Powertrain

(Image: Audi)

A tale of two motors: A Look at Audi’s new plug-in lineup for 2019

Audi is committed to advancing its electrification strategy and this is evident with its comprehensive plug-in hybrid offensive available for order during 2019. That is no more evident than with Audi’s new hybrid variants of the models A8, A7 Sportback, A6 and Q5. These cards provided an electric range of more than 40 kilometers in the WLTP cycle at the Geneva Motor Show. Audi attributes this to different output levels, that provide the customer with a choice between a comfort variant and a sporty performance variant, depending on the model series.

Selection drives plug-in hybrid strategy of Audi. According to Audi, Plug-in hybrids from medium-size SUV to luxury sedan – with Q5, A6, A7 and A8 TFSI e, it is expanding its range of plug-in-hybrids for sustainable mobility. Depending on the model series, Audi stated there is a choice of two variants with different performance and equipment: A comfort model and a variant with a sporty configuration with S line scopes, a more tightly tuned suspension and drive setup with higher boost performance of the electric motor for more dynamic handling. Going forward, the new plug-in hybrid models will carry the “TFSI e” signet. In the future, Audi points out, the “e-tron” label will remain reserved exclusively for electrically driven cars.

Versatility of the two-heart drive concept. The plug-in hybrid electric vehicles (PHEV) create enthusiasm thanks to their versatile character, Audi stated. In electric-only mode, for example, free of local emissions in the city, no range anxiety when driving long distances, sporty and dynamic with the with the power of two hearts from the combustion engine and electric motor working in tandem

The electric-only range of the PHEVs will account for more than 40 kilometers in the WLTP cycle for every model, Audi stated. The hybrid drive concept is designed so that customers can travel on around a third of their usual routes in electric-only mode during day-to-day driving, Audi stated.

All new plug-in-hybrids by Audi use a turbo-charged gasoline engine with direct injection that works together with an electric motor that is integrated in the transmission. A lithium-ion battery beneath the luggage compartment floor supplies the electrical energy. As a result, Audi points out that the electric motor can support the combustion engine during acceleration. The result is high start-off performance and powerful acceleration.

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Let’s talk about recuperation for a moment.  According to Audi, the drive system resembles that of the new purely electrically driven Audi e-tron. From that standpoint, it is designed for high efficiency and maximum recuperation performance. When breaking, the new Audi PHEV models recover up to 80 kW of energy. Moreover, the electric motor handles slight decelerations, the majority of which are predicted to involve everyday traffic. For medium brake applications, Audi states the task is divided between the hydraulic wheel brakes, which perform this task alone only with a deceleration of more than 0.4 g.

Now let’s move to the battery specs. The lithium-ion battery for the A6, A7 and A8 is made up of 104 pouch cells, which are combined in eight modules. It stores 14.1 kWh of energy at a voltage of 385 V. The lithium-ion battery in the Q5 comprises prismatic cells and has the same capacity, Audi states. In each case, the cooling circuit of the battery is integrated in the low-temperature circuit, which supplies the electric motor and the power electronics.

Audi describes the power electronics as performing the critical task of transforming the direct current of the high voltage-battery into a three-phase current for the electric motor. However, when recuperating, it does the opposite. The standard heat pump ensures efficient vehicle climate control and can generate up to 3 kW of heat energy from 1 kW of electrical energy with the waste heat occurring in the vehicle.

Putting it all together requires combing an efficient combustion engine, coupled with a high-performance electric motor that is served by a large lithium-ion battery capacity.

On that note, Audio points out that the A8 with plug-in hybrid drive has a combustion engine and a permanently excited synchronous motor as an electric motor it can depend upon. It is integrated together with the clutch in the eight-gear tiptronic, which passes the torques to the quattro permanent all-wheel drive. Moreover, the luxury liner drives as a 5.3-meter long A8 L variant with an extended wheelbase.

According to Audi, the Audi A7 and A6 models with plug-in hybrid drive use the same powertrain. The battery capacity is identical to that of the Audi A8 PHEV. Taken together, we have an electric motor that is integrated in the dual clutch transmission, while a gasoline engine ensures that there is ample output and torque. Both models are available in two output levels with different boost performance, Audi stated.

The hybrid management of the plug-in-models is designed for maximum efficiency and customer comfort and automatically selects the optimum operation strategy. Start takes place electrically in “EV” mode as standard; the combustion engine is switched on depending on the situation.

The plug-in hybrid models have the following drive modes: “EV,” “Auto,” and “Hold.” With the operating mode button, the driver can select from these three basic settings: Priority for the electric drive, fully automatic hybrid mode or save power for a later phase of the journey. In “Auto” mode, the PHEVs use the intelligent interaction of the electric motor and the combustion engine for maximum efficiency. In “Hold” mode, the drive management controls the powertrain so that the current charge status of the battery is maintained, e.g. for driving later in electric-only mode in urban areas.

