FULL TECHNICAL STORY: Scania’s new engine platform offers more uptime, longer service life, less maintenance and reduced weight. It is the heart of the new powertrain that offers fuel savings of up to eight percent in total.
It also heralds the introduction of digital mirrors and new interiors – story here
Key points:
- Scania’s new engine represents the cutting-edge of internal combustion engine technology for heavy commercial trucks
- Scania Opticruise with two iterations, the new G25CM and G33CM
- Industry-leading aftertreatment technology behind remarkable fuel savings
- Scania’s low-rev philosophy taken further with an integrated powertrain
- New exhaust system with built-in flexibility regarding position and outlets
- HVO capabilities for all power outputs
- Biodiesel FAME optional for two power outputs
- The sum of what Scania engineers have learned over decades is paired with the latest in engine management, aftertreatment systems and mechanical engineering such as CRB, plus the smooth, high-tech Scania Opticruise
It may all appear to be something of a contradiction but it is not; it is all about limitless know-how and determination.
Magnus Henrikson, Chief Engineer for Scania’s inline engines, guides us through the finer details regarding the main technical solutions. With four different engines and two different Opticruise gearboxes to choose from, the best truck just got even better.
“Developing a new engine platform of this magnitude is a once-in-a-lifetime opportunity for most engine platform engineers,” says Magnus Henrikson, Chief Engineer and the person who has been heading the five-year development process.
“We in the team were given the task of developing an engine platform based on Scania’s low-rev philosophy, capable of exceeding all coming regulations and dealing successfully with all potential competition for the rest of this decade. In my humble view we have accomplished that goal.”
Many contributions
Developing a new combustion engine platform like this from the ground up means combining a lot of existing knowledge with new ways of solving things. Some targets are a given, such as low weight, but during the development process thousands of minor or major decisions contribute to shaping the final result.
And Scania’s engineers had a tough benchmark to start with – Scania’s existing DLU platform has proven its capabilities in countless daily customer operations all over the world, and in hundreds of successful tests
in media.
“We knew from the beginning that dual overhead camshafts (DOHC) in combination with four-valve cylinder head technology and SCR only was a requisite,” says Henrikson. With the DOHC solution in place, we were able to develop the optional Compression Release Brake system to the expected performance level. And precise valve control from overhead cams is also a must for the advanced Scania Twin-SCR system with dual dosing of urea.”
There has been no carry-over from the earlier range to the new one; it’s all been revised.
Everything had to be a perfect fit right from the beginning, with new injectors and an optimised fuel pump. Also the very heart of an engine, the crankshaft, is weight and strength optimized for efficiency and durability; Scania’s new platform is designed and produced with the latest technology and the technical life-length has increased with 30% compared to the previous generation, despite decreased maintenance requirements.
The swept volume is 12.74 litres and the compression ratio is 23:1, which also means that inlets and outlets are of special interest for these high-performing engines. The “breathing” is vital for everything from the efficiency to the actual power output. Scania’s new engines have carefully tuned inlets and outlets, which secure good flow through the engine.
The turbo itself and interface to the manifold have been optimised for the same reasons. The peak pressure inside the cylinders at their combustion stroke is now 250 bar, something that together with the refined injectors secures a very thorough and complete usage of the energy in the fuel.
Scania Twin SCR makes the difference
But when optimising internal combustion engines for fuel efficiency and high power output, one runs the risk of having NOx-related emission challenges; high combustion pressures and temperatures could lead to unacceptable NOx levels. So how does Scania deal with this contradiction?
“Our Scania Twin SCR system, first introduced on the new V8 in 2020, takes care of this very effectively,” says Henrikson. “By injecting a first dose of AdBlue in the close-coupled position to the turbo charger, immediately after the Exhaust Brake Flap where the exhaust gases are still very hot, we dramatically increase the total efficiency of the aftertreatment system.
“The second dose is then injected in the usual position inside the aftertreatment system. But by then the task is easier since the peak NOx level has already been reduced.
