Knowledge Centre

What is?

The exhaust system plays a crucial role in making sure that the toxic and dangerous burnt gasses which are released after the fuel/air explosion are directed safely away through steel tubes from the engine area and away from human inhalation. These gasses are extremely hot and contain nitrogen (N2), water vapor, carbon dioxide (CO2) carbon monoxide (CO) from incomplete combustion, hydrocarbons and nitrogen oxides (NOx).

We can supply a direct-fit exhaust or build you one from high quality stainless steel which will improve the performance and give you better fuel economy.

Most exhaust systems are made of Mild steel which are prone to corrosion fairly quickly, not only by being attacked by road debris and salts, but internally too, because the gases have a certain amount of moisture, put these together and you will soon realise that the system has started to corrode and leak and will need replacing. Some up market cars use stainless steel to reduce the damage however due to the cost of stainless steel it is not in every manufacturer’s interest.

The best solution is to have a custom built stainless steel exhaust system installed which comes with a lifetime warranty.

An exhaust flange is a method of attaching two pieces of exhaust tube together to create a join. Usually made from pressed steel or flat 8mm to 10mm thick section which has 2 or 3 bolt holes for attaching, in order to prevent leakage a gasket is sandwiched in between the two sections. Flanges are available in Mild or stainless steel.

It is crucial to have them fitted flat to prevent leaks. There are many other types of flanges depending on the application, a well fitted exhaust system with flanges also allow quick removal should any maintenance work be required.

We can supply you with any flange configuration you require, with our state of the art Plasma cutting table we can cut any shape in minutes in mild. or stainless steel.

Americans say Muffler and Europeans call it a Silencer, Mufflers are fitted within the exhaust system of most internal combustion engines; they do not have a specific exhaust function other than that to control the sound. The muffler is manufactured as an acoustic soundproofing device designed to reduce the loudness of the sound pressure created by the engine.

In an engine, pulses are created when an exhaust valve opens and a burst of high-pressure gas suddenly enters the exhaust system. The molecules in this gas collide with the lower-pressure molecules in the pipe, causing them to stack up on each other. They in turn stack up on the molecules a little further down the pipe, leaving an area of low pressure behind. In this way, the sound wave makes its way down the pipe much faster than the actual gases do. exhaust-open

Inside the muffler is a set of tubes. These tubes are designed to create reflected waves that interfere with each other or cancel each other out.

The exhaust gases and the sound waves enter the center tube. They bounce off the back wall of the muffler and are reflected through a hole into the main body of the muffler. They pass through a set of holes into another chamber, where they turn and go out the last pipe and leave the muffler.

A chamber called a resonator is connected to the first chamber by a hole. The resonator contains a specific volume of air and has a specific length that is calculated to produce a wave that cancels out a certain frequencies of sound resulting in a quieter exhaust.

The second area has the fiber to further reduce the sound. The downside of this is that it creates a lot of back pressure which decreases engine efficiency by not allowing the burn chamber to vacate the gasses quickly enough.

The best solution is to install an aftermarket exhaust system, Profusion Customs and Magnaflow supply some of the best exhaust systems in the world they are engineered differently but have the same primary function and that is to reduce the sound, the result is you have a durable stainless steel exhaust system which will improve the performance, improve the fuel economy and come with a lifetime warranty, unlike baffled systems these mufflers have a straight through design which allows the gasses to vacate quickly, the acoustic fiber material keeps the sound low and produces a deep tone.

002Custom Built Stainless Steel Exhausts

QUALITY – As Market leaders, we supply and fit high end custom stainless steel exhausts using premium components and the latest technology, backed with a lifetime warranty for total peace of mind.

POWER – With years of experience we’ve learned that automotive enthusiasts always want more. If it doesn’t produce power, we don’t supply it.

SOUND – You want to have the best sound possible. With this in mind, our mufflers have a free flowing, straight through design with a perforated stainless steel core mesh wrap and acoustical fiber fill to deliver that smooth distinct, deep tone, to ensure long life and no sound degradation.

