The valve that Yamaha dubbed the "exup" that supposedly regulates backpressure is action an emissions control device. There have been test done with the valve manually adjusted to different positions that have shown that the valve is nothing more than noise emissions. You would be better off removing and remapping, I'll post later.

 

thanks redEIK!
i did read through the posts. twice.
but the way you summed it up really did help me understand it alot better.
i am definately looking foreward to seeing the site that has the formulas to achieve ideal exhaust! its funny- what got me started looking at making my own pipes was looking at my steel ones and wanting them to be alum.
people have suggested that alum couldnt take the heat. im not sure. i bet people here know how hot our pipes get right? im curious. i used to have a job welding one-off mufflers and exhaust for boats. and we used aluminum but it was pretty thick. also weight wasnt an issue. they were BIG boats. engines ran much lower rpm.
The tail on your blue bike is gorgous! i dont know much about new rrs so please forgive if this is dumb- what is that tail? is that the stock sub. showing(black) or is that part of an undertail kit? it looks so nice. thanks for all your energy making sense of this stuff. is that your new exhaust pictured?

 

does the above graph say the valve makes almost no difference unless you shut it and then it sucks?
(im colourblind. so my math skills are further hindered here)

 

leo, heres that awesome formula that made me break down and just buy a pipe that pro's had made, if you're willing to put the time into researching the values specific to your bike and actually make the correct pipe, i bow down
http://www.mez.co.uk/mezporting/exhaust_length.html

anyways, what are you trying to gain from your bike with changing the pipe from alum to steel, i assume just weight savings right? the mgfr's (esp yama and honda) make pretty dam^ good headers, it's that cats and enscans that are the compromise. when trying to cut weight from a bike you want to remove as much weight as possible from points that are farthest from the Cog of the bike, like the nose and tail. you want all of the weight that is there to be low and balanced between the two wheels. the headers of a bike are hung at the lowest point and located between the wheels pretty evenly, so losing weight there would be not a beneficial as losing weight from the endcan on a 600rr, as it hangs high and far back away from the Cog. If you save say 5lb from the headers/collectors (not even possible imo) on a new rr you MIGHT notice it, if you cut that same 5lb's from the can that hangs far and away from the Cog you would REALLLLLYY notice it when flicking the bike from side to side. leo, if you can already work metal some just delete that cat your self, and get a quality made slipon (akra/arrow/leovince). if you decide to do something like that make sure that you don't change the i.d. of the pipe from the collector to the midpipe. remember too big / too small causes prob with flow velocity. the only reason that i would consider investing time to make a full set of headers from alum is if you are racing pro for money and have a built/higher comp motor then you could change the whole pipe i.d. and would possibly (not!) get some return on your investment.





PS- misc crap... On a 600rr, the undertail exhaust was initially thought to offset the negative of hanging that weight high and far back by being more aerodynamic, a theory which has been disproven by top forms of racing, esp in wsbk and ss. i personally just like the style of the undertail, to me it's sexy and part of the 600rr, although i know that the underslung exhaust that the 1000rr's and r6's is far more effective in hiding that weight.

PSS- if you want to save weight that will be most beneficial from your bike get some race glass, and delete all the lights, alum subframes both ends and move that electrics/batt. my 2 cents

 

leo, the graph and article state that the "exup" (sometimes called the power) valve is emissions control device, they manually adjusted the valve and gained 1 (1!) ft/lb more torque and only in certain spots on the motor of a gsxr1000, so maybe .6ft/lb more on a 600 i'm guessing? the valve when left to it's own devices (o a pun!) closes and actually cuts a little power throughout, ESP in the zones that a bike has to be ran during emissions testing for noise. even if you adjusted it to make that .6 ft/lb more is it worth the added weight of the valve, cables, and solenoid (which is kept in the tail on 600rr!). not to mention the added complication. also the blue bike is not mine, that's a daytona 675 that somebody actually made a carbon monoque tail with the carbon side exhaust. the fairing i think is from a moriwaki 250 or honda 125 I THINK. not 100% on that, just guessing

 

thanks for all that info redEIK. no my main inspiration for the alum pipe wasnt so much weight but that and looking really noce and not rusting ever. im not planning on building my own headers and i agree that youre right and the best thing i could do is buy the proper pipe from leo vince or somesuch-
my bike isnt nearly as high performance as most people here- im riding an f4 now and was on the 600rr page because some of us had been trying to figure out shortened/ modfd pipes and id seen rr undertail stock can go on ebay for really cheap-
it got me thinkin.
i was fantasizing about finding a 600rr tail with roadrash and fitting it- exhaust and all to my f4-
i knew you needed the right pipe for the right engine and was sorta tryin to figure out how different the exhause needs of two different cbrs might be-
i feel kinda dumb for totally not knowing what kind of bike that is (blue triumph) but im so used to it now - im askin all sorts of silly questions and learning soo much lately (ive had my bike just over a month now!)
anyway thanks-
ps. i just saw a cutaway view of a 2010 aprilla sportbike muffler! holywow! its got tons of crazy stuff in there - bafffle-wall seperate pipes of different sizes splitting into chambers and back again.
i dont know where to start. you should check it out. it looks sooo cool.

 

Leo, for you're purposes I think it would possibly be beneficial to you to build you own out of Al, mgfr's usually compromise to save weight and use a gauge that makes the Al pipes pretty weak, if you were going for rustproof/longevity then make yours out of a thicker gauge pipe and it should last forever and prob weigh the same as a thin gauge steel one. What about SS and alumized steel? Just curious don't know to much about the character of those two metal but isn't aluminzed steel pretty easy to work with? If you're going for power than yeah, buying a full system from a reputable and established mgfr, someone who has put the time into R&D, is the way to go, but man don't get the stock 600rr cans, those things are so heavy! esp pre-07' years. Try to find a cheap slipon! And again man that's putting the weight high and far out back, but if you're not racing then again I guess who cares! It's your bike, do what YOU want! Good luck with your project, anything is possible... with enough money!

PS-The new rsv is SEX SEX SEX, if I ever feel like I ever get to a point where I can really ride a litre that is definately at the top of the list. If the can has multiple chambers with valves that change the routing then aprilia is probably using that to beef up the powerband in different spots, changing the length is different from the noise emissions valves, i know porshe and ferrari use the same idea on their cars.

PSS-Don't feel dumb for asking "silly" questions, if you don't know, ask man. I know a lot about bikes as thats all i do/think/dream but the other day I had to have a friend help me pick out wood from lowes to make a picnic table as I know nothing about that kind of stuff, basic guy stuff and I can't do it myself. Everyone has their thing.