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havnt really torn into my motor yet but...with cat and doo making 155+ hp, poo making 145hp, lets take a look
pipe design, cat and doo are both pulling 155+ hp out of relatively cramped pipe and can set ups inside their chassis's, also i dont know what the angles on the stock pipe is, shallow diffuser tapers=broad powerband but low top end, shallow baffle cones=broad power band and not as good top end numbers, steep tapers on the pipe diffuser(sometimes called a megaphone)=narrow powerband and good top end performance, steep baffle cones=narrow powerband with good top end performance and a very steep over-rev power drop off...i havnt really looked at mine but if any of you know these specs it would help everyone understand what the pipe is designed for, are the diffuser tapers steep or shallow? is the baffle cone steep or shallow?
y-pipe design, while i havnt looked alot under the hood, i do know...the y-pipe is angled upwards...this is a very big no no, reason being is...the exhaust port tunnel drops downward, the exhaust port in the cylinder is about 1 inch higher than where the y-pipe bolts to the cylinder, and when you angle the y-pipe upwards it will disrupt flow of exhaust and weaken the exhaust pulses from the tuned pipe, now i havnt looked into the y-pipe much, but it should have a very gradual direction change to minimize the flow disruption, if it changes in a fairly short time and isnt well rounded off a redesigned y-pipe could get up to 2-4 hp in bottom end and midrange with a probable 2 hp on top
Can/muffler design, can looks fine, and even if it is a bad design it will not impede hp by more than 2 at most
Cylinder heads, dont know what they look like, or what the stock compression ratio is supposed to be for year to year, but a wide squish band will reduce heat and will fight off detonation, if you move the combustion chamber to the intake side you will further fight off detonation because it will be away from the hot exhaust side and on the cooler intake side of the cylinder, the angles in the combustion chamber also have affect, steeper angles make more top end power and shallow angles make mid range and low end, bikeman claims no hp with cylinder head redesign with stock compression ratio, only leaning out and better cooling capabilites
Fueling, im not clear on the exact specs on the cfi, but ive been told the injection is pointed towards the boost port(away fromt exhaust), not sure about fuel mapping, and when the injector fires, and when it stops, but if it is pointed toward the boost port, i assume you can pick up lots of hp with staggered porting(more on this later), and usually carbs will bring more hp than fuel injection...if any of you know where the injector is located, and where its pointed, please spill the beans as it will help me, and everyone else understand why the poo isnt making the power as the other 2
Porting, I have no idea of what the ports inside this motor look like, but tall exhaust ports make for good top end, and narrow powerbands, wide exhaust ports make for good top end power with out the affect of a narrow power band, but reduced piston ring life, transfer ports can be messed with to little affect unless something else major is done to induction, exahust port, and exhaust pipe, taller than stock transfer ports make for fuel/air loss out the exhaust port(shouldnt be an issue if the cfi is actually effective at minimizing fuel loss out the exahust), and crankcase being filled with exhaust at low rpm's from exahust blowing into the transfer ports and into crankcase on the exhaust return wave, transfer port angles also matter, transfer ports that angle upwards will flow fuel/air streams that all slowly, and easily meet together in the upper cylinder, transferports with no angle send fuel/air streams across the top of the piston crown to crash together at the rear of the cylinder(away from exhaust), this leaves a pocket of unscavenged exahust at the top of the cylinder, port staggering can take care of this because the boost port is still angled upwards towards the top of the cylinder, port staggering is when the transfer and boost ports are all opened with different timings from one another, port staggering can make more hp at the top end and midrage, or all through out the powerband if the transfer ports have no angle...if you know the specs on the cfi ports please post, transfer angles, and if they are staggered(all open at different times from one another)
Crankcase, high crankcase compression(low crankcase volume) will help in pushing the exhaust out of the cylinder and pushing a fresh charge of air into the cylinder, meaning more hp, it also will increase the amount of fuel/air lost out of the exhaust when you are below the power band(again, should not be an issue if the cfi injection system was actually effective at reducing fuel loss out of the exhaust), bikeman claims 4 hp from more cylinder volume with their cylinder spacers and longer piston from their durability kit, they told me there was not enough volume in the crankcase to begin with so when they added volume they got better breathing with more air getting into the cylinder, this may or may not be from smoother airflow into the transfer ports, if you know what the crankcase looks like, tell us if there is any airflow blocks to the transfer ports and to the boost port(bad crankcase to cylinder matching), or if there isnt that much volume
reeds, boyeson claims 4 hp with their reed valves, reeds dont seem bad
Oiling, despite what you might think, most of the time...MORE 2 stroke oil makes MORE power, due to better lubrication and better cylinder wall to pistion sealing, while it may not be as crisp on the throttle, more oil usually means more power on top and in the midrange, turning up the pump isnt really effective for oiling because the fuel injector will spray gasoline onto the cylinder wall and wash the oil away, turning up the pump a little, and mixing your gas is effective
Bore x Stroke, the polaris has a larger bore than stroke, this isnt where power is being lost
adding lots of little things will all add up to big things, etec (153-158 hp) from 145 is deffinitly easy to grasp, the cat is 158-161, it is certainly possible to get there cheaply if we all know a little more on the subject, so if you have any info please post if you have pictures of a torn down polaris 800, please post up aswell
discuss your theories
pipe design, cat and doo are both pulling 155+ hp out of relatively cramped pipe and can set ups inside their chassis's, also i dont know what the angles on the stock pipe is, shallow diffuser tapers=broad powerband but low top end, shallow baffle cones=broad power band and not as good top end numbers, steep tapers on the pipe diffuser(sometimes called a megaphone)=narrow powerband and good top end performance, steep baffle cones=narrow powerband with good top end performance and a very steep over-rev power drop off...i havnt really looked at mine but if any of you know these specs it would help everyone understand what the pipe is designed for, are the diffuser tapers steep or shallow? is the baffle cone steep or shallow?
