The Truth About 5 inch Exhaust Pipe: Breaking the "Bigger Is Faster" Myth

Walk into any diesel shop, and you'll probably hear something like this: "The stock pipe is too small. Go bigger and you'll make more power." On the surface, it makes sense—an exhaust is just there to let gas out, right? The less restriction, the better?

That logic sounds bulletproof, but it misses a key player: speed.

Exhaust gas doesn't just need to "get out." It needs to rush out quickly. Slow-moving gas is like a crowd backed up at an exit—it just holds everyone else up. That's why blindly upsizing your exhaust can sometimes make your truck feel more sluggish, not stronger. 

Exhaust Pipe Works

When hot exhaust gas leaves the turbo on a 6.7 Cummins, the pipe diameter determines what happens next:

• A smaller pipe (within reason) keeps the gas packed together so it moves fast. That high-speed flow creates a low-pressure area behind it, which acts like a vacuum to help pull the next pulse of gas out of the turbo.

• An oversized pipe gives the exhaust too much room to spread out. The gas slows down and stalls. That vacuum effect disappears, and the engine has to push harder to force the stagnant air out—wasting energy in the process.

4-Inch vs. 5-Inch: What the Numbers Really Mean

Let's look at three real-world driving scenarios and how each system performs.

Highway Cruising

Situation: Empty truck, flat road, 70 mph. This is what most pickups do every day.

Compare:

• This 4-inch exhaust system has a peak exhaust temperature (EGT) controlled within the range of 600°F to 650°F. Throttle response is instant. You barely know the exhaust is there.
• The 5-inch system runs the same EGTs, but turbo response is slightly delayed, and there's a noticeable low-frequency drone in the cabin.

Bottom line: For daily highway driving, a 5-inch pipe gives you zero performance gain and makes the truck less comfortable to drive.

Heavy Towing

Situation: 15,000 lbs behind the truck, a 6% grade, at 65 mph. This is where an exhaust system earns its keep.

Compare:

• The 4-inch system runs EGTs between 1150°F and 1200°F, with a drive pressure-to-boost ratio of 1.2:1. That's well within the safe range and genuinely good performance.
  

• The 4-inch system runs EGTs between 1150°F and 1200°F, with a drive pressure-to-boost ratio of 1.2:1. That's well within the safe range and genuinely good performance.

Bottom line: Yes, there's a difference, but it's not huge. For a 6.7 Cummins, sustained EGTs below 1350°F are generally safe. That means the 4-inch system is already doing the job.

Full-Throttle Runs

Situation: A 150+ horsepower tune, from 0 to 80 mph as hard as it'll go. This is the fun stuff—and also where things can go wrong.

Compare:

• The 4-inch system hits peak EGTs over 1450°F. Backpressure builds noticeably at high RPM, and the turbo starts to feel choked.

• The 5-inch system shines here. It moves that massive volume of hot gas efficiently, keeping peak EGTs between 1300°F and 1350°F. At high RPM, backpressure is nearly zero, and the turbo breathes freely.

Bottom line: This is what the 5-inch system was built for.

Getting to Know the 5-Inch Exhaust System

Reduce Back Pressure

A 5-inch pipe has roughly 56% more cross-sectional area than a 4-inch pipe—and that's not just a number on paper. It represents a real-world increase in exhaust flow capacity. The larger diameter provides a wide, fast pathway for all that hot, high-volume gas to escape almost instantly, minimizing backpressure to the greatest extent possible.

Sound

The 5-inch is a completely different animal. That deep rumble gets noticed everywhere. If you like the attention, that's a win. If you need to start your truck early in the morning without waking the neighbors, it's a problem.

Installation Considerations

Installing a 5-inch exhaust on the rear axle of an L5P truck presents two common physical challenges. The space underneath the chassis is already tight, with the shock absorbers, leaf springs, and spare tire all competing for room. Clearance for the exhaust pipe is extremely limited.

