Exhaust recommendations

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I have just bought a motorcycle. What exhaust would you recommend as the best choice for my bike?

The choice depends on many factors, such as the model (road, offroad), the intended use (street, track etc.), your riding style, desired noise level, price etc. At Akrapovič we produce five lines of exhaust systems which differ in their physical properties, performance characteristics and purpose: Bolt-on, Slip-on, Slip-on SP series, Racing and Evolution. There are a lot of possibilities, but the final choice has to be made by the rider. For a more thorough description of the lines, click on the links under Product Lines.

I bought an Akrapovič exhaust system. Do I have to rejet the bike? Which jet kit do you recommend for use with your exhaust system?

The exhaust systems are designed to function properly using the stock carburetor or electronic fuel injection set-ups. This means that no changes to the stock set-ups are necessary in order to use Akrapovič exhaust systems. Also, all of the performance specifications which we measure and list for each exhaust system model are based on stock set-ups. We assume full responsibility for the accuracy of these specifications. However, we also believe that it is possible to improve the original set-ups when our exhaust systems are used.
Of course, the market for tuning kits is extremely large, covering practically every motorcycle component. Tuning of the exhaust system includes the carburetor and EFI settings in addition to aftermarket components. There is a huge demand for this particular combination.
If you decide to rejet your bike in addition to purchasing an Akrapovič exhaust system, we recommend that you check out the range of products offered by the American company Dynojet. They have achieved excellent results with their carburetor and EFI jet kits, which they test themselves and which are specifically tuned for Akrapovič exhaust systems. However, they only cover certain parts of our range, so it’s best to make sure that Dynojet has a kit for your motorcycle and the Akrapovič exhaust system of your choice.

NOTE:

• The Akrapovič company assumes no responsibility for the performance specifications given by the Dynojet company or any other tuning company for their products!
• We guarantee only the accuracy of the performance characteristics given for Akrapovič exhaust systems, which are based on the motorcycles’ stock engine set-ups, and which are officially issued by the Akrapovič company.

IMPORTANT:

• Tuning of electronic fuel injection systems requires precision and care, since unlike carburetors there are many possible settings which could exceed the useful limit for the engine! This could eventually lead to decreased engine performance, i.e. damage to the engine. We assume no responsibility for the proper operation of Akrapovič exhaust systems in the case of rejetting the carburetor or EFI system. (We suggest that you start tuning using the presets given by the manufacturer).
• Never change the exhaust system and the jet's or EFI mapping at the same time.
• First replace the exhaust system, then the other items. Even when replacing the stock air filter with a modified filter, rejetting/remapping has to be performed.

What to do with models with EX-UP?

When the original exhaust system is dismounted, it is necessary to remove the cables from the servo (which changes the exhaust valve opening). However, the servo must stay connected to the harness and MUST NOT BE removed.
For all these special cases a detailed set of installation instructions are included with your Akrapovič exhaust system.

How loud is an Akrapovič exhaust system?

Akrapovič exhaust systems are louder than stock exhaust systems. Noise measurements are made following the standard procedure: 50 cm from the exhaust outlet at an angle of 45° to the side of the outlet.
Typical measured noise levels for individual product groups depend most of all on engine type and vary from:

• 92dB to 98dB (street legal Slip-on, Bolt-on)
• 98dB to 102dB (Racing, Evolution) 
• 94 dB (offroad)

The Street Legal series maintains the same noise levels as the stock exhaust systems. However, the color and the tone of the sound are changed, giving it a much sportier growl. The increase in performance is also less marked than with our other types of exhaust systems.

How much does an Akrapovič exhaust system weigh?

The weight of an Akrapovič exhaust system varies from line to line and from bike to bike.
Typical weights for individual product groups for sport bikes:

• Bolt-on, Slip-on = 1.6 to 2.4 kg
• Racing = 4.8 to 5.4 kg
• Evolution (titanium) = 3.3 to 4.2 kg

Exact weights are given in the technical specifications for each exhaust system, along with a comparison with the weight of the stock exhaust.

Flow of gases in exhaust tubes: physical conditions, factors (gases, heat, sound)

When exhaust gases leave the combustion chamber their temperature is around 900°C and they travel at speeds lower than the speed of sound. Therefore due to the explosions in the combustion chamber they give off heat, and they give off sound due to pressure variations (compression and decompression of air).

Extreme racing conditions are a different story from everyday riding. How is a racing exhaust system different from one designed for street use? How does a street engine respond to a racing exhaust and vice versa?

A racing exhaust system is designed to provide a useable torque and power in the range where racers need it on the track. The design is adjusted to the engine type, race conditions (riding style), the motorcycle’s center of gravity (handling), the bike’s aerodynamics, and the physical limitations of the motorcycle’s design (so that the exhaust does not touch the ground when the bike is leaned or settled on its shock absorbers). Minimal weight and maximum durability always have to be taken into account.
During development and manufacturing we also have to take into consideration the regulations on maximum exhaust system noise levels for various competitions (FIM/AMA MX, FIM/AMA SBK, FIM ENDURO etc.), which differ from competition to competition.
Since racing exhaust systems are custom manufactured for custom racing bikes with special engine settings, gear-boxes and frame designs, such systems usually cannot be mounted on stock motorcycles, and if they are, the system’s functioning is not adjusted to the stock engine settings, which of course has a major effect on the engine performance and the ride itself. In practice this means that certain systems work poorly at the low revs necessary in street use.

Influence of materials on exhaust system design: weight, forming methods, conductivity, flexibility, durability of the material in everyday use, durability of the material in race versions etc.; how the parameters are reflected in ridability etc.

Materials affect the weight and temperature resistance of the system. In developing and manufacturing Akrapovič exhaust systems we use many types of materials appropriate to the specific conditions for producing the individual exhaust systems:

• Titanium: in comparison with stainless steel, titanium offers a major weight reduction. It is also highly resistant to corrosion. We use it for the majority of component parts of our systems, depending on requirements and combinations. We recommend full titanium systems for racing.
• Stainless steel: in comparison with titanium it is lower cost, slightly heavier, but extremely durable. We recommend it for everyday riding (especially stainless steel header tubes, since they are the part of the exhaust system most exposed to high temperatures). Even with stainless steel header tubes our systems are much lighter than stock systems. Stainless steel is also used in our SP series exhaust systems.
• Carbon-fiber: its advantage is its low weight, good temperature resistance and stiffness, and excellent ability to take any shape, as it can be formed into heat shields, all types of brackets and muffler outer sleeves.
• Aluminum: we use special billet aluminum alloy, which is light weight and well-adapted to CNC machining. It is used mainly for header tube flanges, front rosettes for our Bolt-On line and various brackets.

As far as the influence of exhaust system materials on handling, any reduction of the overall weight of the motorcycle (including the use of a lighter exhaust system) results in better handling characteristics and braking.