building an exhaust.. any guru advice or tips?

[monsta]

I want to build a new exhaust for the monsta. Currently I have a Quat D- Xbox on it.
I love the look of an under engine exhaust but the X Box is robbing heaps of power, my guess is because there is no crossover inside it. The exhaust just goes in, has a change of direction and comes out. I'm thinking because there is no crossover, there is no scavenging.
So, the plan is to build an an under engine exhaust of similar styling, but with a crossover inside.
I have an old exhaust from a 600 that I plan on cutting up to use the crossover and any other bits needed.



The problem I have is that I want the exhaust to narrow like the xbox, but the 600 headers (like the 900) exit the crossover and make a wide radius toward the back, which will make the fab'd exhaust also wide.



I could cut off the pipework as it exits the crossover, but I'm thinking that it would probally ruin the scavenging effect of the unit?? because it would need that run-on to help draw the gas through. any ideas?



Maybe I should just go and get some tighter radius bends from an exhaust shop and fab it from scratch, or reposition the crossover somehow?
Any experts here that may have some suggestions?

[brad black]

swap the inlets and outlets so to speak, or rotate it 45 degrees so you can have more exit length in the same space.  or run the vert down and foward and loop it back towards the back so you can y the horiz in there.  they'll be different lengths tho.

you theory will be overruled by the reality of making it fit.  make what you want fit and asthetics wise, then throw it away if it doesn't work and start again on something different.

maybe try two uncollected pipes with mufflers on them.  dyno it with std headers and slip ons (the control) then the x box then try other things.  two single pipes of the right size might work ok.  ok enough for the simplicity to suffice.

exhaust formula here - http://www.mvagusta.net/forum/showthread.php?t=43891

[monsta]

thanks Brad. I have a bit of spare stainless sheet, so yeah, there will be a bit of trial and error.
That link is good. I offten wondered if there was a formula or was it hit n miss.. and why Ducatis had different lengths!

Tomorrow I'm gunna try n get an exhaust donut locally and cut it up to see if I can make it fit.

exhaust donut = tighter radius...

[Raux]

Thanks for the link to that site.
how do you order from them?

[monsta]

i couldn't see how to order either..  but thay arn't local, I hope to get on local so I dont have to wait...

[Roaduser]

swap the inlets and outlets so to speak, or rotate it 45 degrees so you can have more exit length in the same space.  or run the vert down and foward and loop it back towards the back so you can y the horiz in there.  they'll be different lengths tho.

you theory will be overruled by the reality of making it fit.  make what you want fit and asthetics wise, then throw it away if it doesn't work and start again on something different.

maybe try two uncollected pipes with mufflers on them.  dyno it with std headers and slip ons (the control) then the x box then try other things.  two single pipes of the right size might work ok.  ok enough for the simplicity to suffice.

exhaust formula here - http://www.mvagusta.net/forum/showthread.php?t=43891

hey brad, im just playing with the formulae on that page, but dont have cam specs. with your experience in ducati, do u have a exhaust bbdc value for an 800?

EDIT: found cam specs on your site of all things.. haha cheers!
looking at your site, i assume the figures posted are btdc? your listing 57 for the 800. looking at his formula, do u think i should just use your 57 instead of his [bbdc+180]? same thinG?

ok so that obviously didnt work at 6 inches primaries.. ill now assume your reading is bbdc.
his formula for length is
850x [exh bbdc+180] / rpm @peak power
850x [57+180] / 8500 = 23.7 in long

that seems fair....

for diameter of pipe
2x the square root of swept cylinder volume[in cc]/8.2/L/Pi
2x square root of 400/8.2/23.7/3.14
2x square root of 0.655
2x 0.809
1.618 inch

[Roaduser]

so for an 800. my ideal is 41mm id pipe, 60cm length before merge/crossover. im thinking that seems quite doable with the rear primary going down, forwards then hooking at the right point (prob a touch tight a bend but unavoidable) to make them merge a bit before the 60 cm mark to accomodate for the length of the head port.

but what diameter pipe should be used when you combine two 41mm primaries would depend on the phase of the cylinders wouldnt it? but that i dunno mucha bout that, so discarding the phase of the cylinders, with the tapering rule for exhaust to maintain air speed id want to go a little smaller than the combined area of the primaries after the merge.

