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The EEV emission standard: a stepping stone to Euro 6?

It was back in 1999 that the EU authorities set both Euro 4 and 5 truck and bus emission limits and the dates for their implementation, even though Euro 5 standards were not scheduled to become law for all newly registered vehicles until October 2008. So, manufacturers had some nine years to progress their powertrain - including aftertreatment - technologies to meet the stringent Euro 5 requirements. With hindsight it can be seen that the lawmakers or, to be more precise, their technical advisers in Brussels, were astute enough back then to predict what would be possible some nine years ahead, by way of advancing emission control technologies and achieving volume production of the necessary hardware.

Earlier rounds of commercial vehicle emissions legislation in Europe had been widely criticized by manufacturers, not so much for the NOx (oxides of nitrogen) and PM (particulate matter) limits themselves, but for the legislators’ procrastination in setting the deadlines for compliance. Confirmation by the European Commission of Euro 2 and 3 NOx and PM limits and the relevant compliance deadlines was not forthcoming until 18 months or two years beforehand. As a result, the producers of diesel engines and their all-important fuel-injection systems and turbochargers were effectively asked to perform technological and manufacturing miracles in uncomfortably hurried development and production programmes.

What is perhaps even more remarkable about the foresight shown in the EU legislators’ 1999 emission law announcement was the inclusion of a further non-mandatory emission standard, which could have been called “Euro 5 plus”. But in fact it was given the rather clumsy label of “EEV”, which stands for “enhanced environmentally friendly vehicle”.

The EEV ultra clean exhaust standard, which was largely ignored during the first half of the decade, required no reduction in NOx beyond the 2g/kWh Euro 5 limit, but it called for a one-third lower PM level at 0.02g/kWh, as measured on the European transient test cycle and an accompanying reduction in exhaust smoke opacity.

The creation of the EEV standard enabled the R&D man-hours and costs previously demanded in satisfying minor sectors of the market to be channelled more productively

The EEV standard was (and is) intended to create an internationally agreed benchmark which can be adopted by EU member states and air quality conscious urban authorities in establishing truck operator tax-concession incentive schemes and low-emission zone entry rules. As such it is designed to discourage the unilateral imposition of what had previously been quite arbitrary standards, set locally by politically as well as environmentally motivated officials keen to curry favour with voters.

A multiplicity of local standards had come into being from the late 1990s. Some focussed on a PM limit that was plucked out of the air, with NOx being ignored; others set a maximum NOx value to the exclusion of PM levels. Manufacturers consequently faced a bewildering array of compliance problems. The creation of the EEV standard enabled the R&D man-hours and costs previously demanded in satisfying minor sectors of the market to be channelled more productively into meaningful advances towards the next EU-mandated emission reductions.

Up until the advent of Euro 4 enforcement in 2005/6, the EEV standard had been largely ignored, partly because it was, to all intents and purposes, unachievable with diesel power. But with more advanced electronic engine (mainly fuel system) management and the availability of add-on catalyzed DPFs (diesel particulate filters) - mainly Johnson Matthey’s continuously-regenerated trap (CRT) - EEV requirements could be met. The more widespread requirement for EEV compliance also stimulated natural gas (NG) engine development; an NG-fuelled engine was able to meet the required NOx and PM limits comfortably.

Having to reduce a diesel’s PM level by 33% compared with the statutory Euro 5 limit initially meant EEV compliance requiring the addition of a DPF, which added considerable cost. It also increased exhaust back pressure, to the detriment of fuel consumption. But incremental advances in engine technology, most notably increases in injection pressure, have boosted combustion efficiency, to the benefit of not only fuel consumption but also PM emissions. The result is that more and more truck and bus diesels are able to meet the EEV standard without a DPF.

With the next round of truck and bus emission limit reductions some three years away, there is an expectation in parts of Europe that the EEV standard could be invoked as an interim qualification

As an indication of the trend, it was recently announced that buyers of DAF Trucks‘ middleweight LF and CF65 two-axled truck chassis in the 10 to 18 tonnes gvw category can now, for the first time, specify the six-cylinder 6.7 litre Cummins ISBe diesel engine which powers those models in EEV compliant form - without the need for a downstream DPF. The ISBe-6 engine, which carries a Paccar GR designation in DAF vehicles, is listed in ratings from 220 to 300bhp. Its certification follows that of its 4.5-litre four-cylinder Cummins stablemate which has been available in EEV form in lighter DAF LF chassis since 2008.

In its heavier CF85 and XF105 trucks, DAF is also now offering its 12.9-litre (in-house) MX engine to EEV specification, though only in output ratings up to 410bhp. Again the requirement is met without the need for a costly and heavy (around 30kg) filter. More powerful MX engine variants cannot meet the EEV standard without a DPF, although those power units are specified mainly in long-haul versions of DAF’s tall-cabbed XF truck range, whose operations are less likely to involve the kind of urban conditions where EEV standards are locally demanded.

With the next round of truck and bus emission limit reductions - under the “Euro 6″ heading - some three years away, there is an expectation in parts of Europe that the EEV standard could be invoked as an interim qualification for more widely-applied environmental programmes. The best-known example is the MAUT motorway toll reduction scheme in Germany, which rewards operators of vehicles complying with future, more demanding, emission limits than those currently in force.

Euro 6-based early-compliance schemes cannot yet be implemented because no Euro 6 trucks or buses are yet in volume production. Until they become available, possibly during 2011, the German transport legislators and their counterparts in the Netherlands and other EU countries could make use of the EEV standard as a temporary means of incentivization.

The opinions expressed here are those of the author and do not necessarily reflect the positions of Automotive World Ltd.