i love the 1m vs tt-rs debate
i just registered to say when the 2012 tt-rs arrives in the US, it will have 360hp, something nobody mentioned. audi says due to engine improvements. i contacted them to make sure it's not a misprint or something. the only car in the world that beats the tt-rs horsepower/L ratio is the veyron SS btw.
http://jalopnik.com/5637726/
some tech reading
This engine is based on the naturally-aspirated 2.5-litre inline five that powers Volkswagen Jetta sedans in North America. The port-injected 2,480cc unit develops 125kW (168hp) and 240Nm of torque at 4,250rpm.
Since Audi wanted to double its power output, it had to uprate or replace many components. Packaging was also a headache.
The basic engine architecture has been carried over, including the 82.5mm bore, 92.8mm stroke and 88mm bore pitch.
But the block had to be shortened to make it fit. Running the ancillaries from two belt drives and offsetting the second helped, but more radical measures were needed. Reducing the conrod and main bearing widths allowed the two outer main bearings to be moved inboard. This enabled the timing chain to move to the transmission side of the engine and the sealing flange and torsional vibration damper to go under the block’s cooling jacket, reducing the engine’s length.
But the main bearing’s diameter remained unchanged at 58mm. The resulting increase in stresses was beyond the grey cast-iron block’s limits.
“So we chose compacted graphite iron (CGI) with a tensile strength of 450N/mm,” says Böhme. “We’ve used this for V6 and V8 diesel engine blocks since 1999 but this is the world’s first mass-produced CGI gasoline engine block.”
Audi’s experience with CGI was invaluable in redesigning the R5’s block – manufacturing methods are demanding. Eisenwerk Brühl casts the blocks in Germany. Machining is handled by VW Mexico.
The cylinder head uses a better grade of aluminium alloy than before. A phaser has been added to the exhaust cam. The timing drive now uses two types of chain and is stronger and quieter.
The forged-steel crankshaft has induction-hardened crank pins and rolled fillet radii. The forged conrods are stiffer. The cast aluminium Mahle pistons are 10% lighter.
The Conti 120bar direct-injection system uses side-mounted six-hole injectors. This is similar to the set-up used on Audi’s four-cylinder engines but the flow rates are 25% greater.
Direct injection and fully variable valve timing improve scavenging. Low residual gas content means greater knock resistance. In fact, the boosted engine’s 10:1 compression ratio is higher than the naturally-aspirated version’s.
Close attention went into maximising the charge air cooler’s efficiency, says Quattro’s head of engine development Michael Ganz, because this is responsible for most losses on the intake side.
In a first for Audi in a transverse-engine application, the matrix is mounted right at the front of the engine compartment. The entire surface is cooled directly by the incoming airflow.
“Maximum air throughput of 1,000kg/h is high but the pressure loss from the charge air cooling system is only 135mbar, and full-load cooling efficiency is 80%,” says Ganz.
Just as much effort went on getting gases out of the engine. The way in which exhaust pulses react with each other before reaching the turbine wheel is critical to achieving good turbo response at low revs.
A water-cooled BorgWarner K16 turbo was the basis for development. The turbine housing is integral with the cast steel exhaust manifold. Given that it has five branches, it’s a complex component. “The big challenge was developing the manifold design to separate the gas flows in order to get the turbine running at low engine speeds,” says Audi gasoline engine development engineer Heiner Müller.
Twin-scroll turbos are ideal for inline fours but the odd number of cylinders precludes it here. Instead, the engineers designed the manifold so that the feed from cylinder number three is kept apart from the others until it enters the turbine housing volute.
A ceramic pre-catalyst is located immediately downstream of the turbo, minimising light-off time. But at low loads much of the exhaust gas is bypassed through the wastegate, which could give uneven temperatures over the catalyst surface. Rapid heating had to be ensured under these conditions too. Extra material was cast around the wastegate duct to direct exhaust gas towards the cat’s centre.
Audi says the R5 TFSI, at 494mm, is the most compact engine of its type in the world, and also the most powerful.
The TT RS hits 100km/h in 4.6 seconds before reaching its maximum speed of 280km/h. Fuel consumption is 9.2 litres/
100km with CO2 emissions of 214g/km.
Having a turbocharged five-cylinder all-wheel drive coupe in the range again must please the engineers as much as it will the people who drive it.