Scania’s new 410 hp six-cylinder gas engine is a long-awaited engine for demanding and sustainable long-distance and regional transport operations. With biogas in the tanks, CO2 reduction can be as much as 90 percent compared to a similar diesel engine.
Interest in running on gas is growing greatly, thanks to good access, a growing infrastructure and good operating economy. The sustainability aspects are also important.
Until now, gas engines have either been too weak or had too small a range for serious long-distance transport. But Scania has solved these issues with a ground-breaking Euro 6 gas engine with full potential for heavy, long-distance transport and construction-site applications that is equivalent in all respects to a diesel engine of the same size. The foundations were laid by Scania’s well-known 13-litre engine, which has been successfully developed to run on gas.
“We have great hopes for this unique engine,” says Henrik Eng, Product Director, Urban, Scania Trucks. “There is a considerable and genuine interest among existing and prospective customers to be able to have, for example, long-distance transport solutions for heavy goods that run on gas, and this engine meets this demand in all respects. It’s powerful, it gives customers a lower operating cost, and it reduces emissions.”
The new engine provides 410 hp and gives 2,000 Nm from 1,100 and through to 1,400 r/min – respectable figures that compare well with diesel engines of a similar size. With LNG (liquefied natural gas) in its tanks, a typical semi-trailer truck with a gross weight of up to 40 tonnes can drive 1,100 kilometres without refuelling under favourable conditions. With twin LNG tanks on a rigid truck, the range is approximately 1,600 kilometres.
Best possible driveability
“An important goal for us in the development work has been to ensure the best possible driveability, so that the performance and characteristics will correspond to what one expects from a modern diesel engine,” explains Folke Fritzson, a Senior Engineer who is part of the team developing Scania’s gas engines.
The new 13-litre gas engine always runs in combination with Scania Opticruise, Scania’s automated gearboxes. This means that the driver has first-class gear changing and driving comfort, with fast, unhesitating gear selections. A new, more robust spark plug and modified software have resulted in extended intervals between spark plug changes.
An important aspect of gas engines is the tank solutions on offer. Both tanks for compressed gas and tanks for refrigerated liquid gas can be ordered directly from Scania. LNG generally provides a greater range, as a significantly larger amount of fuel is carried.
With LNG, the range is up to 1,100 kilometres for a typical semi-trailer on a flat road. But a CNG (compressed natural gas) solution, which usually provides a range of up to 500 kilometres, is also more than sufficient for many customers, for example if the assignments primarily involve regional operations with a return to the home base and refuelling point every day. But the mileage that can be achieved before needing to refuel also depends, of course, on the type of driving and usage.
Longer maintenance intervals
A special safety aspect is that Scania’s engineers have turned the tank valves backwards, away from the direction of travel. This is a seemingly simple but thoughtful detail that reduces the risk of the valves becoming damaged by being hit by stones or chippings.
Gas engines that run using the Otto principle (with pre-mixing of fuel and with spark plugs) have shorter service intervals than diesel engines. However, Scania’s engineers have implemented a series of measures that help bring about a significantly longer service interval, and it is currently the life span of the spark plugs that sets the limits.
“We have defined the interval as 45,000 kilometres for both spark plug replacement and oil changes with normal use,” Fritzson says. “This is a clear improvement over previous generations of gas engines, which had 30,000 kilometres as their normal interval. This reduces maintenance costs and increases uptime, since fewer workshop visits are required during a given ownership period.”
“Everything indicates that we are making a breakthrough for gas engines, including those for heavier trucks for long-distance transport and construction-site vehicles,” Eng says. “Nobody now has to do without characteristics such as good driveability or driver comfort. At the same time, we are seeing that a rapidly growing infrastructure goes hand in hand with an increasing interest among potential customers to start using all the gas that is available in markets such as France, Italy and Switzerland, to mention just a few.”
Gas engines work according to the Otto principle, relying on spark ignition as opposed to the compression ignition used in diesel engines. A significant advantage of an Otto engine is the low noise level, much quieter than a diesel engine. In addition, thanks to the lower compression ratio and combustion pressure in the cylinder, the strain on engine components is considerably lower, making for a long service life.