Author: Lawrence Z, Diesel Performance Specialist at DPFexhaust
For any 6.7L Powerstroke owner performing a delete, the final decision often comes down to one thing: sound. Once you choose a straight pipe setup over the restrictive stock exhaust, the next question is unavoidable: Should I go with the 4-inch or the 5-inch pipe?
Most of what you find online—from quick YouTube clips to forum posts—offers subjective takes on volume. But if you drive your truck daily, or rely on it for long-distance hauling, the difference between a 4-inch and a 5-inch system goes far beyond just volume; it affects in-cab comfort, EGT management, and even low-end responsiveness.
As diesel performance experts, we're here to settle the debate by breaking down the sound characteristics, busting the performance myths, and guiding you to the best choice for your specific needs.
1. The Sound Science: Tone, Volume, and the Dreaded Drone
When analyzing the difference between a 4" and 5" straight pipe on a 6.7L Powerstroke, you are primarily comparing the resonance frequency and the sheer air capacity.
A. Volume (Decibels)
| Feature | 4 Inch Exhaust | 5 Inch Exhaust |
| Overall Volume | Loud. A massive improvement over stock. | Extremely Loud. Noticeably louder than the 4-inch, especially under load. |
| Takeaway | If maximum sound is the goal, the 5-inch wins. If you need a slightly more tolerable volume, the 4-inch is a safer bet. |
B. Tone and Pitch (The Sound Quality)
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4-Inch Tone: Tends to be slightly sharper or more metallic (raspier). The pitch is slightly higher, giving it a more aggressive, cutting sound, especially during hard acceleration.
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5-Inch Tone: Offers a much deeper, bassier, and guttural sound. It moves more air, producing a lower frequency rumble that feels (and sounds) more powerful and "heavy."
C. The Daily Driver Killer: Highway Drone
This is the most critical difference for anyone using their truck for daily commuting or long trips. Drone is the low-frequency humming or resonant sound that occurs when the engine is held at a steady RPM (usually 1800 to 2200 RPM, common highway cruising speeds).
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4-Inch Drone: The drone is present, but due to the pipe's smaller cross-section, the frequency is slightly higher, making it easier to dampen with factory sound deadening or to mask with music.
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5-Inch Drone: The drone is typically significantly worse. The deeper resonance of the 5-inch pipe hits a lower, more intrusive frequency that is extremely fatiguing over long distances. This is the main reason daily drivers switch back to 4-inch systems.
2. Performance Myth Busted: Is the 5-Inch Necessary?
A common sales pitch is that the 5-inch pipe is "required" for performance. This is a myth for 95% of users.
| Performance Metric | 4 Inch vs 5 Inch | Expert Verdict |
| Max Horsepower (HP) | Virtually no measurable difference up to 650-700 HP. | Both systems flow massive amounts of air. Unless you are running custom twin turbos, the 4-inch is not a restriction. |
| Low-End Torque | 4-Inch may slightly retain better low-end torque. | A marginal benefit: the slightly higher exhaust velocity in the 4-inch pipe can aid in spooling the turbo faster at low RPMs compared to the massive 5-inch diameter. |
| EGT Management | Both offer drastically lower EGTs compared to stock. | Both systems are excellent at cooling exhaust gas. Choosing one over the other based on temperature alone is unnecessary. |
Conclusion: Base your decision entirely on sound and comfort. If you aren't building a 700+ HP competition truck, the 4-inch system poses no performance disadvantage.
3. The Smart Choice: Prioritizing Comfort and Aesthetics
Once you accept that performance is largely equal, your choice boils down to your driving habits:
➡️ Scenario A: Daily Driver & Commuter (Recommended: 4-Inch)
If you spend more than 30 minutes a day on the highway, the 4-inch system is your clear winner. If you still crave that deep rumble but want to kill the drone, pair the 4-inch pipe with a high-quality, high-flow muffler or resonator. This combination eliminates the annoying frequencies while preserving the deep tone.
Need to silence the drone? [Explore our premium 4-inch exhaust kits with resonator options].
4" 2011-2025 Ford 6.7 Powerstroke DPF Delete Race Pipe w/Muffler Overview Fit 2011-2019 Ford F250/F350/F450, High-Quality T-409 Stainless Steel
Upgrade Your 6.7 Powerstroke
➡️ Scenario B: Weekend Warrior & Show Truck (Recommended: 5-Inch)
If your truck is primarily a weekend toy, only sees short trips, or is being built purely for sound and visual presence, the 5-inch straight pipe delivers the maximum auditory impact.
Fit 2011-2019 Ford F250/F350/F450, High-Quality T-409 Stainless Steel
Upgrade Your 6.7 PowerstrokeAesthetics: The Tailpipe Factor
Don't forget the exit. A 4-inch pipe can easily be fitted with a 5-inch, 6-inch, or even 7-inch exhaust tip to give the truck that aggressive, beefy rear-end look without suffering the drone of the larger pipe throughout its entire length.
Final Verdict: Which Exhaust is Right for Your 6.7 Powerstroke?
| If Your Priority Is... | Go With This Setup... | Why? |
| Daily Driving & Comfort | 4-Inch Exhaust with High-Flow Muffler/Resonator | Eliminates nearly all drone and keeps the interior quiet enough for phone calls and music while giving you all the performance. |
| Maximum Volume & Deepest Tone | 5-Inch Straight Pipe | Unmatched low-frequency rumble, perfect for show trucks, but be prepared for intrusive highway noise. |
| Heavy Towing Reliability | 4-Inch Straight Pipe (as minimal restriction is needed) | Both are excellent, but the 4-inch can be a marginal benefit for maintaining velocity and low-end torque. |
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