It's Exhausting
by The Vette Nut's

There have been many articles published concerning the benefits and pitfalls of selecting an appropriate after market exhaust system. In terms of adding performance to an engine the exhaust system falls into one of the top three basics of classic hot rodding which include exhaust, intake and ignition. Besides yielding a significant boost in available horsepower an after market exhaust system can also increase the "cool factor" of your car.

Late model Corvettes are prime candidates for exhaust modifications as they completely lack the growl that is expected from a high performance vehicle. A well balance exhaust growl is music to the ears of any high performance auto enthusiast. Unfortunately when it comes to high performance exhaust systems the auto manufacturers have to take a very conservative approach.

Case in point, the stock C5 exhaust system. On paper the factory exhaust on a C5 is a very well engineered system. The stock system feature large diameter pipes that extend form the manifolds to the mufflers with relatively few bends or obstructions. The aluminized stainless steel construction also makes the stock pipes and mufflers virtually corrosion proof. 

We once had to bring a C5 into a local muffler shop for some emergency welding repairs after hitting an overly aggressive speed bump. The guy's in the shop had never really seen a C5 system up close and didn't believe us when we told them it was stock. They were old school hot rodders and admitted that it would be hard for them to come up with a better system.

The only problem with the stock system is that it's way too tame for a serious gear head. It seems that GM went out of its way to keep the C5 as quiet as possible. The uninspiring exhaust note satisfied federal, local and state requirements. It also appealed to the new majority of Corvette buyers that were more into looks than performance.
The C5 opened up the door to many people who had never previously considered a Corvette purchase. The new C5's rock solid reliability and comfort levels enabled people to use it as a daily driver.

The recent drop in C5 prices is really a testament to just how good this car really is. The C5's recent devaluation is a direct result of an over abundant supply. The C5 had a seven year run; out of that run 246,012 units were produced. The C5 is a victim of its own high standard of quality. For the first time ever GM mass produced a vehicle that was virtually flawless. The price drop can be credited to the fact that most of the C5's out of the 1997 to 2004 production run are still on the road.
This is in stark contrast to past years where only a small fraction of a production run was still in service after five or six years. It's just a simple function of supply vs. demand. Supply is very high and demand has shifted to the C6. For the time being the high supply of excellent quality C5's has depressed prices.

Getting back to the C5 exhaust system, as I have said the stock system is very hard to improve upon. The only thing that it really needs is some more growl. The after market responded to this need with many confusing variations of high end exhaust components. The typical after market system is referred to as a "cat-back" exhaust. This simply means that the entire exhaust system from the catalytic converters to the tail pipes is replaced.

The confusion comes into play when it comes time to choose your tolerance to noise. Most after market systems offer a choice of sound levels. Exhaust sound output levels are usually rated on a scale of one to three. Level one being slightly louder than stock and level three being noticeably louder than stock. 

Most of the high decibel growl associated with all of these systems is most noticeable at idle and under acceleration. At cruising speeds the loud noise tends to mellow out to a low drone. Some people will hate it others will consider it sweet music. Our advice is that if you are not a "hot rodder" at heart stick with the stock system as you may not be happy with the growl.

After market exhaust systems tend to be a little pricy. The typical price for a good system will run you about $1,200. Unless you have your own lift add another $300 for a professional installation. To justify the high price after market producers construct most systems out of polished T304 stainless steel. They offer polished tip styles and as previously mentioned various sound levels.

All the after market systems claim increases in horsepower and torque. The truth of the matter is that if all you are looking for is increased power this may not be the mod for you. A cat-back replacement is not a very good value in terms of horses for the dollar spent. We have never seen more than a 12 to 15 hp increase with any of these systems. Some systems may even cost you a few horses compared to the factory setup.

As far as sound goes we recently installed a complete after market system that registered a quieter exhaust note on a decibel sound meter than the stock system it replaced. That was a real disappointment; we will not divulge the manufacturers name until we get a response from them. In any case most after market systems will deliver a stronger exhaust note at idle and on acceleration.

As you know we tell it like it is. One of our favorite systems is the Corsa cat back pace car exhaust. It has a great sound at idle and acceleration and quiets down at cruise. The fit and finish of the Corsa system is also world class.

One of our readers asked us if there is an easy alternative to a high priced system if all you want is some more sound. As we have said the stock system is a pretty good design. It would be nice if someone came up with a simple mod that would extract more growl out of the stock system. The idea sounded silly to us at first but after thinking about it we came up with a very simple yet effective solution.

The C5's exhaust is unique in that the mufflers are transverse mounted and are located just a few inches from the actual exhaust outlets. This means that in theory a small mod to the muffler inlet pipe could release both back pressure and more exhaust note. We were in the process of a muffler replacement on a C5 so we figured we had nothing to loose by testing our theory out.

Using a simple electric drill and a cutting wheel we made two one inch long cuts into both of the muffler inlet pipes.

It took all of five minutes to complete the two cuts. When we fired up the Vette we were treated to the sweet music of a liberated exhaust system. The note sounded almost as good as most of the milder after market exhaust replacements we had encountered. We decided to take our liberated C5 out for a drive. The exhaust note was considerably louder than stock on acceleration. At cruise things quieted down and there was absolutely no drone or difference from stock.

We decided to take this mod a step further and cut an additional slot in each of the two inlet pipes. Things got interesting as the exhaust note got noticeably more aggressive at idle and on acceleration. We were pleasantly surprised by an only a slightly louder than stock note at cruising speeds.

Take this for what its worth, an experiment. We are sure that the after market people can come up with a hundred different reasons why you shouldn't attempt this modification. To protect ourselves we must add the disclaimer that this type of modification is for off road vehicles only. That being said, make up your own mind on this one. If that $1,200 is burning a hole in your pocket go ahead and buy an aftermarket exhaust system.