Audi Magazine: Oliver, the 10-cylinder engine was a joint project between Audi and Lamborghini. How did the story start?

Oliver Hoffmann: The first step in the development of the 10-cylinder was the 5.0l MPI, i.e. the five-litre with multi-point injection which appeared in the Lamborghini Gallardo in 2003. In the years that followed, we worked with our Italian colleagues to take the engine to the next level.

What did that involve?

Hoffmann: The aim was to optimise the dynamic performance, which needed fine-tuning in one or two details. I was in charge of the oil circuit and its ventilation, which is necessary to keep oil foaming and aeration to an absolute minimum under extreme driving conditions. We used test beds able to simulate the Nürburgring Nordschleife, and we optimised aspects such as the cylinder walls and fine-tuning of the intake ports and intake manifold.

And how did things evolve for you after that?

Hoffmann: I subsequently moved to the Neckarsulm plant, where I was responsible for the development of the high-revving V engines. Following on from the technically similar V8 FSI, which was used at the time in vehicles like the RS 4, we turned our attention to the 5.2-litre V10 FSI, which we completely re-engineered. It was systematically configured for motorsport use, although obviously under the Audi production conditions we had at the time.

What does that mean in specific terms?

Hoffmann: Alongside the series-production engine, we also wanted a virtually identical racing unit. In order to make use of the available equipment at our Györ plant in Hungary, we had to stick with the base dimensions. That included the cylinder spacing of 90 millimetres. This determined the relatively small bore of 84.5 millimetres and the resultant long stroke of 92.8 millimetres. That’s how we got to the high maximum piston speed. When the revs max out at 8,700rpm, the pistons are traveling at an average speed of 26.9 metres per second – that’s way above the speed of a present-day Formula 1 engine.

Another given was presumably the cylinder angle of 90 degrees, like in the V8 …

Hoffmann: 72 degrees is the ideal angle for a V10 engine because it gives a regular firing sequence. But in the interests of stiffness, we used the 90-degree angle to do something very special and opted for a so-called common-pin shaft with unsplit journals. Our V10 engine is basically two five-cylinders working in sync and firing alternately at 90 and 54 degrees of crank angle. And that’s what gives it its unmistakable sound.

What were the biggest development challenges?

Hoffmann: Firstly, the dry-sump lubrication, which comes straight from motorsport. This technology enables an extremely low mounting position because there is no need for an oil sump. Instead, the oil is sucked out of a separate tank. The system can circulate and de-foam more than 85 litres of oil per minute. An oil pump fills the external tank with five different suction levels. Oil feed is via the pressure level fed centrally into the crankcase. The whole system is designed for lateral acceleration forces of more than 2 g and sucks the engine oil separately out of the crankcase, the chain housing and the cylinder heads. For extreme racing demands, we developed a dedicated oil supply for the main and conrod bearings to ensure a continuous oil feed at sustained high revs. It took an awful lot of fine-tuning to get all that sorted.

Can you carry out a high-tech project like that without external assistance?

Hoffmann: We worked with the best external experts in many areas, including some who have worked on Formula 1 engines. When it came to the pistons, literally every single gram counted. The enormous centrifugal forces mean that one gram less at the piston takes a huge amount of load off the conrod bearing. We learnt a great deal from this engine. Our piston pins, for instance, were coated with a diamond-like carbon layer. As well as reducing friction, this also prevents wear on the racetrack. We used radionuclide technology to measure wear in a lot of components such as the bearing shells. To do that, you charge the part you’re testing with a small amount of radioactivity and then measure how the intensity of the radiation changes during operation.

What was the most emotional part of the development process for you?

Hoffmann: I can distinctly remember the moment when the first complete engine ran on the test bed and then revved up to more than 8,500rpm. Total goosebumps … We conducted endurance testing for up to 800 hours and full-load durability testing for 330 hours. Later, on the Nürburgring, we covered distances of more than 8,000 kilometres. Our Race driver, Frank Stippler was totally bowled over by the engine. And then came the first rollout of the R8 LMS and our first 24-hour race on the Nürburgring, where we finished as class winner and second in overall ranking. I worked at our Györ plant at the time and wasn’t able to get any time away that weekend. I watched the race via a special video feed on my phone. We won the European GT3 championship in our first season. That was the foundation for the great racing career of that car and that engine.