Contact us now and speak to one of our exhaust technicians.

Exhaust resonators are usually add-on features in exhaust systems. They are fitted together with the mufflers along the exhaust pipe and work primarily to decrease exhaust noise. The exhaust noise passes through the resonating chamber, which in turn tunes the sound to cause destructive interference in order to be cancelled out by the opposite sound waves.

We have created a great name for ourselves by supplying you the best sounding exhaust, with a huge range of resonators to choose from, we make sure the correct one is fitted to your car for maximum results, contact us now to see what we can do for you.

A Glasspack, also known as a Pro bomb is a type of exhaust muffler in which the exhaust gas passes straight through the center of the muffler. It has less packed fiberglass than a regular muffler and only absorbs a small amount of -frequency sound.

Glasspacks are an old, simple, and relatively inexpensive design. They are very effective at reducing back pressure, but not very effective at muffling noise. Thus, they preserve more of the engine’s power while sounding louder than conventional mufflers If Dyson had not improved the vacuum cleaner we would still be using bags and bulky cleaners which did a poor cleaning job, the same goes for the bomb style glasspacks, Profusion Customs have redesigned this to bring you the latest version called the ProBomb.

We stock a huge range of Glasspacks and can supply and fit to your project, so call now and speak to one of our exhaust technicians.

A diesel particulate filter (or DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine. It is not fitted to petrol engines. DPF’s remove 85% or more of the soot and under certain conditions can attain soot removal efficiencies of close to 100%.

Some DPF’s are designed to be replaced once they are full of accumulated ash. Others are designed to burn off the accumulated particulate either passively through the use of a catalyst or by active means such as a fuel burner which heats the filter to soot combustion temperatures; engine programming to run when the filter is full in a manner that elevates exhaust temperature or produces high amounts of NOx to oxidize the accumulated ash, or through other methods. This is known as “filter regeneration”. Cleaning is also required as part of periodic maintenance and it must be done carefully to avoid damaging the filter. Failure of fuel injectors or turbochargers resulting in contamination of the filter with raw diesel or engine oil can also necessitate cleaning. The regeneration process occurs at road speeds higher than can generally be attained on city streets; vehicles driven exclusively at low speeds in urban traffic can require periodic trips at higher speeds to clean out the DPF. If the driver ignores the warning light and waits too long to operate the vehicle above 40 miles per hour (64 km/h), the DPF may not regenerate properly, and continued operation past that point may spoil the DPF completely so it must be replaced.

The DPF is simply a filter used in the exhaust system to remove the majority of soot particles in turn this causes a blockage in the exhaust system which will increase your fuel intake Most vehicles fitted with a DPF will need to have the filter replaced at some point as part of the service schedule if it hasn’t become a problem already.

The DPF is not a legal requirement or needed for the MOT test so the most cost effective solution is to remove the DPF from the exhaust system and deactivate the DPF functions from the ECU.

Most companies will just program the ECU to ignore the DPF but this is not the correct solution because the filter is still in place and will at some time block.

Contact us now, and speak to our DPF technician.

A catalytic converter is fitted to combustion engines in the exhaust system near to the hottest part which is the manifolds and the function to convert three harmful compounds in car exhaust into harmless compounds.

The three harmful compounds are:

* Hydrocarbons (in the form of unburned gasoline)
* Carbon monoxide (formed by the combustion of gasoline)
* Nitrogen oxides (created when the heat in the engine forces nitrogen in the air to combine with oxygen)

Carbon monoxide is a poison for any air-breathing animal. Nitrogen oxides lead to smog and acid rain, and hydrocarbons produce smog.

In a catalytic converter, the catalyst (in the form of platinum and palladium) is coated onto a ceramic honeycomb or ceramic beads that are housed in a muffler-like package attached to the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide. It converts the hydrocarbons into carbon dioxide and water. It also converts the nitrogen oxides back into nitrogen and oxygen.

We can supply direct fit cats or universal ones, please contact us with your requirement.

