Changing Royal Enfield Silencers & Their Effect on Engine

by | Feb 21, 2019

In the earlier days of automobiles, the exhaust system was considered as an unimportant component of the whole setup, just to aid the removal of obnoxious fumes from the engine.

But with the advancement in technology, several changes were brought about in the entire automobile field out of which the exhaust system remains the one which received a major overhaul from the past.

From the aerodynamics of the exhaust pipe shape to the type of materials used for the pipe construction, every last bit of specification now determines the overall performance of a vehicle, especially a two-wheeler.

In this article, we’ll discuss the lesser known facts about such exhaust systems in motorbikes available in the market.

Most of the factors mentioned here cater broadly to all types of motorbikes, not just the Royal Enfield.

So even if you own a different bike other than Bullet, don’t hesitate to read.

Functions of a motorcycle exhaust system

exhaust-muffler-working

As we have said earlier, the exhaust system is no longer considered as a mere waste gas removal structure.

The three main functions of an average exhaust gas system are:

1. Venting out combustion gases away from the engine

A motorbike is an active mobility vehicle where the rider and the passenger are in direct exposure to the surroundings.

Without a proper mechanism to transfer noxious fumes from the engine, these harmful gases will come in direct contact with the rider and the passenger, which is very harmful to breathe in.

Thus an exhaust pipe will carry these fumes away from the rider, always ensuring a clean breathable air supply.

2. Muffle engine noise

An engine consists of numerous mechanical moving parts. While in operation, these parts work in tandem and produce a lot of noise.

An exhaust system helps to muffle this noise to a large extent.

It helps keep the sound levels from the motorbike under its legal limits.

3. Better engine performance

The aerodynamics of the exhaust pipe plays an important role in determining the efficiency of the engine.

The tube length and diameter are two major factors governing the performance of a motorbike.

The exhaust system, if designed properly can enhance the exhaust gas scavenging process, improving the overall efficiency and performance of the vehicle.

Why you need custom exhausts?

In this section, let’s discuss the few benefits of installing a custom exhaust rather than riding with the stock factory system on a bike.

1. Weight reduction

Stock exhausts systems maybe often designed with budget in mind. This leads to the use of low cost, high-density material for exhaust pipe construction.

This, in turn, increases the overall weight of the motorbike. More weight directly results in increased fuel usage and decrease mileage.

But with custom exhaust kits, you can install exhaust pipes made of a variety of lightweight materials, which not only does positively impact the mileage but also the acceleration.

Here is a pointed chart which will help you choose the best exhaust system for specific use cases.

  • Titanium and carbon exhausts – for low body weight
  • Aluminium exhausts – lightweight and durable
  • Chromed steel exhaust – for the aesthetic appeal
  • Stainless steel exhaust – for durability

2. Maximum utilization

The exhaust systems which comes standard with the motorbikes might not be as versatile as the aftermarket ones.

The specially designed exhaust systems improve the performance, efficiency and even the exhaust sound note of the engine.

This lets you fine-tune your bike as you may please.

There are two types of silencer upgrades available for motorbikes, namely – mufflers only upgrade and full system upgrade.

Muffler only upgrade involves only a minor facelift for the stock exhaust for improved sound notes and performance boost from the engine.

Full system upgrade involves the complete swapping of the exhaust system right to the fuel lines from the engine.

Now, let’s understand how an exhaust system really works.

Working of an exhaust system

As the name implies, one of the major purposes of a silencer/exhaust is silencing the engine exhaust sound.

The silencers have pathways specifically designed to minimize the sound coming from the exhaust.

Hot gases are released out from internal combustion engine on each blast and these gases have to be absorbed and the noise should be reduced.

The real purpose of a good exhaust system is to expel out these gases while maintaining the power and performance of the vehicle.

Catalytic converters

Sometimes mufflers (silencers) also happens to have a catalytic converter which can reduce the emission of certain pollutants that come with the exhaust gases out of the engine.

catalytic-converter-inside-exhaust

The catalytic converter is a vessel in the exhaust system containing catalysts like Platinum, Palladium, and Rhodium.

Platinum and Palladium convert harmful exhaust gases by further oxidation of Carbon Monoxide and unburned Hydrocarbons into Water and Carbon Dioxide, and Rhodium breaks the toxic Nitrogen Oxides into non-toxic Nitrogen and Oxygen.

Backpressure

The most misunderstood and one of the most important factors about the Royal Enfield silencers is the back pressure, which affects the power delivery of the engine to a large extent.

Back pressure refers to the pressure opposed to the desired flow of gases in a confined place such as a pipe.

It is created with the help of obstructions in the exhaust system using mufflers, barriers or shape of the silencer to maintain an optimum pressure level of the exhaust gases for optimum power delivery throughout all the RPM ranges.

A certain level of back pressure is important for every engine and Royal Enfield stock silencers meet this requirement perfectly because the company has scientifically designed them for their own engines.

The general rule about back pressure is, the lesser the back pressure, the louder the silencer.

However, a small amount of back pressure is crucial for optimal engine performance.

Back pressure in the exhaust system pushes any unburned intake back into the engine.

Without this sufficient back pressure, some intake is lost, leading to higher fuel consumption.

When it comes to the aftermarket exhausts, the amount of back pressure is different on various silencers.

Most of the silencers from unknown brands don’t provide a sufficient amount of back pressure to the engine.

So, if you are replacing your RE’s stock silencer with an exhaust which doesn’t provide enough back pressure, it will definitely affect the performance of the machine in the long run.

