2018 Audi RS 4 Avant 2.9 V6 Twin-Turbo B9

2018 Ian Kuah & Drive-My

Back to the Future! New model. The all new 2018 Audi RS4 Avant 2.9 V6 twin-turbo! The new RS 4 returns to its roots, with twin-turbo V6 power and after driving it Ian Kuah concludes that it is much the same as the original, only very much better…

If looks can kill then the new RS 4 Avant has it nailed. Unlike its predecessor, whose Wheel arches had to be tailored to fit with the standard A4 front and rear lights, this time the designers were given the go-ahead to make the fourth generation RS 4 fully look the part.

At the front, the small air vents on the outer edges of the headlight units allowed the designers to stretch the arches enough to give them a more resolute form, for a greater air of aggression. The single-frame grille with 3D honeycomb mesh and optional LED Matrix headlamps with dark-tinted background conspire to give the car an angry look. Overtaking presence is certainly there in spades.

The rear arches end in air outlets that match the front intakes, giving the rear a similar 30mmboost in width per side. In between, the optional carbon pack, which my test car had, provides the lovely carbon-fibre side sill inserts that add to the car’s perceived width between those big arches.

Those big arches are filled by 9.0J x 19-inch diameter (ET24) forged alloy wheels shod with 265/35 ZR19 tyres, while the optional 9.0 x 20-inch (ET26) forged wheels come in different designs, including a fully milled finish, and are shod with 275/30 ZR20 rubber.

The massive brakes behind these wheels feature 375mmand 300mm vented discs front and rear respectively, clamped by six-pot callipers in front. Ceramic brakes are an option, with the cross-drilled front discs measuring a massive 400 mm.

Audi RS4 Project Manager, Benjamin Holle, explained that the suspension is by MacPherson struts in front, with a five-link independent system at the rear.

‘The ride height is 7.0mm lower than the S4’s or an A4with the sport suspension option, and it has active damping with the Dynamic Ride Control option,’ he said. ‘The valve regulator, which was previously outside the damper housings has been integrated, so it is now inaudible from the cabin, but this was only apparent in very cold temperatures below what would normally be experienced in the UK.’

The interior has an air of sporty luxury, and features supportive sports seats with integrated headrests wrapped in Nappa leather with the characteristic Audi RS honeycomb stitched pattern. These seats have the option of an adjustable leg support and massage function, which we were told is the choice of 90 per cent of buyers.

An RS Design Package, which costs a reasonable €1,500 in Germany, consists of Alcantara seat centres, honeycomb stitching on some of the leather surfaces, RS floor mats, and special seatbelt colours. The one disappointment is the lack of leather dashboard trim, even as an option, as this always lifts the interior of a car. In the scheme of things, the 2.9- litre TFSI bi-turbo V6 engine that gives life to the new RS 4 Avant makes perfect sense. This is where the RS 4 Avant legend began with the B5 model that went on sale in 2000, powered by a 2.7- litre five-valves-per-cylinder, twin-turbo V6 engine developed by Cosworth. Its 380 hp and 440Nmof torque was hot property in its day.

Taking a leaf from the book of its bi-turbo V8-powered RS 6 big brother, the new RS 4 engine makes Audi the first manufacturer in the world to debut a twin-turbo HSI (Hot Side Inside) V6 unit. While this engine is based on the 3.0-litre single-turbo V6 that powers the S4 and S5, it has been downsized to 2894cc using a 3.0mm shorter stroke to allow for its higher state of tune.

As Technical Project Manager, Matthias Nöthling explained, ‘The new RS4 engine has a modified crankcase with a stronger crankshaft and uprated bearings. Its 84.0 x 86.0mmbore x stroke is accompanied by an increase in compression ratio from the 9.1:1 of the single-turbo V6 to 10.0:1 on 1.5 bar of boost.’