The exhaust system needs to be held in place and therefore at various points of an exhaust system, is held up using hangers, these are usually made of the same material as the exhaust and are welded in place. They consist of a bar and sometimes have a larger end to help the hanger stay in place. Exhausts cannot be welded to the body of the car because there is constant movement caused by the engine, not just vibration but up, down and in and out as the exhaust expands and contracts, therefore there has to be some kind of flexible material which must be used between the body of the car and the hanger of the exhaust system, most common ones are made of rubber but other materials are used where extra rigidity is required.

An exhaust manifold of an internal combustion engine is the very first exhaust component which is bolted directly to the engine. It is a collector which collects all the burnt gasses from each cylinder and directs them to merge into one area where the exhaust pipe starts which will help carry the gasses out.

Some vehicles may have two manifolds, located on either side of the engine or stacked one in front of the other. The purpose of two manifolds may be to offer dual exhaust or simply to increase the horsepower of an engine, they are usually manufactured in cast iron, mild steel or stainless, racing engines can use other materials to help keep the heat in while remaining light.

We can build you a stainless steel manifold so please contact us.

Headers are one of the easiest bolt-on accessories you can use to improve an engine’s performance. The goal of headers is to make it easier for the engine to push exhaust gases out of the cylinders.

The idea behind an exhaust header is to eliminate the manifold’s back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder’s exhaust gases arrive in the collector spaced out equally so there is no back pressure generated by the cylinders sharing the collector.

The downpipe section of an exhaust system connects the headers or exhaust manifold to the catalytic converter(s). For most vehicles, the downpipe section is essentially incorporated with the catalytic converter section, most vehicle downpipes are never given much thought.

However, on a vehicle equipped with a turbocharger, an after-market downpipe it can offer a significant improvement in performance. Because a turbocharger is essentially a pump, it’s important for the pipes entering and exiting the turbo to have unrestricted airflow. On many turbocharged vehicles, the exhaust pipes coming in and out of the turbo contain numerous bends. If these pipes are bent using a cheap, crush bending process (a common situation for many vehicles), they can restrict exhaust gas flow in and/or out of the turbo therefore it is crucial to use mandrel bends.

By reducing exhaust gas restrictions, the turbocharger can spool up more quickly. Faster spool-up times mean more power and/or better fuel economy. As a result, many after-market exhaust manufacturers offer over-sized exhaust downpipes with mandrel bends, we can supply and build mandrel bent downpipes for any vehicle.

Vehicles which have transverse engines need to have a section of the exhaust which can move with the engine, if the exhaust is too rigid then the system will crack and break, therefore to reduce this chance a flexible tube is fitted, normally after the downpipe, this will also reduce noise and vibration. Exhaust pipes get extremely hot from the exhaust gas passing through the system and out the tailpipe. Due to this, when an exhaust system needs to bend, shift or be flexible, the manufacturer cannot use traditional materials like rubber. The flex pipe is made of metal strips woven into a lattice, and thus can withstand exhaust gas heat. Cheaper Flexi pipes are made from mild steel but do not last long, stainless steel is the preferred choice which is built to last longer.

We can supply either a weld on flexi pipe or a clamp on flexi pipe complete with clamps, we have all sizes.

A header back system normally refers to building a bespoke exhaust system from the headers onwards headers are also referred to as manifold.
A turbo back system normally refers to building a bespoke exhaust system from the turbo onwards, normally this has a V clamp section which starts the system.
A De-cat pipe is just what it says, it is a section of tube which is fitted in place of the catalytic converter, this modification is often used for non-road vehicles for off-road use only to increase the performance of the vehicle.
Heat wrap is a type of high temperature wadding and comes in various lengths; it is used to insulate the exhaust tube which prevents the hot gasses from cooling down, the right type of wrap will keep the exhaust gases of your engine at much high temperatures, by maintaining the exhaust gases at higher temperatures increases performance on several levels At high speed the wrapped exhaust system causes increase a scavenging effect therefore improving the performance of the intake and exhaust systems as a whole. The exhaust gases are therefore removed much faster from your vehicle when hot.
Ceramic coating is a specialised process where ceramic is heat treated directly on to exhaust manifolds, this is a specialised treatment and often used on high end and race cars.

