Tech Tip: Snowmobile Exhaust 101

An Inside Look at Your Sled's Exhaust

Published in the November 2013 Issue Byron Strickland, MBRP

The days when a snowmobile ex­haust was just a can filled with fiber­glass and steel wool are long gone.

Today we expect our sleds to handle greater loads, go farther, go faster and sound awesome at the same time. When you throw in widely differ­ent sled configurations, each with its unique characteristics, maximum performance requires careful and precise exhaust design and engineer­ing. Anything less can result in serious damage to your expensive machine and compromise safety and performance.

The good news is that advances in the design and engineering of aftermar­ket exhaust products more than meet the requirements of today’s snowmobile enthusiast.

Basics Of A Great Exhaust

To start off, we must distinguish between the hard core, extreme perfor­mance crowd and the enthusiast who is simply looking to get a more enjoyable sledding experience.

The former is prepared to risk reli­ability and reduced drivability, and potentially endure more rebuilds in exchange for potential maximum gains in horsepower. To achieve that goal their exhaust systems, not to men­tion their entire drivetrains, are highly modified, often to the point where they are unrecognizable from the stock sleds that they started from.

Most enthusiasts, however, have more modest objectives. They are look­ing for performance gains that will let them travel a bit farther on a tank of gas, have that little power boost when they need it, get improved throttle response and more out-of-the-corner power. Of course, having a machine that produces a rich and distinctive sound is a definite bonus.

Fortunately, current performance ex­haust technology provides the enthusi­ast with a wide array of choice, allowing him to modify his sled without difficul­ty. Well-built and designed aftermarket products deliver improved performance while avoiding the risk of damage to the sled. They are also considerably lighter than stock, an important consid­eration for high altitude mountain rid­ers and those looking to get maximum performance from their sled.

(Some) Back Pressure Is Your Friend

Unfortunately, some enthusiasts have, through harsh experience, come to the conclusion that aftermarket cans will lose power compared with stock. In many cases that is actually true. A recent comparison of four aftermarket manufacturers’ canisters conducted by BRP found that three lost power when tested on the same dyno under identical conditions.

One reason for such power loss is an attempt by some manufactur­ers to maximize sound volume. The simplest way to do this is by opening up the exhaust flow, severely reducing or even eliminating the back pressure that your engine needs to achieve peak performance. Keeping in mind that your sled’s performance depends on a complex, dynamic collection of many different components working in con­cert, modification to one part can have significant impact on others.

In the case of the muffler, as back pressure is reduced, the engine burns more lean, that is, a higher level of oxygen is mixed with the fuel making its way to the combustion chambers. When it is too lean there is not enough fuel in the mixture to provide maxi­mum explosive force. Such a mixture can also lead to serious engine damage.

Performance By Design

Properly designed and engineered canisters can be tuned to achieve the precise amount of back pressure needed by each individual model of sled to pro­vide predictable and consistent power gains. Fine adjustments to the bends and flow diameters at various points in the inlet and outlet pipes can have massive impact on performance and sound quality. More importantly, such canisters achieve the critical balance between maximum performance and safe operation.

Unfortunately, not all aftermarket exhaust manufacturers carry out the level of technical development or the extensive flow bench and dyno test­ ing required to engineer a canister that achieves this balance. Many of the products that you see online or at snow shows are in fact poor copies of more sophisticated products. There are even cans on the market with pipes that are not mandrel bent. Fortunately, such cans are easily identified by visible creases and ripples at the bends. Such ripples disrupt exhaust flow and cause substantial performance degradation.

In truth, it takes many hours of careful prototype development, as well as precise design and engineering, to provide a finished product that will improve horsepower, sound great and guarantee a safe sledding experience.

Another benefit of a canister specifi­cally tuned to provide the maximum performance and reliability for the type of sled it is installed on is that every en­thusiast can get exactly the right sound for him. The mountain rider can enjoy more aggressive sound levels while those riding the trails can keep to a nice mellow exhaust note.

Clutching And Jetting, Oh My

Again, recognizing that the needs of the snowmobile enthusiast are not the same as the more extreme activities like racing, careful consideration should be given before purchasing any exhaust system that will require clutching or jetting. A properly designed canister can product measurable horsepower gains without having to resort to such measures and still be a simple bolt-on DIY install.

The Right Can For The Job

In selecting the right snowmobile ex­haust product for your sled there are a number of things to keep in mind. One would be the local regulations regarding sound levels with many jurisdictions prohibiting sleds generating greater than 88 dB. Other considerations would be the elevation and terrain you will be traveling in, the load levels and type of sledding you will be doing. Someone using their sled to haul gear will have different requirements than someone trekking along the trails.

There are three broad categories of aftermarket exhaust available to the en­thusiast. The first of these are the race cans which significantly increase horse­power and are the lightest of the three categories. While this category includes the more extreme products mentioned above, there are also bolt-on race muf­flers. By reducing the amount of sound-baffling material in the canister and making adjustments to the structure of the inlet and outlet pipes, they provide an extremely satisfying boost to both power and performance.

Next would be the standard canister category. These are designed to produce a moderate sound level, have lower weight than stock and generally pro­duce measurable horsepower gains.

Finally, there is the trail category. Carefully designed to produce a maximum 88 dB at 4000 rpm, these generally have more baffling material than standard cans and are a bit heavier though still smaller and lighter than stock.

Stealth Power

Before leaving the subject of after­market exhaust there is one more way to gain greater horsepower without waking the neighbors or risking the anger of local law enforcement. Perfor­mance headers are now available that are bolt-on easy to install using only common hand tools. Even when these headers are installed with the stock muffler kept in place you can gain 6-7 hp or more without any significant increase in decibels. Paired up with an aftermarket muffler, these headers will give you even greater performance.

For the typical snowmobile enthu­siast the ideal performance exhaust product will be easy to install, prefer­ably without having to resort to special­ized tools or equipment, be tuned to their specific model of sled and never compromise safety. Picking the right products for your needs ensures a much more enjoyable sledding experience.

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