What Materials to Use for Motorcycle Exhaust Headersby John Willis
Header material and design are critical to increasing power in four-stroke motors. There is some argument about the best designs and materials, but two things are commonly understood. One, headers that increase flow of spent exhaust gasses tend to build more power. Two, headers that are insulated, keeping the heat from quickly dissipating through the header walls, increase exhaust velocity and prevent cylinder scavenging, which creates more power.
Mild steel is the most common header material and for some applications is the best. Every material is a trade-off between weight, heat properties, ease of manufacture, and durability. Mild steel offers a high value in that it's the least expensive to manufacture, stands up well to heat cycles, and offers high performance, given a good design.
Stainless steel offers slightly better performance because it retains heat better than mild steel and most would say it looks better. The material is more expensive and it is more difficult to work with, making the manufacturing process more expensive. The biggest downside is a poor ability to withstand heat cycles. It is more likely to fail from high temperatures than mild steel.
Ceramic Coated Steel
Ceramic coated mild steel offers better insulating properties than stainless steel and is generally thought to perform better. In most cases, ceramic coated headers would be more expensive, but that's not always the case depending on the complexity of the design. You can expect greater longevity from ceramic coated mild steel. The choice comes down to value for your specific application.
Titanium is the most expensive header material and it's the most expensive to manufacture. It may not be bendable like steel; turns in the titanium may have to be created by TIG welded wedges of titanium tubing which is extremely labor intensive and doesn't flow as smoothly as bent tubing. However, titanium offers the advantage of extreme heat durability for applications such as high rpm turbos. It also weighs less.
- Motorcycle Exhaust image by Billy Tait from Fotolia.com