These guys supposedly did a top speed test, and got to something like 175 MPH, I wonder because when they take off it doesn't seem like they are stepping on the gas pedal very hard, and secondly, Mario Andretti drove a 2003 SL55 AMG for a Motor Trend episode .... at 208 MPH. Something is wonky here.
I know that factory setting for the USA came with a speed limiter programmed into the ECU at 156MPH, but adding a different supercharger pulley and a ECU tune to go with that, removes that limiter. My former R230, a 2004 SL600 had a Renntech tune and the guy I sold that car to, lives in Montana where they have some highways where you can go super fast. He's used his phone with a GPS to track his speed and although the car's speedometer only goes to 160 (LOL) he's had the car up to 178 MPH and says the car still had a LOT of gas pedal left. He brings the car here every summer for a BBQ and pool fest. I haven't seen how fast my SL55 will go, but with an aftermarket supercharger pulley and an ECU tune to go with, I'm sure the 156MPH limiter is gone, and I bet the car will easily exceed 200 MPH.
The episode of Motor Trend where they bring the SL to Mario Andretti was on Youtube, but they had to block it due to Motor Trend copyright. If you use a TOR browser, which makes it appear that you aren't in the USA, you can view that video. Mario absolutely LOVES that SL55!!!!
These cars are so fast already that you don't have to do much at all to make them really stratospheric.

 

Motor Trend is big media. IMHO everything they do is to promote their brand, integrity be damned. I fully expect that they heavily modified this car even though they called it stock. I also suspect that Mario Andretti wouldn't drive an untested car.
Physics suggest that a stock SL55 cannot hit 200 MPH.
An average car needs about 300 HP to reach 150 MPH.
The HP need to reach a higher speed is the THIRD power of the speed difference. So (200/150)**3 is 2.37. Yes, more that double the power (HP) needed to reach 200 MPH than 150MPH.
300HP * 2.37 = 711HP.
A very aerodynamic car might need less, but generally the cars tested reaching 200 MPH all have 700+ HP.

 

I've had my '03 since new. I delimited the car shortly after I took delivery and on an un-named road in an un-named state quite a few years ago....... My SL55 did 202mph. It pinned the 200mph speedo and went a little bit more, before I ran out of road!

It was such a non event and so stable that I reached down and hit the seat massager....... just to say I did!

Taken shortly after said run on one of straightest, most desolate roads in the country...

 

I doubt 202 indicated was really 190mph.

 

Years ago I did the same in my 911 Turbo S....at about 150mph I noticed that the car had more, I did not......

 

With newer tires, I took my 2007 up to 175 mph. That’s faster than my airplane at cruise. The car felt pretty solid, but things were moving fast and I got nervous. The car is stock as far as I know. There was more left in the car.

 

Sounds like the R230 is more aerodynamic than an average car and therefore only needs 250HP (or less) at 150 MPH. Multiply by 2.37 and you get 592 HP.. With a 10-20 MPH tailwind, true 200 MPH might be possible.
I've been reading car magazines since the early 1970s. Companies like Ferrari or Lamborghini always claimed their next car would top 200 MPH, but for decades it didn't happen.
The Ferrari F40 is generally considered the first production car to reach 200 MPH in 1987, although Car and Driver "only" reached 197. Interestingly this car was only rated at 471 HP, but since it was only 44" tall and weighed 3018 lbs versus the SL55 51" tall and weighing 4319 lbs, the F40 was much more aerodynamic and had much lower rolling resistance.

From an AI Overview:

A typical, production-based car generally requires around 250 to 350+ horsepower to achieve a top speed of 150 mph, depending heavily on aerodynamics and gearing. While some lightweight or exceptionally aerodynamic cars can hit 150 mph with less (e.g., ~200 hp), most standard vehicles need higher output to overcome air resistance.

Fun stuff although I doubt I'll ever have a (reasonably) safe opportunity to try a top speed run.
I hope to get back into some 1/4 mile drag racing at the local track this year and get some times in my SL600/SL65. Goal is 11.5.

 

In the world of automotive engineering, aerodynamics plays a critical role in efficiency, stability and performance. Today, wind tunnel testing is standard practice across the industry, but decades ago it was still a developing science. Mercedes-Benz built one of the most advanced wind tunnels of its time and fundamentally changed the way cars were designed.

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