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.
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.
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.
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.
“THE 5-INCH SYSTEMS ARE GOING TO HAVE A MUCH DEEPER AND THROATIER EXHAUST NOTE.”
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.