Car Tuning Glossary


Aftermarket is a term that basically describes any parts or services or replacements made after the manufacturing of the vehicle of any type. This includes performance parts and also general remanufacturing of parts for cars, trucks and motorcycles. Because of this it gives consumers the opportunity to modify or repair the cars on their own terms – or take them to certified locations and repair shops. The Aftermarket itself is a 250 billion dollar industry that employs roughly 4 and a half million Americans.

Aftermarket Kits

An Aftermarket kit is usually a kit that is released by the manufacturer of the automobile it is to be used on, and differs from a normal kit in that it doesn’t change so much the car to look like a different car, but rather enhances the car to look more “sporty” or “luxurious” depending on the style. Many aftermarket kits also enhance performance, even going so far as to change out the engine and fuel injection systems in favor of more powerful non-standard flavors.

Aftermarket Exhaust Parts

An aftermarket exhaust part is usually a part that will replace the factory installed exhaust parts and system for performance increase, efficiency, noise, or just the aesthetics of the part. One of the most common replacement is the exhaust tips, which are the parts you see at the end of a vehicle, while others are headers, catalytic converters, mid-pipe, glass packs, silencers, resonators, stick mufflers and exhaust piping modifications.

Aftermarket Exhaust — Headers

Headers replace the manifold found on many common engines and decrease what is called backpressure, and in so doing increase the ability of the engine to have a higher performance when used at the higher half of its power range. What happens with the her headers is that the smother inner surface and less resistance allows the pressure to go the correct way efficiently – reducing backpressure to the engine, and when the engine is revved up to full there is much less backpressure, which means less energy used on pushing exhaust out and more energy used on mechanical locomotion.

Aftermarket Exhaust — Catalytic Converters

Catalytic Converters reduce emissions, but they also increase backpressure and workload on the engine. By replacing this with a more efficient model it can reduce the backpressure and increase performance of the vehicle. However this may be illegal in states with stringent emissions controls, such as California, Colorado, Washington, and Oregon. Some custom made Catalytic Converters along with more recent technological advances have made converters that create only 1psi at full throttle.

Aftermarket Exhaust — Mid-pipe

The mid-pipe is the pipe that is between the catalytic unit and the muffler on the vehicle on vehicles that have a dual muffler setup. This pipe keeps pressure equalized in the exhaust and prevents buildup of backpressure. There are also modifications to the classic H shaped design, such as the X setup which has a merger between pipes and can marginally decrease backpressure (however at higher power it is much more efficient in doing so).

Aftermarket Exhaust — Glasspacks

Glasspacks, also called cherrybomb, is a variation on the muffler for vehicles that has the gasses pass through the center while being surrounded by fiberglass. However they can be modified to make the engine louder with a different sound if tampered with, as many noise enthusiasts do to their modified vehicles. The efficiency of actually lowering sound is poor, however backpressure reduction is good.

Aftermarket Exhaust — Silencers

Silencers are based on the same principal as a suppressor for a gun, by having small concentric pipes with flat ends all around the exhaust pipe to bounce the sound back. However the impedance on airflow creates some additional backpressure and their efficiency really is not as good as other methods. It beats glass packs, but not by much. They are also expensive to manufacture, and the cost doesn’t cover the result for many car modification enthusiast.

Aftermarket Exhaust — Piping

The piping of the system that comes from the engine to the catalytic converter through the midpipes (if a dual exhaust system) and out the muffler is also subject to much modification to reduce drag and increase flow, thereby eliminating backpressure. Many modifications are made by people who are ill-informed and think the bigger the diameter, the better the efficiency. This is not true, as it takes more for the engine to pump it out. Constrict it too far, and you’ll have it shooting like a jet – but severely inefficient. Balance is the key for the right tuning.

Aftermarket Exhaust — De-exhaust

The only way to have the most efficient exhaust system is not to have one at all – basically a pipe that juts out with no converters, no mufflers, nothing to impede flow. There is no backpressure, no condensation, and no noise reduction. This increases the peak power the engine can run at, increases mileage, and of course increases noise. However this is probably illegal in most areas due to the pollution and emission output and the noise, and also cause a loss of torque unless accounted for.

Aftermarket Add-ons

An Aftermarket Add-on is an addition released usually by the manufacturer to grant the vehicle in question better performance, or additional options, and can even in some cases cover replacement parts for repair – however because it is called an “add-on” it is more so an addition to the vehicle. Some Aftermarket add-ons can be from other manufacturers if they are made for the model of car (concerning things such as mirrors and lights).

