Audi A4s come with a decent amount of stock power, but modifying them is where the real power comes in. If you buy used, Audi A4 1.8Ts have the most available mods, and 2.8s have the least but are more reliable. This is a good way to acquire an inexpensive luxury car and bring it into the realm of high performance automobiles. Some of the common mods include the chip, exhaust, intake, water injection, and turbochargers.
1. Chip (ECU) – For the 1.8T engine you can get around 50 hp for $500 or so, as long as you stick to brand names like Giac. For the 2.8 you can only get an additional 10 or so hp, for around the same price.
2. Exhaust – This is primarily for the sound, although a good flowing exhaust might net you a few extra hp. Neuspeed makes some of the loudest exhausts on the market. Custom exhaust pipes can also sound good, as long as you can find a good custom shop.
3. Test Pipe – Also mainly for sound, although you might get a few extra hp, a test pipe replaces your catalytic converter. The cat converter cleans your exhaust, so if your state has emissions tests you won’t be able to pass them if you have a test pipe installed.
4. Intake – Another sound mod, some of the better brands are Evo and Carbonio, although they can run a bit expensive. Some owners just make their own intakes, but you need to know what you are doing or you may suffer water leaks.
5. Diverter Valve – This should generally be done when you upgrade the chip (above). The stock DV on Audi is cheap plastic, and you will want to upgrade to a good brand such as Forge to handle the added power.
6. Water Injection – This mod injects a mixture of water and methanol into the intake manifold, to cool the intake. This helps cut down on knocking and misfiring. It simultaneously increases the octane rating of your fuel, which can give you added power if you also have a supercharger/turbocharger.
7. Super/turbo charger – This will cost several thousand dollars, and is the most powerful of all the mods you can add. For the 2.8 you will want to go with a PES G2 supercharger. For 1.8T engines the selection is huge; some of the best brand turbocharger are K04 and Elims, among others.
Modding your used Audi can be a fun and rewarding experience. Taking it from a stock 150 hp to 300 hp on your own, and getting a good sound will help bring a so-so used A4 up into the realm of cool, powerful, high efficiency vehicles.