That's because Audi doesn't make a fuel efficient V8 engine because they are either unwilling or unable to adopt a pushrod 2-valve design! Think about it...

• For the port injected generation, the Audi 40-valve 4.2 V8 made 340 hp / 302 lb-ft, weighed 195 kg and got 14 / 21 mpg.
• Moving to Direct Injection, their 4.2 32-valve 4.2 FSI V8 engine made 414 hp / 317 lb-ft, weighed 212 kg and got 13 / 20 mpg

That's horrible! And the only way they know how to deal with it is to go to a V6 and bolt on a blower or pair of turbos. For comparison:-

• For the port injected generation, the GM 16-valve 6.2 Pushrod V8 made 426 hp / 420 lb-ft, weighed 183 kg and got 16 / 24 mpg (Camaro SS).
• Moving to Direct Injection, the GM 16-valve 6.2 Pushrod V8 made 455 hp / 460 lb-ft, weighed 211 kg and got 17 / 29 mpg (Corvette Stingray - albeit not weight comparable to the S4/RS4)

Pushrods + Displacement = lighter, more powerful, much more torque and significantly better economy

And, that's despite 48% greater displacement. If that doesn't call into question the "superiority" of low displacement, high complexity and high specific output designs, well... it should.

It will be a twin turbo V6 because they have that available from the Porsche Macan. With Bentley getting more and more turbo V8s, and the Audi's big gun the S8 has a turbo V8, it makes sense that the smaller vehicles in the VW stable get turbo V6 power. If this is a Europe only car, maybe they'll go with a 3.0 liter to try to beat displacement taxes, not sure why they wouldn't sell it in the USA, unless they just figure no one will buy it over an M3 or C63.

Crazy waste of time when they could drop in like dwight points out a solid pushrod v8. Turbo's are over rated.

Anyway... with the 460 bhp LT1 and the 630 bhp LT4, GM has plenty of firepower to throw onto a super sedan. The Europeans can try to get 600+ hp out of a turbo V6 or turbo V8 (of a smaller displacement). It's doable. But it'll be neither lighter, nor smaller, nor more fuel efficient, nor offer better drivability. And, it'll certainly cost a lot more and be a lot more complex. But, hey, it looks like they are committed to the path.

VW has a twin turbo V6 on the shelf they can use, they aren't going to make up a new V8 for a car with tiny sales volume. And Audi's have grip, let's remember a 420 hp S6 is quicker 0-60 than a 556 hp CTS-V. It is all about low end torque and grip. If the Porsche Macan turbo can do 0-60 in 4.4 seconds, I imagine the same engine in an RS4 that weighs less will be near the 4.0 second mark, that is pretty quick I bet the Audi S6 goes V6 also, saving the V8 for the RS6 with an insane price.

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VW has a twin turbo V6 on the shelf they can use, they aren't going to make up a new V8 for a car with tiny sales volume. And Audi's have grip, let's remember a 420 hp S6 is quicker 0-60 than a 556 hp CTS-V. It is all about low end torque and grip. If the Porsche Macan turbo can do 0-60 in 4.4 seconds, I imagine the same engine in an RS4 that weighs less will be near the 4.0 second mark, that is pretty quick I bet the Audi S6 goes V6 also, saving the V8 for the RS6 with an insane price.

Well, that has everything to do with AWD and nothing to do with the engine.

VW has a twin turbo V6 on the shelf they can use, they aren't going to make up a new V8 for a car with tiny sales volume.

^^This

I don't really like how Audi prefers V engines in their vehicles. I personally prefer the sound of a straight six and why Audi never uses that configuration is interesting to me. I'm sure there is a reason.

Despite this the old V8 was not a very fuel efficient engine but it sure did sound good.

I don't really like how Audi prefers V engines in their vehicles. I personally prefer the sound of a straight six and why Audi never uses that configuration is interesting to me. I'm sure there is a reason.

Despite this the old V8 was not a very fuel efficient engine but it sure did sound good.

Far be it for Germans to admit that the Americans build a superior V8 engine.

 

I don't really like how Audi prefers V engines in their vehicles. I personally prefer the sound of a straight six and why Audi never uses that configuration is interesting to me. I'm sure there is a reason.

Despite this the old V8 was not a very fuel efficient engine but it sure did sound good.

Far be it for Germans to admit that the Americans build a superior V8 engine.

 

The only European V8 engine that I really like would be the V8 in the E39 M5. Not a huge fan of the others to be honest.

I don't know about you guys but I think that the RS4 needs a V8. Why? Let's be honest, it looks like a normal Audi A4 with a cheap bodykit, but that engine gave it that beautiful sound and power that really makes you turn your head. Maybe the new V6 will deliver the power, but I doubt it will sound as beautiful as the V8. I guess we will see, I'm just too scared that too many car companies are ditching the V8s.