y-pipe design, while i havnt looked alot under the hood, i do know...the y-pipe is angled upwards...this is a very big no no, reason being is...the exhaust port tunnel drops downward, the exhaust port in the cylinder is about 1 inch higher than where the y-pipe bolts to the cylinder, and when you angle the y-pipe upwards it will disrupt flow of exhaust and weaken the exhaust pulses from the tuned pipe, now i havnt looked into the y-pipe much, but it should have a very gradual direction change to minimize the flow disruption, if it changes in a fairly short time and isnt well rounded off a redesigned y-pipe could get up to 2-4 hp in bottom end and midrange with a probable 2 hp on top
Can/muffler design, can looks fine, and even if it is a bad design it will not impede hp by more than 2 at most
Cylinder heads, dont know what they look like, or what the stock compression ratio is supposed to be for year to year, but a wide squish band will reduce heat and will fight off detonation, if you move the combustion chamber to the intake side you will further fight off detonation because it will be away from the hot exhaust side and on the cooler intake side of the cylinder, the angles in the combustion chamber also have affect, steeper angles make more top end power and shallow angles make mid range and low end, bikeman claims no hp with cylinder head redesign with stock compression ratio, only leaning out and better cooling capabilites
Fueling, im not clear on the exact specs on the cfi, but ive been told the injection is pointed towards the boost port(away fromt exhaust), not sure about fuel mapping, and when the injector fires, and when it stops, but if it is pointed toward the boost port, i assume you can pick up lots of hp with staggered porting(more on this later), and usually carbs will bring more hp than fuel injection...if any of you know where the injector is located, and where its pointed, please spill the beans as it will help me, and everyone else understand why the poo isnt making the power as the other 2
Porting, I have no idea of what the ports inside this motor look like, but tall exhaust ports make for good top end, and narrow powerbands, wide exhaust ports make for good top end power with out the affect of a narrow power band, but reduced piston ring life, transfer ports can be messed with to little affect unless something else major is done to induction, exahust port, and exhaust pipe, taller than stock transfer ports make for fuel/air loss out the exhaust port(shouldnt be an issue if the cfi is actually effective at minimizing fuel loss out the exahust), and crankcase being filled with exhaust at low rpm's from exahust blowing into the transfer ports and into crankcase on the exhaust return wave, transfer port angles also matter, transfer ports that angle upwards will flow fuel/air streams that all slowly, and easily meet together in the upper cylinder, transferports with no angle send fuel/air streams across the top of the piston crown to crash together at the rear of the cylinder(away from exhaust), this leaves a pocket of unscavenged exahust at the top of the cylinder, port staggering can take care of this because the boost port is still angled upwards towards the top of the cylinder, port staggering is when the transfer and boost ports are all opened with different timings from one another, port staggering can make more hp at the top end and midrage, or all through out the powerband if the transfer ports have no angle...if you know the specs on the cfi ports please post, transfer angles, and if they are staggered(all open at different times from one another)
Crankcase, high crankcase compression(low crankcase volume) will help in pushing the exhaust out of the cylinder and pushing a fresh charge of air into the cylinder, meaning more hp, it also will increase the amount of fuel/air lost out of the exhaust when you are below the power band(again, should not be an issue if the cfi injection system was actually effective at reducing fuel loss out of the exhaust), bikeman claims 4 hp from more cylinder volume with their cylinder spacers and longer piston from their durability kit, they told me there was not enough volume in the crankcase to begin with so when they added volume they got better breathing with more air getting into the cylinder, this may or may not be from smoother airflow into the transfer ports, if you know what the crankcase looks like, tell us if there is any airflow blocks to the transfer ports and to the boost port(bad crankcase to cylinder matching), or if there isnt that much volume
reeds, boyeson claims 4 hp with their reed valves, reeds dont seem bad
Oiling, despite what you might think, most of the time...MORE 2 stroke oil makes MORE power, due to better lubrication and better cylinder wall to pistion sealing, while it may not be as crisp on the throttle, more oil usually means more power on top and in the midrange, turning up the pump isnt really effective for oiling because the fuel injector will spray gasoline onto the cylinder wall and wash the oil away, turning up the pump a little, and mixing your gas is effective
Bore x Stroke, the polaris has a larger bore than stroke, this isnt where power is being lost
adding lots of little things will all add up to big things, etec (153-158 hp) from 145 is deffinitly easy to grasp, the cat is 158-161, it is certainly possible to get there cheaply if we all know a little more on the subject, so if you have any info please post if you have pictures of a torn down polaris 800, please post up aswell
discuss your theories
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