A high performance exhaust system is one of the easiest and most cost effective modifications you can make to your car. Not only is a high performance exhaust system very effective and affordable, it is also fairy easy to install. These days, due to the rising cost of gas, the subject of gas mileage is on just about every driver's mind. A high performance exhaust system will help increase mileage too.
If it seems too good to be true that a single modification such as an exhaust system would give so many benefits, it is most definitely not. Even better is that so many of the benefits of a well designed performance exhaust system, such as better performance and gas mileage, are usually mutually exclusive. Not the case here, though. Why are so many advantages to be had by simply installing an exhaust system?
It all comes down to the compromises made by the auto manufacturers. They have to balance many things when designing a vehicle; cost, weight, noise, performance, gas mileage, and a myriad of other things such as supplier relationships. In short, they can't give you the best exhaust system available because it would raise the price of the vehicle too much. In addition, they have to abide by EPA noise restrictions and build a vehicle for the broadest number of car buyers. That alone requires compromise. The car, or any of its parts, simply can't be perfect in every respect, for every car buyer.
Once it's your car, on the other hand, you're free to make any improvements you see fit. If a nice, low rumble doesn't bother you, a performance exhaust could be just the answer you're looking for. Like may performance enhancing modifications, the quality of available systems run the gamut from truly pathetic to finely engineered works of automotive art. Where on the spectrum you want to be is determined by your requirements and budget.
Keep in mind that to properly design exhaust system requires specialized knowledge, equipment and experience. If the system is improperly designed, chances are it will make more noise, but no more power or gas mileage. In fact, due to the high level of factory engineered systems these days, you may even hurt your cars' performance with a poorly designed exhaust.
Because they are relatively inexpensive, offer decent performance gains, and is easy to install, most people opt for a system that comprises only the system from the rear of the catalytic converter to the exhaust tip. This is known as a "cat back" system. More performance can be had by installing a complete system from the exhaust manifold to the tip, however. You can even install a high performance catalytic converter to maximize performance and fuel economy.
There are some features you should look for when selecting an aftermarket exhaust system. The first is the type of material it's made of. Any of the better systems will be either coated steel or stainless steel. The standard stainless steel alloy for a high quality exhaust system is T-304, steel alloyed with about 10% nickel and 20% chromium for strength and corrosion resistance.
You may also find exhaust components made from T-409 stainless. While this is a good material, it doesn't have the strength or corrosion resistance of T-304, so it will exhibit discoloration over time and won't last as long as a system fabricated from T-304. T-304 is harder to work with and more expensive to procure, so be prepared to pay a premium to buy a system made from it. As with many things in life, if you want high quality, be aware it costs more.
If you are after the finest quality exhaust system, you may find it's made from T-316L stainless. This has even lower carbon content than T-304, and is used extensively in marine exhaust products, due to its superior corrosion resistance. The absolute best stainless steel material for an exhaust system is T-321 stainless, steel alloyed with the wonder metal titanium. As you might expect, T-321 is extremely expensive, and fairly rare in street exhaust systems, although common in race units, such as IRL and F-1. You'll also find T-321 used in aircraft construction, where the margin for error is small indeed. If you're after a price no object exhaust system, you can have one custom fabricated from Inconel 625, a nickel alloy used in construction of the X-15 rocket research plane. No, unless you're driving a Ferrari, you probably can't afford it.
Another advantage of stainless steel as an exhaust material is that it conducts heat less readily than does mild steel. This serves as a thermal barrier, keeping exhaust heat inside the exhaust tubes. If you are investing in headers or exhaust manifolds made form stainless, the benefit of the lower thermal conductivity will be better exhaust velocity. The higher velocity will give better scavenging, so you'll get more complete exhaust flow out of your cylinders. This means more efficient engine operation, increased power and better gas mileage.
If you're not prepared to pony up for a stainless exhaust system, you can find fine products made from varieties of coated steel, such as aluminized steel or ceramic coated steel. These have some of the properties of stainless, such as corrosion resistance, or, in the case of ceramic coated products, low thermal conductivity.
The next thing to look for in a high performance exhaust is mandrel bending. Mandrel bending ensures the tubes are bent without reducing the diameter, and thus adding restriction. This restriction will hurt exhaust flow, power and efficiency. With mandrel bending, there is actually a piece of tooling (the mandrel) placed inside the tube as it is being bent to prevent the exhaust tube from being reduced in interior diameter. While the best method of forming bends in exhaust tubing, it is quite expensive, and most low priced systems don't use this method. The performance of the finished system will suffer, however. Some estimates are that for a system with 5 bends, mandrel bending reduces exhaust backpressure by about 30%.
A new high performance exhaust system is one of the fastest, most cost effective performance enhancements you can make to your vehicle. In addition, you'll reduce weight, save gas, increase longevity, make it look better, and oh, that sound!
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