Audi's 2.9L V6 turns a '90s Joke into a 2020 V8-Beater
With those 444 ponies, the 2.9L V6 bosts the same horsepower level as the 4.0L twin-turbo V8 it has replaced.
While new vehicle reveals grind to a near-halt, Audi is taking some time to share more about the tech and people that make the brand what it is. This time, it’s one of Audi’s latest and most technologically impressive engines, the 2.9L V6 that makes the 2020 Audi S6 and S7 home, and gets them home more quickly with 444 hp.
With those 444 ponies, the 2.9L V6 bosts the same horsepower level as the 4.0L twin-turbo V8 it has replaced, along with 443 lb-ft of torque that makes it 37 lb-ft torquier than the older, bigger V8. Since the old one already had turbos, how did Audi do it?
By adding some tech that would have made you the laughing stock of the industry just 10 years ago: an electric supercharger called the Electric-Powered Compressor (EPC).
It wasn’t long ago that adding boost electronically was a joke. The kind of product you saw advertised on late-night infomercials or Saturday mornings before the car shows started, along with a pricetag that was both too high and too low for what you got. Or for what they claimed you would get.
That’s because those old 12V blowers couldn’t really huff or puff like the EPC that takes advantage of Audi’s 48V electric system.
48V allows Audi to spin the compressor with four times the power of a traditional electrical system without raising the current. Instead of a light breeze, this electrical compressor is driven by a motor that spins with 10 hp of its own.
The EPC can spin up in less than 250 milliseconds, at blink-like speeds, using energy captured by the 9.6 Ah lithium-ion battery that is charged up during coasting and braking.
It’s located downstream of the two turbochargers, but before the air-to-water intercooler. So it pushes cooler air through the throttle bodies. It can spin at speeds up to 70,000 rpm, but at higher engine speeds, a valve closes and bypasses it completely letting air from the turbos follow a different path.
So it spools up quickly, but how does that accomplish anything?
Turbocharger sizing is always a compromise, even with a variable geometry turbo. You need to pick one that can flow the right amount of air at peak flow but is small enough to spool up quickly. Like any compromise, that means that performance suffers at the extremes. It could spool more quickly, or it could flow more air, but not both.
Having the EPC add boost near-instantly at idle means that the turbos can be sized to flow air at peak power. It removes some of the compromises. That lets the engine make more power and more torque once the conventional turbochargers are spooled up and in play. It also makes the engine more responsive from idle or throttle tip-in, because you’re never waiting for the conventional turbos.
The best part of all of it? Audi says that in its standing-start tests, the newer engine has “response characteristics that rival Audi’s torque-rich, turbocharged 4.0-liter TFSI V8,” but it offers 22 percent greater estimated fuel economy thanks to being smaller and more efficient.