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> Diesel Exhaust Systems Research Guide

Diesel Exhaust Systems Research Guide

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Publish Date
April 25, 2018

ATS Diesel Performance diesel exhaust rigid industries soflo diesel fabrication specialty forged sema 2017

Performance Diesel Exhaust vs. Factory Diesel Exhaust

The major advantage of a performance diesel exhaust system, such as a Magnaflow exhaust system, over a factory system is the ability to move exhaust flow more easily, creating less strain on the engine to push the exhaust through the system. Increased flow is achieved by two primary methods. First, using mandrel-bent tubing creates a consistent diameter for full-flow of exhaust, where OEM exhausts have points of high-pressure created by pinched tubing that reduces flow. Second, large diameter tubing allows for greater volume to travel through the system with less back-pressure, which in turn helps reduce turbo-lag. Also, a larger diameter tubing is going to create that awesome deep growl that every diesel truck owner is after. A good rule of thumb is that a larger exhaust will create a deeper tone, while a split-dual system will create more of a throaty tone closer to a gas engine.

T-304 vs. T-409 Stainless Steel

Production materials used is another area in which performance exhaust systems outpace the systems used by the factory. The majority of performance diesel exhausts are constructed using T-409 or T-304 stainless steel. Stainless steel is very durable, corrosion-resistant, and looks much better than aluminized steel. Due to lower production cost, aluminized steel is commonly used by automotive manufacturers. While sound and performance are not affected by aluminized tubing, it's more likely to rust and corrode than stainless steel.

What's the difference between aluminized and stainless steel? Aluminized steel is very similar to galvanized steel. Instead of being coated with zinc, the steel is coated in an aluminum-silicon alloy which makes it more resistant to corrosion than steel alone would be. Stainless steel is an alloy created by combining steel with chromium, nickel, and other elements. The combination and ratio of these other elements is what determines the grade.

T-304 vs. T-409 Stainless Steel visual chart

DPF-Back, Cat-Back, Downpipe-Back, and Turbo-Back Explained

DPF-Back and Cat-Back

DPF-back exhaust systems are the most common for diesel trucks made after 2007. In this setup, the exhaust system replaces everything behind the diesel particulate filter to the tailpipe. Some pre-2007 trucks used a catalytic converter. In a cat-back system, everything behind the catalytic converter is replaced.

Downpipe-Back and Turbo-Back

A downpipe-back exhaust system replaces everything behind the downpipe. Since many pre-2007 trucks don't have a catalytic converter, this is a very common style. The only difference between turbo-back and downpipe-back exhaust systems is the inclusion of the downpipe itself. Both will create similar gains in power and efficiency, with a turbo-back system getting a slight advantage because of a wider-diameter performance downpipe. Turbo-back systems create greater increases in power than cat-back or DPF-back systems. Keep in mind, if a truck or SUV was originally equipped with a catalytic converter or DPF, then installing a turbo-back or downpipe-back system will render the vehicle illegal for highway use. The following diagram provides a great visual for the differences between DPF-Back, Cat-Back, Turbo-Back, and Downpipe-Back.

What is a DPF?

Since 2007, diesel trucks used for on-highway applications have been required to have exhaust treatment systems that reduce emissions by screening out large particulate matter. A diesel particulate filter (DPF) is designed to filter soot from the exhaust flow, and then a regeneration process removes the accumulated soot. During this process, exhaust temperatures can reach 932F or higher.

Diesel Particulate Filter cross section

Diesel Particulate Filter

Intercooled Exhaust Tips

Diesel exhaust is hot - much hotter than exhaust created in a gasoline engine. With the required implementation of diesel particulate filters (DPF) to reduce emissions in 2007, temperatures skyrocketed. For the regeneration process to work within a DPF, the internal temperature must hit at least 932F. Driving around blasting out 1,100F exhaust will cause issues, so intercooled exhaust tips came into action. Louvers at the base of the exhaust tip pull in the outside air, which mixes with exhaust and, in turn, dramatically lowers the exhaust temperature exiting at the tip.

aFe Exhaust Tip, 409 Stainless Steel

aFe Exhaust Tip, 409 Stainless Steel

aFe Exhaust Tip, black powder-coated 409 Stainless Steel

aFe Exhaust Tip, Black Powder-Coated 409 Stainless Steel

aFe Exhaust Tip, 304 Stainless Steel

aFe Exhaust Tip, 304 Stainless Steel

Diesel Exhaust Muffler – Do You Need It?

In terms of exhaust volume, diesel engines are naturally quieter than those of gas trucks, and that's why you can get away without a muffler. Most diesel engines produce a distinctive whistling or rattling sound instead of the harsher tones created by a gas engine. While most opt to use a muffler to ensure there is no droning, it's a matter of personal preference.

Diesel Exhaust Muffler cross section diagram

Diesel Exhaust Muffler

Check out products that'll complement your diesel. From the best running boards to tonneau covers to organizational accessories, RealTruck has you covered.

If you've got questions about diesel exhaust or other exhaust components, give our product experts a call at 877-216-5446. We're here to help.