The Texan tuning, customisation, racing and supercar company has announced its intention to take the new Cadillac CTS-V and turn it into the world's fastest production family sedan.

The standard CTS-V will come with a 640hp 6.2-litre V8 engine when it goes on sale later this year and, according to Cadillac, the result is a 0-100km/h time of less than 4 seconds and a top speed of 200mph.

For most people that would be more than enough, but for John Hennessey and his Hennessey Performance Engineering team, those figures are simply "a good starting point," and he plans to pick up where Cadillac left off.

The Hennessey HPE1000 Twin Turbo CTS-V will be limited to just 24 examples a year but will up the power to 1000hp and in doing so seriously recalibrate its top speed. "I believe that our 2016 Twin Turbo CTS-V will have a top speed approaching 240 mph (386 km/h)," says Hennessey. "I've owned and driven several Cadillac CTS-Vs over the past 5 years. I love the practicality and the ease of driving these cars every day. They are also a great platform from which we can create our own special 4-door supercar."

Bolting two turbos on to an engine will increase the power, and any tuning shop could do that, but Hennessey will be rebuilding the engine to take the extra strain -- so new pistons, cylinder heads and crank shaft -- so that it will continue to work as a daily driver.

The special model will also get some aerodynamic upgrades and some much larger carbon ceramic brakes and, like other special Hennessey editions, some interior customisations, too.

At the moment, another equally American car, the Dodge Charger SRT Hellcat is officially the world's fastest, most powerful production sedan.

Thanks to a supercharged, 6.2-liter Hemi V8 engine under its air-scooped hood, it comes with 707hp on tap and a top speed of 204mph. However, since its launch late last year it seems to have really stirred up the competition, which isn't surprising considering that it has more horsepower on tap than a Ferrari 458 Italia and a higher top speed than any four-door Bentley, Mercedes or Maserati.

And as well as taking the title off the Hellcat Dodge, Hennessey is also planning to offer step-by-step upgrade packages to Cadillac CTS-V owners that will offer more 'modest' 100-150hp power increases over the standard 640hp engine.