as a newbie asks, sorry if sounds a bit dumb;
with the after market slip ons and cutting the stock pipe has any one found that thier bike runs a bit lumpy. just asking before i buy a R6 can. cause i thought the little GS would of relied on back pressure alot. :dunno_white:
pretty much all gas eneings run on back pressure. but i had straight pipes on my gs and it ran just fine. i probably should have rejetted it but never got around to it and decided to get rid of the pipes. basically as long as you rejet the bike you really shouldnt have any problems
so it wont really matter if i dont rejet. cause it will make it alot easier. for now any way.
well i dont really know if you have to with a stock exhuast from another bike but if you put an aftermarket one on its suggested by pretty much everyone on here.
your a star mate; :cheers: ill post when i find out if it works or not.ill probably be putting a stock r6 exhaust on it any way. just thought id be a bit F***ed if i sawed off the standard and then i got to jets or if it wouldnt run any good.
Back pressure is always bad and to be avoided.
Quote from: Nikolas on July 14, 2007, 12:56:42 PM
Back pressure is always bad and to be avoided.
you might want to do alittle bit of research before you say something like that
Quote from: solosociety on July 14, 2007, 02:53:31 PM
Quote from: Nikolas on July 14, 2007, 12:56:42 PM
Back pressure is always bad and to be avoided.
you might want to do alittle bit of research before you say something like that
Maybe you should. How can restricting exhaust flow be good? It can't, plain and simple. You want the engine power to reach the wheel/s, not go into forcing gases out of the exhaust.
Maybe you're confusing backpressure with maintaining proper exhaust velocity. A properly sized exhaust will have no backpressure. To big and the exhaust gases are slow, causing them to cool down too fast, increase in density, and cause a restriction, too small and the pipe can't flow the necessary volume of gases which results in a restriction. The ideal exhaust would not even be of a constant diameter, but would be a megaphone to keep the gases at a uniform speed and temperature, requiring minimal work by the engine. Get the length right and the sonic pulses will suck the gases right out, and be quieter without a restrictive muffler too.
For a single cylinder you want the exhaust pipe to have twice the volume as its displacement. The ideal length is the exhaust duration times the wave speed (1700ft/s at MSL) over the engine rpm you're tuning for. I don't recall the formulas for multiple cylinders off the top of my head but they're floating around on the internet somewhere.
I build post cat exhausts for Toyota MR2s that run in SCCA solo ES which win national events and drive around on the street with no muffler using this. If I ever get this damn GS registered I'll give a go at a better slip-on and possibly full system.
Go get your leaf blower,start it up,then cover the end just enough to cause pressure to back up in the tube.If you have an older one it'll choke the engine.This is the same thing that happens with a restrictive exhaust.If you remove that restriction,both on the intake and exhaust,you can get more fuel/air mixture through it.Then the only thing restricting the engine is the cylinder(s) volume.
Quote from: Nikolas on July 14, 2007, 04:23:11 PM
How can restricting exhaust flow be good? It can't, plain and simple.
:icon_confused: Ever hear of the Yamaha EXUP valve?
ok.......saw off the pipes before the 2-1 and smear shaZam! on the inside of the tube...........no backpressure.....it'll figuratively and literally be a shitty ride
crucialval's bike has been rejetted with a lunchbox airfilter and his ran wonderful with no muffler.Loud as hell though.Much louder than a Harley.
alright the only time you dont need back pressure is when you are running a turbocharger on an engine. the gs is not a turbo charged enine so it will be needing back pressure. no i never said that it has to have a tremendous amount of back pressure but it needs some. if you are so confident that the bike needs no back pressure the get yourself a camera, go take the exhaust off your bikle from the engine back. then fire up the bike and tape yourself rididng it around getting on it and shaZam!. then put your exhaust back on and do the same exact shaZam!. when your done post your video so we can all see it. well that is if your valves dont bend and lock up the motor. i really dont care about your job making cat back systems because if you knew alot about catalytic convertors you would know they are involved in creating back pressure along with having headers and manifolds that go from 4 into 1. so im pretty sure i have done my research and unless gas engine designs have changed since i graduated from UTI then well i guess im right.
