When you first start modifying the B7 A4 platform, its best to know what direction you want to take before starting off on your adventure. Last week we went over intakes and when/if you need one. This week will be the same involving high flow catalytic converters (HFC).

In terms of power goals, the stock catalytic converter is fine for a stage 1 build. Which is generally around the 250-270 wheel horsepower (whp) mark. However, once you enter a stage 2 build it is almost always mandatory to have a HFC. This is due to the increase in boost pressure; the turbo needs an easier path to dispose of the exhaust gases. Without a HFC, the turbo would experience lag and premature wear on the internals.

As far as options go, multiple companies have created their own version of a HFC with varying cell counts. The top three HFC’s for the B7 A4 platform that I have seen were designed by 034 Motorsport, ECS Tuning, and CTS Turbo.

My recommendation to you is to watch some videos on the sound quality of the HFC and get a feel for the sound. If possibly, go out to a car meet, find a B7 A4 owner, and see what is done to their build. I guarantee they will have no issue talking about their Audi.

-Devan

When it comes to the B7 platform, there are various manufacturers that make an aftermarket cold air intake. However, depending on the horsepower you are looking to make, you may not need one.

According to other blogs and just all around research, the stock intake can support around 300 horsepower. Given that most Stage 1 tunes keep you 30-50 horsepower under that mark, they are really not necessary. But once you break into the stage 2 threshold and start making more than 300 horsepower, you will need to upgrade.

Here is the only perk of having a cold air intake under the 300 horsepower; the induction noise. The car makes an amazing sound under boost with the correct supporting mods. Now, most cold air intakes will run you anywhere from $300-500 dollars. So it could possibly be skipped if budget is a concern.