The resulting 450 PS (155.5 PS / litre) between 5700 and 6700 rpm is underpinned by a massive 600 Nm of torque from 1900 rpm to 5000 rpm; 179 Nm more than its naturally aspirated V8 predecessor, and at lower engine speeds. On paper, the new RS 4 certainly appears to have the right stuff.

Another advantage is that the new (EA 839) twin-turbo engine weighs 182 kg without ancillaries, a reduction of 31 kg over the naturally-aspirated V8.The car itself has a kerb weight of 1718 kg, which is 80 kg less than before thanks to the use of high-strength steels and aluminium in critical areas.

Another area of weight-saving comes from the V6 bi-turbo engine requiring just 7.6 litres of oil compared to the 10.7 litres needed to top off the naturally- aspirated (EA 824) V8 that it replaces. The oil sump has bespoke baffles that keep the oil pump supplying the life-sustaining fluid to all the moving parts under a peak lateral acceleration of 1.5 g.

The fuel, ignition and boost are looked after by the latest generation Bosch MG1 ECU. This sits high up in the engine bay, on the right-hand side as seen from the front, and on the opposite side from the air cleaner box. The direct fuel-injection system uses one injector per cylinder and runs at 140 bar system pressure. There is no requirement for additional manifold injection.

The water / air intercooler is positioned on the left of the car, as seen from the front, with the oil cooler placed horizontally in front of the bottom of the main water radiator.

If you are used to the deep NASCAR grade V8 rumble of the outgoing RS 4, your initial take on the new car’s soundtrack may not be altogether positive. While the new engine sounds as good as it gets for a V6, it undoubtedly lacks the head-turning muscle car growl that has enthusiasts so captivated by AMG cars.

However, the first time you have the chance to get on the throttle out on the open road the snappy response and relentless push in the back first takes you by surprise, and then keeps you in a strong enough grip that you yearn for a challenging stretch of road.

I found just such a challenging road in the hills above Malaga in Southern Spain, and quickly fell into step with the newRS4’s considerable charms. Okay, so it no longer growls deeply, nor does it have the lovely offbeat five-cylinder snarl like the TTRS, but the slightly under-square V6 revs like its pants are on fire, thrusting you towards the horizon on its beefy torque curve. And if you are using the 8-speed Tiptronic paddle shift transmission in manual mode you can so easily hit the rev limiter in the lower gears.

With less weight and more punch than its predecessor the stopwatch numbers are good. The 0-100 kph sprint takes just 4.1 seconds, thanks in part to the total traction off the line from the quattro all-wheel-drive system. As usual, the electronic limiter calls a halt to proceedings at 250 kph, but if you habitually ply the German autobahns you could be tempted to pay the extra for this to be opened out to achieve 280 kph (174mph).

The V6 has a fine soundtrack of its own, but as the turbo chargers mute the 2.9 bi-turbo’s singing voice, it is far from the spine-tingling Mk 5 Golf R32, which featured a silk-ripping V6 crescendo. However, with the exhaust flaps open in Sport mode and the window down you get a fair go at it, especially in a tunnel!

To this end, Audi offers an optional sport exhaust. This also ends in oval tailpipes of the same size, but they are distinguished by a black finish as opposed to the polished ends of the standard exhaust. The engineer I spoke to said it has slightly lower back pressure and a ‘more interesting’ sound, although it is not actually louder in decibel terms since that would cause the humourless grey bureaucrats in Brussels to raise their collective eyebrows.

The counterpoint of the new RS 4’s live lines when prodded is its sophistication and refinement, something it has in spades as an everyday driver able to transport four, and occasionally five people in relative comfort over distance.

Alight throttle 120 kph motorway cruise is a quiet and restful affair, with engine noise absent from the proceedings until you decide to drop a couple of gears and nail the throttle.

This quieter side of the RS 4 is good for fuel efficiency, which can be a reasonable 8.8 l/100 km(32.1mpg) in mixed driving according to Audi’s official figures.

