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A word to the wise is that "more sound does not necessarily equate to more power." There are a number of strategies that can be employed in a muffler to reduce sound. In fact, you could probably write a book on the theory and practice of these strategies. However, it's only important to realize that some of these strategies are more effective than others at sound control. The technology and experience of the exhaust system manufacturer ultimately plays a crucial role in determining if the exhaust will have an acceptable sound to your ears.

There is also a legal aspect with respect to noise emissions in many states. One of the manufacturers that has taken an active role in working with the California Highway Patrol and the California Air Resources Board (CARB) is GReddy Performance Products of Irvine, California. Back in the days, GReddy was the first to support the enthusiast with documentation regarding the compliance of its exhaust systems. Today, a number of other manufacturers also provide this support. If you live in a state that has noise compliance restrictions (and most states have these), be sure to purchase an exhaust system that complies with the noise restrictions to eliminate hassles.

To silence or not to silence. Some performance exhaust systems offer removable silencer inserts. With the silencer inserted, the restrictor helps cut down on noise production. However, the silencer also chokes off power production. Therefore, the silencer must be removed to realize peak performance. While these exhaust systems feature dual-personalities, they are not for all personalities. If you are lazy and you don't want to be swapping inserts in and out depending on your driving intent, you may want to make sure that the insert-style exhaust system is quiet enough for your ears with the insert removed.

We had hoped to include sound testing data of the exhaust systems in this test. However, the standards used for testing don't tell the entire story in our opinion. As a result, we are currently developing testing equipment and our own standard that we will share with the performance community. This testing procedure will log the noise emissions in both a light load and full load cycle. Additionally, we will be recording both in-car and out-of-car readings. By the time we revisit another exhaust comparison we should have our test cell ready to go.

Touch
I touched the exhaust and nothing happened. When referring to touch, you need to consider the contact made between your back and your car's driver seat. Does the exhaust system you've chosen maximize the pressure between your back and seat under acceleration? Without bolting on every exhaust system to your own vehicle and putting a host of sensors on your back hooked up to datalogging equipment, you could look at the dyno graphs and virtual quarter mile performance that we've included in the upcoming pages.

Exhaust systems are like a baseball glove, they need to be broken in to work their best. Believe it or not, a "broken-in" exhaust system will make more power than an identical exhaust system that is new. Hard to believe? We dyno tested our Civic Si with a brand new aftermarket performance exhaust system. Two weeks later, we dyno tested the car again with no other changes except the "broken-in" exhaust. Versus a brand new exhaust, the result was an increase of 1.5 horsepower at the wheels. Due to this phenomenon, we ensured that all of the exhaust systems were new. While this test was conducted under conditions to maximize repeatability and accuracy, this test is what it is. The results are valid for identical vehicles in an identical state of tune. However, the results should also be applicable to like vehicles in similar states of tune. Can you assume that the exhaust system that generate the best performance in this test will also produce the best performing exhaust system for your car? That's up to you to decide. Just consider that while one manufacturer may seem challenged in producing maximum performance for this application, they may produce a top performing exhaust for a different application. Use what you learn in TPR, then call around, ask around and do your research.

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