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Familiar yet new: the exhaust on the Porsche 911 RSR.

A conversation with Christian Eifrig.

Iconic sound, legendary design and numerous titles from around the world – all this sounds like the Porsche 911 RSR. But who is actually behind the race car that continues to set standards? Christian Eifrig is the technical project manager for the Porsche 911 RSR and is therefore responsible for technical development. The unchanging goal: to bring a high-performance, reliable vehicle to the race track within the framework of the rules and regulations. In an interview, he reveals what fans and customers can look forward to in 2021. Because there are some new features for the latest RSR. One of them: the exhaust system.

I. Topic: technology

Why did you return to a central exhaust system?
The RSR has now been delivered to our customers and, in this context, we have decided to approve a quieter exhaust variant again. This is because there are noise restrictions on almost every race track in the world. They are suspended for races, but not for private tests. We wanted to make sure that our customers are always able to test and practice on all race tracks. This is the main reason why.


What are its technical advantages?
Actually, there are no real technical advantages gained from the position of the exhaust. The focus was on our customers being able to use the vehicle on all race tracks. The sidepipe system might have meant that they had to compromise.


What effects does the centrally placed exhaust have on aerodynamics and driving behaviour? And, does shifting the weight play a role?
Of course, there are smaller factors that have an influence, but ultimately it does not have a direct effect on the handling. As we race in a Balance of Performance class, any advantages or disadvantages will be transparently shown and balanced out in the interests of fairness.


With the exhaust system at the side, the susceptibility to damage at the rear area was minimised – but now you are returning to the central exhaust. Is that taking a risk?
The risk is marginally greater. But this is also clearly calculable and, statistically speaking, failures due to a defective exhaust system are very rare. A collision at the rear may be more common, but it must also be quite clearly stated: during hard wheel-to-wheel racing, as we often experience with the RSR, we have also seen slightly displaced tailpipes on the side.

II. Topic: sound

That's the biggest acoustic effect.

Christian Eifrig
When the exhaust moved to the side, the sound of the vehicle changed. Does the new central exhaust now affect the sound of the RSR?
Exactly. Combining the six individual cylinders into a single area at the rear naturally completely changes the sound characteristics. This makes a huge difference to the exhaust on the side where the cylinders are separated. That's the biggest acoustic effect.

You get the feeling again that the engine is roaring more.

Christian Eifrig

What is your personal opinion: exhaust on the side or in the middle?
Of course, its position has an acoustic influence. With the exhaust on the side, the six cylinders of the horizontally opposed engine are effectively acoustically separated: you hear three cylinders on one side and three cylinders on the other. This gives it a completely new sound profile and a lower frequency range. The rear exhaust system combines both cylinder banks, which increases the frequency of the engine. You get the feeling again that the engine is roaring more. This classic sound can be heard in the 2017 RSR. And that's the direction we're now taking again.


Fans rave about the RSR sound – what can they look forward to courtesy of the new exhaust: how do you think the new RSR sounds?
The new RSR is already very reminiscent of the 2017 RSR. It has to be said. Fans who know the RSR from 2017 will certainly be able to recognise it from the sound characteristics in the new model. But, of course, it doesn't sound 100% the same.

III. Topic: design

As an engineer, my eye perhaps isn't sharp enough to be able to answer this design question.

Christian Eifrig
Do you think the central exhaust seems more harmonious with the overall appearance of the RSR?
(Laughs) Of course, this is a difficult question for an engineer to answer. I like both. With the rear exhaust system, we are returning a little to the exhaust system arrangement of the GT standard-production vehicles. I also liked the look of the ones on the side, it was a different approach. At Sebring, I saw how the RSR with the side exhaust system was also celebrated. Both the design and the sound are very well received and create a harmonious overall concept. I really wouldn't be able to make up my mind. As I said: I think both are great. Which is more harmonious in the end? Perhaps, as an engineer, my eye isn't sharp enough to be able to answer this design question.