to much higher outputs has established a tradition of expecting that kind of performance direct from the factory,leading to the modern down-sized Turbocharged units we see from Detroit today, but none of that has anything to do with Green transport, only Ego-nursing.
Posted by: Peterww | 12 May 2015 at 07:41 AM
Whenever discussing supercharged engines, displacement no longer matters, as it is effectively supplanted by boost pressure. The meaningful metric is power density (i.e., weight) and general fuel economy. They don't mention weight in the article, but Audi's 2.0 liter is now making about 1KW per 1KG, and I would expect this engine to have at least as good a ratio. In comparison, the other engines mentioned are probably also pretty close to that mark but not quite as good. As to fuel economy, well, I don't think any of these engines are built with that in mind, and so they may all pretty much suck.
On a related subject, for those who are curious about such things, I was trying to determine the current production engine with the highest cylinder pressure. The Alfa 4C's 1.7 liter engine has 9.25 compression and 21.7 pounds of boost, and the Cadillac ATS's 2.0 liter engine has 9.50 compression and 20 pounds of boost. These were the highest combinations I could find.
Posted by: jzj | 12 May 2015 at 03:02 PM
How exactly are you going to use full throttle for more than a few seconds?
10 seconds at wide-open throttle will likely have you driving over 160 km/h. Maintaining that speed only requires a fraction of the available power.
Being a German car, it is voluntarily limited to a 250 km/h top speed, which again only requires a fraction of the total available power to maintain.
I don't believe that there's much incidence of people towing heavy trailers on endless hills at 250 km/h, and I've driven on three continents in the past year.
The fact is that this engine will behave like any other large 4 cylinder engine 99% of the time, while having the ability to provide an occasional "overboost." Conceptually, it's not dissimilar to a V8 engine with cylinder deactivation.
The way to tell for sure is to look at the cooling system. If it's built to provide 500 hp continuously, it will have huge radiators (like inter-city transport trucks). If it has normal-sized radiators, then it's using the engine as a heat sink to absorb momentary full-power demand, and radiating that heat over time. Modern engine management software and sensors will prevent it from providing more power (and heat) than it can dissipate.
Posted by: Bernard | 13 May 2015 at 04:54 AM
Is this the same electric turbo charger that they were going to use on the Audi RS5 concept?
I thought the R18 race car ditched the set-up because turbo lag is becoming a non issue. Wouldn't it trickle down to the street cars?
Posted by: DannyS | 19 May 2015 at 04:48 PM