1989 – 2019



Whenever vehicle manufacturers wish to introduce a new engine onto the road, tests first need to be carried out to establish whether the emissions meet the statutory requirements. This has been the task of the Institute for Vehicle Technology and Mobility (IFM) of TÜV NORD for over 30 years. At that time, all the talk with diesel engines was concerned with visible smoke. These days, TÜV NORD measures particles in the nanometre range and advises the EU in its debate about CO₂ limits. Martin Kleinebrahm and Dr Martin Goschütz on the exhaust emissions tests of yesterday, today – and tomorrow.


 Martin Kleinebrahm (57) studied mechanical engineering in Aachen. In 1989, he returned to his home city of Essen, to TÜV NORD’s Institute for Vehicle Technology and Mobility (IFM). Martin Goschütz (34) also studied at Aachen, but his specialism was power plant technology. He came to the IFM in 2017, having previously studied for a doctorate at the Institute of Combustion and Gas Dynamics in Duisburg. As employees in the powertrain / emissions – engine dynamics field, both now work on TÜV NORD test rigs as well as with the carmakers.



Mr Kleinebrahm, you’ve been working on the test rigs since 1989: what has kept you interested in the job all this time?


Martin Kleinebrahm (MK) An engine is never perfect: no matter how well it runs, it’s still a machine, in which losses are inevitable. Hundreds of the best engineers work their whole lives to minimise these losses. And it’s our job to check whether they’re paying sufficient attention to the exhaust gases. In this way, we gain direct insights into all the innovations and are always right there at the cutting edge.


Dr Goschütz, you’ve been with TÜV NORD for two years: what particularly surprised you when you started?


Dr. Martin Goschütz (MG) The diversity of the tasks; I’d never imagined the job profile would be so complex. I obviously knew about the TÜV from the periodic vehicle inspections and emissions tests. But I didn’t know what was involved in securing initial approval for new engines. It was also news to me that TÜV NORD was advising the European Commission in Brussels. I was happy to take on this task, because I think it’s really important for us to use our technical expertise in discussions with the decision-makers about meaningful measurement procedures and tolerances.


Were exhaust emissions an issue 30 years ago?


MK Oh yes, people started talking about them back in the 1960s. But all the conversation with diesel engines was about “visible smoke”: in other words, no-one worried about emissions unless you could actually see the fumes. These days, we think in other dimensions. Back then, the exhaust emission regulations might have filled 40 pages. These days, even for the same engine type they would easily cover 400 pages …
MG … the content of which is also constantly changing. We measure the emitted particles in nanometres, that is billionths of a metre. Which means that the measuring technology needs to be correspondingly effective.


Why are exhaust emission measurements more complicated nowadays?


MK All engine control systems used to be mechanical, meaning that there were hardly any set screws to change the exhaust emissions values. That changed in the 1990s with the advent of electronically controlled fuel injection systems: This opened up whole new vistas for vehicle developers, and whenever new freedoms arise, there we are. We test the exhaust gases – and put the measurement methods themselves through their paces.


What does such an adaptation look like?


MK Engines used to be tested at constant speeds and loads, exhaust emissions came out of the back – and we measured them. These days, there’s a whole mini chemicals factory behind every engine which reduces the emissions. In other words, if we’re going to measure the emissions at all realistically, the testing methods now have to simulate road use. It’s for this reason that the test rigs are now dynamic or even mobile.



TÜV NORD works at the interface between car manufacturers and licensing authorities. How do you see your role?


MG On the one hand, we advise the legislature by telling them what’s technically possible.
MK On the other, we travel around as a technical service provider and work with the carmakers to carry out all the tests required for cars to be approved for road use. We make sure the statutory checks are carried out properly and document the results. This is how we provide rule-compliant type testing for vehicles.
MG At the end of the day, there are clear requirements for our work: The measurement procedures are governed by regulations, and the measurement technology provides unambiguous data with no room for interpretation.


But only if everyone does their job properly.


MG Our advantage is that we operate our own test rigs. For a measurement to be valid, various parameters need to be satisfied in the thirty-or-so minutes that the test takes to complete.
MK We know from experience what’s required. Other service providers who perform measurements without their own test rigs are often less well positioned to assess that.


Is technical progress making your job easier – or more complicated?


MK It helps us to keep developing new measuring technologies. One example would be the mobile emissions testing devices that we attach to a car before we let it out on the road. Or in a measurement procedure where we send a laser beam through the measuring chamber, and, whenever it strikes a particle, it produces a minimal but measurable pressure vibration. This is how we carry out soot measurements.
MG Digitalisation also helps us evaluate the measurement results – because the more complex they are, the more complicated it becomes to assess them. Progress is also leading to changes in the engines themselves, meaning that the manufacturers are also using new control units, which in some ways act like a black box for us: We test the overall functionality of the engine, the exhaust gas treatment and the ECU.


Which new scenarios will the future bring?


MK Artificial intelligence is going to present new opportunities. I’m thinking of smart engines, which will be able to optimise themselves for different uses, depending on whether they’re driving long distances or in stop-and-go traffic.
MG Things will get to the point that we’ll have to use an individual simulation for virtually every vehicle, depending on which components it’s kitted out with and how it’s used. This is already happening with commercial vehicles, with the aim of giving the customer exact data about fuel consumption at the point of purchase. This creates transparency but also means a lot of work.


Will we still need internal combustion engines once alternative propulsion systems manage the crucial breakthrough?


MG I’m quite sure that internal combustion engines are going to be with us for a long time to come. A sea change is coming for private cars, but as far as commercial vehicles and mobile machinery is concerned, I still think diesel is going to be the main fuel of the future. To date there’s been nothing to rival the energy density of one litre of fuel, its availability and its price.