Why is there a bulge in the exhaust pipe of my dirt bike? That bulge is called an expansion chamber, and it is used to increase the horsepower of the engine (see this page for a photo). This technique only works on two-stroke engines, which is why you see it on a lot of dirt bikes but not on street bikes..
In this manner, why do 2 strokes have fat pipes?
The 2-stroke exhaust system uses an expansion chamber - the prominent bulge in the exhaust pipe - to increase the engine's horsepower. In short, the expansion chamber creates a pump, by using the momentum and pressure of the exhaust gases, and squeezes more air and fuel into the cylinder during the intake stroke.
Likewise, why do 2 strokes need expansion chambers? Simply put, it's because the two-stroke exhaust system, commonly referred to as an 'expansion chamber' uses pressure waves emanating from the combustion chamber to effectively supercharge your cylinder. Of course those waves don't radiate in all directions since there's a pipe attached to the port.
Subsequently, one may also ask, which type of exhaust pipe is used on a 2 stroke engine?
On a two-stroke engine, an expansion chamber or tuned pipe is a tuned exhaust system used to enhance its power output by improving its volumetric efficiency.
Can you run a 2 stroke without exhaust?
2-strokes run fine without mufflers, if your muffler pipe is an expansion chamber you might notice a low to medium power loss, but you should be fine.
Related Question Answers
Why do two strokes sound different?
The real reason why 2 strokes are louder is based on the mechanics of the stroke, and the build of the engine. Automobiles (mostly) are 4 stroke. The engine covers the combustion chamber in a water jacket to cool it, which also greatly reduces sound.Which is better FMF or Pro Circuit?
Pro Circuit Vs. FMF: The Pro Circuit has a little more throttle to rear wheel connection down on low end, but the FMF pulls stronger through the mid range. Up on top end both seem on par with each other and of course both have less over-rev than the stock muffler.How does a 2 stroke silencer work?
A two-stroke pipe uses its reflective pressure wave to keep the fuel/air mixture inside the combustion chamber. Most of this tuning is done in the pipe itself, but muffler length and diameter play a part. There is no power difference between one brand's high-end and low-end pipes.Do 2 strokes need back pressure?
In a piston-ported two-stroke engine, however, the situation is more complicated, due to the need to prevent unburned fuel/air mixture from passing right through the cylinders into the exhaust. The exhaust port opens while there is still significant pressure in the cylinder, which drives the initial outflow of exhaust.What is a dirt bike silencer?
Inside your dirt bike muffler or silencer is the exhaust core, which is a tube with holes in it and is often covered in steel wool on newer pipes. The purpose of exhaust packing is to absorb as much of the sound waves coming from the combustion of the engine as possible.What does a fatty pipe do?
With well over 35 years of racing experience behind it, the Fatty pipe delivers race-proven performance. The Fatty broadens and smoothes out the power curve while boosting gains throughout the entire power band, more low-end, more mid, and increased over-rev. Provides power gains throughout entire power band.What is a 2 stroke power band?
"Powerband" is the HP/torque curves of any engine. The sudden hit of a 2-stroke that people refer to as "hitting the powerband" or "coming on the pipe" happens when the engine hits its sweet spot. 2-strokes rely on the frequency of waves. Notice how the exhaust of a 2-stroke is shaped.What does an exhaust expansion chamber do?
The basic idea behind an expansion chamber is to use the momentum and pressure of the exhaust gases to create a pump that squeezes more air and fuel into the cylinder during the intake stroke. It does the same sort of thing that a turbocharger does, but it does it without moving parts.How hot does 2 stroke exhaust get?
Depending on where you take the temps, between 150-250 deg F.What is engine back pressure?
Engine exhaust back pressure is defined as the exhaust gas pressure that is produced by the engine to overcome the hydraulic resistance of the exhaust system in order to discharge the gases into the atmosphere. The term back pressure can be also spelled as one word (backpressure) or using a hyphen (back-pressure).Can I put a 2 stroke exhaust on a 4 stroke?
2 stroke mufflers are NOT meant for 4 Strokes. will it work yes. but there are different packing's for 2 and 4 stroke. If you do put this thing on a 4 stroke please repack it with the 4 stroke packing. you will start a fire if you don't.How do tuned pipes work?
A tuned pipe has a set of cones- Divergent (meaning the cone gets bigger) and Convergent (meaning the cone gets smaller) that are built to cause "echoes" or pressure waves to reflect back, which if done properly can increase the power of the engine.How does a megaphone exhaust work?
With a megaphone, the exhaust stream enters the megaphone at the inlet, and begins to expand at a rate which is controlled by the flare of the megaphone shape. As the exhaust stream expands, it gains pressure as it loses velocity in the larger volume of the megaphone(Bernoulli's Principle).How does a motorcycle exhaust system work?
In a four-stroke system, as the exhaust valves begin to open, a pulse of exhaust pressure enters that cylinder's header pipe. It is a positive wave, which stuffs exhaust gas back into the combustion chamber, back through the intake valves and into the intake system.What is expansion stroke?
expansion stroke. The stroke in the operating cycle of a reciprocating engine in which both the inlet and exhaust valves are closed, the fuel-air mixture has been ignited and burned, and the piston is being forced downward by expanding gases. This is the only stroke in which power is produced.Can you run a chainsaw without a muffler?
Not advisable to run a chainsaw without a muffler. A chainsaw needs a certain amount of back pressure it operate correctly and the muffler also keeps junk from getting into your cylinder and possibly causing serious damage.Is it bad to ride a bike without exhaust?
If by “exhaust” you mean “silencer” then the answer is no, no damage will be done. A little re-tuning may make the engine run smoothly and even more powerfully than before also without a silencer, but it won't make your bike any less loud.Will a moped run without exhaust?
Re: Can you ride a moped with no exhaust? No exhaust will lean out your air fuel ratios and cause you to soft seize. 
