The Mazda MX-5 has never been about outright speed, but cram in an LS7 V8, and then the little roadster will become seriously fast. The owner of a fourth-generation Miata in the hardtop Retractable Fastback specification has been documenting his build on YouTube, culminating with a video shot on the Autobahn with the RF at full tilt. While a standard car will do around 140 mph (225 km/h), this little beast managed to hit 187.4 mph (301.6 km/h).

If you're wondering about how much power the eight-cylinder engine makes, a dyno test from a year ago showed a colossal 514 hp and 675 Nm (498 lb-ft) of torque. That's quite the bump over an ND1 or ND2 Miata, which tops out at just 181 hp and 151 lb-ft (205 Nm) for the facelifted version launched with the 2019MY.

Squeezing in a big V8 has certainly added weight over the four-cylinder 2.0-liter engine while impacting the car’s ideal 50:50 distribution from the factory, but this still must be an impressively light car by today’s standards. Even in the slightly heavier RF flavor, the hardtop Miata weighs around 1,100 kg (2,452 lbs for the US model) in stock form.

The first attempt to smash the 300 km/h barrier didn't exactly go as planned. While the pint-sized roadster was zoom-zooming its way to top speed, the upper windscreen trim flew off at 178 mph (286 km/h). Let's just say the diminutive Mazda wasn't engineered to reach these kinds of speeds. Since the analog speedometer only goes to 150 mph (240 km/h), a professional data logger (Racelogic VBOX Sport) had to be used to accurately measure the vehicle's velocity.

According to the owner, his beefy Miata could've gone even faster as the "speed was steadily climbing" but there just wasn't enough straight road ahead on the famous German highway. Even though it "only" reached 187.4 mph (301.6 km/h), this still might just be the fastest road-legal MX-5 in the world.

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