DAF yet to unveil a Euro 6 version of its 13 litre MX engine
Dutch maker DAF is yet to unveil a Euro 6 version of its 13 litre MX engine – now branded as a PACCAR engine on the rocker cover – for its popular CF85 and flagship XF105 models.
However, US-built versions of the same in-line six MX have been available in Kenworth and Peterbilt chassis since last year and the emissions technology that keeps a Stateside MX clean and green both today and tomorrow will surely find its way across the Atlantic in time for Euro 6.
The fundamentals of this engine are, of course, the platform for an MX engine which will be eventually offered in some Australian Kenworth models after a long and detailed test program under Aussie conditions.
Meanwhile, the Dutch have just made some interesting tweaks to the MX, notably the unusual adoption of a fully thermally-encapsulated exhaust manifold and turbocharger. By preventing the heat in the exhaust gases from being lost through radiation via the manifold and turbocharger, DAF’s engineers have been able to maintain exhaust gas pressures so turbo boost levels remain high, making the turbocharger more responsive and more efficient.
Moreover, 360, 410 and 460 hp versions of the MX also gain lighter-weight pistons with new crowns and revised injectors. The upshot of all this is that the latest MX engines have lower fuel consumption by up to three percent as well as reduced CO2 emissions.
In other European developments, Scania’s two new 13 litre Euro 6 engines, offered at 440 and 480 hp, unashamedly use both SCR and EGR emission reduction technologies, with the Swedes saying they’ve been working on their Euro 6 solution since 2007.
Yet while Scania’s green duo have yet to be officially certified due to delays in the legislation being ratified by European Union bureaucrats in Brussels (Belgium), the Swedes at Scania headquarters in Sodertalje have no doubts they’ll fit the bill.
I was recently able to drive both versions at 40 tonnes in Switzerland at Scania’s official Euro 6 driving event, although it was something of an anti-climax, endorsing the claim that, “Performance is virtually identical to a Euro 5.”
More important for operators, however, is the assertion that fuel economy is unchanged for Euro 6. That’s because, like Iveco, Scania has tuned its Euro 6 diesels for maximum economy before coming to grips with the increased NOx levels using a highly-sophisticated after-treatment unit which includes the latest urea injection kit that actually uses less AdBlue than its Euro 5 counterparts.
When you add up all the equipment used on Scania’s Euro 6 engines it sounds like a competition for the most three-word abbreviations. For starters there’s the ‘XPI’ high-pressure fuel injection system developed jointly with Cummins. Once combustion has taken place, the exhaust gases next go through an EGR unit before entering the VGT (variable geometry turbocharger). Next they pass through the DOC (diesel oxidation catalyst or oxicat). Then it’s on through the DPF (diesel particulate filter which, it needs to be pointed out, is continuously regenerating) before passing through the AdBlue dosing unit and thence onto the parallel twin SCR/ASC (ammonium ‘slipcat’) catalysts.
In operation the EGR and SCR processes are continuously balanced to optimise emissions; typically, around 50 percent of NOx is eliminated at source by the EGR system and of the remainder, another 95 percent is removed by the SCR catalysts. Meanwhile, the DPF is said to reduce particulates by 99 percent.
Although the DPF normally regenerates itself whilst the truck is on the move, if there happens to be an accumulation of unburnt ash the driver gets a warning in the dashboard display to either drive briefly “on a more demanding route on higher engine load” or to stop and press the filter regeneration button which will automatically cause engine revs to be raised.
In the unlikely event of a more serious ash build-up, the driver is told to take the truck in for service. However, service intervals on the Euro 6 engine are the same as for an EGR Euro 5 unit and Scania reckons the service life of a DPF will be up to 240,000km, at which point it can be quickly replaced in the workshop by an exchange unit.
For SCR to work well, exhaust gas temperatures typically need to be between 250 and 300°C. To maintain that range, Scania’s Euro 6 engines have a new intake throttle butterfly valve which restricts the amount of ‘cold’ air coming from the charge-cooler when the engine is not pulling hard, thereby helping to keep up temperatures in the exhaust system.
And finally, in case you’re wondering, it’s all for this: The forthcoming Euro 6 exhaust regs affect all new heavy trucks registered in the European Union from January 1, 2014, and mean even further reductions in permitted tail-pipe emissions. For instance …
- NOx emissions reduced by 80 percent compared to Euro 5.
- Particulates reduced by 66 percent compared to Euro 5 with the further introduction of a ‘particle number’ limit that will result in an actual overall particulate matter reduction of 95 percent.
- The introduction of an ammonia emission limit.
- The inclusion of crank-case emissions if a closed system is not used.
- Enhanced emissions durability requirements of up to 700,000 km or seven years for the largest vehicles.
- Further enhanced On Board Diagnostic (OBD) system performance.
- Euro 6 also sees the introduction of a harmonised world emissions test cycle standard for engine certification.