Audi’s S5 Is Now A 342bhp Diesel With An Electric Turbo

The next S5 will use a diesel engine just like the S6 and S7, Audi has confirmed. The 3.0-litre petrol V6, already an efficiency-minded replacement for the 4.2-litre V8 you also used to find in the R8, has been axed.

Available as a three-door Coupe and a five-door Sportback, the 2020 S5 will switch to a low-friction 3.0-litre TDI diesel, supported by a big ol’ conventional turbo and an electrically-powered compressor (EPC) that fills the laggy low-rev torque gap.

This compressor sits in a valve-controlled bypass close to the engine itself, between the head and the intercooler. Although it looks a lot like a traditional turbo, the turbine wheel is replaced with an electric motor that spins the compressor wheel up to 65,000rpm in just three tenths of a second. That forces vast quantities of air into the cylinders and all-but eliminates lag. Audi says that in its acceleration tests, EPC-equipped cars steal several metres of an advantage from a standing start.

The EPC can’t generate peak torque, though, so that only arrives at a surprisingly late (on paper) 2500rpm, when the large blower has woken up. The S5 TDI then maintains a handy 516lb ft until 3100rpm, when the final run towards the 342bhp peak takes over.

The Coupe will sprint to 62mph from rest in just 4.8 seconds. The slightly heavier Sportback manages the same in 4.9. Both are limited to 155mph and share a fast-shifting eight-speed Tiptronic automatic gearbox with the first four ratios set closely for urban efficiency and the upper four leaning more towards tall gearing for economical cruising.

That gearbox is tuned to work with the S5’s new 48v mild hybrid system. Thanks to a host of small but important upgrades it can deal with the hybrid system’s ability to shut the engine down altogether for up to 40 seconds when you lift off at speeds between 34mph and 99mph. It’s also designed to avoid ‘unnecessary’ shifts in stop-start traffic. Stop-start operates as soon as you drop below 13mph but the engine restarts as soon as the car in front moves away even if you’re still pressing the brake.

Based around a belt alternator-starter motor that can start and restart the engine more quickly and more smoothly than a conventional starter motor, the S5’s hybrid setup will be able to recoup energy from deceleration at a peak 8kW flow rate.

But that’s all a bit boring. Much more interesting is the revelation that the S5 will use a combination of the two most popular types of torque vectoring. It will be able to independently brake its inside wheels under hard cornering, ensuring they don’t spin, but an optional quattro sport differential at the rear axle provides active torque vectoring for an even more dynamic and rear-driven feel. The S5 will be heavy, but spec’d properly it should munch fast corners for breakfast.

Naturally it also has permanent all-wheel drive, normally sending 60 per cent of the diesel V6’s muscle to the rear. If needed, it can shuffle up to 85 per cent to the back wheels or 70 per cent to the front.

Another given on the spec sheet is the adjustable drive mode system, Audi Drive Select. It tweaks the throttle response, gearbox behaviour, steering feel and more. The standard profiles span Comfort, Auto, Dynamic and Efficiency, but with the MMI navigation system added from the options list you also get an Individual mode, where you can take the various chassis characteristics you prefer and combine them into an overall package that suits you.

LED headlight clusters with strafing indicators will be standard alongside electric and heated front sports seats. Both S5 models will arrive in the UK in late 2019 for the 2020 model year. Prices are yet to be confirmed.