Quote from: solosociety on July 15, 2007, 08:16:43 AM
alright the only time you dont need back pressure is when you are running a turbocharger on an engine. the gs is not a turbo charged enine so it will be needing back pressure. no i never said that it has to have a tremendous amount of back pressure but it needs some. if you are so confident that the bike needs no back pressure the get yourself a camera, go take the exhaust off your bikle from the engine back. then fire up the bike and tape yourself rididng it around getting on it and shaZam!. then put your exhaust back on and do the same exact shaZam!. when your done post your video so we can all see it. well that is if your valves dont bend and lock up the motor. i really dont care about your job making cat back systems because if you knew alot about catalytic convertors you would know they are involved in creating back pressure along with having headers and manifolds that go from 4 into 1. so im pretty sure i have done my research and unless gas engine designs have changed since i graduated from UTI then well i guess im right.
Hahahah graduated from UTI, I'm sure you are an expert. Running with NO exhaust at all IS bad for the motor, however it has nothing to do with "backpressure". Running with no exhaust AT ALL is bad because the valves are constantly being exposed to hot air (exhaust) and then cold air (surrounding atmosphere air).
Quote from: solosociety on July 15, 2007, 08:16:43 AM
alright the only time you dont need back pressure is when you are running a turbocharger on an engine. the gs is not a turbo charged enine so it will be needing back pressure. no i never said that it has to have a tremendous amount of back pressure but it needs some. if you are so confident that the bike needs no back pressure the get yourself a camera, go take the exhaust off your bikle from the engine back. then fire up the bike and tape yourself rididng it around getting on it and shaZam!. then put your exhaust back on and do the same exact shaZam!. when your done post your video so we can all see it. well that is if your valves dont bend and lock up the motor. i really dont care about your job making cat back systems because if you knew alot about catalytic convertors you would know they are involved in creating back pressure along with having headers and manifolds that go from 4 into 1. so im pretty sure i have done my research and unless gas engine designs have changed since i graduated from UTI then well i guess im right.
Turbochargers cause immense backpressure and pumping losses. If you pull the exhaust off an engine, you will be forcing the engine to do work forcing exhaust gases out because you will have destroyed scavenging. Read up on this guy named Bernoulli, he wrote the book on moving fluids through tubes. An engine is just a glorified airpump; the more air you move through it, the more power you'll make. A restriction is never a good thing.
But I guess you're right since you went to UTI. My University of California, San Diego engineering education and Society of Automotive Engineers membership can't match a tech school.
Yeah well my non-complete geology degree and various combat skill from the army say smear shaZam! on it and blow it up :flipoff:
Quote from: Gisser on July 14, 2007, 11:13:09 PM
Quote from: Nikolas on July 14, 2007, 04:23:11 PM
How can restricting exhaust flow be good? It can't, plain and simple.
:icon_confused: Ever hear of the Yamaha EXUP valve?
Yes, it improves scavenging at all rpms by changing the exhausts sonic properties. Without such a system you can only tune an exhaust for one rpm. Ideally you'd have a long narrow exhaust that got short and big as the revs increased, but that's not really possible... Although there are intakes with multiple runners that work off that principle. It's all a compromise.
I guess 12 years of building car engines taught me nothing.All internal combustion engines work on the same principles.So I guess all that back pressure is what made the 1100 hp my 65 mustang had. :dunno_white:
Off topic , but i bet that Mustang was a Beast , i want to run my bike withno muffler , just a slash cut pipe poking out? ben , u sed some1 run it fine with it ? didnt mess the engine up? :thumb:
Quote from: Jay_wolf on July 15, 2007, 09:47:56 PM
Off topic , but i bet that Mustang was a Beast , i want to run my bike withno muffler , just a slash cut pipe poking out? ben , u sed some1 run it fine with it ? didnt mess the engine up? :thumb:
Crucialval ran his bike with the exhaust cut off right below the can.Didn't seem to effect it,but his engine has been heavily rejeted with a K&N lunchbox filter.As long as the engine doesn't lean out through the rpm range,I don't see a problem with strieght slash cut pipes.
