For BMW M4 Competition (M4 Comp) owners seeking to amplify their driving experience, upgrading the midpipe is a popular and impactful modification. The debate often boils down to choosing between a single midpipe and an equal length (EL) resonated midpipe. As a seasoned automotive technician and content creator at cardiagxpert.com, I’ve delved into the intricacies of both options to help you make an informed decision for your M4 Comp. This article breaks down the key differences based on real-world experience, focusing on sound, performance, and overall driving enjoyment.
The Equal Length (Resonated) Midpipe: High-RPM Screamer?
The allure of the EL resonated midpipe lies in its promise of a refined, high-pitched exhaust note, particularly at higher RPMs. Proponents often describe it as a “clean scream,” reminiscent of high-revving sports cars. Indeed, under aggressive acceleration, an EL resonated midpipe can deliver a unique and aggressive sound profile. Some enthusiasts even draw comparisons to legendary engines like the Honda Integra Type R’s VTEC engagement at high RPMs.
However, the experience isn’t universally praised across the entire rev range. In daily driving scenarios, particularly at lower RPMs and in confined spaces like parking garages, some drivers find the EL resonated midpipe to produce a less desirable “rattling tin can” sound. This can detract from the premium feel expected from an M4 Comp. Furthermore, the effectiveness of an EL resonated midpipe can be heavily influenced by other exhaust components, especially downpipes. There’s a prevailing theory that these midpipes are optimized for use with catted downpipes, suggesting that the intended sound profile might not fully materialize with catless setups.
The Single Midpipe: Deep Tone and Turbo Spool Symphony
In contrast, the single midpipe configuration takes a different approach, emphasizing a deep, resonant tone throughout the RPM range. Especially when paired with catless downpipes, a single midpipe unleashes a raw and aggressive exhaust note that commands attention. At high RPMs, the sound can be described as almost “brassy,” projecting a powerful and unmistakable presence.
The true strength of the single midpipe, however, shines in normal driving conditions. It delivers a deep, satisfying rumble, particularly noticeable at lower speeds and in enclosed environments. A key highlight for many enthusiasts is the enhanced audibility of the turbo spool. The single midpipe allows the distinct sound of the turbos to become a prominent part of the driving experience, creating an engaging and visceral connection with the car’s performance. Subjectively, the positive reactions from onlookers, the “nod” of appreciation, suggests the single midpipe delivers a sound profile that resonates with car enthusiasts beyond just the driver.
Performance Implications: Dyno Results Speak Volumes
Beyond sound, performance is a critical factor when modifying your M4 Comp. Real-world dyno testing has revealed a potential downside to the EL resonated midpipe in terms of power output. In one documented case with a tuned, turbo-upgraded S55 engine (the engine in the M4 Comp), switching to an EL resonated midpipe resulted in a measured power loss of 7-22 WHP (wheel horsepower).
The likely explanation for this power reduction lies in the design characteristics of the EL resonated midpipe. The “resonated” aspect, combined with the equal length design, inherently creates a slightly more restrictive exhaust path. This increased backpressure, while potentially contributing to the refined high-RPM sound, can also hinder turbo spool and ultimately limit power output.
Conversely, single midpipes are often associated with performance gains. Manufacturers frequently highlight “quicker turbo spool” and “increased low-end and mid-range power” as benefits of single midpipe designs. This is consistent with the principle that less restrictive exhaust systems generally promote better turbocharger efficiency and power output. The original manufacturer’s product descriptions themselves support this observation by not claiming any power gains for EL midpipes while explicitly stating gains for single midpipes.
Installation and Fitment: A Practical Consideration
Practicality also plays a role in choosing a midpipe. The EL resonated midpipe, due to its more complex design and resonators, can present installation challenges. Achieving proper fitment without rattling can be a time-consuming process, potentially requiring multiple adjustments and heat cycles to settle correctly.
Single midpipes, on the other hand, are generally considered easier to install. Their simpler design often translates to a more straightforward fitment, minimizing potential issues like rattling and reducing installation time. In some cases, switching back to a single midpipe from an EL design can feel like a significantly easier and less problematic process.
Conclusion: Choosing the Right Midpipe for Your M4 Comp
Ultimately, the best midpipe for your M4 Comp depends on your individual priorities. If your primary focus is achieving a refined, high-pitched scream at high RPMs and you are willing to potentially compromise on low-end sound depth and potentially experience a minor power reduction, the EL resonated midpipe might appeal to you. However, if you prioritize a deep, aggressive exhaust note across the rev range, enhanced turbo spool sound, and maximizing power output, the single midpipe emerges as the stronger contender. For most M4 Comp owners seeking a balance of exhilarating sound and optimal performance, the single midpipe is often the preferred and more rewarding choice.
