sredish Posted November 23, 2006 Report Share Posted November 23, 2006 (edited) Understanding of 4-stroke exhausts must begin with some explanation of the tuned 2-stroke exhaust system since no other exhaust system uses sound energy more effectively to enhance engine performance. Two stroke pipes are commonly called expansion chambers. The more accurate, but lesser known term for two stroke exhausts, is pulse charger". Until the invention of the pulse charger style exhaust, the 2-stroke was more of a utility power plant used in chainsaws, weed whippers, scooters, etc for its simplicity and light weight but not because of its high output. The pulse charger changed all of that. If everything else was optimized on a 2 stroke engine, changing from a non-tuned exhaust to a pulse charger would increase the horsepower by approximately 40%. That change alone was enough to tip the power scale for competition cycle engines in favor of the 2-stroke. Imagine an exhaust system that so greatly affects the output on a 2-stroke, it's the same as bolting a supercharger on to a 4-stroke! As a result, 2-strokes are highly sensitive to pulse charger designs. No other component can alter the 2-strokes performance characteristics, for better or worse, as much as their exhausts. A 4-stroke has 4 basically discrete strokes of the piston for each power cycle: 1) Intake 2) Compression 3) Power 4) Exhaust Whereas, a 2-stroke power stroke has a combination of things happening in each piston stroke and produces a power stroke on each downward movement of the piston, instead of every other downward stroke like the 4-stroke. Until a basic understanding is gained, standard physics terms associated with sound waves referring to negative pressure and sign inversion with increasing or decreasing confinement area will not be used. A much more intuitive understanding will come from this model. Think of the exhaust pipe as a giant syringe? and think of the sound wave as being not a wave but just a single pulse. This pulse is the equivalent of the rubber plunger inside the syringe, except that this plunger is thin like a rubber diaphragm and it can change its shape instantly to perfectly seal any shape of syringe. A pulse charger has 5 distinct sections: 1) Headpipe - small diameter tube/ connects to exhaust port 2) Megaphone- 1st cone section diverging away from headpipe- extends suction action of sound pulse 3) Belly- Fatter center section with constant diameter 4) Reverse Megaphone- Converging cone- reflects sound pulse (think echo)- reverses direction of sound pulse energy 5) Stinger- tailpipe- regulated pressure bleed When the piston has partially uncovered the exhaust port and the sound pulse (plunger) is in the megaphone. As it leads the exhaust charge, it leaves a partial vacuum (suction) in its wake. This aids greatly in exhaust removal by adding a ? Edited November 23, 2006 by sredish Quote Link to comment Share on other sites More sharing options...
sredish Posted November 23, 2006 Author Report Share Posted November 23, 2006 might be worth a pin... :beer: Quote Link to comment Share on other sites More sharing options...
letsgetthisdone Posted November 26, 2006 Report Share Posted November 26, 2006 might be worth a pin... :beer: I agree Quote Link to comment Share on other sites More sharing options...
Animalman294 Posted November 27, 2006 Report Share Posted November 27, 2006 might be worth a pin... :beer: Thats about right to me................. :beer: Quote Link to comment Share on other sites More sharing options...
atvaddiction Posted December 6, 2006 Report Share Posted December 6, 2006 there is a lot of good info in there good job Quote Link to comment Share on other sites More sharing options...
06BaNsHeE Posted December 6, 2006 Report Share Posted December 6, 2006 Understanding of 4-stroke exhausts must begin with some explanation of the tuned 2-stroke exhaust system since no other exhaust system uses sound energy more effectively to enhance engine performance. Two stroke pipes are commonly called expansion chambers. The more accurate, but lesser known term for two stroke exhausts, is pulse charger". Until the invention of the pulse charger style exhaust, the 2-stroke was more of a utility power plant used in chainsaws, weed whippers, scooters, etc for its simplicity and light weight but not because of its high output. The pulse charger changed all of that. If everything else was optimized on a 2 stroke engine, changing from a non-tuned exhaust to a pulse charger would increase the horsepower by approximately 40%. That change alone was enough to tip the power scale for competition cycle engines in favor of the 2-stroke. Imagine an exhaust system that so greatly affects the output on a 2-stroke, it's the same as bolting a supercharger on to a 4-stroke! As a result, 2-strokes are highly sensitive to pulse charger designs. No other component can alter the 2-strokes performance characteristics, for better or worse, as much as their exhausts. A 4-stroke has 4 basically discrete strokes of the piston for each power cycle: 1) Intake 2) Compression 3) Power 4) Exhaust Whereas, a 2-stroke power stroke has a combination of things happening in each piston stroke and produces a power stroke on each downward movement of the piston, instead of every other downward stroke like the 4-stroke. Until a basic understanding is gained, standard physics terms associated with sound waves referring to negative pressure and sign inversion with increasing or decreasing confinement area will not be used. A much more intuitive understanding will come from this model. Think of the exhaust pipe as a giant syringe? and think of the sound wave as being not a wave but just a single pulse. This pulse is the equivalent of the rubber plunger inside the syringe, except that this plunger is thin like a rubber diaphragm and it can change its shape instantly to perfectly seal any shape of syringe. A pulse charger has 5 distinct sections: 1) Headpipe - small diameter tube/ connects to exhaust port 2) Megaphone- 1st cone section diverging away from headpipe- extends suction action of sound pulse 3) Belly- Fatter center section with constant diameter 4) Reverse Megaphone- Converging cone- reflects sound pulse (think echo)- reverses direction of sound pulse energy 5) Stinger- tailpipe- regulated pressure bleed When the piston has partially uncovered the exhaust port and the sound pulse (plunger) is in the megaphone. As it leads the exhaust charge, it leaves a partial vacuum (suction) in its wake. This aids greatly in exhaust removal by adding a ? Quote Link to comment Share on other sites More sharing options...
4everwantedbanshee Posted December 6, 2006 Report Share Posted December 6, 2006 wow!!wow!!! i learnedso much. i knew somethings but learned many more. good write up. :beer: :beer: :beer: :beer: Quote Link to comment Share on other sites More sharing options...
BANSHEEMANIAC Posted December 6, 2006 Report Share Posted December 6, 2006 (edited) Damn did you writ all of that?Definately deserves a pin :shoothead: naaa! the tooth fairy wrote it for him!! just having some fun with you man!!! :laugh: dont take it the wrong way. :biggrin: Edited December 6, 2006 by BANSHEEMANIAC Quote Link to comment Share on other sites More sharing options...
shee rips Posted September 10, 2007 Report Share Posted September 10, 2007 wow thanks for that. i knew some of that but never really the theory behind it. good job :beer: Quote Link to comment Share on other sites More sharing options...
letsgetthisdone Posted September 10, 2007 Report Share Posted September 10, 2007 i can't beleive this was never pinned.. Quote Link to comment Share on other sites More sharing options...
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