Air/Fuel Tuning

This is the process of tuning the density of the fuel and air intake, along with the amount that is taken in at a time. By running at an optimal mixture a very noticeable gain in power and fuel efficiency can be achieved, thereby actually making this tuning a favorable one for emission and for efficiency. Keeping a vehicle as efficient as possible saves the driver money and gives the driver more power at his disposal while also helping to pollute less. The tuning is accomplished through most modern cars in the ECU

Air Vents

Adding air vents to the engine air intake can increase the oxygen supply and greatly increase efficiency. These kinds of vents also improve the power of the vehicle as long as the change is accounted for in the ECU for the air and fuel mixture. Other vents for airflow are used to create a more streamlined flow, or to stabilize the vehicle and push it down so that it maintains traction.

Body Kits

A body kit can be aftermarket or not, and is a collection of materials meant to alter the exterior and interior of a car, all in one package. However some kits are just cosmetic. The kits are manufactured for specific car model or models and usually are only able to work for that exact model of vehicle, as the assembly on a different vehicle would not match up. Most are cosmetic and use carbon fiber, polyurethane, or fiberglass. Other materials can be used as well, and many are now factory made rather than custom.

Bumper Canards

Basically you add a small wing to the bumper to modify the way the airflow on the car effects it. Usually they are used to increase the pressure downward for traction, and increase the handling performance. Many people use them just for the cosmetic effect, as they rarely approach the speeds of usefulness, however some do use it for performance and do have a noticeable difference at higher speeds. The jury is still out on whether these are worth the cash put into them.

Butterfly Doors

Butterlfy doors are a hybrid of the Scissor Door and the Gullwing Door, performing both actions at the same time, however slightly modified in the case of the Gullwing action. The action of the door is to move up like the scissor, and then tilt inward – much like the gullwing, and provide room to exit the vehicle in use.

Car Tuning

A hobby, an industry, an obsession. Car tuning has been around since the first Model T’s rolled off the lot, by painting them custom colors and improving engine output, along with replacing the magneto’s with batteries. The tuning of a car can take on many forms, from the suspension, to the engine and exhaust, to the body, and even “detuning” where the modifications are removed and it is returned to factory default. It is a multi-hundred-billion dollar industry in the United States and Europe, and much the rest of the world.

Custom Shaped Muffler

Basically a custom shaped muffler is nothing more than the muffler tips being fancy or shaped in unusual ways – usually with little regard to their effects on backpressure and noise levels. However many motorcycle enthusiast have custom exhaust that are both functional and aesthetically pleasing, as well as some Semi-trucks that do the same. Some extreme modifications actually do shape the muffler itself into new ways, but these usually impede on efficiency and serve as nothing more than eye candy.


Decals are the addition of images or designs to the exterior or interior of a vehicle. There are many kinds of Decals, with many ways of transferring them from one medium permanently to another. The simplest is adhesive “stickers” however these eventually peel and look unprofessional. Other kinds use a heat or water transfer from a ceramic, cloth paper, or plastic medium. Most often the heat transfer type last the longest and look the most professional – however because of this they are hard to remove without buffing or chipping the paint of the vehicle’s exterior.


Detuning is the process of Tuning in reverse. It constitutes the removal of all additions in order to bring the car back to a “factory” state, and is used often times in vehicle restoration. It still facilitates the use of adding replacement parts; however these parts are usually original, and replace those that were modified. The final result is a factory-build level car that has no trace of ever being tuned.

ECU Tuning

ECU tuning is the tuning of the Engine Control Unit which monitors many functions of the combustion engine in a vehicle, from the control of the fuel injection to ignition timing, valve timing, and starting. It essentially regulates the fuel and air portions of injection which is what is most commonly adjusted for optimal mixture. The modifications are made by actually programming the ECU’s and in many cases replacing them with ones that can be accessed easily from a laptop and a USB or Serial cable.

Exterior Modifications

Exterior Modification are modifications that target the body and the look of the vehicle, from painting to the addition of spoilers and vents. Exterior modification is one of the most common, as even a bumper sticker is classed as such, seeing how it is a decal. Many exterior modifications are made through kits, while others are made through custom machining – and yet more are made by unskilled enthusiasts with nails and a hammer.


Flushing is the process of attempting to make the car more aerodynamic by removing the handles on doors and also bumpers and other emblems, along with trim and key locks. The locking mechanisms and opening of the vehicle are facilitated by remote openers and un-lockers, thus also adding a security benefit as a criminal would be unable to open the door from the outside or pick a lock. However a smashed window still has not been defeated.

Front Bumper Modding

Front bumper modding involves the modification of the front bumper by replacing it or by adding spoilers or small wings that will enhance the performance at higher speed by forcing the vehicle down, and also balancing it if there is too much of a rear balance. However many bumper modifications are just for looks, and have absolutely no function at all. Many times they are added to to make them lower in addition to side skirts.

Fuel Injection Tweaking

Fuel injection tweaking involves modification of the fuel injectors themselves and differs from the air/fuel modifications as it deals with the amount of fuel that can be injected at once. Increasing the output can increase the power but also increase the emissions and the fuel consumption – however if done correctly and the mixture being tweaked right with the added fuel a boost can be noticeable.

