From indirect-injection to XPI efficiency

From indirect-injection to XPI efficiency

Scania launched its first diesel engine in 1936. The company has released a long line of diesels since then, most recently its extra-high-pressure injection (XPI) engines in 2007, employed lately to fuel all of Scania’s Euro 6 engines. 

Scania-Vabis unveiled its first diesel engine in 1936. The indirect fuel-injection engine was one of three options in a new range, alongside a petrol engine and a Hesselman variant (a hybrid between petrol and diesel, using diesel fuel with spark ignition). All three were based on a design that could be easily adapted to the variant and fuel-type required.

Scania-Vabis’ first pre-combustion diesel engine. 6 cylinders, 7.74 litre, 120 hp.

Scania-Vabis’ first pre-combustion diesel engine. 6 cylinders, 7.74 litre, 120 hp.

In the indirect-injection diesel, combustion occurred in two stages. Rather than being injected directly into the cylinder, fuel was injected into a small antechamber where the heat of compression ignited the fuel mixture. Insufficient oxygen meant only partial combustion was possible and the unspent fuel was subsequently expelled as a gas into the cylinder where combustion was completed.

Modular product system

Just a few years later, in 1939, Scania introduced the Royal, a unitary engine. This was the first Scania engine to use modular components and it marked the start of the company’s modular product system. The Royal was available in carburettor and diesel versions.

Scania-Vabis 8-cylinder Royal unitary engine developing 120 hp.

Scania-Vabis 8-cylinder Royal unitary engine developing 120 hp.

Ten years later, Scania-Vabis launched its first direct-injection diesel engine, offering four-, six- and eight-cylinder versions. The eight-cylinder engines were only available for industrial and marine applications. By this time, all engines supplied by Scania-Vabis relied on direct fuel injection. This diesel engine proved to be so durable that it became known as the “400,000-kilometre engine.” Doing such a mileage without overhauling the engine was outstanding for its time and customers managing this were awarded a coveted badge on the radiator grille.

Scania-Vabis direct-injection diesel engine from 1949.

Scania-Vabis direct-injection diesel engine from 1949.

Long service life

Then in 1958, Scania introduced a completely new 10-litre diesel engine that was suitable for turbocharging. The development team’s mission was to design a powerful, yet fuel-efficient, engine. Team members first decided on the power output – 165 hp. They then decided on a peak-output engine speed figure of 2,200 r/min in order to achieve a long service life. Using these two parameters, the team arrived at a displacement of 10.27 litres and this in turn gave them the figures for both piston stroke and cylinder bore. The DS10 was the first turbocharged engine of its kind and was made available for trucks in 1961.

Scania Vabis D10 165 hp 10-litre 6-cylinder diesel engine.

Scania Vabis D10 165 hp 10-litre 6-cylinder diesel engine.

Two years later, an 11-litre version was launched. The turbocharged version, the DS11, produced 220 hp. In 1964, a ten percent increase in power was achieved in the turbocharged 11-litre engine, primarily as a result of an improved fuel-injection pump. The pump was fitted with a fuel-saving pressure regulator, which optimised combustion by matching the volume of fuel released to the oxygen available.

Electronically controlled fuel injection

The first Scania V8 engine was introduced in 1969. The engine was developed continuously over the years and in 1987 Scania launched the 3-series truck range. This featured three new V8 variants, topped by a 470 hp unit with electronically controlled fuel injection.

Scania 470 hp 14-litre V8 with electronically controlled fuel injection.

Scania 470 hp 14-litre V8 with electronically controlled fuel injection.

At the end of the 1990s, several steps were taken to further increase fuel-efficiency. Scania introduced unit-injector engines and in 2001 production began of a new high-pressure fuel injection system that had been developed by Scania and Cummins.

The unit injectors delivered the right amount of fuel at the right instant and at precisely the right pressure. Combustion in each cylinder was individually controlled to minimise both fuel consumption and harmful emissions.

Increased reliability

Each unit injector had its own integrated high-pressure pump that was individually controlled at the point of injection. There was no longer a need for a centralised high-pressure pump or a complex system of pipes to feed each injector. This, in turn, made the system inherently more reliable than previous solutions.

In 2001, Scania introduced a 470 hp Euro 3 version of its 12-litre six-cylinder engine. This was fitted with Scania HPI, a new high-pressure fuel injection system, developed and produced jointly with Cummins. The new engine also featured Scania-developed engine management, as well as turbocompounding, an energy-recycling concept first pioneered by Scania in the early 1990s. The system centred on a turbocompound unit – a second turbo that extracted residual energy from the exhaust gases. This energy was recycled to the crankshaft, boosting output and improving efficiency.

Assembly of Scania 470 hp 12-litre engine with Scania HPI fuel injector.

Assembly of Scania 470 hp 12-litre engine with Scania HPI fuel injector.

Just a few years later, Scania and Cummins took the next step in further increasing fuel-efficiency by developing the Scania XPI system for extra high-pressure injection. Scania XPI enabled Scania to offer customers outstanding operating economy, performance and driveability.

Euro 5 without exhaust gas aftertreatment

In 2007, Scania introduced a new range of Euro 5 engines. These featured both EGR (exhaust gas recirculation) and the new Scania XPI common-rail fuel injection system and were aimed at the mainstream long-haulage segment. Scania was the first truck manufacturer to achieve Euro 5 without exhaust gas aftertreatment. The V8 range introduced simultaneously featured SCR (selective catalytic reduction) aftertreatment. This was the result of a number of groundbreaking technologies, including a new fuel injection system, which Scania uses to control performance and fuel efficiency.

Scania 13-litre Euro 6 powertrain with integrated silencer and exhaust aftertreatment.

Scania 13-litre Euro 6 powertrain with integrated silencer and exhaust aftertreatment.

For its new range of Euro 6 engines – Euro 6 will be mandatory in the European Union in 2014 – Scania uses its vast experience of EGR, SCR and powertrain control to steer the processes in the complex Euro 6 aftertreatment, along with all other performance-related features.