Page 19 - Commercial Vehicle Engineer - November 2018
P. 19

Coming right at you: tougher in-service emissions checks are on the way.
of it. How so? In essence because heavy- duty diesels do not deserve to be tarred with the same brush as their lighter brethren.
That certainly was the consensus among delegates last month at the latest in a long- running series of biennial events on this topic run by SAE International, a highly- regarded US-based engineering association and standards-setting body formerly called the Society of Automotive Engineers.
A study by respected engineering consultancy Ricardo con rms that most Euro 6 trucks actually do live up to NOx reduction expectations, not only in engine test-cells but also in daily use. “Published heavy-duty NOx data show that vehicles mostly meet real-world NOx limits,” says Ricardo, conceding however that “in some cases, under unladen congested traf c conditions, the SCR (selective catalytic reduction) after-treatment is not able to maintain an effective temperature for
NOx conversion.”
Concern about NOx, a by-product
of high-temperature combustion, is understandable, given the adverse effects
it has on respiratory health and on the environment – essentially smog and acid rain. So, no matter how clean Euro 6
diesel truck and bus emissions may be, any shortcomings in NOx control cannot be ignored. And some have been revealed by the in-service compliance (ISC) checks of real working trucks introduced under Euro 6 rules (Euro VI, to be strictly accurate and distinguish them from those applying to cars and vans).
Iveco Eurocargo trucks were recalled early this year following discovery of excessive NOx emissions. And only last month Volvo Trucks announced that a component in its exhaust after-treatment system had been found to be “degrading more quickly than expected, reducing
its ability to convert NOx.” Sounds like premature deterioration of the NOx catalyst, in other words, though Volvo Group has still to con rm what exactly is meant by “degrading quickly”. US in-service checks have also detected a problem with NOx catalysts behind Cummins engines. More such catalyst problems could yet emerge.
Excessive emissions under cool, low-load conditions; and age-related performance tail-offs are two particular targets of the latest updates to the Euro VI legislation governing trucks and buses. As a policy of cer based at the European Commission’s Brussels head of ce, Bart Thedinga knows the latest Euro VI re nements inside out. They are collectively referred to as “Euro 6d”, and will apply to newly-registered trucks and buses from 1 September 2019.
Reality check: trucks in service do match lab tests on NOx emissions.

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