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PERFORMANCE MOTORCYCLE PARTS AND KITS FOR AMERICAN V-TWINS

S&S Cycle logo

What exhaust should I run on my S&S engine and are drag pipes ok?

If you have an existing 2-into-2 system that uses slip-on style mufflers, whether it is an OEM or an aftermarket system, we recommend the new S&S slip-on mufflers. 

S&S dyno tests achieve almost 8 more horsepower and 5 ft. lbs. of torque on a stock Twin Cam 88 engine using stock header pipes and S&S slip-on mufflers, and S&S Super Sidewinder engines have produced 1-1.1 horsepower per cubic inch using stock style exhaust and S&S slip-on mufflers. These mufflers will allow your engine produce more horsepower and torque than straight-through drag pipes in street and highway driving, and work equally well on both stock and large displacement engines. If you don't already have an exhaust system that accepts the S&S Slip-On mufflers, and you need to buy a complete exhaust system, the RevTech staggered dual, or Python 3 systems work well. 

Exhaust selection is critical for optimal performance. Open drag pipes work reasonably well for peak horsepower numbers on some engines but limit low speed performance on the street and can be nearly impossible to carburet. S&S has not had good results with baffled drag pipes due to the increase of exhaust gas restriction (back pressure).

Special low restriction Cycle Shack XP baffle is available through most retail suppliers, and will help with tuning in some cases. Overall, drag pipes are a poor choice for street use. Drag pipes offer nothing to break up the reversion wave pulse. This wave goes down the pipe and then the wave returns back up the pipes. When this wave is in proper time sync to hit the exhaust valve when it is open (pipe length affects the rpm that this happens) it allows the wave to enter the cylinder and when the intake is open during cam overlap it travels across the top of the piston (it is near top of the cylinder at this time) and out the intake valve. This wave continues out the intake through the carb where the next intake stroke draws it all in again. Each time this wave passes through the carburetor the venturi adds gas and makes the next incoming charge richer creating a flat spot or stumble or worse a blubber at this rpm. The longer the duration cam the worse this situation is. Also larger diameter drag pipes and fishtails seem to make this situation worse.