How Mercedes SL550 crams 600hp into a supercar

image: Flickr via Michael Chambers

Editor’s Note: This article was originally published at on September 19, 2019. It has been republished here with permission.

Ever wonder how a supercar develops so much power (on average, better than any sedan, sedan-mini, or crossover), does all that scooting around in a corner, and still has legroom? Amazingly, it’s all one thing: powertrain optimization.

There are several steps to powertrain optimization. The first step is to make sure you are using only the horsepower you need to drive the car. Next, the powertrain should be tweaked to make it as efficient as possible, but still provide enough torque for you to glide around town. Finally, make sure it’s balanced so that it provides power with the push required, but doesn’t over-provide that big, explosive shove that you need when you’re zooming through a corner.

Depending on your driving style, the latest Mercedes SL550 sedan employs or adapts to each one of those steps.

Image: Roger Kingdom, Mercedes-Benz

For example, to maximize the displacement you need—2.5 liters for the SL550 (2.9L for the SL65 AMG—and thanks to the new, shorter size of the engine, the SL4 and SL5—vs. 2.7L and 3.0L in the past) you can adjust the air intake and compressor to get more supercooled air. This is a common trick for reducing both weight and fuel economy, which can help even out powertrain efficiency. Another common trick is to adjust the amperage of the three cylinders. Currently, Mercedes is using the zero centimeter pitch ignition, which gives the SL550 an additional 83 bhp for each additional cylinder, up to 5.1 by four, rather than the 4.5 required for the SL65. This trick also explains the sudden loud revving of the engine at around 4,000 rpm, which happens when you slow down.

If you want to shift even quicker through your corners, a switch can be placed that increases the rocket like action, and the SL50i also incorporates what’s called a panoramic system. This allows the air suspension and steering to drop to the floor, which means you’re going through the corners a lot more quickly. Similarly, a dial can be set that uses the throttle to alter the gear ratio and the torque converter to adjust the ratio between gears to optimize the driving experience.

Image: Roger Kingdom, Mercedes-Benz

You can also set options to boost the walloping transmission 5 lb-ft per second. A further feature allows drivers to select a different transmission gear in how they want to operate the transmission. Reducing the ratio of the C and B-arm ratios reduces vibration and reduce steering dervishing.

The only brake booster now on the SL550 is driven by a fuel gas generator. As you accelerate out of a corner, the computer applies throttle to the left and the right rear wheel. This can seem a little odd at first, until you realize that it really makes for more stable driving.

Image: Roger Kingdom, Mercedes-Benz

What’s more, the Mercedes SL550 has become a highly understated convertible, making its vehicle look less than the knockabout, Ferrari-sipping silver beast it can be. So, even though it can pack 600hp, it looks and sounds like it might have been made to drive on a park bench, just as people tend to do in real America.

All of that tweaking makes for a ton of power—474 lb-ft on the test car—and a more controlled driving experience. How much fun is it?

It’s definitely worth the $107,000 base price. Our SL550 tested was a $1,152 a month test sticker (SL, body on metal), but that includes $1200 for all maintenance, and $8500 in options. The test was roughly $5,200 more than the sedan-mini version of the SL, but $4,680 less than the AMG SL65, making the price $33,100 before the initial delivery and handling expenses.

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