Jeremy Clarkson reviews the Mercedes SLR and then brings out a car to compete in a short race. Put your hands together for the Porsche Carrera GT. The Mercedes SLR has a 5.5 liter V8 engine that produces 617 horse power while the Porsche Carrera GT has a 5.7 liter V10 engine that produces 605 horsepower. Watch the brilliant cars race around the Top Gear track.