“The particulate filter, which is positioned between the two SCR catalysts, is regenerated without post-injecting extra fuel to the exhaust system. All-in-all the Scania Twin-SCR system is a clever way to make the best possible use of the energy in the exhaust stream.”
Scania’s new exhaust aftertreatment system is very compact and can be mounted in three standard positions for increased flexibility for bodybuilders. It can be ordered with different outlet directions with lower outlet velocity thanks to a bigger opening, which is reduces dust problems.
In fact, it is fair to say that the Scania Twin SCR system is the single most important reason behind the impressive fuel savings from Scania’s new engines. It has moved the limits for how thoroughly a modern, clean and sustainable truck engine can be allowed to release the energy in the fuel without sacrificing compliance with the legal aspects of NOx emissions.
In some operations, these engines will reach a thermal efficiency level above 50%, which is remarkable. The new aftertreatment system is a very compact one-box solution and offers increased flexibility regarding its position and outlet directions. This will be particularly appreciated by bodybuilders looking for space on the frame sides.
“We believe that the new aftertreatment system with the Scania Twin SCR solution is of
great interest for our industry,” says Henrikson. “It brings increased efficiency to Scania’s internal combustion engines and ensures that they are compliant with – or even exceed – current and expected emission legislations around the world, for the foreseeable future.”
Low friction and optimised lubrication
Modern-day engines like the new Scania use advanced, ultra-thin long-life oils and disengageable auxiliary systems in order to reduce losses.
But it is equally important that the base design is created with the lowest possible internal friction in mind. In the new engine range, Scania’s engineers have used all their experience to reduce parasitic losses by optimising the systems that make an engine run smooth and at favourable temperatures.
“Everything is geared towards the lowest possible friction, with polished surfaces and fine-tuned fittings inside the engines,” says Henrikson.
“And the cooling system contributes correct cooling at the right spots and at the right time, which is essential for both engine performance and durability. By keeping the operating temperature at optimal levels, based on the actual operation, we make sure that our engines perform exactly as expected while also safeguarding uptime, robustness and the kind of peerless service life that is part of Scania’s offer to our customers.”
Smooth engine brake performance
Scania long-distance trucks have long been renowned for the optional auxiliary retarder braking system. However, the new engine range comes with Scania’s new Compression Release Brake (CRB) auxiliary brake system as an option.
The CRB technology means that many tractor combinations will not need a retarder, as long as the topography is not too hilly. This applies to many of the combinations that form the core of Scania’s sales and
customer base in Europe.
“Retarders will still be needed in tougher operations with higher gross tonnage weights,” says Henrikson. “And I do believe that many of our Scania customers still want to have one on their trucks, regardless of its actual operation. It adds extra safety margins, less maintenance and increased residual value.”
In fact, a truck with the new engine can be equipped with a combination of the traditional exhaust brake (butterfly valve in the exhaust manifold), the new CRB system and a (disengageable) R4700D retarder, creating an auxiliary brake blending system with outstanding capacity for the most demanding operations.
Lower revs at cruising speed
Scania’s successful low-rev philosophy is well-known in the transport industry.
A truck that can cruise at just over 900 r/min will, in most operations, use less fuel. With the new range, Scania is taking this even further.
The powertrain is truly regarded as an integrated unit where the engine, the aftertreatment system, the gearbox and the driven axle are working as a team, monitored by management systems with unique processing capabilities.
To that end, Scania is now introducing a new rear axle with fast gearing options; the fastest one is 1.95:1. The truck will normally try to run in 12th gear though, since that is the direct gear and offers the least transmission losses. The OD is only engaged when the conditions are favourable. This also means that the truck will probably do more shifting than some drivers are used to, in order to optimise the fuel savings.
“The introduction of the new Scania Opticruise last year opened up new possibilities for us,” says Henrikson. “It has a wider spread, with a direct 12th gear and a true overdrive gear on top, which means that we are able to lower the engine revs at cruising speed a bit further. In combination with the fast rear axle gearings, fuel savings of eight percent are possible”.