Hanger adjustment: You will typically need to bend or slightly alter them so the pipe sits in exactly the right position, avoiding contact with the frame rail during driving.

Spare tire risk: On many trucks, a 5-inch exhaust ends up sitting very close to the spare tire. If the truck is used frequently for heavy towing, exhaust temperatures will climb extremely high, the sidewall of the spare tire is at real risk of being melted or damaged by the intense heat.

Choosing the Right 5-Inch Exhaust for Your 6.7 Cummins

Whether you own a 2013-2018 or a 2019-2024, whether you want a straight turbo-back replacement or a full delete kit with EGR removal, we have the right setup for you.  

2013-2018 6.7L Ram Cummins 5" Turbo Back DPF Delete Pipe

If you want the purest, most direct exhaust upgrade, this 5" DPF upgrade kit is your answer.

Why choose this system?

• T-409 stainless steel strikes the perfect balance between heat resistance and corrosion protection.This is the practical choice for trucks that actually work.

• What you get is the purest, most direct exhaust path—and that deep, head-turning roar that lets everyone know this isn't a stock truck.

• installation-friendly. It comes with all required clamps, pre-weld contour bent hangers, and stronger flanges.We've taken care of those details so you can focus on doing the job right.

What will you gain?

After installation, you'll feel the difference in torque, throttle response, and fuel mileage. And the sound? Deep, powerful, and unmistakably aftermarket—not the kind of harsh noise that makes you want to turn the radio up to drown it out.

2019-2024 6.7L Ram Cummins 5" DPF Delete Downpipe Back Exhaust

If you're driving a newer truck and want a more flexible, targeted solution, this 5" DPF Downpipe Back Exhaust was designed for you.

Product 1 is a "turbo-back" system—it replaces everything from the turbo outlet back. This one is a "downpipe-back" system, picking up where the factory downpipe ends. For newer truck owners, this is a more flexible option.

Design philosophy: flow above all else

We removed all of them to create a smooth, uninterrupted flow path. Exhaust gas moves through this system like a sports car on an open highway.

Material and build quality

Fully stainless steel construction built to last. We're not using paper-thin material here—you can feel the quality when you pick it up. The OE-style hangers make installation straightforward. 

2013-2018 6.7L Ram Cummins 5" Turbo Back DPF Delete Pipe & EGR Cooler Delete Kit

If you want to go all-in—no second purchases, no second installations, no second shipping fees—this complete kit is for you.

What's included?

T the T-409 stainless steel 5-inch turbo-back exhaust system (with muffler) . It replaces everything from the turbocharger to the tailpipe. Unlike Product 1, this one includes a muffler—perfect if you want 5-inch performance and sound without scaring the neighbors every time you start the truck.

The complete EGR cooler delete kit. It properly reroutes engine coolant to maintain optimal operating temperature. And it improves exhaust flow and speeds up the start-up of the turbocharger.

The bottom line on this kit

After installing this combo, you'll have a 6.7 Cummins that breathes better, spools faster, and runs cooler exhaust temps. This system sounds great and delivers real-world gains in torque, throttle response, and fuel mileage. It's the all-in-one package for serious builders who want to do the job right the first time.

When Should You Actually Run a 5-Inch?

Based on the data and real-world experience, a 5-inch system only makes sense in these situations:

• You've upgraded to a larger turbo

• You're running oversized injectors and high-flow fuel pumps, targeting over 600 rear-wheel horsepower

• The truck is used primarily for drag racing, extreme sled pulling, or other high-load applications where full throttle is the norm

• You don't mind highway drone and you want maximum exhaust volume and an aggressive look
  

A Critical Check Before You Buy

Here's something that gets overlooked all the time: will a larger exhaust pipe actually fit under your truck?

Replacing the stock pipe with a larger diameter can create clearance issues. The exhaust has to snake past suspension components and fuel lines. Check your chassis clearance before you spend a dime.

Step-by-Step Installation

The following steps are based on standard procedures for a 6.7 Cummins.

