Page 20 - Commercial Vehicle Engineer - November 2018
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One of the key changes from then will be a bee ng up of in-service compliance checks (ISC) using the latest PEMS (portable emissions measurement system) equipment, Thedinga told the Gothenburg symposium. Testing authorities will be encouraged to check exhaust systems working at low temperatures - precisely the sort of conditions in which below-par exhaust after-treatment performance and high NOx emissions are most likely to be found. The minimum power threshold
for the test is being cut from the current 20% to 10% of the engine’s maximum. Vehicle payload may be anything from
10 to 100% of the maximum during
the check, compared with 50 to 60% at present. Payload has a direct impact on exhaust temperature and hence catalyst performance.
Yet another tightening of the legislation, Euro 6e, is being  nalised at present by the commission. This will makes the ISC PEMS test more challenging still, not least because NOx measurement will begin when the engine is cooler. The test starts at present when engine coolant temperature reaches 70 degrees Celsius. The 6e test adds a new cold cycle, probably between 30 and 70 degrees C. The same PEMS test will be used as part of the original type approval test, explains Thedinga, pointing out that it makes sense for the two tests to follow the same protocol. But ISC testing has a “conformity factor” of 1.5, meaning that emissions may be up to 50% above type-approval values.
The Euro 6e legislation is expected
to be  nalised by next May, according to Thedinga, probably starting to come into force in September 2020.
Johnson Matthey, BASF Catalysts and Umicore were among the catalyst suppliers represented at last month’s Gothenburg symposium. They outlined promising recent catalyst developments which are said to be boosting NOx conversion rates by 5-15 percentage points in the critical low-temperature zone below 200 degrees C. The implication is that the SCR systems needed to meet Euro 6e demands will not have to be radically different from those
of today.
PEMS testing (above): soon to be used at lower temperatures. Heart of the matter: Euro6e demands better catalysts and  lters.
The performance of diesel particulate  lters (DPF) is also being put under the spotlight more than ever by the updated legislation. In-service checks will include particulate numbers (PN) for the  rst time under Euro 6e.
Engines going through type approval tests already have to comply with PN limits. The smallest soot particles, which can penetrate deep into lungs, are not just weighed but counted as well. In future there will also be a PN test in the ISC check, with the aim of ensuring that
diesel particulate  lters continue to work effectively on in-service vehicles. The likely impact of this new check
has been studied carefully by Volvo Trucks and DPF manufacturer NGK Europe. One  nding is that a DPF’s particle number  ltration ef ciency varies with soot-loading. Particulate numbers can be “surprisingly high” at some points, particularly under high-load conditions, according to Volvo Trucks’ particulate  lter specialist Martin Petersson.

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