BMW 135is Exhaust: The Ultimate Guide to Sound and Performance Upgrades
If you own the incredible BMW 135is, you already appreciate the perfect balance of performance and size it offers. It's truly a special car, packing the powerful N55 engine and a slightly more aggressive factory tune than its 135i sibling.
However, many owners feel that the factory setup leaves something to be desired, especially when it comes to sound. If you are looking to unlock that deep, aggressive tone that the N55 is capable of, you need to upgrade your Bmw 135Is Exhaust system.
We're here to walk you through everything you need to know, from understanding the stock system to choosing the perfect aftermarket setup that suits your driving style and budget.
Understanding the Stock Bmw 135Is Exhaust System
Before diving into modifications, it's important to know what you are starting with. The 135is is unique because it came standard with the BMW Performance Exhaust (often referenced as the "PE" exhaust) straight from the factory.
This factory upgrade already provides a significant improvement over the standard 135i mufflers. It features less baffling and generally allows the engine to breathe better, but it is still designed to meet stringent noise regulations.
The N55 Engine and Factory Sound Profile
The N55 single-turbo inline-six is an engineering marvel, known for its smooth power delivery and broad torque curve. When it comes to sound, the N55 naturally has a deeper tone compared to the older twin-turbo N54.
However, the stock performance exhaust on the 135is still keeps the volume relatively low, especially during highway cruising. While this is great for daily commuting, enthusiasts often want more aggression, more burbles, and a louder roar under acceleration.
The Role of the Performance Exhaust Package (135is Specific)
The specific "is" package means you have a valuable starting point. The 135is muffler is sought after by standard 135i owners because it offers a throaty sound without being overwhelmingly loud or producing excessive drone.
For those looking for a slight bump in volume without replacing the entire system, sometimes just upgrading the downpipe while keeping the Bmw 135Is Exhaust muffler can be enough. However, if maximum performance and volume are your goals, a full replacement is necessary.
Choosing Your Perfect Exhaust Upgrade Path
When you decide to move past the factory setup, you are faced with a crucial decision regarding how much of the system you want to replace. This choice often boils down to budget, desired volume, and performance gains.
Do you want a mild change, or are you aiming for a noticeable performance bump with a much louder sound? Let's break down the primary options available for your 135is.
Axle-Back vs. Cat-Back: Which is Right for You?
These two terms define the scope of your exhaust replacement. Understanding the difference is key to managing expectations regarding sound and cost.
The biggest difference is usually the complexity of installation and the resulting volume change. Here is a quick comparison:
- Axle-Back System: This replaces only the muffler section, starting from the rear axle backward. It's generally the most budget-friendly option and easiest to install. It focuses purely on altering the sound profile and tip appearance, offering modest performance gains.
- Cat-Back System: This replaces everything from the catalytic converter back, including the mid-pipes and the rear muffler. This setup offers better flow, a more aggressive sound change, and noticeable horsepower and torque increases, especially when paired with a tune.
If you're happy with the PE muffler but want a slight volume increase, an axle-back is a great choice. If you want the full performance experience, go for the cat-back system for your Bmw 135Is Exhaust.
Top Performance Brands for Bmw 135Is Exhaust
The aftermarket world for the N55 is vast, and many reputable brands offer high-quality exhaust solutions. Choosing the right brand often comes down to the specific sound characteristics you are looking for—some are raspy, some are deep, and some are aggressive.
We've compiled some of the most highly regarded options for the 1-series platform:
- Akrapovic: Known for its exceptional quality, often utilizing titanium construction. It provides a distinct, exotic, high-pitched wail. This is typically the most expensive, premium option.
- Remus: Offers a more profound, deep, and aggressive tone compared to stock. Many Remus systems retain the factory exhaust valve functionality, which is excellent for drone management.
- Eisenmann: Provides that classic, powerful German touring car sound. Eisenmann systems are typically louder than stock and offer a glorious roar under load.
- Active Autowerke (AA): A long-time BMW tuner offering fantastic mid-pipe and axle-back combinations that are popular for achieving a great sound without breaking the bank.
- Corsa: Known for its drone-canceling technology, Corsa is a great choice if you prioritize a loud sound when driving aggressively but need quiet comfort on the highway.
Installation and Tuning Considerations
Once you've purchased your new exhaust, installation is the next step. While an axle-back can often be installed by an experienced DIY enthusiast, a full cat-back system usually benefits from professional installation.
Crucially, if you are upgrading your exhaust for performance reasons, you may need to consider tuning adjustments. Downpipe upgrades, in particular, almost always require software adjustments to avoid throwing error codes.
Dealing with the Electronic Valve
The stock Bmw 135Is Exhaust utilizes an exhaust flap, or valve, typically controlled by the Dynamic Drive Control (DDC) modes. In standard modes, this valve is often closed at low RPMs to maintain quiet operation.
Many aftermarket mufflers eliminate this valve entirely, resulting in a constant loud sound. However, some premium systems integrate the valve or offer optional bypass plugs. If you want the ability to switch between loud and quiet, ensure your chosen system supports the factory valve operation.
Legal and Emissions Compliance
This is arguably the most critical consideration if you are replacing sections before the axle. If you install an aftermarket downpipe that removes the catalytic converter (a "catless" downpipe), your car will no longer be emissions compliant for street use in many jurisdictions.
Even if you choose a high-flow catalytic converter (HFC) downpipe, you must check local regulations. Always be aware of the noise limits in your area, as some aggressively loud exhausts might lead to unwanted attention from law enforcement.
Remember that while cat-back systems generally do not affect emissions, altering the downpipe significantly changes your car's legal status.
Conclusion: Unlocking the N55 Roar
Upgrading your Bmw 135Is Exhaust is one of the most rewarding modifications you can make to this fantastic car. Whether you opt for a mild axle-back setup to enhance the existing PE sound or go for a full cat-back system paired with a performance downpipe, you will transform the driving experience.
The key is to balance the sound you desire with acceptable highway drone levels. Research sound clips, read owner reviews, and choose a reputable brand that aligns with your performance goals. Once installed, that glorious N55 six-cylinder roar will be ready to impress!
Frequently Asked Questions About the Bmw 135Is Exhaust
- How is the 135is exhaust different from the standard 135i exhaust?
- The 135is came standard with the BMW Performance Exhaust (PE), which is a high-flow muffler system. The standard 135i used a more restrictive, quieter muffler. The PE on the 'is' already provides a deeper sound than the base model.
- Will an aftermarket exhaust system void my warranty?
- Generally, no. Under the Magnuson-Moss Warranty Act, an aftermarket part only voids the warranty if the manufacturer can prove that the specific aftermarket part directly caused the failure of a factory component. However, extreme modifications like catless downpipes may complicate claims related to emissions or turbo failure.
- What causes drone on the highway?
- Drone is a low-frequency, monotonous humming noise often experienced at cruising speeds (usually 2000–3000 RPM). It is caused by resonance in the exhaust system. To minimize drone, look for systems specifically designed with anti-drone technology or systems that retain the factory exhaust valve.
- Do I need a tune after upgrading my exhaust?
- If you install only an axle-back or cat-back system, a tune is generally not required, although you may benefit from one. If you replace the downpipe with a catless or high-flow option, a tune (specifically a "downpipe flash") is mandatory to avoid engine check lights (CEL) and ensure proper air/fuel ratios.
Bmw 135Is Exhaust
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