Preparation

Disconnect the battery. Let the exhaust system cool completely before you start working.

Removing the Stock Exhaust

Unplug all exhaust sensor wiring harnesses. Remove the flange bolts holding the stock exhaust and DPF assembly in place. Take out the DPF assembly and its related vent tubes. Apply lubricant to the exhaust hangers, then carefully work them out of the rubber isolators.

Disconnecting at the Turbo

Use a 15mm socket to remove the four-bolt flange that connects the stock exhaust to the turbo outlet. If you need more room, remove the transmission crossmember. Trim exhaust hangers as needed to get them out of the way.

Installing the New Exhaust

Install the first section of the new exhaust. Align the four-bolt flange with the turbo outlet and loosely fasten it with bolts—don't tighten anything yet.

Connect the second section to the downpipe. Align the slip joint and loosely clamp the connection. Hang the whole assembly using the factory rubber isolators.

Extending the Pipe

Select the correct extension pipe for your truck's wheelbase. Install it between the muffler inlet and the tailpipe.

Tightening

Start at the downpipe (the first section after the turbo outlet) and gradually tighten all V-band clamps and fasteners. After each connection, check clearance and alignment. Make sure the pipe isn't rubbing against the frame rail, suspension parts, or fuel lines.

Final Inspection

• Double-check every clamp, flange, and sensor connection.
• Reconnect the battery. Start the engine and let it idle.
• Check each exhaust joint for leaks—you can feel for airflow with your hand near the joints or use a smoke tester.
• Confirm there are no warning lights on the dash.

Conclusion

A 5-inch exhaust pipe isn't a universal "bigger is better" upgrade—it's a purpose-built tool for extreme conditions. The 5-inch system only truly shines when your 6.7 Cummins is equipped with an upgraded turbo, high-flow injectors, targeting over 600 rear-wheel horsepower, and is primarily used for drag racing or extreme heavy towing—where its ability to move massive amounts of hot gas with near-zero backpressure makes all the difference.

Choosing the right diameter beats choosing the biggest diameter every single time. Not sure which one fits your truck and your lifestyle? Hit www.trucktok.com. Tell us how you actually drive. We'll point you to the right exhaust—no guesswork, no melted spare tires.

FAQs About 5" Exhaust Pipe

Q1: My truck is mostly for daily commuting. Do I really need a 5-inch exhaust?

A1: Probably not. The 5-inch system only shows its true value under extreme conditions: full throttle, heavy loads, and 600+ horsepower. If you're not drag racing or pulling heavy equipment for a living, a 4-inch system is the smarter, more comfortable choice.

Q2: How hard is it to install a 5-inch exhaust myself? Do I need special tools?

A2: For a DIYer with some mechanical experience, the difficulty level is moderate to above average. A 5-inch pipe is significantly larger than the factory pipe, and getting it to fit under the chassis takes time and adjustments. You'll need to check and re-check clearances to make sure the pipe isn't rubbing against the frame rail, suspension parts, or fuel lines. 

Q3: How different is the sound between the no-muffler version and the muffled version?

A3: The difference is significant. The no-muffler version sound is pure, raw, and deep—a full-throated roar that gets loud fast under wide-open throttle. The muffled version still deep and powerful, but the volume is pulled back to a more reasonable level.

Q4: What are the long-term maintenance benefits of deleting the EGR and DPF?

A4: From a long-term maintenance perspective, removing the EGR and DPF systems eliminates several common failure points—specifically, the clogging issues tied to DPF regeneration cycles and the carbon buildup problems caused by the EGR system. 

Q5: If I block the EGR valve, what happens to the DPF?

A5: Blocking the EGR valve prevents exhaust gas from being recirculated back into the intake system. As for the DPF, blocking the EGR valve doesn't directly change its physical condition or structure. However, combustion conditions and exhaust gas composition will change as a result, and that indirectly affects how fast particulates accumulate in the filter.