The differential provides a 40 / 60 per cent front / rear power distribution in normal driving, and this can send a maximum of 70 per cent of the engine power to the front and 85 per cent to the rear in extremis. ‘The quattro Sport two-step clutch has the capability of sending as much as 1200 Nm of torque to each wheel, and is governed by an electronically controlled hydraulic pressure regulator,’ says Matthias.

The new RS4’s electric power steering is something worth remarking on. While it is a variable ratio system, once you select dynamic driving mode the system maintains a constant 14.0:1 ratio so as not to confuse the driver on a twisty road or racetrack. This ratio gives the car a ‘pointy’ front end, but not to the extent that it feels nervous, thanks to an agile chassis that nicely matches its turn-in rate.

The lighter V6 engine, positioned further back in the car, also contributes to amore favourable weight balance compared to the V8-powered car. Significantly, you also no longer feel the influence of the Audi Sport Differential, which gave the outgoing model a subjectively artificial-feeling rear-steer effect when turning into bends on throttle at low speeds on high grip surfaces.

Light throttle cruising and normal driving are good partners for the active damping’s Comfort mode. My test car looked good on its 20-inch wheels, and its ride quality on less than billiard table smooth Spanish country roads was firm but supple in Comfort mode, and should be similar on UK roads.

Sport, however, is a different matter. Here it feels like the damping is also trying to do the work of the springs in its bounce stroke. You don’t notice it when you are attacking a twisty road where suspension control is iron-fisted and grip relentless.

In combination with quattro traction, This makes for a blindingly fast point-to- Point machine with impressive poise and seemingly unending grip in the bends. However, when you are just driving normally, the slight jouncing motion quickly had me reverting to Comfort mode as the favoured travelling companion.

This seems to be a problem with all the rivals in this segment that rely on active damping as opposed to the much wider remit of air springs used in the cars of the class above. I have a beef with the ride comfort of the C63 AMG saloon too, a car I have spent many days in, driving around Germany where I found its ride a bit too stiff for my liking even in Comfort mode. In this respect, the current BMW M3 F80 is actually the best riding of the bunch, but it would not see which way the Audi went the moment it rains. I encountered the same ride issues with the previous RS 4 on its launch in Austria. Back then I swapped my test car with 20-inch wheels for one on 19’s, which made a positive difference to the ride quality. I didn’t have the chance to repeat that exercise this time but I rather suspect that the same will hold true for the new car. The on-going tussle between good looks and practicality lives on!

If the last RS 4 Avant did not have a V8 engine it would be that much easier for enthusiasts to get their heads around the new car, which really is better in every way barring its soundtrack. But, if you think about it, the RS 4 Avant has simply returned to where it began, with a bi-turbo V6 powerplant. The old saying, ‘the more things change the more they stay the same, ’most definitely applies here.

Above: The interior features supportive sports seats with integrated headrests wrapped in Nappa leather with the honeycomb stitched pattern.

Engine configuration

The HSI (Hot Side Inside) arrangement of placing two turbochargers in the Vee between the cylinder banks works perfectly with the 4.0-litre V8, to the point where Audi, BMW and Mercedes all use this configuration for their high-performance V8 engines.

The advantages of the HSI configuration are both logical and far-reaching. From a packaging point of view, without turbochargers and exhaust manifolds on either side, such an engine is more compact and lighter.

The much shorter intake path that comes from using turbochargers with integrated manifolds results in significantly lower pumping losses and better throttle response. As the engine runs on Lambda 1 for longer under full throttle it does not require fuel to cool the turbo. Meanwhile, the faster warm- up from a cold start sees the catalytic convertor reaching working temperature much sooner, helping the engine to meet emissions targets more easily.

Heat is the enemy of power, and with the hot exhaust and turbochargers at the top of the engine, so long as the cooling airflow is properly arranged, the engine bay heat-soak that plagues conventionally placed turbocharger installations is reduced. This in turn means the engine and its cooling system are under less thermal load, which is good for both power and longevity.





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