Mercedes-Benz SL 43 AMG review: Reduced size but improved quality
The SL with a 2-liter engine sounds ridiculous, but it does work - most of the time.
... The electric motor activates the turbocharger before the exhaust gases, reducing turbo lag and improving responsiveness.
What we liked:
Reduced prices and road taxes
The feeling inside the car is just as special when the roof is down
The handling and power are top-notch
What we don't like is:
The drivetrain is not as efficient or stable as the SL 55
I have an R107 SL with a 3.5-liter V8 small-block engine. I love the driving feel of that car – when it's working properly. In addition to my own SL, I have test-driven several generations of Mercedes-Benz cars, and I think that cars in the Sonderklasse class, including SLs, are better equipped with V8 engines.
So, when I saw that the SL 43 was powered by the 45-liter engine of the A2 popular hatchback, I was a little dismissive. How can it live up to the SL and AMG name?
First of all, this engine was not cut and pasted from other Mercedes-AMG models. This hand-built M139 engine comes with an electric exhaust gas turbocharger on the SL 43, which is not on the other M139s. The turbocharger is said to be derived from F1 technology and operates through a 48-volt electrical system that also powers a belt-driven starter generator (RSG). Essentially, the electric motor starts the turbocharger before the exhaust gases, reducing turbo lag and improving responsiveness. The result is 375 hp and 481 Nm, numbers that we are more common with V6 or V8. Sounds a lot more interesting now.
There's no doubt that the SL 43 is powerful. In fact, the thrust created when pressurized is actually a tsunami of torque. However, progress is usually not as smooth as the SL 55 because there are always trade-offs when you're pulling a lot of power out of a small engine. Although the electric motor assists the turbocharger, the turbocharger is still subjected to a huge boost pressure that takes time to accelerate. That is, when the gears are accelerating, the drivetrain is the most powerful, because the car reacts in an almost frantic way when the turbocharger is already activated. In addition, RSG has done an excellent job of smoothing the SL 43's coasting and start-stop.
The AMG 9G MCT is exactly the same as the one used in the SL 55 and features a wet-start clutch instead of a torque converter. Oddly enough, it feels best paired with a twin-turbo V8 and seems to work in harmony. But in the SL 43 things aren't so good, and I suspect it's because it's not so easy to manage all the different boost pressures of the engine. The actual shifts are very fast, but the gearbox is not as responsive to input.
The SL 55's grip is impressive, and the SL 43 has similar characteristics, with powerful steering, front and rear multi-link suspension made of forged aluminum, and lightweight coil springs glued to spring pads (to prevent wear and tear). The previous generation didn't have that tightness, and you feel very confident when you really push.
Like the SL 55, the SL 43 was designed from the ground up by AMG. It features an aluminum space frame and achieves 2+2 seats for the first time since the R129 SL. While rear seat space is still limited, for me, it's still a big plus for the SL because it can accommodate more people at the same time – especially kids. Despite the improved practicality, the torsional stiffness is 18% higher than its predecessor.
Only experts can tell the difference between the SL 43 and SL 55/63 from the outside, with the front trim, rear apron and round exhaust pipes being the main differences. Everything else is exactly the same, including the electric soft top, which weighs 21 kg less (compared to the metal folding roof of the previous model) and the interior, which is both digital and analogue (at least geometrically).
On our island, which has a strict road tax system, the SL 43 is undoubtedly an attractive option for our congested city roads, especially since it also saves you money (cheaper than the SL 55). It turns out that even with a 4-cylinder engine, the SL 43 still feels like AMG. But more importantly, when the roof is lowered, the feeling is still present and correct, which has earned this car the SL badge.