Exhaust Tech 101: Picking the Right Exhaust for Your Car
If you are looking to replace your current exhaust with an after-market performance exhaust, there are a few things you should take into consideration before spending a few hundred or even a few thousand dollars to quench your performance thirst. The OEM exhaust on your car has but few purposes. One: it reduces the noise from the engine to a low hum, two: it meets the EPA standards for emissions control by filter exhaust through catalytic converters and resonators, and three: it creates a certain level of backpressure to boost your MPG ever so slightly. Most after-market exhausts have two main functions: power and sound.
Now buying a new exhaust for your car is as simple as searching your favorite companies online, flipping through a performance catalog, or even going down to your respective car dealership and talking with a performance specialist about OEM performance systems. The idea is that someone else has done all the research to produce a product and all you have to do is go pick it out and have it installed. This is true only to a certain extent. A true enthusiast will sit down with you to discuss what you expect from your new exhaust in terms of performance, sound, quality, and looks. Some shops will only insist on the "bigger is better" moniker and sell you a 4" mess of pipe big enough to crawl through and pass it off as the best. The theory is sound because the bigger the pipes, the more exhaust can pass through to increase the efficiency of your engine, right? Well, yes and no.
One important aspect of the OEM exhaust is the small diameter to increase backpressure and thusly, increase initial torque. Opening up that restriction does increase the flow enough to promote some top end horsepower gains, but leaves the low end torque less than desirable. For normal, daily driving, this would be a wasted investment and in some states, get you a nice fine to boot for the db (decibel) level. Also, exhaust gasses are very hot. A larger exhaust will actually allow the gasses to cool more so than an OEM system before exiting the rear section. Cooler air is more dense and according to physics, weighs more. So in essence, the larger exhaust moves the exhaust at a higher rate than OEM, yet it does not move it as efficiently.
It is very easy to have the best of both worlds. There are many after-market companies that make exhausts ranging from 1.5" to 5" depending on the application. Some of these companies manufacture performance exhausts that give an OEM look but an aggressive sound with great performance gains. Before purchasing a "vehicle specific" exhaust online or from a retailer, do some research and think about what you want from the system. Companies selling a "vehicle specific" exhaust fail to mention that the whole idea of being specific is that the pipe bends are formed to the exhaust path of the car, NOT that the exhaust is tuned specifically for your application. More often than not the best exhausts are going to be in the upper end of the price spectrum and usually come from a company that has direct affiliation with your cars manufacturer, i.e. Mopar/Dodge, Ford Racing/Ford, Nismo/Nissan, Mugen/Honda, etc.
The best thing to do is research as many manufacturers as possible. Listen to sound clips, read in forums, watch videos (youtube is GREAT for excellent comparison videos of many manufacturers) and talk to enthusiasts at car shows to get their perspective. There are lots of options out there ranging from great budget minded systems to the exotic and expensive. Whatever your need, there is one out there for you.
