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Corvette Exhaust Tech Article

Corvette Exhaust Tech Article
A definitive part of being a muscle or sports car is the exhaust tone that they produce. Corvettes are no exception to this rule and have their own distinct tone, different from mustangs and lamborghinis and everything in between. The purpose of the page is to describe the components that create the exhaust system, and in doing so what each part of the system does and also to explain the overall importance of the dynamics that create the exhaust tone you love to hear when you mash that go pedal to the ground and unleash the power of your corvette.
 

Corvette Exhaust System





Manifold | Crossover Pipe | Catback System
Absorption | Restriction | Reflection


Corvettes are not unlike any other car when it comes to the basics. This means that the Corvette runs a similar exhaust layout to other cars, consisting of an exhaust manifold, crossover pipe and a cat-back or axle-back exhaust system from the factory. Below these are broken down into their respective sections, and remember that the function of the exhaust system is to guide exhaust gases from the car as quickly as possible. So, without further ado let’s talk some shop.

Exhaust Layout




Manifold -
From the factory all Corvettes come with an exhaust manifold that bolts to the cylinder heads and takes the exhaust gases away from the motor. Most aftermarket replacements are known as shortie and long-tube headers. The difference between an exhaust manifold and headers is in the design. Headers give each cylinder of the motor its own exhaust port to release the gases which are then joined in the collector, while a manifold has multiple cylinders sharing a larger collector. On the surface this seems like the manifold would create more power because it has a larger port, but this actually creates excess backpressure and hinders performance. A good way to think about backpressure is as a form of turbulence in the exhaust pipes where the gases get turned in the wrong direction and hinder other gases from escaping.

The issue of backpressure affects the entire exhaust system and both shortie and long-tube headers will help eliminate this. Shortie headers have individual ports for each cylinder but have their collector within a short distance from the exhaust port, hence its name. The long-tube headers as you might expect have the individual ports for each cylinder but the collector is located further away from the exhaust port on the cylinder headers. This results in less back pressure because each exhaust port gets to flow freely from the cylinder head without interference from the other exhaust ports for a longer period of time. This is why upgrading from the stock manifold to a shortie or long-tube header for your Corvette will release lost horsepower that your bow-tie was being robbed of. Carrying this throughout your entire exhaust system will net a fair gain in power over your stock exhaust system.

Crossover Pipe -
Connecting your headers or manifold to the cat-back is the crossover pipe, designed in either an X or H shape. This part of the exhaust system serves two purposes. First is to balance the exhaust pulses, since your Corvette doesn’t fire all cylinders at the same time the exhaust flows out in waves from each side of your V-8 engine. The crossover creates a balance of this flow by having a connected segment of these two near parallel pipes sending your exhaust out to the back of your ‘Vette. The second function of the crossover pipe is to convert harmful pollutants into less harmful emissions before exiting the exhaust system. This is done by the catalytic converters that are part of your stock Corvettes exhaust system. Some aftermarket H and X pipes are offered without catalytic converters and are not approved by most State Emission Regulations because they are intended for track use only.*

*This is due to pollution and noise regulations.

Cat-Back System –
This is the most commonly replaced part of the exhaust system because most stock mufflers tend to rust and are very restrictive. Also changing out the cat-back system will create the most drastic change in exhaust tone for your Corvette. The cat-back system gets its name because of its placement after the crossover pipe with the catalytic converters. The main piece to the cat-back system is the mufflers, which are designed to muffle the sound of the exhaust. With this being said there are multiple ways that muffler designers do this andeach method gives each different brand their distinct tone. Those methods are: absorption, restriction and reflection.

Types of Mufflers



Absorption –
Is a way of muffling sound by having a perforated pipe running through the muffler with an insulator, usually fiberglass or steel wool, packed around the pipe. This design is great for allowing for exhaust gases to flow freely through the muffler but is not the greatest at muting the sound created by high powered sports car like a Corvette.

Restriction –
Right off the bat this does not sound like an appealing aftermarket part to be putting on your Corvette, considering the term restriction in the automotive world is a bad thing, (i.e. "The stock intake manifold was restrictive so I replaced it"). This is the same with exhaust, the last thing you want to do is restrict the exhaust gases from exiting your car. This is for two reasons, first because if the exhaust gases don’t leave your Corvette in a hurry it will create backpressure and not allow the gases behind it to escape causing your Corvette to rev slower and this is defiantly not ideal.

The Second reason is based on the scientific theory of thermodynamics which essentially says that hot air rises and cold air sinks. What this means is that hot air is less dense and thus light while cold air is more dense and heavier, so if there was a mass of cold air in your Corvettes exhaust it would use more energy to push it out then if that same air mass was hot. So a restrictive muffler set-up should definitely be out of the question. OEM exhaust systems are the most restrictive systems you will find on the market and any aftermarket muffler and cat-back system will release lost horsepower.

Reflection –
Uses acoustics to eliminate sound traveling through the exhaust. This is done by creating interference of the sound waves, in this case deconstructive interference. Muffler designers do so by creating partitions within the muffler that reflects certain segments of a sound wave that will cancel out another sound wave coming into the muffler. This is great for dampening the sound of the exhaust but isn’t as free flowing as an absorption style muffler.

Overview


In summing up, the importance of the exhaust system and why an aftermarket system is essential to overall performance gains for your Corvette is probably the reason why you’re here. So, let’s keep a few things in mind when selecting an aftermarket exhaust system. First, and foremost, by changing to an aftermarket exhaust system no true horsepower is made it is only freeing up lost horsepower from a restrictive OEM system.

Secondly, when making a selection of headers and/or cross-over pipe, you must consider both because if you have long-tube headers you will need a short cross-over pipe and vice versa. This shouldn’t affect your cat-back since most cross-over pipes, both short and long, are designed to match with almost any cat-back kit.

Lastly, since your Corvette is already a high horsepower machine upgrading the exhaust is not a bad idea, but if you intend to upgrade other parts of your bow-tie like the cylinder headers and intake or add some form of forced induction or power adder then upgrading your exhaust is essential to optimizing the potential of your Corvette. Think of it this way: if your Corvette still has the OEM exhaust and other performance modifications have been made, the exhaust will not properly reflect the results you should have. By upgrading the exhaust it compliments other performance mods, or preps your Corvette for other future modifications.



Author: Ryan McDonald

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