Quote from: Nikolas on July 15, 2007, 12:25:34 PM
Quote from: Gisser on July 14, 2007, 11:13:09 PM
Quote from: Nikolas on July 14, 2007, 04:23:11 PM
How can restricting exhaust flow be good? It can't, plain and simple.
:icon_confused: Ever hear of the Yamaha EXUP valve?
Yes, it improves scavenging at all rpms by changing the exhausts sonic properties. Without such a system you can only tune an exhaust for one rpm. Ideally you'd have a long narrow exhaust that got short and big as the revs increased, but that's not really possible... Although there are intakes with multiple runners that work off that principle. It's all a compromise.
But EXUP improves scavenging by using
back-pressure to prevent
overscavenging (sucking intake charge out the exhaust during valve overlap at low RPM). Or so the story's told:
QuoteThe Exhaust Ultimate Power Valve (EXUP®) alters the back pressure in the exhaust system at various revs. At lower revs the valve restricts the exhaust gas flow improving the scavenging of the motor and increasing torque. Above 6000 rpm, the valve is completely clear of the gas flow and the system performs like any other non-EXUP® equipped exhaust.
Poster is inquiring about an R6 can which, if stock, should work fine, but the aftermarket crap do seem to overscavenge (all that annoying
popping). :dunno_white:
Quote from: Gisser on July 16, 2007, 07:44:06 PM
Quote from: Nikolas on July 15, 2007, 12:25:34 PM
Quote from: Gisser on July 14, 2007, 11:13:09 PM
Quote from: Nikolas on July 14, 2007, 04:23:11 PM
How can restricting exhaust flow be good? It can't, plain and simple.
:icon_confused: Ever hear of the Yamaha EXUP valve?
Yes, it improves scavenging at all rpms by changing the exhausts sonic properties. Without such a system you can only tune an exhaust for one rpm. Ideally you'd have a long narrow exhaust that got short and big as the revs increased, but that's not really possible... Although there are intakes with multiple runners that work off that principle. It's all a compromise.
But EXUP improves scavenging by using back-pressure to prevent overscavenging (sucking intake charge out the exhaust during valve overlap at low RPM). Or so the story's told:
QuoteThe Exhaust Ultimate Power Valve (EXUP®) alters the back pressure in the exhaust system at various revs. At lower revs the valve restricts the exhaust gas flow improving the scavenging of the motor and increasing torque. Above 6000 rpm, the valve is completely clear of the gas flow and the system performs like any other non-EXUP® equipped exhaust.
Poster is inquiring about an R6 can which, if stock, should work fine, but the aftermarket crap do seem to overscavenge (all that annoying popping). :dunno_white:
the gs doesn't have any overlap in the cams,at least not enough to cause over scavenging.it takes a pretty big cam to cause that problem.one with a lot of lobe lift and tight duration.
oh my god...I love how every redneck has an idea about how back-pressure is important or how back-pressure is heinous and none of them agree but everyone's right...I REALLY love how every time "back-pressure" gets brought up there's at least two people with opposing views who pop up that claim they know what they're talking about because they majored in fluid dynamics or some shaZam! like that...especially when I know that if you talk back-pressure to anyone who has a real background in fluid dynamics and mechanics they'll slap the shaZam! out of you...
Without getting too in-depth, back-pressure is completely irrelevant. If you spend time really thinking about whether back-pressure is hurting you or not, you should retire your tools and stop modifying things. What's important is volume and velocity. You want to move the absolute largest volume of atmosphere and fuel through an engine at a given time as possible. Back-pressure is something that you have to take into account when building or modifying an exhaust because IT IS EVER-PRESENT! So I guess you can think it's important...or that it's bad...or that back-pressure is where babies come from...it's there regardless of whether your "thinks he's a NASCAR driver" neighbor or your uber-educated doctorate holding fluid dynamics professor says it's important or not.
Regardless of how it ran.. I bet val's bike sounded like poop with no exhaust.
I'm suffering from a bad case of back pressure. I think it was the Indian food.