With regard to speed limiters, Mercedes are governed to 155 mph. There is a "gentlemens agreement" among Germany's car manufactures that no car will go faster than 155, regardless of engine size or horsepower. This applies to "passenger cars", not sports cars ie; Porsche. I don't know if AMG Mercedes fall under this self imposed rule. So whether you have a 4,6,8, or 12 cylinder engine, your not going faster than 155, which works out to be about 250 Kph.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member