Nitrous is the best thing you can ever install on your car. No, it's not illegal nor expensive. Actually it's the cheapest option per hp gained compared to turbos and super charges.
To make your engine run, your car burns fuel mixed with air. When you step on the pedal what do your do? You Add more gas to the engine. The only problem is the atmosphere doesn't have enough air to burn all the fuel you want, so they invented turbos and super charges that are nothing but turbines to add more air to the engine, but the maximum increase is never more than 40%... So what's the next solution?
Nitrous!
This system is able to add as much as 2000 hp to your engine, provided the engine can handle it! It works like this, when you press the magic button, the bottles will release the nitrous oxide mixture to the engine. When the mixture reaches the engine the molecules will break into oxygen and nitrogen. Can you see the whole picture? N2O to N2 and O2. This will add more oxygen to burn more gas and an intercooler gas to cool the engine so it doensn't melt down with so much burning. Also the lower the engine temperature the bigger the power increase because of the intercooler effect.
With a simple nitrous system you can quickly increase your hp by 40% with no necessary engine modification. If you want to go further you will have to replace the pistons and the manifold or you risk having to walk home!
Next time someone challenges you in a wide open place, don't hesitate, smack'em!
