Ever since exhaust emission controls started to force truck engine manufacturers to introduce new technologies onto their engines to meet the ever decreasing allowable concentrations of harmful exhaust gases, Scania has offered both the main competing technologies in different parts of its truck range. In the past, some engines were available with EGR systems while others were available as SCR versions.
With the introduction of the new 13L engine from Scania, customers now have an opportunity to choose either/or. All power outputs for the new 13L will now be available at ADR 80/03 with an SCR system, matching the outputs available on the version of the 13L engine which uses EGR to meet ADR 80/03.
The new SCR version is based on the Euro 6 engine being introduced into the European market in the run-up to the introduction of lower exhaust emission rules in Europe next year. By combining the sophisticated new engine model with tried and trusted technologies, Scania has come up with a solution that will work well as an alternative in truck markets like Australia, where Euro 5 is mandated but Euro 6 is still some way off.
This is a pragmatic solution which means Scania can offer, throughout its 13 litre engine range, a choice of two diametrically opposed engines, an SCR or a EGR. There are many fleets for whom the major factor in engine choice is their preference for one or the other exhaust emission technologies. For some, the need to carry a supply and refill another tank with Adblue is unacceptable and they insist on EGR only. For others this extra tank is of little consequence but the higher heat rejection of an EGR engine takes them down the SCR route.
Offering two different engine philosophies in the same truck gave Prime Mover a chance to drive the two engines side-by-side on the same track with the same load on the trailer. This is an opportunity to get a handle on the feel from the driver's seat, comparing one of the engines against the other. The limitations of the test track at Anglesea in Victoria meant it was only possible to get a first impression of the differences between the two engines, but even in a relatively short trip it is very clear the engines have completely different characteristics.
How these different characteristics play out in the real world, out on the road, is difficult to tell at this stage. How the differences play out in terms of fuel consumption and durability will only come to be known with much longer testing, when fleets are using them in the real world out on the highway.
The new Euro 5 SCR engine represents a significant update on the technology available from Scania. This new engine replaces the 12L engine fitted with SCR which had been offered here in Australia in the past, as an alternative to the 13L EGR engine for fleets who preferred it. This has the effect of rationalising the engine options supplied by Scania and reaffirms the pragmatism of the modular engine design which minimises the number of engine parts needed across the entire range.
By utilising the core engine technology being used for the Euro 6 engines in Europe, Scania has been able to scale back the sophistication of the other technology used in the engine. The fuel injection system uses a PDE pushrod driven injection system as opposed to the high-pressure XPi system used in the EGR engines. These are the same as those used in the larger V8 engines from 500 to 620 hp. The new SCR engine also only needs a simple turbocharger fitted and not the variable geometry turbocharger required for the EGR models.
“In designing this new engine, Scania were looking to simplify the engine design,” says Ian Butler, Scania Market Application Analyst. “The markets we are looking to put this into are South America, South Africa and the East European countries. One of the reasons behind the development is the issue of fuel quality. Some of these countries are still dealing with high sulphur fuels and EGR has to have 10ppm of sulphur as a maximum. SCR can cope with sulphur up to 2000ppm.”
Out on the track, the differences between the 440hp 13L EGR and the equivalent 13L SCR are plain from the word go. Where the EGR version picks up speed and demonstrates its power as the truck goes up through the gearbox, the low rumble of the engine goes up and down with the increase and decrease in rpm. Taking off in the SCR engine gives a completely different engine note, with a higher pitch and an engine that sounds much more free running. The truck feels more willing to get going.
The way the experience differs from the driver's seat can be explained by the different technology being used by the engine and the different way in which the system controls emissions. One is using some recirculated exhaust gases to lower temperatures inside the combustion chamber while the other goes through a complicated process in the exhaust system to reduce nitrogen oxides.
The question is how this difference may or may not affect overall performance of the truck in working conditions. The apparent free running nature of the SCR engine suggests to the driver that this truck is performing better. In fact, both power and torque curves are exactly the same. Most of these engines have been tuned to perform identically. It would appear to be simply a matter of perception on the part of this driver, although anecdotally, other drivers who have had a similar experience report the same feeling.
The new engine is available in four power outputs, the same as those available for the EGR engine – 360, 400, 440 and 480hp. The torque outputs for each engine also match those available from the EGR version of the engine, except for the 480hp version which puts out 2400Nm compared to the EGR version which puts out 2500Nm of torque.
According to Scania, the choice between an EGR or an SCR engine is simply the operator's preference. Fuel consumption on the SCR version will be lower but, of course, there is the added expense of the Adblue additive. The difference is expected to vary according to the application and driver behaviour. Ian Butler suggests prime movers used on local distribution will probably choose an EGR option whereas those running longer distances may well opt for the SCR version.
Scania says that the durability of the trucks is also fairly similar. The manufacturer has been selling both EGR and SCR engines in its trucks for quite some time, and during this period, it has been working to get the lubricant specifications fine tuned to optimise longevity.
“In the total washout, when you are looking at overall weight, a truck fitted with an SCR engine will be around 100kg heavier than the same truck fitted with an EGR engine,” says Ian. “You have a single tank with the bracket to secure it, plus a muffler and a control unit. It is basically the tank and the fluid which adds the weight.”
One of the most important effects of the introduction of an SCR alternative engine is the possibility of now fitting the more powerful 440hp SCR engine under the redesigned P Series cab. In the past, the larger cooling requirement for the EGR version of the engine meant the top power available in a P Series was 400hp. This opens up more possibilities for Scania trucks in single trailer distribution at higher weights.
Apart from the engine itself and its revised cooling package, safety technologies like adaptive cruise control will now also be available on the smaller cabbed P Series models. The grille design on the P Series has changed to match that which has been available for some time on the G Series and the R Series.
What is clear about the new engines being introduced by Scania is that they are leaving the choice up to the customer. The debate among operators and manufacturers about the pros and cons of EGR and SCR will continue as some find one technology better than the other, while others, the opposite. The jury is out, in many cases, and there are many subtle differences between applications and driver behaviour which will continue to make small differences which may or may not be attributed to the exhaust emission control technology.
Scania has come up with a pragmatic solution that enables the company to offer a real choice to its customers, at least with its 13L engines. The modular engine system means that the same components can be used in many different parts of Scania’s engine range. Scania has simply taken components used elsewhere and put them together in a different way to come up with an EGR solution and an SCR solution.
This kind of innovation is what we expect to see from Scania. The manufacturer continues to bring a no-nonsense pragmatic approach to most of its design solutions. While the EGR versus SCR debate continues among operators, it can't be a bad idea to offer both alternatives to as many of your customers as possible. In the coming years, the debate will become redundant as the introduction of Euro 6 will force just about every truck and engine manufacturer into using both EGR and SCR.