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Most powerful 4 cylinder: 421-hp Mercedes-AMG GLA 45 4MATIC+

If you've been hesitant to buy a little 4-cylinder because you thought it won't have enough get up and go, the new 2021 Mercedes-AMG GLA 45 4MATIC+ could change your mind. Its 2.0-liter engine -- each one built by hand -- is the most powerful series-produced 4-cylinder turbo engine out there. This is not your average about-town five-seater. It's a sophisticated luxe-sport race car in compact SUV guise.

This is the second generation of Mercedes' compact sports model. It is available in two output and torque versions: the base model 387 hp and the 421-hp S-variant. Both will give many larger-engine models in their class some stiff competition. The S does 0 to 62 mph (100 km/h) in 4.3 sec. The base model is only .1 sec slower. Top speed of the S is limited to 168 mph.

The new engine excels with numerous intelligent design features. According to Mercedes, "In contrast to the likewise transversely installed four-cylinder in the 35-series models, the new engine has been turned around its vertical axis by 180 degrees." This means the turbocharger and the exhaust manifold are now positioned at the rear, on the side of the firewall when viewed from behind. The intake system is positioned at the front. This configuration allows for the flattest possible and most aerodynamically advantageous front section design. Furthermore, the new arrangement improves air ducting with shorter distances and fewer diversions, both on the intake and exhaust side.

The new twin-scroll turbocharger combines optimum responsiveness at low engine speeds with high power in the upper rpm range. The shaft of the compressor and turbine wheel is mounted for the first time on anti-friction bearings, minimizing mechanical friction in the turbocharger. The charger responds even more readily and reaches its maximum speed of up to 169,000 rpm more rapidly. With a maximum charge pressure of 2.1 bar, the 2.0-liter four-cylinder turbo engine is also the leader in its segment in this respect. The electronically controlled wastegate (exhaust relief valve) allows the charge pressure to be controlled even more precisely and flexibly while optimizing responsiveness, especially when accelerating from partial load. Numerous parameters are taken into account in this process.

For the first time, the new high-performance 4-cylinder has two-stage fuel injection. In the first stage, the particularly fast and precisely operating piezo injectors supply fuel to the combustion chambers at a pressure up to 200 bar. This is a multi-step process at times, and is controlled by the engine management system as required. In the second stage, there is additional intake manifold injection using solenoid valves. This is needed to achieve the engine's high specific output. The electronically controlled fuel supply has an operating pressure of 6.7 bar.

The high output requires an intelligently conceived cooling system. With this design, the cylinder head and crankcase can be cooled to different temperature levels. This innovative measure allows a cold cylinder head for maximum output with efficient ignition timing, and a warm crankcase to reduce in-engine friction. Cooling of the cylinder head is ensured by a mechanical water pump, while cooling of the crankcase is via a second, electrically driven high-performance water pump. After a cold start, this pump remains passive until the engine has warmed up. In operation, it is regulated by the engine control unit so that the crankcase is always cooled according to need.

The new engine is entirely assembled by hand on a newly designed production line in the AMG engine production facility in Affalterbach, Germany, where Mercedes-AMG has raised the "One Man, One Engine" principle and Industry 4.0 processes to a new level.

The 8-speed AMG SPEEDSHIFT DCT 8G dual-clutch transmission also contributes to the car's agile and dynamic character. The gear ratios have been configured so that the driver experiences very spontaneous acceleration in all speed ranges, combined with fast shifting and optimum connections when shifting up. Depending on the selected AMG DYNAMIC SELECT driving mode, the driver receives a specific drive configuration with different accelerator and gearshift characteristics.

The standard RACE-START function allows maximum acceleration from a standstill. It provides partial ignition interruption when changing up a gear, and the automatic double-declutching function when changing down. In "Comfort" mode, the ECO start/stop function is active; the "gliding" function can be selected in the "Individual" driving mode.

Variable all-wheel drive is standard. The AMG TORQUE CONTROL in the new rear axle differential has two electronically controlled multi-disc clutches, each of which is connected to a rear axle drive shaft. With this setup, the power cannot only be variably distributed between the front and rear wheels, but also selectively between the left and right rear wheel. The result is consistently optimum traction, even in adverse road conditions and during extreme cornering maneuvers.

Control of the drive torque to the front and rear axle, and between the two rear wheels, is electromechanical. Mercedes says the main advantages of electromechanical control over an electrohydraulic system is more refined driving dynamics, primarily due to the significantly faster response and speed-independent actuation of the discs over the entire adjustment range.

The characteristics of the all-wheel drive control are dependent on the driving mode and the AMG DYNAMICS setting. In "Basic" and "Advanced," the 4MATIC system is in "Comfort" mode. In "Pro" and "Master" (standard for S-Model, included in the optional AMG DYNAMIC PLUS package for the base model) the 4MATIC system switches to "Sport" mode, for even more agile handling and an even higher threshold for the critical limits.

A McPherson strut design is used at the front axle. Suspension is taken care of by one transverse control arm below the wheel center -- one suspension strut and one tie rod, respectively. The special axle geometry reduces torque steer for exceptional comfort and agile handling. The new aluminum wishbone reduces the unsprung masses, enabling a more sensitive response from the springs. The brake callipers at the front axle are radially bolted -- a technology from motorsport that brings added stability. The front axle carrier is rigidly attached and additionally stiffens the front section.

Other features include an adaptive damping system called AMG RIDE CONTROL that enables the driver to choose between three different suspension control modes, electromechanical AMG speed-sensitive power steering, and six AMG DYNAMIC SELECT drive programs (Slippery, Comfort, Sport, Sport+, Individual, and RACE).

Inside, the standard upholstery is a combination of black ARTICO man-made leather and DINAMICA microfiber with double topstitching in red. Four different leather upholsteries are also available.

Yellow highlights feature throughout the interior on the S-Model, emphasizing the motor-racing character of the more powerful models, an AMG Performance steering wheel in nappa leather/DINAMICA microfiber with contrasting yellow topstitching, a yellow 12 o'clock marking, AMG steering wheel buttons and AMG logo, plus ambient lighting.

In all models, the center console in piano-lacquer look with a touchpad as standard has a further control array with additional switches for controlling the 3-stage ESP, the manual transmission mode, the adaptive damping system AMG RIDE CONTROL, and the optional AMG Real Performance Sound.

Voice control activated with the words "Hey Mercedes" is also on board. Mercedes says its MBUX infotainment system recognizes and understands nearly all sentences from the fields of infotainment and vehicle operation, even if they are expressed indirectly.

And for that true track hound, AMG TRACK PACE (a virtual race engineer) is standard equipment for the S-model and available as an option on the base model. The software is part of the MBUX infotainment system, and it continuously monitors more than 80 vehicle-specific data points (e.g., speed, acceleration, etc.) when negotiating a race circuit. Lap and sector times are displayed, as well as the respective difference from a reference time. Because specific display elements are shown in green or red, the driver is able to see at a glance without reading numbers whether they are currently faster or slower than their best time.

Pricing for the 2021 Mercedes-AMG GLA 45 4MATIC+ has not been released, but will probably come in above the 2019 model, which started at $53,350. There was no 2020 model.

Source: Daimler AG

Published April 2020

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