Stock Exhaust Manifold vs Aftermarket Headers
Differences between Exahust Manifolds and Headers
Most people know that replacing their factory exhaust manifold with a set of aftermarket headers is one of the best bolt on upgrades they can do to their car or truck. But many people may not know that headers are built differently than OEM manifolds or that they offer benefits beyond just adding horsepower and torque.
Overview of Stock Exhaust Systems
Nearly all new automobiles roll off the assembly line equipped with an exhaust system that serves the purpose of decreasing noise levels, reducing emissions, and transporting the exhaust gases from the engine to the rear of the vehicle. Every properly designed exhaust system will accomplish these primary goals. Unfortunately, do to production cost constraints most exhaust systems are not optimized for maximum horsepower, torque, miles per gallon, or performance acoustics. The best example of this design neglect is the stock exhaust manifold.
Limitations of Factory Exahust Manifolds
Factory exhaust manifold performance is sacrificed in favor of saving space, decreasing material quantity, and reducing material quality. For example, OEM manifolds are constructed from cast iron, which has the benefit of being inexpensive, but also has many disadvantages. The nature of the casting process limits both the size and shape of the exhaust manifold. Despite its small size, it also creates a very heavy manifold, as anyone who has every lifted a cast iron skillet knows. It is also susceptible to deterioration at the hands of rust and corrosion. These limitations result in an exhaust manifold that is built to the lowest possible price, but that does not optimize the flow of exhaust the gases from the motor. Due to the firing order of each combustion chamber, the exhaust exits the exhaust ports at different intervals that can create back pressure(bad) if not properly tuned by altering each header runner length. Unfortunately, the stock manifolds design joins the pipes together in such a sort distance it is not possible to properly size each runner for optimal performance or even to smoothly transition the bends. Both of these factors contribute to reductions in exhaust velocity, thereby robbing your vehicle of its peak torque and horsepower potential.
Benefits of Headers
Unlike your stock manifold, a set of aftermarket headers are designed to squeeze the maximum amount of performance out of your engine. Instead of cast iron, headers utilize sections of stainless steel, coated mild steel, or aluminized steel circular steel tubing welded together. Some header manufactures even offer space age ceramic coatings to keep your engine bay cooler and boost exhaust velocity by increasing exhaust gas temperatures. Designers of exhaust systems manipulate mandrel-bents in order to smoothly transition each pipe, to equalize the length of each runner, and to direct pressure waves away from the combustion chamber. All these benefits translate into less back pressure and increased exhaust velocity, which increases power and extends miles per gallon. Additionally, headers are tuned to a specific RPM power band. Some headers offer top end performance for drag racing, while others are optimized for low end torque on street rides, and some are in between the two. Headers also offer users larger piping diameters than those found on their OEM manifolds. The larger header size offers benefits to completely stock cars because car makers are generally too conservative with exhaust pipe diameters(smaller diameter = less material) and even larger gains to those who have modified vehicles, whose exhaust pipe diameter is severely limiting power gains of the cumulative effect of their upgrades. Overall, headers give your vehicle improvements in horsepower, torque, and miles per gallon. If you are interested in a set of headers, check out American Racing Headers, Edelbrock, Kooks, PaceSetter Performance, SLP, and all the other header bands shop4exahsut carries.