Most third party bullet silencers have drastically reduced back pressure levels to increase pick up and create a more bassy scavenging effect.

Because of this, motorcycles fitted with these exhausts tend to have reduced top speed, slow acceleration at high RPM and dismal performance when going uphill.

On top of this, this type of exhausts creates a high decibel noise that can even damage the rider’s ears.

Hence, you need to have an exhaust with a sufficient amount of back pressure depending upon the kind of machine you are using in order to achieve better performance and more mileage.

Changing silencers and their effect on engine

The Enfield owners are often concerned about changing the stock exhaust due to the fear of affecting the engine in any harmful way.

During our research for finding the best bullet silencers, we have seen a lot of people inquiring about the same, everywhere on the Internet.

Let me tell you the real truth behind this.

Believe me, changing your stock exhaust to an aftermarket unit is safe most of the times, but if the exhaust system is designed so badly, there are chances that the engine could be affected.

There are a lot of silencers out there in the market with prices starting from Rs.1,000 to even Rs.15,000, and many of them are not up to the mark in terms of quality and performance.

But, if you are purchasing from reputed brands like Barrel Exhaust, Greasehouse, Red Rooster, Moto Torque, Swagman etc you can be assured of the performance and durability you desire.

Mileage after changing the silencer

With regards to mileage, it can both increase or decrease, but it depends on a lot of other complicated factors also.

Though mileage depends on the type of exhaust you use, the actual fuel consumption directly depends on the working conditions of the engine.

If the engine is well tuned according to the new exhaust, it will give out the best fuel economy for sure.

More than these, fuel efficiency also depends on how you ride the bike.

Aftermarket exhausts free the engine up a bit, so it produces a little more torque and power.

Whenever you ride your motorcycle without revving on the throttle, the engine runs at a lower RPM than before and thus will get slightly better mileage.

On the contrary, the new exhaust will make your Enfield sound beefier, and this could motivate you to ride faster.

If that’s the case, then the mileage will plummet for sure.

Types of Royal Enfield silencers

Before discussing the types of Royal Enfield exhausts, let’s understand a little about the design and working of an exhaust system.

royal-enfield-silencer-design

An exhaust pipe has an outer sheet metal cover which protects the silencer and inside it, there is a perforated tube through which exhaust gases pass out.

Some silencers have a packing material wrapped around the perforated tube which absorbs unnecessary noises and gives out a bassy sound.

The packing material also acts as a thermal insulator and it absorbs a specific amount of heat from the expelled gas.

Glass wool and ceramic wool are the two types of packing materials commonly used in silencers.

They are a type of man-made fibres with high thermal insulation and low thermal conductivity.

Strategic placement of these packing materials around the perforation tube gives a different thumb and bass for the exhaust sound.

Mainly, there are three types of Royal Enfield exhausts out there.

Free flow silencer

Free flow silencers are made by creating minimum obstructions inside the silencer and thus it provides an easy path for the exhaust gases to flow.

Here, the sufficient backpressure is created inside the silencer by making some modifications in the design of the exhaust pipe or with the help of baffles.

Compared to glass wool and ceramic wool exhausts, free flow silencers has lesser backpressure and thus they have a high scavenging effect.

Free flow silencers range from Rs.1000 to Rs.2000.

Glass wool silencer

In Glass wool silencers the material packed inside the exhaust is either glass, silica or sand.

Glass wool is an insulating material made from fibres of glass arranged using a binder into a texture similar to wool.

It traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties.

Compared to ceramic wool, glass wool has a tendency to deteriorates over time and might need replacement in the long run.

The price range of Royal Enfield’s glass wool silencers starts from Rs.2000 to Rs.3000 in India.

Ceramic wool silencer

Ceramic wool is another type of packing material used in the Enfield silencers.

These are more durable than glass wool and it has a higher thermal insulation capacity.

Because of this, these silencers doesn’t get too hot even after a long ride.

Ceramic wool silencers costs around Rs.4000 to Rs.10000 in India.

Please note that some Glass Wool and Ceramic Wool exhausts are considered as Free Flow silencers as well.

These are some commonly available Royal Enfield exhausts categorised based on sound and design.

Long bottle

Gives slow strong and long strokes. Bass is heavy and strong treble is recessed. These are very long and protrudes out of chassis.

Short bottle

The sound is similar to Original Cast Iron beats, it’s very pleasant and balanced tune, very soothing for ears, not that much loud.

Red rooster

The silencer with a perfect balance of performance and bassy exhaust sound.

Wildboar

Emphasises especially on Bass. The bass is deep, heavy and thumpy. The sound seems artificial and hurts ears at higher RPMs.

Dolphin

Looks like a mouth of dolphin, large sound with high bass.

Goldstar

Has a very Techno- Bassy tune. The hearing sound seems very artificial and not very soothing for ears. Treble is boosted as well.

Monster

Looks tiny, but gives heavy beats, and has the deepest bass of all.

Megaphone

Loud, fast beats, emphasized on Bass, the sound is much more continuous without interval.

Falcon

Heavy tune, authentic and balanced tune interval. Non-fatiguing tune.

Final thoughts

Using a custom made exhaust kit for your Royal Enfield does have a significant positive impact on its performance most of the times, provided you’ve chosen the best exhaust system.

But you should be careful about the fact that modified vehicles are not exactly legal in India and companies won’t entertain warranty on such vehicles.

Also, make sure that your modifications stay under the legal limits – be it the sound level, raw engine power and the maximum speed.

Last but not least, ride safe!