Long-term test of the ADAC: cars with hardware conversion consume significantly more diesel

Federal Transport Minister Andreas Scheuer (CSU) is doing these days as if he had always been the biggest friend of retrofitting older diesel vehicles with nitrogen oxide catalysts. He had adopted the rules for the conversion, the manufacturers had promised him to complete first systems in the first half of 2019. "I assume that the schedule is respected by everyone," he recently told the "Hannoversche Allgemeine Zeitung" - as if everything could not go fast enough for him. He had fought the hardware upgrade for a long time.

The pioneering work was done by others, such as the ADAC. One year ago, the Automobile Association started testing hardware retrofit kits. Specialists drove tens of thousands of kilometers with one

• VW T5 , equipped with a catalyst from the manufacturer Oberland-Mangold ,
• an Opel Astra (exhaust gas cleaning by Twintec )
• and a Fiat Ducato (catalyst from HJS ).

However, the Fiat suffered after about 30,000 kilometers an irreparable accident. In addition, the ADAC examined the cars on the test bench.

On Monday, the ADAC presented the results - and they are mixed: Although the nitrogen oxide emissions of the examined vehicles are significantly reduced thanks to the new emission control system. But that is often not enough to comply with the official limits. In addition, the cars sometimes swallow much more diesel.

Especially in winter, the energy demand increases, because the catalysts must be warmed up to an operating temperature of more than 200 degrees. This requires electricity that is generated by diesel. All tested models consume more fuel. "While the system of Oberland-Mangold in the VW T5 manages with an additional consumption of 7 percent and is close to the permissible excess consumption, the value of the Fiat Ducato and the Opel Astra with 12 to 13 percent are significantly higher," the ADAC auditors state ,

Devices can still be optimized

Thus, none of the vehicles tested by ADAC meet the official requirements of the Federal Ministry of Transport. According to newly issued guidelines from the scouring authority, converted cars can only consume six percent more.

However, according to the experts, this does not mean that hardware upgrades generally mean high levels of overconsumption. Rather, the providers are still at the beginning of the development, the devices could still be optimized. Above all, the energy management must be refined.

The additional consumption should also be lower for vehicles in which the SCR catalytic converter can be attached closer to the engine. There, the exhaust gases heat it up faster. Retrofitters could initially focus on diesel models, where a shorter distance between the SCR catalytic converter and the engine is possible due to the construction.

photo gallery

3 pictures

Further development effort could be worthwhile, because the systems fulfill their actual task quite well. The systems reduce nitrogen oxide emissions by up to 70 percent, according to the study.

"The basic performance of the SCR catalysts has not diminished even after 50,000 km," write the examiners to ADAC Chief Technology Officer Reinhard Kolke. The best results were achieved by vehicles, which - like the VW T5 - had been prepared by the manufacturers for the installation of an SCR system - for example for export to the USA.

The Fiat Ducato also had enough space to allow the retrofitters to easily install the SCR catalytic converter, tank and control unit. The trickiest thing to do was to retool the Opel Astra: with him, umpire Twintec had to trick around to accommodate all the components. As a result, the Astra suffered most frequently from technical malfunctions.

Systems do not (yet) comply with legal requirements

The biggest challenge for the retrofit manufacturers, however, was the high level of nitrogen oxide emissions that the vehicles had before the conversion. The sensors registered up to 2000 milligrams of nitrogen oxides per kilometer driven before the exhaust gases flowed into the retrofitted SCR catalytic converter. The limit for Euro 5 vehicles is 180 milligrams, measured by official procedures on the test.

Already at autumn temperatures between 5 and 13 degrees Celsius, the software largely switched off the exhaust gas cleaning. "The very high series emissions then do not get enough control even effective retrofit systems, even if the nitrogen oxides [...] can be reduced by up to 1400 mg / km," write the ADAC experts.

Even such a high reduction is not enough to comply with the technical guidelines for retrofitting SCR. These allow a maximum of 270 milligrams per kilometer and 540 milligrams at temperatures below 5 degrees Celsius. Only below these values, retrofitted diesel get a permit to enter cities with driving bans for Euro 5 diesel.

ADAC demands guarantees

In summer temperatures, the converted Fiat, Opel and VW keep the limits with the retrofitted catalyst. In autumnal temperatures, however, the cleaning system of the three cars tears the 270 milligrams mark sometimes twice. In winter, the additional cleaning performance of the systems is still between 38 and 53 percent. But the cars still miss the winter limit of 540 milligrams still clear.

From the customer's point of view, the test leaves many questions unanswered, concludes the ADAC. "Drivers need to be sure they can buy a reliable and durable product that will ensure mobility in the coming years without worrying about follow-up costs." The traffic club demands technical improvements and guarantees for holders of the retrofit companies.

In politics, the demand is louder to help the companies. The federal government should help them financially, suggests the SPD. For the Nachrüster it is not easy to get loans. The future market seems to be too uncertain for the money houses, which strongly depends on how many cities will end up with driving bans.