The new Scania R756 rear axle can be ordered with eight different gearings; the fastest version will give 1.95:1. Having this many gearings to choose is a vital contribution to decreasing the engine revs in long-distance trucks at cruising speed, while the increased spread in the Scania Opticruise gearbox is securing the necessary startability.
First out in the new axle range is the R756, eventually available with eight different options regarding the gearing, the fastest a 1.95:1 version. Thanks to the wide spread in the G25 and G33 gearboxes, there is also good startability with these fast gearings.
But operational factors (such as the average gross tonnage weight and how hilly the would-be roads are) must of course be considered when specifying the truck together with Scania.
Flexible PTOs for all kinds of applications
Scania’s new powertrain range will offer nine power take-off (PTO) solutions, capable of meeting all kinds of customer demands, regardless of application.
They are characterised by their increased performance, reduced drag losses and their vast flexibility when it comes to possible interfaces. They are lubricated via a port at the gearbox, which makes them suitable for tough operations such as hydraulic pumps.
New Scania Opticruise gearboxes; the first one introduced in 2020
Last year, Scania started to introduce a new range of automated gearboxes that eventually will replace all current automated Scania Opticruise solutions.
G33CM was the first member of the new range, and it is now joined by the G25CM, an iteration aimed for slightly lighter operations.
They will both be paired with the new Scania engines: with its stellar capabilities, all Scania Opticruise gearboxes provide a crucial part of the total performance from the new powertrain.
“The G25 and G33 are both indispensable for reaching the results we have achieved,” says Henrikson.
“The Scania Opticruise gearboxes are the enablers, thanks to their spread, for the whole set-up with the engine torque at low revs and the fast axle gearings.”
The automated manual gearboxes under the Scania Opticruise name were introduced in the 1990s. The latest generation, first represented by the G33CM, is some 60 kg lighter than the former ones due to all-aluminium housings and smaller dimensions.
Another key achievement is lowered noise, a prerequisite for meeting legal demands.
Scania’s new gearbox range now consists of two iterations: G25 and G33. They have all-aluminium housings and slightly smaller dimensions, which gives a weight reduction of 60 kg compared to the predecessors.
With less internal friction and a wider spread, they meet the requirement from Scania’s low-rev engines. They contribute to increased fuel savings by being a truly integrated part of the overall powertrain management.
Just like with the new engine range, the oil change intervals were greatly improved, due to higher precision and the use of bigger oil filters and high-quality oil. The new Scania Opticruise gearbox range has already reached customers and media.
During its first months of service (autumn 2020), a G33CM was used in two major comparison tests against tough competition. In both of them it passed with flying colours and received much acclaim for the fast gear shifting and its almost seamless transfer of power.
Scania’s low-rev/high torque philosophy: how it works
Modern-day Scania diesels like the new range offer their peak torque from revolutions just a few hundred r/min above idling – and the torque build-up is very fast from idling.
The massive torque also means that these engines have extreme stamina – they keep on delivering the necessary torque and propulsion effortlessly at RPMs where engines of older generations would long since have demanded downshifts for higher revs.
So how do Scania customers benefit from this?
The simple answer is that less revolutions also means less fuel injections (since a fourstroke engine needs a fuel injection on every fourth stroke).
And when you pair the outstanding stamina from the new engines with the new gearbox, the new aftertreatment system and the new rear axles, you end up with excellent fuel performance since they all work together and are monitored and managed electronically in parallel.
This means that a regular > 40 tonnes tractor-and-trailer combination will typically cruise in 12th direct gear most of the time when laden. It does so by taking advantage of:
1) the torque from the engine;
2) the low transmission losses on the direct gear
3) the fast gearing in the rear axle (made possible by the wide total spread in the Scania Opticruise gearboxes).
And when the truck is lightly loaded or unloaded or going slightly downhill, the low-rev philosophy can be taken even further by engaging the true OD above the 12th direct gear.