The real benefit is that it Reduces under bonnet temperatures by up to 50°C (122°F) 30-40% By keeping the exhaust gases hot they flow more easily through the exhaust and this aids cylinder scavenging. Keeping heat in the exhaust gas allows turbochargers to spool up more quickly making turbocharged engines more responsive.

Homologation is the granting of approval by an official authority. This may be a court of law, a government department, or an academic or professional body, any of which would normally work from a set of strict rules or standards to determine whether such approval should be given.

In motorsports a vehicle must be homologated by the sanctioning body to race in a given league. Where a racing class requires that the vehicles raced be production vehicles only slightly adapted for racing, manufacturers typically produce a limited run of such vehicles for public sale so that they can legitimately race them in the class.

You can’t get an MOT certificate if your vehicle’s exhaust emissions are too high. Emissions may also be tested as part of a roadside checks.

Most vehicles have their exhaust emissions tested as part of the MOT using an emission analyser. Usually, they’re tested using a meter. Petrol vehicles used before August 1975 and diesel vehicles used before August 1979 are tested by sight.

If your vehicle fails the emission test it fails the MOT. The problem must be fixed before you can get an MOT certificate.

There can be numerous components that can cause high emissions. Components such as spark plugs, plug leads, and filters can affect emissions if defective.

Emissions is a generic term used to describe certain harmful gases in the exhaust. Hydrocarbons (HC), Carbon Monoxide (CO) and Oxides of Nitrogen (NOX) are usually measured in an emissions test.

When your car attends its annual MOT test a reading is taken and this is where you will know if you are within legal limits, armed with a test report indicating what gases are high can help you determine what systems may not be functioning as it should. If warning lights show up on the dash this should be diagnosed before attending any testing, if the vehicle fails as a result of high CO and HC, the CO failure should be looked at first.

CO Failure is probably the result of an excessively rich air fuel mixture. Here is a list of some of the common causes – Defective Oxygen Sensor
– faulty Air Injection System
– defective Fuel Injectors
– Blocked air filter (if high CO is present only at high revs)
– Vacuum leaks resulting in improper MAP sensor operation
– Defective air mass or air flow sensor
– Malfunctioning fuel evaporation system or purge valve
– faulty Catalytic Converter
– thermostat stuck open
– Oil contaminated with fuel, excessive miles between oil changes or use of cheap oils.

HC Failure is the result of incomplete combustion. The most common causes are: – faulty spark plugs
– Defective spark plug wires
– Worn distributor cap and/or rotor
– Improper ignition timing, usually over advanced
– Vacuum leaks
– Engine mechanical failure, low compression, worn valves, excessive oil consumption.

NOX Failure is the result of combustion temperatures that are too high. The most common causes can be:

– Faulty (EGR) Exhaust Gas Recirculation
– Cooling system malfunction, engine running too hot (restricted radiator, defective thermostat, leaks etc.)
– Over advanced ignition timing
– Excessively lean air fuel mixture (defective oxygen sensor, MAP sensor or Air Mass Sensor)


Most issues can be avoided by simply making sure the vehicle maintenance is carried out during its correct intervals. It is also advisable that if the vehicle has covered over 60,000 miles the reason for the failure is CO then replacing the oxygen sensor aka lambda sensor may be a wise investment.

Many people think of backpressure as if it is a crucial thing to have, there seems to be a myth around this subject and the basic theory of an exhaust system and the main function is to vacate the gases from the chamber as quickly and efficiently as possible, when the air fuel mixture ignites in the engine it causes a mini explosion and when the valves open the gases at high velocity are diverted to the exhaust system, when this high velocity gas hits atmospheric pressure this creates a positive resistance to flow.

