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If you’re like most diesel truck owners, one of the first modifications you’ll make to your truck is a high-flowing exhaust system. With a cold-air intake and some kind of performance tuner on that list of first mods, replacing the stock exhaust kit with a mandrel-bent 4-inch system just makes sense. When trying to decide what route to take with your truck, it can be tough to narrow down the field and make the choice that is best for you. The aftermarket exhaust market is huge and there are so many options. Is 4 inches enough, or should you jump to a 5? Aluminized or stainless piping? Single or dual exit? Cat-back or turbo-back? Muffler or muffler delete? Let’s dive into each of those questions a little deeper and hopefully help you make a more educated decision before you fork over your hard-earned cash.


A quality, high-flowing 4-inch exhaust system like this stainless-steel kit from Magnaflow is a great first modification to any diesel truck. The stock system was designed more for sound control than performance, so replacing it with the right aftermarket kit can really help reduce EGTs, improve exhaust flow, and with the right muffler offer great sound without increased in-cab noise.

4 or 5 Inches

When it comes down to exhaust diameter, for 90% of the trucks and owners out there, a 4-inch exhaust is going to flow more than enough exhaust to meet your engine’s needs. A 4-inch exhaust with smooth mandrel bends and a high-flow muffler should be all the average daily driver will require to reduce EGTs and exhaust backpressure. There are 800+ horsepower trucks out there running around with 4-inch exhaust kits, so no worries there. Five-inch exhaust systems are more about sound; the larger pipe diameter will obviously allow for more flow and may show a minor difference when it comes to EGT control, but it isn’t going to be anything substantial.


With dozens of exhaust systems available on the market, making the right choice can be tough. A buyer needs to look into his or her overall needs and wants for the truck, as well as considering budget. For this particular truck, a Magnaflow single 4-inch stainless kit was just the ticket and came with a 5-inch dual-wall tip pre-welded for a perfect fit and finish.


Magnaflow mufflers use a straight flow-through design with a perforated core that allows exhaust and sound waves to enter the muffled section for a fairly quiet, throaty tone at idle and cruise speed. But lay into the throttle and the flow-through design allows exhaust to bypass the muffler for an aggressive exhaust note without the dreaded in-cab drone.


While some owners may be intimidated by an exhaust install, it really is a job most anyone with basic mechanical knowledge can tackle. Getting the stock system out of the truck will be your most challenging task since most aftermarket kits are direct bolt-in replacements that re-use all the factory hangers and require no welding. All you need to do is piece the pipes together in the right order, align everything and tighten up the supplied clamps.

The 5-inch systems are however going to have a much deeper and throatier exhaust note. The aggressive tone from a 5-inch kit will be an attention grabber on the streets, no question, but keep in mind, that may also mean more in-cab drone. If you spend a lot of time on the freeway or towing, a 5-inch system will be more noticeable in the cab and at some rpm may be something even the loudest stereo won’t drown out while cruising. Also keep in mind that a 5-inch system may be tougher to install in some applications due to a tighter fit around crossmembers and over axles, so be prepared to spend a little more time on the installation making sure everything clears and fits just right.

Aluminized or Stainless Steel

While exhaust shopping you’ll see two options for the exhaust material from most manufacturers: aluminized steel and T409 stainless steel, which is also where you’ll see the big difference in price. In talking with Magnaflow Exhaust, one of largest and most popular exhaust companies in the country, we learned the main difference between the two is how it will hold up over time. Obviously, stainless steel costs more than aluminized, but you’ll also see a longer lifespan from stainless. Magnaflow’s stainless steel mufflers offer a polished stainless-steel shell and are 100% stainless construction inside, whereas their aluminized mufflers use the same stainless internals and necks but use an aluminized outer shell to save on cost. Aluminized steel has a protective coating that if scratched off may lead to premature rust and corrosion, whereas stainless steel will never rust. Depending on the climate and road conditions where you drive, this can have a major effect on your overall choice of material. With a Magnaflow system, you’ll see no difference in performance or sound between the stainless and aluminized kits, but how that system holds up over a few winters will be significantly different.


