A grudge car is a term used to describe a racing vehicle that has been specifically built for the purpose of competing in illegal street races. The cars are often highly modified with advanced engine, suspension and aerodynamic components to give them an edge over their opponents on the track. These modifications can range from simple bolt-on parts such as cold air intakes, exhaust systems and ECU tuning, to more complex upgrades like turbochargers or nitrous oxide systems. They also have special touches such as wild paintjobs and body kits designed to make them look flashy on the streets. Grudge racers typically compete against each other in short sprints where they try to outrun their opponent through speed alone rather than cornering ability or technical skill. It's a dangerous pastime due to the high speeds involved but it's become increasingly popular amongst hardcore enthusiasts who want something truly adrenaline-filled.