Friday, January 24, 2014
Define Cat Back Exhaust
Cat-back (a.k.a. "catalytic converter back") exhaust systems are a popular add-on for enthusiasts seeking an increase in horsepower, fuel economy and torque. Additionally, these systems can add personality to any car by making the exhaust note deeper, louder and overall more aggressive. The fact that cat-back exhaust systems do not affect emissions in any way has made them a universally accepted mod in every state in the union.
Definition
An exhaust system has between five and eight basic parts, depending on the car. The system starts at the exhaust manifold(s) or header(s), which combine the exhaust output of the individual cylinders into one port (called a "collector"). The collector can connect to a mid-pipe (which links the manifold and converter) or can feed directly into the converter itself. Everything after that is the cat-back portion, which includes the crossover (on dual-exhaust, V-configured engines), the main tube section and the muffler(s). Some exhaust systems use one or more small intermediary mufflers (called "resonators") in the main pipe to deepen and smooth the exhaust note.
Power Benefits
When it comes to the cat-back, most original equipment manufacturers (OEMs) put far more emphasis on noise level and production cost than engine note and performance. The original pipes (especially on older cars) are often too small to allow exhaust to flow as freely as it could, and stock mufflers can be a significant impediment to exhaust flow. Almost any cat-back system will enhance power, torque over a stock system. These benefits can range from 1 to 2 horsepower on four cylinders to 30 to 40 on large engines with restrictive exhausts.
Fuel Economy
With all the emphasis manufacturers place on fuel economy, it might seem surprising that they dont just install larger exhaust systems in the first place. Cat-back systems help the engine to run more efficiently, which is always good for at least a small boost in fuel economy. Turbodiesel engines generally stand to gain the most; 10 percent improvements in fuel efficiency are not unheard of when used with a freer-flowing air filter.
Design
Aftermarket cat-back systems are generally made of large and free-flowing "mandrel bent" tubing, which doesnt have the flow-inhibiting kinks that most stock systems do. Many dual exhaust systems incorporate an X-pipe crossover to balance exhaust flow for increased horsepower and a smoother-sounding exhaust note. You have a choice of higher flowing fiberglass or steel-packed mufflers (such as those that originally came in the car) or "chambered" mufflers that often yield a quieter and lower exhaust note.
Sound
Although you might be tempted to buy the thinnest and lightest exhaust system on the market, youll probably regret it. Engines (particularly small ones) produce a whole spectrum of high-frequency sound, which vibrates the system and causes it to act like a giant speaker. This "drone" sounds bad and is certain to drive you insane with migraines. Thicker, larger diameter pipes will contain the exhausts high frequency sound and promote propagation of more pleasing low-frequency soundwaves.
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