Officials with BMW, Mercedes, Audi and Volkswagen say they doubt the long-term durability of the brand's D-Cat system, which the Japanese manufacturer describes as "revolutionary."
For the purification of exhaust gases, the system combines a denox catalytic converter with hydrocarbon trap with a soot particulate filter. It has been used in the medium-sized Avensis model since 2003.
Toyota officials say the technology not only complies with the current euro 4 exhaust-emission standards but also has the potential to comply with the euro 5 levels currently under discussion.
Automobilwoche was told that, in endurance tests, German manufacturers have found that the Avensis D-Cat's reduction of nitrogen starts to diminish significantly after 5,000 to 8,000 kilometers.
"Then it doesn't even comply with euro 4 anymore," says a senior BMW engine specialist. He says that the Toyota system is too fragile and cannot cope with European operating conditions.
A senior VW engineer confirms that tests show "that the D-Cat exhaust emission purification is not stable." The system's efficiency decreases "rapidly," he says.
This engineer said he believed Toyota wants to suggest to politicians that nitrogen oxide (NOx) reduction is not a problem with diesel engines. That would put pressure on German manufacturers to take action.
"They want to throw a wrench in the works regarding diesel technology and then massively push their hybrid engines."
Toyota Germany has rejected the accusations.
FEV, an engineering services company, has tested the D-Cat diesel on behalf of the German Automobile Association (VDA). The result: The system only works for a short period when driving during a normal cycle. The denox catalyst melts and smolders out, which also destroys the particulate filter. The customer doesn't notice any of this. The system just about complies with the euro 4 norm because of the engine's good standard levels.
German manufacturers fear that Toyota could force a denox catalyst on them and influence NOx levels that will be part of the future euro 5 standards.
The automakers have pointed out the problems they see to the EU commission.