Audi offers predictive efficiency assist to make an essential contribution to increasing the electric range and ensuring maximum customer comfort. For this purpose alone, the intelligent drive management integrates the route profile into the control of the powertrain.


(Image: Audi)

The predictive operation strategy then is in position to assess both the navigation data during active route guidance and the information of the predictive efficiency assist as well as of the vehicle sensor system.

Using this information, connected systems create a rough planning for the entire route and fine planning for the upcoming kilometers or miles. As a result, situations are recognized in which the driver should take their foot off the right pedal. This is accomplished by providing the driver with corresponding visual indications on the display and haptic feedback delivered through the active accelerator pedal. At the same time, anticipatory recuperation is initiated.

The driver in context of the drive is another aspect of Audi’s hybrid engineering versatility. The driver can select between the “comfort,” “efficiency,” “auto” and “dynamic” drive modes by using the familiar switches in the Audi drive select dynamic handling system. As a result, a driver is enabled to influence the setup of the drive, suspension, and steering.

Depending on the setting, the thresholds from which both drives work together or the electric motor supplies the boost and thus the maximum torque change when accelerating. In “dynamic” mode, the electric motor supports the combustion engine more intensively with its electric boost performance for maximum dynamic handling.

The active accelerator pedal with variable pressure point for driving in electric-only mode supports the drive with haptic feedback for operation that is as efficient as possible. When the driver removes their foot from the accelerator, the vehicle glides freely in the automatic gear D and in the Audi drive select profiles “auto” and “efficiency” (under 160 km/h), where both the combustion engine and the electric motor are decoupled and switched off. On the other hand, in the S gear and in the “dynamic” profile, the electric motor remains active in deceleration mode and recuperates, i.e. it converts the kinetic energy into electrical energy.

Connectivity powers additional features with the optional Audi virtual cockpit and the MMI display able to present all important notifications concerning electric driving: a power meter, the range and all energy flows.

Consumers might find the first models of hybrids to be somewhat unexciting, but these hybrid cars are sporty and stylish. Audi offers the A6, A7, and Q5 each as comfort models and sporty and dynamic variants. According to Audi, the latter are being launched with particularly sporty equipment: Apart from the increased boost of the electric motor, they have an S line exterior package as standard. In addition, the A6 and A7 have a black styling package with darkened trims, brake calipers painted in red, and privacy window glazing in the rear compartment. The performance hybrids also place sporty touches in the interior. The A6 and A7 have a sport suspension as standard.

The compact charging system is also part of the standard equipment of the new Audi plug-in hybrids and that is good news. This system comprises cables for the domestic and industrial sockets and a control panel. As an added option, Audi supplies the wall-holder clip and a mode 3 cable for public charging stations. At a charge connector with an output of 7.2 kW, a full charge of the battery takes a good two hours.

Out and about, customers can charge the new plug-in hybrid models conveniently. A charging service owned by Audi, the e-tron Charging Service, grants access to many public charging stations in 16 European countries on request with preparations being made to introduce these stations in other countries. It should be noted that just one card is enough to begin charging with numerous providers. To do that, customers must register on the myAudi portal and agree to a charging contract that is subject to a fee. Invoicing always takes place at the end of the month using the stored method of payment.

Making it easier for customers to charge these cars at home, Audi customers can supply their house and their garage with eco-electricity, generated free of CO2 emissions, from the “Volkswagen Naturstrom” brand. This power is generated 100% from renewable sources, such as hydroelectric power plants, and its origin is certified by TÜV every year. In addition, and if necessary, Audi supports customers in getting them in contact with an electrician for implementing a suitable charging solution in their own garage.

Managing your car with the myAudi app provides a practical tool for dealing with the vehicle. The app brings services from the Audi connect portfolio to the customer’s smartphone. Using the app, the customer can remotely check the battery and range status, start the charging process, program the charge timer and view the charge and consumption statistics.

Additional functions of the myAudi app is the pre-entry climate control, which is made possible because the compressor of the air conditioning and the auxiliary heater in the vehicle work on a high-voltage basis. As a result, a customer can determine exactly how the interior should be heated or cooled while the vehicle is parked, or the battery is being charged. Depending on the respective vehicle equipment, heating of the steering wheel, seats, mirror, windshield and rear window as well as the seat ventilation can be activated via the pre-entry climate control too. Rapid start of the climate components is also possible when unlocking the vehicle with the key.

Matt De Reno is SAE MOBILUS web portal manager at SAE International. His interests include automated and connected vehicles, micromobility, smart cities, and automotive cybersecurity.