You may think that it would make sense to have bigger pipes which would help the gases vacate quicker, this notion may sound sensible however it does not help the velocity, think of a running tap, when the tab is open the water runs out however as soon as you start to restrict the end of the tap with your finger the same amount of water increases a speed and causes a faster flow, so in other words having the pipe larger does not help the gases vacate any quicker in fact it can have an adverse effect.

A smaller diameter pipe will produce higher velocity at lower revs but will create an undesired amount of backpressure at high revs so it also depends how you drive the vehicle and way you want to maximise your performance at a lower end rpm or higher end rpm.

Advocating the gases at a high velocity there is a scavenging effect that takes place which helps to draw the gases out even faster and acts like a vacuum pulling the low pressure air behind it.

A dyno is like a test bench for your vehicle, it can give you information such as how much power the is that the wheels, how much power loss you may have, the level of torque produced as well as all temperature etc.

The term mandrel refers to a process, when round tube is bent at any angle there are two types of machines that can do this, one will bend the tube by holding the outsides of the tube only and bending it around a specific die, this process will cause the tube to restrict in the center, this will certainly not have any adverse effect to any vehicle that is not being used for race, so for the average vehicle having an exhaust manufactured by this process will not mean any loss of power or performance.

The other method of bending tube is where a die is inserted inside the tube so while it is being bent the die inside the tube stops this area from restricting therefore whatever the diameter of the tube is, it will remain constant throughout the bend, this is a much more preferred method for racing vehicles as it is also a very expensive process, at Profusion Customs we can offer both of these services, we are also one of the largest suppliers of mandrel bent tubing in the country.

An X pipe is only used on V engines such as V6 V8 V 12. It is a must for any performance system it works by balancing the exhaust banks resulting in a smoother flow. Power gains are mostly noted at higher rpm, exhaust gases are vacated faster and the X pipe merges these two streams to allow a smoother flow. As one bank empties it causes of scavenging effect and pulls the other bank through.

A Y pipe can be used in both directions it allows 2 pipes to merge or 1 pipe to divide off into two, a typical example would be 2 pipes from the header can be joined together using a Y pipe and a single pipe can then be used to vacate the gases, in the opposite direction it can be used where a single pipe needs to be branched off into two for example to install a dual exhaust system, one on either side. The key for a purpose-built Y pipe is that it allows equal amount of flow through both directions, a badly manufactured Y pipe will cause more gases to go from one side than the other.

A free-flowing performance exhaust system will produce more power purely for the fact that a standard exhaust system muffler is built up with a series of plates which restrict the gases but this is an economical way to silence the exhaust system, a performance exhaust will not have any baffles but a straight through design which allows gases to vacate quicker resulting in better performance and better fuel economy, the silencing is done by the acoustic fibre packaging surrounding the perforated core.

A lot of people think that having a bigger pipe means a better exhaust system, this is certainly not the case by having larger tubing can result in loss of performance, manufacturers normally calculate the right diameter tubing to be used to vacate the gases efficiently, before deciding on a larger tube diameter firstly decide how you tend to use a vehicle for day-to-day running trips or will you be using it for racing because this is what will determine the correct diameter to go for.

Direct fit means that an exhaust system can be supplied with all of the necessary parts that may be required and the work can be conducted by any competent DIY person as no specialised tooling may be needed. It is a simple way of removing the old system and bolting a direct fit system in its place this is normally vehicle specific.
Custom exhaust means when the entire exhaust system is fabricated from starts to finish and it is built on the vehicle for the vehicle this is by far the best way of making sure you get a perfect fit and the system can be fitted as high as possible to keep the ground clearance to its maximum, we are often asked if a custom-built system can be posted for the customer to bolt onto their vehicle, unfortunately not because all the dimensions angles et cetera are taken from the vehicle.
A dual exit system can mean that even if there is a single pipe from the manifold to the back as the pipe reaches the rear end it is branched off where you will see two tailpipes emerging from the back of the exhaust system, a true dual system is where there are two pipes emerging from the manifold and both have their own individual paths.