Q&A: Stefan Rosenberger

Audi's powertrain engineer on developing the compact A3 mid-cycle and the lessons learned from using the MQB platform four years in

Four years ago, the A3 was the first vehicle to use the MQB architecture, what have you learned?
We have learned that the platform is very well developed meaning that the driving dynamics in the Golf are as good as the Audi. What that means, however, is that it is getting even harder for Audi to differentiate ourselves from the others – which is one of our goals.

Other brands in the VW group on the MQB platform benefit from Audi technologies, but what advantages does Audi receive?
We of course benefit from the cost savings in the platform which is the aim, so we have scalable advantages that we would not have without it. It also means that we can come quicker to market.

What did you want to achieve with this vehicle?
Regarding the engines, it was important for us to be the benchmark in terms of performance and consumption. With the 2-litre diesel with 141kW/320Nm achieved exactly that goal.

What technologies were used to help you meet emissions targets?
We always have objectives, with fixed goals. We have developed a new combustion process – the Miller/Atkinson process – and this means we take out some of the constrictions in the power unit. At the same time, we also improve the part load consumption figures. Our current four-cylinder petrol engines have an integrated exhaust manifold, so there is an exhaust manifold integrated and this means that it is no longer necessary to protect our components against high temperatures. This is a very engine specific process.

Have you introduced selective catalytic reduction technology?
It could be necessary at some point when the emissions standards become tougher but for now the technologies we have are meeting our targets sufficiently without it.

What were the chassis development goals when you started the project?
When the current model came out to the market, the level of driving dynamics and driving comfort was already very high. So the goal was to, first of all, maintain this high level, sharpen in some areas, to improve a little bit here and there, but the main goal was to differentiate the S3 more in terms of driving dynamics, quicker control and transmission.
And the second goal was even more important to offer best in class driver assistance systems and that is where we mainly worked on – apart from design changes. Also we developed a completely new generation of tyres, in order to lower emissions.
The suspension set up is the same as the previous model and we have the magnetic ride suspension.

How much scope for development is there to improve dynamics with tyre technology? 
There is always a trade-off between rolling resistance and driving dynamic performance, so you have got to find the right balance. Of course the tyre manufacturers continue to improve their products, finding new rubber mixtures and formulas to achieve their goals. A performance tyre for the S3 has different rolling resistance criteria due to the differing customer needs. Overall, we achieved a considerable reduction of roll resistance. In the past, we used to improve the tyres only once at the beginning of the life cycle but now since the tighter regulations requiring emissions labels but we decided to renew them for the facelift.

tags: Audi mqb Powertrain
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