Swoboda's turbo electrification lets internal combustion engines breathe easier

Cross Charger aims to meet Euro 7 emissions targets and enhance driving pleasure

Wigensbach/Schorndorf, Germany, March 22, 2022. Internal combustion engines are facing ever more stringent requirements for reducing emissions and fuel consumption, even with drastically reduced development budgets. The electric exhaust gas turbocharger actuator, called Cross Charger, offers vehicle manufacturers a solution: it enables energy savings of up to 10% and cleaner, more powerful gasoline, diesel and hybrid drive systems without "turbo lag" - at manageable costs. The innovation, which Swoboda has realized in cooperation with its technology partners, offers three unique advantages of an electric turbo: a medium-gap electric motor, energy recuperation and a modular additional concept for easy integration. Premium car OEMs are already testing the Cross Charger for series use. The system is also suitable for hydrogen drive systems in passenger cars and commercial vehicles.

From a European perspective, all attention may be focused on all-electric drive trains at the moment. However, from a global perspective, the internal combustion engine is far from obsolete: According to a recent study, it will still be the main drive unit for half of all new passenger cars in 2030 – around 50 million, including hybrid vehicles. It is also indispensable for commercial vehicles. But the internal combustion engine must be significantly improved. "With our Cross Charger, a new electrified solution for exhaust gas turbochargers, gasoline and diesel engines are fit for purpose for the enormous demands they face," says Christian Göser, Managing Director of Sales and Development at Swoboda.

Electrification inspires emotion without increasing emissions

The innovation promotes driving pleasure by temporarily increasing torque and power by up to 80 percent, eliminating turbo lag and increasing acceleration from a standing start by up to 55 percent: With the electric turbo upgrade, the test passenger car reached 55 km/h after 2.5 seconds – with conventional charging, the speed is only 25 km/h. In addition, the Cross Charger can significantly reduce fuel consumption and emissions. In test bench tests, a 2-liter diesel engine consumed up to 10 percent less fuel and emitted 40 percent less nitrogen oxides (NOX). With the Euro 7 standard scheduled to be implemented in 2025, the latter must be significantly reduced, and this after significantly shortened engine warm-up times. Swoboda makes it easier for vehicle manufacturers to achieve these goals: "As many vehicle types and applications as possible can benefit from the Cross Charger, from downsized gasoline engines in plug-in hybrid vehicles to large-displacement diesel engines for commercial vehicles. Therefore, the main development goals were easy installation of the system and relatively low costs," said Göser. Swoboda has achieved this goal through numerous detailed innovations in design and concept, which make the Cross Charger stand out from the electrified series-production turbochargers already on the market.

The original exhaust gas turbocharger can be retained

Thanks to the Swoboda innovation, existing superchargers can be electrified retrofitted. In this case, the actuator is placed in front of the compressor wheel of the turbocharger as a precisely matched additional solution ("add-on"). As a result, it does not have to be developed from the outset as an integrated component of a new, expensive supercharger system. "Up to 90 percent of the components of existing production superchargers can be taken over by our solution. And yet it takes up almost no additional construction space," says Holger Gödeke, Managing Director of the engineering partner G+L innotec, which was responsible for the basic development of the Cross Charger technology.

Furthermore, this additional principle is particularly suitable for turbochargers, which are used to achieve different power variants based on the basic unit being charged: in this case, the Cross Charger provides a power boost for the top engine. In addition, it can also switch to generator mode and perform energy recovery, i.e. converting the unwanted exhaust gas energy into charging current for the battery. The electronic control system developed by Swoboda can be installed directly on the turbocharger as an integrated solution or separately, depending on the installation space available.

The dielectric gap allows the motor to cool

The new installation position of the electric motor in front of the compressor wheel also offers great advantages for the electric motor. There it is exposed to temperatures of up to 120 degrees Celsius. This means that there is no need for complex cooling systems or the risk of demagnetization of the heat-sensitive rotor. Due to the design, the rotating mass of the turbocharger is only slightly increased (< 5%) by the dielectric-gap motor used. This represents an essential difference from conventional concepts: in which the electric motor is located on the bearing between the exhaust gas turbocompressor and the air compressor, one of the turbocharger components subject to the greatest thermal (up to 350 °C) and mechanical (up to 300,000 rpm) loads. However, this conventional solution also increases the moment of inertia by more than 20%, which significantly affects the response characteristics of the turbocharger.

The Cross Charger's electric motor can be located in a more advantageous forward installation position because of its unique design: This so-called medium-gap motor has a large space between the rotor and the stator, so that all the air drawn in can flow through it. As a positive side effect, this also allows for additional cooling of the machine. The greater distance between the main components does not affect the efficiency of the motor - with an efficiency of 95%, it is at the same high level as conventional competitors.

Clean energy draws huge interest

The Cross Charger shares its basic operating principle with other electric turbochargers. In the low load range, i.e. at low engine speeds and low exhaust pressures, when the accelerator pedal is depressed, the electric motor with a power of several kilowatts quickly fires up the intake turbine: the required boost pressure starts "straight from the basement". In addition, the internal combustion engine gains more maximum torque as a result: the current reference turbo engine 2 is enhanced from 380 Nm to 475 Nm, thanks to the Cross Charger alone. This also allows the unit to operate longer in the efficiency-optimised range. This reduces fuel consumption. Especially with the Cross Charger, the efficiency of the exhaust gas recirculation (EGR) is increased and the aftertreatment system reaches operating temperature more quickly. Both significantly reduce NOX emissions, especially in the face of the Euro 7 standard.

The automotive industry is showing a corresponding interest in this innovation: "We are currently in talks with several OEMs. A German premium car manufacturer is testing the Cross Charger for series use in its new generation of internal combustion engines," says Göser. The electrified charging system is also suitable for e-fuels as well as hydrogen applications, whether in the form of fuel cells or modified internal combustion engines.

Image caption: Swoboda's innovative Cross Charger® is an electrified turbocharger that helps to significantly reduce fuel consumption and harmful emissions in internal combustion engines.

Image: Courtesy of Swoboda