8 Things to Know Before Upgrading Your BMW M4 Exhaust

Upgrading the exhaust system on your BMW M4 can be one of the most rewarding modifications—both in terms of performance and driving experience. Whether you're chasing a deeper growl, better airflow, or a few extra horses under the hood, there are some essential things to consider before making the switch. Let’s dive into the 8 things every BMW M4 owner should know before upgrading their exhaust system.

1. Know Your Exhaust Types: Cat-Back vs. Axle-Back vs. Full System

Before anything else, it’s crucial to understand the types of exhaust systems available. A cat-back system replaces the exhaust from the catalytic converter back, including the mid-pipe, muffler, and tips. Axle-back systems only swap the components after the rear axle—mainly the muffler and tips. A full system, which includes headers and sometimes the catalytic converters, delivers the biggest performance gains but is also the most expensive and complex to install.

Pro Tip: If you're mostly after sound and style, an axle-back may suffice. For serious performance upgrades, consider a full or cat-back system.

2. Check Local Emissions and Noise Regulations

Not all aftermarket BMW M4 Exhaust are street-legal, especially in areas with strict emissions or sound regulations (looking at you, California). Some systems remove or bypass emissions components like catalytic converters or increase decibel levels beyond legal limits.

What to do: Research your local laws before purchasing. Look for systems labeled CARB-compliant if you’re in California or other regulated states.

3. Material Matters: Stainless Steel vs. Titanium

Most performance exhausts are made from either stainless steel or titanium. Stainless steel is more affordable, durable, and corrosion-resistant—perfect for daily drivers. Titanium, on the other hand, is ultra-lightweight and has a more exotic look and tone, but comes with a hefty price tag.

Recommendation: Go for stainless steel if you're on a budget or daily the car. Choose titanium if weight savings and exclusivity matter to you.

4. Sound Profiles Vary Widely by Brand

Each aftermarket exhaust system has a unique sound signature. Akrapovič systems tend to be refined and exotic, while systems from brands like Armytrix or Fi Exhaust are more aggressive and loud. Listen to sound clips online, watch reviews, and if possible, hear them in person at car meets or shops.

Don’t just chase decibels—choose a tone and volume level that suits your driving style and preferences.

5. Consider the Need for a Tune

While many axle-back and cat-back systems can be run without a tune, full systems—especially those that remove or modify catalytic converters—often require ECU tuning to optimize performance and prevent check engine lights.

Why it matters: A tune ensures your engine runs efficiently with the new exhaust and maximizes the power gains.

6. You Might Void Parts of Your Warranty

While the Magnuson-Moss Warranty Act protects you from blanket warranty voids, individual components related to your exhaust could still be excluded if they fail as a result of the mod.

Tip: Talk to your dealer or service advisor before making any changes, especially if your M4 is still under warranty.

7. Budget Beyond the Exhaust

Installation, gaskets, clamps, and potential tuning add to the total cost. Some high-end systems also require special tools or additional hardware. Make sure your budget accounts for everything—not just the price of the exhaust kit itself.

Pro Budgeting Advice: Set aside 15–20% extra for unexpected installation needs or adjustments.

8. Resale and Daily Driving Considerations

A louder, more aggressive exhaust might be thrilling at first—but how will it feel during long commutes or in your neighborhood at 6 AM? Think about drone levels, daily driveability, and how the mod could impact resale value.

Balance is key: Some systems offer valved exhausts that allow you to switch between quiet and loud modes, giving you the best of both worlds.

Final Thoughts

An exhaust upgrade can completely transform the personality of your BMW M4—from the way it sounds to how it performs. But diving in without proper research can lead to disappointment or even legal issues. By understanding your options and being aware of these eight key factors, you'll be better equipped to make a smart, satisfying upgrade that complements your M4 and your lifestyle.