Audi A4 B7: Cat-Back Exhaust Reviews and How to Install
Adding a cat-back exhaust to your A4 can dramatically change the performance and the sound of your car.
This article applies to the Audi A4 B7 (2004-2008).
With a high performance exhaust system, the exhaust gasses can leave better and quicker, thus allowing more air and more gas to rapidly enter and exit the combustion chamber. This creates more horsepower, which equates to faster speeds. Aftermarket exhausts are also desired for the sound notes that are produced. Whether or not you are looking for a distinct European high performance sports car sound or a classic American muscle car rumble, the choice of exhaust becomes even more important. With so many brands on the market to choose, how do you decide which company is going to get your hard earned cash? You want to make the right decision the first time, and choosing between power gains and exhaust notes can be exhausting. Use this guide to help make your buying decisions a little easier.
Table of Contents
How to Install a Cat-Back Exhaust
Materials Needed
- Open end wrenches, ratchets and socket set
- Penetrating spray
Step 1 – Get your Audi as high as possible
You'll want to lift your car with a hydraulic floor jack and place on four jack stands at their highest position. If you have access to a lift, even better. Most of us do not, so we'll need to settle for jack stands. You need a good amount of room to work, as the exhaust system goes through just about the largest fluctuation of temperature as possible, as well as exposure to some nasty road grime, salts and other things. Combined, this makes your exhaust system one of the most labor intensive parts on your car to break free from rust and corrosion to disintegration.
Step 2 – Remove the old exhaust
You will need a wrench or a socket set and driver to get some of these bolts loose. You may want to soak these well with a few shots of WD-40 or PB Blaster.
- Remove the bolt at the front exhaust clamp near the cats.
- Remove the two bolts that mount the chassis brace in position. Set the brace or bracket aside.
- From the cats and back, pop all the welded or integrated hangers on the pipes out of the rubber grommets or hangers.
- Make sure you keep control of the pipes, because after the clamp and the brace have been removed, these hangers are the only things left holding it up.
- Pull the old exhaust off from the mid pipe to the tailpipe, including the muffler.
Step 3 – Install your new cat-back system
We'll be installing the new system in sections, since they are brand new and aren't stuck together. Most systems should be plug and play, bolting right on with no modification or welding needed, but your results may vary on this.
- Install the front part of your cat-back, or the mid pipe first.
- Slide the mid pipe into the old section right behind the cats and secure the bolt on the clamp, but don't tighten it down yet. You may need to make some adjustments.
- Insert the hanger for this pipe section into its rubber grommet or hanger.
- Once the first section is in place, install the second section, and you may want to have a helper hold the end up while you install the two bolts at the flange. Some anti-seize on these bolts isn't a bad thing.
- Insert this section into its corresponding hangers.
- Mount the tails and mufflers onto this last section.
- Be sure to use all included hardware, particularly any gaskets supplied for the tail mounting surfaces.
- Secure the bolts at this last flange and hang the mufflers accordingly.
Figure 3. Installing the first section. 
Figure 4. Add the next section. 
Figure 5. Installing the tails.
Step 4 – Tighten down all the bolts and clamps
You have finished installing your new cat-backs; however, you need to go back through and make sure that all your bolts and clamps are nice as well as tight. Make a quick pass and tighten everything down. Lower your car and take her for a spin. Enjoy that sweet sound and the increased horses you just got for only an hour or so of work.
Featured Video: '04-08 Audi A4 Exhaust Installation
Cat-Back System Review
An aftermarket cat-back exhaust system will make a world of difference in the sound and power of your Audi. Determining which to spend your hard earned money on is a daunting task in and of itself. The true sound can only be approximated in a YouTube video, as it is hindered quite a bit by your speaker output for the device you are viewing them on. You really need to be there if the sound is the highest priority for your decision making process. If you are looking for quality, warranty and power considerations or ease of install, you can find many answers below. Use this guide to help your decision along.
AWE |
Magnaflow |
Stasis |
Milltek | |
|---|---|---|---|---|
Price |
$1,100 | $1,200 | $800 | $1,100 |
Piping Size |
2.25" |
2.50" |
2.25" |
2.5" |
Power Gains |
12hp | 10 - 15hp | 5 - 7hp | 12 - 15hp |
Bolt-on? |
Yes | Yes | Yes | Yes |
Warranty |
Lifetime | Lifetime | Lifetime | Limited Lifetime |
Best Value: Stasis
AWE
Price – $1,100
Pipe Size – 2.25"
Power Gains – 12hp
Bolt-on – Yes
Warranty – Lifetime
The AWE cat-back system is perfect for the Audi owner looking for a nice sound, not too loud, but delivers some impressive performance gains. This is a high quality system, with a lifetime warranty and craftsmanship that rivals Magnaflow. Recommended for anyone looking for an increase in performance while maintaining the unassuming stock sound.
Related Video: B7 A4 with AWE Exhaust
Magnaflow
Price – $1,200
Pipe Size – 2.50"
Power Gains – 10-15hp
Bolt-on – Yes
Warranty – Lifetime
The Magnaflow is a very popular and high quality choice to put onto your Audi. The sound is a nice deep rumble, but not as meaty as a classic muscle car. This still leaves a distinct Audi note to it, but the tone is a lot lower and not as tinny. These pipes can contribute up to about 10hp gains or more, which is a nice improvement over stock. Recommended if you are looking for a meaner, deeper tone from your exhaust.
Related Video: B7 2.0TFSI with Magnaflow Exhaust
Stasis
Price – $800
Pipe Size – 2.25"
Power Gains – 5-7hp
Bolt-on – Yes
Warranty – Lifetime
The Stasis cat-back system is perfectly bred for your Audi. These pipes come in touring or racing versions with a distinct difference. The racing will make your ears bleed, while the touring version will give you a much more civilized tone, even at full throttle. While the notes are a bit more tame than the other pipes, they are a bit deeper than the stock setup and will bring a smile to your face out on the super slab. Recommended for those who don't want to spend a ton of money, but still want a little meatier sound and modest performance gains.
Related Video: A4 B7 2.0t with Stasis Exhaust
Milltek
Price – $1,100
Pipe Size – 2.5"
Power Gains – 12-15hp
Bolt-on – Yes
Warranty – Limited Lifetime
For purely sound enjoyment, the Milltek cannot be beat. While this cat-back system is actually quieter than stock when going on the family cruise, it has a secret Dr. Jekyl and Mr. Hyde persona. If you leave the kids at home and stomp her hard, you will find that you have just awoken the beast. These pipes are disgustingly "look at me loud" but they will startle even Sleeping Beauty from her slumber. The notes are only rivaled by the performance increase from these bad boys, as it is dramatically noticeable. Recommended if you are looking to transform your A4 into a loud, mean street machine.
Related Video: A4 2.0TFSI with Milltek Exhaust
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