Sporty Dynamism, Superb Comfort: The Audi 1.8 TFSI

Source: Audi AG

TFSI technology underwent its baptism of fire in the victories at Le Mans, the toughest endurance race in the world. The superiority of this combination of petrol direct injection and turbocharging has now been demonstrated on ordinary roads in the 2.0 TFSI, which has been available since September 2004. Audi is now stepping up its campaign with the successful TFSI concept: the new high-tech 1.8 TFSI engine combines sporty dynamism with outstanding smoothness, and blends a spontaneous power characteristic with ample refinement.

The new engine generation bears the project number EA888 and follows in the footsteps of the already legendary 827 series, one of the most successful families of engines in automotive history. This compact, high-performance, economical four-cylinder version made its debut back in 1972 in the Audi 80. In the intervening years it has been fitted over 40 million times as the power unit for countless Audi models and various other vehicles of Volkswagen group brands. It has been steadily refined over the years, always remaining at the cutting edge of technology.

Pioneering achievement by Audi

The latest evolutionary stage of this engine range is the much-acclaimed 2.0 TFSI. At Audi, it is being used in the A3, A4 and A6, in three different performance versions ranging from 170 to 220 bhp. The 2.0 TFSI has most latterly demonstrated its special potential in the new Audi S3, with an output of 265 bhp and peak torque of 350 Nm.

This engine is yet another pioneering achievement, because Audi has once again become the first manufacturer in the world to combine petrol direct injection with turbocharging in volume production. The result is an engine that is not only very popular with customers for its power characteristic and propulsion, but has also garnered the approval of the experts: a jury of 56 leading journalists from 26 different countries awarded the 2.0 TFSI the title of “Engine of the Year” for two years in succession (2005 and 2006).

This was therefore an ideal basis for developing the next logical stage. Audi’s engineers had drawn up a long list of tasks for the new project. Right at the top – as is always the case at Audi – was maximum driving fun, as the result of high responsiveness, performance and torque even at low engine speeds. The engine was simultaneously to be quiet, smooth and low on vibrations, suitably reflecting the standards of comfort expected of a sporty premium car. The essential requirements of course included reduced fuel consumption, as well as the potential to keep meeting the toughest emission limits in the world, on a wide range of fuel grades. Finally, the new family of engines is to serve as a genuinely universal engine for use on all five continents.

Ultra-fine fuel jets, precisely distributed

Audi regards FSI technology with turbocharging, now systematically refined for the new engine, as the best way to achieve all these objectives. With FSI technology, fuel is injected directly into the combustion chamber. The new 1.8 TFSI does this at a maximum pressure that has been increased to 150 bar. Together with the new six-hole injectors and air movement in the combustion chamber controlled by charge movement flaps, it guarantees highly homogeneous mixture preparation and very efficient combustion. This supports the engine’s agile characteristics and spontaneous power output, as well as its very low fuel consumption in practice.

A new type of high-pressure pump supplies this injection pressure. The pump is driven by a four-fold cam on the exhaust camshaft. This reduces the operating forces required and boosts precision, thus improving the emissions. The high-pressure lines through which the fuel reaches the injectors at maximum pressure are made entirely from stainless steel. The new six-hole nozzles distribute the ultra-fine fuel jets with precision inside the combustion chamber. Dual injection – the distribution of the fuel quantity between the admission stroke and the compression stroke – brings further advantages for the homogenisation of the mixture and heating of the catalytic converters after a cold start.

Turbocharger with improved aerodynamics

The watercooled turbocharger K03, from Borg Warner, maintains optimum cylinder filling. An optimised turbine wheel improves the aerodynamics inside the charger, as a result of which responsiveness lower down the engine range is further enhanced. In the intake system, the redesigned charge movement flap reduces flow losses and simultaneously assures a very homogeneous distribution of the mixture.

The result is an exceptionally spontaneous engine response to the accelerator at all engine speeds: at just 1,000 rpm, the new 1.8 TFSI develops a torque of 165 Nm, with maximum torque available very early on and across the extremely broad range of 1,500 to 4,200 rpm. The peak output of 160 bhp is likewise maintained across an extremely broad plateau of 5,000 to 6,200 rpm. This permits economical gearing that is nevertheless of a sporty character. With a compression ratio of 9.6:1, the engine is designed to run on premium-grade fuel (95 RON). In the A3 with manual gearbox, the combined-cycle fuel consumption is consequently a modest 7.3 l per 100 km.

Excellent refinement

The TFSI concept is underpinned by the entirely new basic engine. In essence, the only thing its engine block has in common with its precursors is the cylinder spacing of 88 millimetres. Audi’s engineers chose this dimension because it keeps the dimensions very compact and allows the engine to be installed either longitudinally or transversely in the engine compartment. Two counter-rotating balancing shafts are integrated into the crankcase. They are driven by the crankshaft via a toothed chain, and completely suppress the free inertial forces of the second degree that are inherent to this design. Low-frequency humming and vibration are consequently eliminated very effectively.

The development engineers were especially eager to achieve very good acoustic behaviour and smoothness. After all, the new TFSI power units were meant to be exceptionally refined, not just very powerful. Grey cast iron was chosen as the material for the engine block in view of its better acoustic properties. With a finished weight of 33 kilograms, the engine block nevertheless genuinely merits being described as a lightweight design.

The extra-rigid basic structure of the block, acoustically optimised add-on parts and acoustically isolated covers reflect how much fine-tuning went on at the design computers and test benches. The crankshaft is instrumental in determining how smoothly an engine runs: what matters are not just the eight counterweights; its optimised rigidity, underpinned by large main bearings with a diameter of 58 millimetres, is really the determining factor. The result is that even at full load, the 1.8 TFSI is a smooth-running, acoustically restrained, spontaneous engine.

High tech in every detail

As Audi’s first four-cylinder engine, the 1.8 TFSI is equipped with a toothed chain to drive the valve gear. The compact chain does not need changing. There are, to be more precise, three chains: the long one to drive the camshafts, and two short ones for the oil-pump and balancing-shaft drives. The use of special toothed chains known as “silent chains” adds further to the outstandingly restrained sound of the new engine. The continuous adjusting mechanism of the intake camshaft has been reengineered; this vane-type system now responds much more swiftly than previous concepts. It promotes a spontaneous response from the engine even starting at low engine speeds.

The engineers also paid attention to keeping the design compact. This led to innovative solutions such as the highly ingenious auxiliaries rack. As well as performing its traditional function, it incorporates the oil cooler, oil filter and oil pressure switch. The formerly basic rack has consequently become the veritable turntable of the oil and water circuits. The integration of the water pump, thermostat and temperature sensor into a single housing also saves space. The turbocharger forms an integral module together with the exhaust manifold. This allows the positioning of the ceramic primary catalytic converter particularly close to the engine, promoting rapid heating-up and, in conjunction with the ceramic close-coupled catalytic converter, keeping emissions low.

Career plan as a universal engine

With these genes, the new 1.8 TFSI has the potential to keep on satisfying the toughest emission limits in the world. After all, it is destined for a career as a true “universal engine”. The highly promising new engine that offers ample scope for further development will be going into production simultaneously at Audi’s engines plant in Györ, Hungary, and in Dalian, China, in autumn 2006, when it will become the first petrol direct-injection engine on the Chinese market. The TFSI concept is likewise ideally equipped for use in the USA and South America, where fuel grades to some extent vary considerably.