S you can see the GLA 250e in the parking lot near the Sindelfingen Mercedes- At the end of the factory, one wonders what should be improved on this compact plug-in hybrid. The prototype, which we are allowed to drive in advance, could make a convincing series vehicle, but it will not be on the market until autumn. In fact, Jochen Eck, Head of Complete Vehicle Testing for the Compact Series, is quite satisfied with the state of development. Nevertheless, he has identified a few little things that he still wants to work on. In addition, he says, he is interested in our opinion, which is why we are already allowed to take a lap through the Heckengäu, a nearby stretch of land.
What would Eck want improved? Mainly drive train and brake system; He is particularly interested in fine-tuning the interface where the old meets the new. So where the combustion engine should switch on the electric drive as imperceptibly as possible. And where the hydraulic braking system must smoothly support the deceleration of the electric motor running as a generator.
Always electric in EV mode and without kickdown
Crossfade is what the engineer calls this process and it is part of the supreme discipline of applying a hybrid. Because the braking system must first of all feel competent in order to convey a feeling of absolute security; we know that from numerous tests. In addition, it must be able to be dosed naturally so that the deceleration can run subconsciously and does not attract any comfort-robbing attention. The initial braking using recuperation is particularly difficult to create an authentic feelingAccording to Eck.
We start purely electrically and the battery capacity display promises a range of 53 kilometers when fully charged. During the brief introduction to the technology of the GLA, Eck pointed out to us that the compact SUV actually lets its combustion engine rest without any ifs or buts. If you first have selected the EV mode and second you do not use the kickdown. It's not even necessary, because the four-door whispers so powerfully that we can easily follow the person in charge of Mercedes in front of us on the country road. In electric mode, the recuperation power can be preselected by pulling the steering wheel paddles: In D-- the GLA can almost exclusively be accelerated and decelerated using the accelerator pedal. In D +, on the other hand, it sails, so it rolls along without braking torque as soon as you take your foot off the accelerator.
Of course we also try the Sport position; In this mode the combustion engine always runs - except when stopping, for example at traffic lights. In this case it switches itself on again when driving off. This also shows why Eck would like to have improvements: You can feel a slight jolt; that should still be sanded. Apart from that, the eight-speed dual clutch transmission works harmoniously and inconspicuously during our short trip.
Acoustically conspicuous combustion engine
What is more noticeable is the roaring noise when the 1.3-liter four-cylinder closes Word reports, for example when you are out and about in comfort mode and the GLA as a hybrid determines its dual drive train itself. The supercharged combustion engine comes from the cooperation with Renault and actually drives the basic gasoline engine. Confidentiality is not necessarily his strength.
With its 160 PS and the 75 kW electric motor, this results in a system output of 160 kW or 218 PS and a system torque of 450 Nm. Eck explains the reference to the rather high performance of the hybrid model as follows: A relatively high electric range requires a correspondingly powerful battery that can also deliver a lot of electricity, whichagain in relation to the kW of the electric motor. According to Mercedes, it should take 105 minutes on a 7.4 kW wallbox for the 15.6 kWh battery to charge. The package sits on the vehicle floor under the back seat, which results in a petrol tank that has shrunk to 35 liters.
If you stand in front of the open bonnet, the 1.3-liter engine is offset far to the left. It connects the gearbox, which shares the housing with the permanent magnet synchronous machine. This neatly fills the engine compartment without the units being crowded together. Eck refers here to the willingness to repair, which requires special attention. When working on the overall package, the weight of the hybridized models is also a decisive factor and alleged setbacks can be explained by the requirements of crash safety. At a certain point, the structure of the body can only be stiffened with additional material.