Gullwing Doors

Gullwing doors are doors that open up and outward, much like the wings of a common gull bird. They are most recognizable on the De Lorean car and have been a popular addition for cars since then. Of course the De Lorean was not the first to use them, but they were made popular by the vehicle’s prominence in use, and also from the Back to the Future trilogy movies.

Lambo Doors

Lambo Doors are doors that open by moving up on the axis and resemble doors from the Lamborghini. They are sometimes called suicide doors – however they6 most definitely are not. They differ from a gullwing in that the scissor door moves much like an actual scissor, moving up and to the front rather than just up and over. Most are motorized, and have automatic servos that will lift the door, along with sensors to insure that it does not close on someone’s leg.


Light modifications are one of the most common, from under-lights that are florescent, to LED displays, and to modifications on the turn signals and the stopping lights – along with replacing the headlights with halogen lights for a brighter and larger field of vision at night. Many interior lights are added, or colors are changed through replacing interior lights with colored LEDs or just putting a color film over the existing bulb.

Performance Modifications

Performance Modifications are modifications to the engine or the exhaust or even the gearbox of the vehicle. Through replacement of the fuel injection system, or modification of the ECU more efficiency and power can be obtained, along with more venting for air intake and less resistance in the exhaust for less backpressure. Any number of performance modifications can be made to any vehicle, and that also includes shaving and streamlining for better aerodynamics.

Rear Bumper Modding

Modifications to the rear bumper are not as common as modification to the front unless it is for lowering it, adding skirting, or adding light displays with LEDs and other such cosmetic effects. Sometimes it is removed, and other times it is beefed up to prevent damage if there is a read end collision.

Semi Tuning

Semi Tuning is any modification made to a Semi Truck, that is, decals, engine tuning, or even kit tuning and streamlining. Not as common due to the cost, however some truckers will modify their trucks and personalize them in. Some of the most common modifications are the mud flaps and the decals, along with the exhaust system.


Skirts are additions that make the car appear lower. They gained much more popularity after the Fast and Furious movie serial. They also can reduce drag in some cases, however they are likely to be damaged if they are too low to the ground and are easily damaged, along with expensive to repair.


A splitter attaches to the front bumper of a vehicle and prevents air from going underneath with the sole purpose of keeping the weight pushing down in the front for better performance. So far it has been featured on the “Car of Tomorrow” for NASCAR and is likely to be adopted by all racing cars for safety. It is relatively cheap and inexpensive to replace.


Spoilers are usually found on the roof and the back of cars and trucks, and they serve to modify airflow. They are not wings, and they are to never be confused with wings. The purpose of a spoiler is to reduce lift, thereby pushing the vehicle down at higher speeds to increase traction and handling, however many placements by armature modders will be ineffective, as it does not grasp the air as the air flows by (think putting it on the rear bumper for a ‘You’re doing it wrong!’ moment).

Suicide Doors

Suicide doors open from the rear position rather than the front position. They are so called because if one flies open you can’t close it easily. They are found quite often in modified and tuned vehicles; however their practicality takes a back seat to their aesthetic looks. Furthermore the risk of having a door slammed into you when exiting is increase, and the doors themselves can be dangerous if their latching mechanism fails and you do not have a seatbelt on.

Truck Tuning

Truck tuning is any modification made to a truck. Some truck are modified for speed while others are modified for power and torque. The most common modification is the modification for power, and also performance. People who own trucks want to show power, and in so doing modify a mild truck into a formidable beast. Many extreme mods turn normal trucks into monster trucks. There are others who prefer to create low riders that can do nothing utilitarian, and yet more who just want their truck to look nice.


Tuning is the process of tweaking and changing the look of the car along with its performance. Any kind of modification to the interior, exterior, engine, exhaust, and other electrical and sound systems can be seen as tuning. Tuning is one of the most common occurrences for cars in the United States and Europe. Many enthusiasts go for making their cars look like different cars, whereas others modify and tune them for power and performance.


Under-lights are a modification in which the underside of a car is fitted with florescent lights of any number of colors for the aesthetic effects of having a “Cool” car. However some are poorly done and un-noticeable, especially cars with low skirts, you have to have a balance. Some lights can also drain battery power, which becomes a problem, and L.E.D.s become the solution – however many LEDs must be used to gain the same level of lighting.

Wheel Modifications

Wheel modifications include the buying of custom wheels, the additions of spinners, or the buying and using of white-wall tires. It is meant more so for the unique effect of having a non-standard tire, however some are performance related with better tires that have longer warranties and will last at least 3X longer than the average Wal-Mart tire. No one should ever use a McTire unless they have a McCar and work at a restaurant that starts with Mc.

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  1. [...] have made Tuning Cars a popular pasttime for many. Today I came across a great site with a full Car Tuning Glossary for the learner or avid enthusiast. There is also a complete guide to street racing and my [...]

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