It’s official! Biglorryblog can reveal that Volvo Trucks has adopted a common-rail fuel injection system for its D9 diesel engine. OK, so it’s only on ONE diesel engine---and that one is a specially-modified version that runs on dimethylether (or DME as we ‘alternative fuel’ buffs prefer to call it) as part of Swedish manufacturer’s maker’s ‘CO²-free trucks’ program--but it’s a start.
For those of your who’ve never heard of DME let me fill you in on the detail. According to many in the truck business DME is the next wonder fuel along with synthetic diesel. And here comes the science bit so pay attention You get DME through a process of breaking down wood cellulose and then gasification. No I don’t understand it either but what you end up with is a fuel that’s got a very high cetane rating, has great emissions characteristics (i.e. it’s clean and green) and can be run in a regular compression ignition engine (i.e. a truck diesel like in this FM9 demonstrator above) without much modification---and is the kind of thing that you could end up running your truck on in 10 years time.
However, it’s not THAT perfect. You need to blend it with additives to help boost its viscosity which is naturally low. It’s also got a lower ‘action range’ than conventional diesel. Which means you need more of it to go the same distance. And it’s fairly aggressive to normal seals in fuel injection kit. However, Volvo has come up with its own special fuel system which is based around a common rail for the nine-litre in its DME FM9 demonstrator. The DME-fuelled D9 six-pot also uses EGR---but doesn’t need any NOx after treatment, because the low emission nature of DME means its reaches Euro-5 relatively easily.
But back to the DME engine’s common-rail fuelling system as Biglorryblog reckons that it (or something like it) will end up on Volvo’s 'normal' heavy truck diesel engines. And I’m not the only one who thinks that as that ‘Peter Pan’ of Her Majesty’s Truck Press (and a man who knows a thing or three about truck engine fuel systems) Alan Bunting, has wagered me that we’ll see a common rail fuelling system on the D9 engine first. (I don’t think I’ll bet against him...)
What is the advantage of common rail over unit injectors? If volvo were to use common rail on its engines would this not mean a major design change to its engine range.