When someone mentions Audi in the context of modified cars, what comes to mind are generally B8 A4s, B5 S4s, the R8, anything with a 5-cylinder, and the likes. Often far down that list, if it’s even present, is the B6 A4 1.8T Quattro. Not for any intrinsic reasons, it’s a great car and has many of the same aspects that make other Audi models easy to improve in terms of performance. However, because it sits in between the ‘classic’ B5 and the more modern and recently quite affordable B8 chassis, the B6 can be quickly overlooked. Despite its more popular siblings, there is still a ton to love about the rounded styling of the B6 A4 and plenty of performance to be had from the four-cylinder turbo that sits ahead of its front axles. Today, we’re looking at what you can do to make your B6 A4 turn all the heads and remind enthusiasts of why it can be such an incredible platform.
While it only made 170hp from the factory, the 1.8T is perhaps the most commonly modified engine VW/Audi produced and regularly sees nearly 100hp gains from simple bolt-ons and tuning. Planted in the B6 A4 with a manual transmission and the Quattro AWD system, roughly 250hp is nothing to laugh at and will certainly keep up with today’s impressive performance figures from even the most mundane commuter cars. Here’s how to get there in your B6 A4.
Naturally, an improved performance intake is the first step in your quest for more relevant power figures. While we have mentioned this several times, it’s worth noting that a cold air intake by itself isn’t going to be a game-changer. What it will do is allow you to improve the engine in other areas and use all the potential power benefits they will offer. A cold air intake upgrade will help improve airflow and reduce intake air temperatures so you can ensure the 1.8T is breathing enough air to support more power.
The real hero when it comes to intake air temperature reductions is the intercooler. A bigger front mount intercooler on your B6 A4 will help keep your intake air cool with some of the modifications we will add on this list. Though, by itself, the FMIC upgrade will give your Audi a slight bump in performance.
The diverter valve, or DV, releases the pressurized air from your turbo when the throttle is closed to prevent compressor surge and damage to your engine. On the B6 A4’s 1.8T, the DV is a common source of boost leaks and requires replacement when that happens. Fortunately, with an upgraded diverter valve, you can solve that maintenance issue and make a performance improvement with a DV that holds higher boost and will support your other upgrades.
The final physical upgrade that allows you to generate impressive horsepower gains from your 1.8T is a turbo-back exhaust. From the exhaust side of the turbo to the mufflers, a turbo-back exhaust is a complete system. With wider, freer-flowing, and less restrictive exhaust, you can expel exhaust gasses at a greater volume and gain quite a bit of power. However, you will need to upgrade your engine software, but that’s next on the list.
Performance engine software tunes will improve your engine performance on its own, perhaps more than any single upgrade on this list, but its biggest benefit is maximizing the efficiency of all the upgrades we’ve already mentioned. By telling the engine the new capabilities it has with the other upgrades, you can tune the engine to use those upgrades’ performance benefits. Without a software upgrade, your bolt-on modifications won’t offer much in terms of power gains since the engine will not understand how much more it could produce by knowing what those parts can doB.
With a nearly 100hp gain, you’ll need to make a few future-proofing upgrades to handle that additional horsepower. While 250hp isn’t a lot, your B6 A4 wasn’t designed to handle it. Specifically, your clutch and drivetrain mounts weren’t designed to handle it. You will want to replace your factory clutch with a Stage 2+ unit rated at roughly 300 hp/tq to give yourself some headroom.
As for the engine mounts, transmission mounts, and drivetrain bushings, you are losing plenty of your new power to deflection through the factory rubber units. Upgrading to stiffer mounts and bushings allows you to reduce or eliminate that deflection so all your power available is sent to the wheels for a more responsive driving experience.