41mm pipe = 13.2cm2
2 pipes = 26.4cm2
so 58mm pipe= 2x 41mm pipes

common sizes for mild steel exhaust is 41.3 and 57.15 how convenient! now to find it in thin wall stainless....

[brad black]

mild steel exhaust tubing comes in 1/8 increments and has 1/16 wall thickness.  so one size will slip nicely over the next smaller and nicely into the next bigger.  get it ceramic coated and forget about stainless. i say.  did that on my sport 1100i.

i'd be more inclined to make the merge smaller, just cutting a 1/3 or so off each pipe and welding them together.  check out a 2004 - 2008 aprilia rsvr or 2006 - 2008 tuono with the 2-2 exhaust.

[Roaduser]

I can get the sizes needed in 409 stainless. not the best grade but worth a shot. i have brought off these guys before when i extended my s-pipes and they are very helpful.

http://www.sassales.com.au/catalogues/Muffler%20Flyer%20211106.pdf

[Roaduser]

http://www.suncoastcyclesports.com/servlet/the-142872/04-dsh-09-Aprilia-RSV-RSVR/Detail

u talking about this one? it is very similar to what i was thinking except i was intending to merge and have a single outlet from there. but I'm not too fussed as long as its short and low. is there a benefit to a 2 to 2 system over a 2 to 1?

The main reason i want this exhaust change is to have a short low exhaust that allows me to remove the huge spacers I've had to use to make my rizoma rear sets clear the high mount dp setup. and i don't like regular low mount pipes.

http://www.apriliaforum.com/forums/attachment.php?attachmentid=157939&stc=1&thumb=1&d=1306264795
this one, the tuono is like what i was thinking

[Raux]

http://www.suncoastcyclesports.com/servlet/the-142872/04-dsh-09-Aprilia-RSV-RSVR/Detail

not a 2-2 pipe. has a crossover where the pipes are cut and welded together.

[Roaduser]

must be a terminology difference there. i thought a 2-2 was two header pipes, a crossover, two tail pipes. or do u call that a 2-1-2?

[Raux]

must be a terminology difference there. i thought a 2-2 was two header pipes, a crossover, two tail pipes. or do u call that a 2-1-2?

2-2 is two separate pipes
2-1-2 is two pipes that crossover/xpipe/etc.
2-1 combine but never separate

the d-16 GP exhaust 4-2 for example. so 2 of the cylinders combine into single pipes but then never combine or separate after that.
a lot of I4 bikes are 4-2-1

pretty much standard I've seen for ducati 2-1-2 with either a crossover or x-pipe.
what I didnt know was the 600SS in europe was a 2-1 or so i've seen them as such.

i am trying to perfect my 2-2 with some anti-reversion chambers (possibly that fat part you are seeing in that 2-1 system  in this thread http://www.ducatimonsterforum.org/index.php?topic=55169.0 ) to alleviate the need for the crossover.

[MonsterHPD]

i am trying to perfect my 2-2 with some anti-reversion chambers (possibly that fat part you are seeing in that 2-1 system  in this thread

Very interesting reading, this thread.
Just curious, could you please explain anti-reversion chambers? I´m not familiar with this expression.

Also, the exhaust donuts are new to me, never seen that before. Where could I find out more about them? Finding tight-radius tube bends is a problem.
I´ve been buying my stainless tubing and other stuff from SR Racing in Germany, beautiful pieces and great quality craftmanship. But I´ve never seen the exhaust donut before     

[Raux]