Exhaust System Basics
Exhaust Product Materials There are a number of materials found in diesel exhaust applications. Some of the materials are appropriate for heavy duty applications and have the mechanical properties to provide good service life. Since materials vary in strength, corrosion resistance, and price, a particular material may be preferred in individual applications and components. Some of the most common materials, their qualities, and their typical uses are listed in the following table. Materials* Used in Qualities Aluminized Mild Steel Mufflers Good Corrosion Resistance Exhaust Components Stainless Steel (with and without aluminized coating) Flexible Tubing Stronger Excellent Corrosion Resistance Mufflers
Backpressure A key performance factor in selecting the proper muffler is backpressure. For the most efficient engine performance it is important to apply a muffler that minimizes backpressure.
Reduced Noise Better Sound Attenuation
Higher
Backpressure
Lower
Better Fuel Economy More Power
Backpressure is the force necessary to flow gasses through the Exhaust system, or the resistance to exhaust flow. System considerations include friction and momentum effects - expansion / contraction / elbows, and velocity head loss at outlet. To minimize backpressure, long tube lengths, small tube diameters, and sudden contractions should be avoided. Backpressure can reduce horsepower and fuel economy. For example, turbocharged diesel engines loose about 0.5% in horsepower and fuel economy per inch Hg backpressure. To help you minimize backpressure, our selection guide provides exhaust flow ratings at 1” (25mm), 2” (51mm) and 3”(76mm) Hg (mercury).
Exhaust components Emissions Products
Chrome
Accessories
Bright Mirror Finish Low Material Cost Temperature Limit 600°F (316°)
Galvanized
Flexible Tubing
Cold Rolled
Accessories
Poor Corrosion Resistance Low Cost
Aluminized steel is the preferred material for traditional diesel exhaust applications. Aluminized steel is a low carbon steel with a thin layer of aluminum alloyed to the surface. The aluminum provides a barrier for protection of the base material. Aluminized steel parts have an ultimate service temperature of 1250°F (677°C) with a continuous duty temperature limit of 1000°F (538°C). This material closely matches the expected service temperatures of diesel engine applications and has excellent corrosion resistance to acidic diesel exhaust gases. Aluminized steel parts provide good field life at a reasonable cost. Series 400 stainless steels are used for many extended service life diesel applications, and often in gasoline applications due to their higher operating temperatures. This material family provides slightly better strength at exhaust system temperatures than aluminized steel.
Conversion: 1.0" (25mm) Hg = 13.6" (345mm)H 2 0
Our muffler spec'ing section outlines the steps you need to take for proper muffler selection.
Structural Another performance factor is the structural durability of the system configuration. Position, mounting support, weight and the type of material that the unit is made from are the key sub-components of system structure. replacement muffler. If you apply a heavier muffler, like one with an emissions device inside, it’s critical to upgrade the hangers, brackets and stanchion with more robust and heavier components. Most exhaust system problems encountered by Donaldson field service are due to improper bracketing and/or use of clamps – not the muffler or muffler construction. For example, the original OE stanchion or chassis mounting components are adequate for a
Type 409 is the most common 400 series stainless
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Medium- and Heavy-Duty Exhaust Products t 3 t 69
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