On the Magnaflow system used on this truck and in most performance kits, each section of pipe will be expanded and notched on one end to allow the end of the next piece to slide right inside it. Supplied clamps will hold everything together, creating a leak-free coupling joint.


One thing that will set some exhaust systems apart from the next is the quality of the fabrication, bends, and piece parts supplied. While some of the cheaper “budget” systems will give you that 4-inch flow, the clamps and hangers will be simpler. This Magnaflow system fits as good as the stock piping did and uses hangers that will fit and hold up better than stock.

Single or Dual Exit

This is purely a personal preference. Since a diesel truck uses a turbocharger that gathers exhaust from every cylinder, a dual-exit exhaust will still come through a single pipe off the turbo, and most split to the dual tailpipe after exiting the muffler, so there will be no performance gains in going duals over single. It’s all about looks and sound at this point. But choosing between a single tailpipe or dual tailpipe kit won’t be your only option when it comes to the final look. In an effort to build something to fit everyone’s style, exhaust companies offer dozens of tailpipe and tip options these days. The single side exit with a simple polished tip is still great, but you now have the choice from some companies of a single side exit with dual tips behind the passenger rear tire. Some offer an over-the-axle exit, which puts the tip up under the truck and dumps onto the ground directly behind the axle, a great option for lifted trucks or for those who prefer to hide the exhaust completely.

Cat-Back or Turbo-Back

This will really depend on the truck you currently drive. If it was equipped with a catalytic converter from the factory, by law that catalytic converter needs to stay on the truck. Since the catalytic converter will be the real restriction in the exhaust stream now, there may be no need to replace the downpipe section between it and the turbo, so a simple cat-back exhaust may be all you really need. The cat-back system will still offer some benefits thanks to a better flowing muffler, which should offer better sound as well. Pay attention to some companies’ turbo-back cat compliant kits however, as there are some that offer a better downpipe while retaining the factory catalytic converter.


Be sure you know what you’re getting from your exhaust kit when you place the order, some supply a polished tip some don’t. You can order one of any diameter or length, dual wall, rolled edge, slant cut, turn down, black or polished. The Magnaflow stainless system comes with a dual-wall 5-inch tip that is computer welded for the perfect fit and finish under this Duramax.


Every manufacturer will have its own spin on a high-flow muffler. Some offer internal baffles, some have perforated fiberglass packing, some kits won’t have a muffler at all. Again, this is entirely up to what you’re after for sound, resonance control, and budget.


If you’ve ever wondered if 4-inch exhaust would be enough for your truck or if a 5-inch system is needed, this 750hp dyno chart shows a 4-inch kit can handle more than enough exhaust flow. Five inch kits are more about sound, as they’ll give a much deeper and aggressive exhaust note. Which one will best fit your build? It’s really up to you.


Muffler or Muffler Delete

Again, totally personal preference here—how much noise is too much noise for you? Most exhaust companies have developed their own version of a high-flowing muffler in their 4-inch exhaust systems, so going to a muffler delete most likely won’t show much improvement in performance. Take the Magnaflow series muffler for example. Magnaflow’s 4-inch muffler uses a straight-through perforated core surrounded by a mesh that will catch and trap exhaust noise at low rpm and idle, keeping it quiet in the cab and at the tailpipe while cruising or idling. But get a little heavier into that throttle pedal and as engine rpm and exhaust flow increase, the exhaust will fl ow straight through that muffler to give a much more throaty and aggressive exhaust note, letting everyone around know you mean business. Obviously, in a straightpipe (no muffler) system there is nothing slowing those sound waves down and you’re going to get a super aggressive exhaust note, one that’ll be more than enough to wake the neighbors, even at an idle in some applications.

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