de autos cars

Tuning is adjusting, modding and replacing components of car to improve it's handling and performance.
Tuning should be done only on healthy engine, unless your budget is too big... first take care of engine's "health", or it will only get worse with further tuning.
NA literally means Naturally Aspirated, pressure of air going to the engine is atmospheric, that means no turbo or compressor.
Where to start NA tuning?
-Cat-back - Improving complete sport exhaust system so the engine can "breathe" is somehow a basic for further tuning of a car. Fi of exhaust pipe should be bigger than stock because we want to increase power and more power means more air going through the exhaust.
-Header - right choice of header is more crucial than cat-back itself. You choose between 4-2-1 and 4-1 header (4 cylinder engines)
- de-cat pipe - It's an empty pipe to replace catalyst, which combines together cat-back and header. There are some loses in catalyst due to cleaning filters inside, de-cat pipe saves it. Alternative solution of de-cat pipe for Greenpeace members is sports catalyst. But if you are a Greenpeace member, you probably drive around in a bike, so no tuning needed for you:)
(Toda exhaust system)

- Air intake system - You can change air filter in airbox for some more breathable sport filter, bigger airbox, SRI or CAI intake. SRI (short ram intake) is mounted directly on throttlebody, it only speeds up reaction of engine, doesn't increase power, that's why I recommend CAI (cold air intake).
(AEM CAI)

It's a pipe with air filter on the end of it from throttlebody to a front bumper usually, it intakes cold air, which gives more power to the engine, than warm air under the hood from SRI.
Than u change OEM intake manifold and Throttlebody for bigger sport ones, so more air can come to the engine, it gives more power and torque.
(Skunk2 intake manifold)

(Blox Throttlebody)

That's it for a start of NA tuning, next level is direct intervention of engine, cams, valves, pistons, ECU re-programing, valve springs... we'll get to there soon ;)
Don't forget, more power means bigger speed. Don't just tune your engine and maximize your power output, be sure you are safe, don't forget to upgrade your brakes.
Not enough? Check out some basics of NA modifications directly on engine.