Compact underbelly exhaust

[TonyB]

On the Ducati, the system is a two into one into two... kind of. There is a X shaped splitter under the bike that directs half of the flow from each header down both pipes.

My question is, what is the concept behind 2 into 1 into 2 systems? Or 2 into 2 with a balance pipe? What would happen if each header had its own muffler, with no balance pipe?

[geoffm]

On the Ducati, the system is a two into one into two... kind of. There is a X shaped splitter under the bike that directs half of the flow from each header down both pipes.

My question is, what is the concept behind 2 into 1 into 2 systems? Or 2 into 2 with a balance pipe? What would happen if each header had its own muffler, with no balance pipe?

It doubles the muffler volume for one. As only 1 cyl is on exhaust at once, then it allows both mufflers to be used for quietening each pot without restricting flow.
G

[TonyB]

Yeah I understand that. I was thinking more in terms of pressure pulses and things more technical. Do they use 2/1/2 exhausts to boost power, or is it simply a matter of getting the right sound and having a larger muffler volume for each cylinder? If sound volume and subjective things like making it sound good are taken out of it, is there any reason why each cylinder can't have its own exhaust with no balance pipes between the two?

[imdying]

Every turn is a restriction... there's (yet another) theory that every 90 degree bends adds the equivalent xxx to the length. It's all essentially bullshit if you haven't got a dyno and lots of testing time (money).

[Mental Trousers]

Depends on the design of the system but using a 2-1-2 with the correct firing seperation you can have each cylinder helping with the scavenging of the other cylinder.

Every turn is a restriction... there's (yet another) theory that every 90 degree bends adds the equivalent xxx to the length. It's all essentially bullshit if you haven't got a dyno and lots of testing time (money).

yup

[Babelfish]

One technique used to find the right length is to calculate the length (the pressure pulse moves at almost the speed of sound and exhaust gas expansion rate is known etc) and add a bit extra for errors, cut a piece of pipe to that length, put it on, test, then cut a bit off, test ...... repeat until you get the best power at the desired rpm. You can then make up a pipe with bends to suit using the best length from the testing.
Of course, that requires a dyno!!

Sweet, I just grab my dyno and....

Otherwise, the OEM pipes are a good place to start for the right length.

...Thank fark for that, I was shiting about having a dyno handy...

[FilthyLuka]

righty ho, i guess i can start photoshopping to show you what it would look like.

If you want to pull a major dodgy (and im talking pretty dodgy here), get the header pipes going into a two into one, then dumb a thin, stumpy silencer (twitch... guh, bye bye power), under the body... and example of said silencer being: http://www.trademe.co.nz/Trade-Me-Mo...n-87040746.htm

or you could get something carbon fibre and not shit... ill get onto gimping some VTR1000 images and ill post them up here so you can see (relatively) what it should (woulda, coulda, shuna) look like.

denden

[vifferman]

I am keen at some point to stick a VFR800 single sided swing arm on the vitter

I guess then you're aware of the conversions others have done?
Oh wait - I see you're already on the UK Firestorm forum. Never mind...

[Babelfish]

I guess then you're aware of the conversions others have done?
Oh wait - I see you're already on the UK Firestorm forum. Never mind...

Yeah, as you noted I've done a bit of research. Look like the viffer swing arm is the way to go to get a little more room too...along with looking incredibly hot Did you see my link earlier in the thread with the guy that had underbelly exhausted his viffer?

[vifferman]

Did you see my link earlier in the thread with the guy that had underbelly exhausted his viffer?

Yeah. A couple of people on VFRD also made some.
Ralph (tok tokkie) also did a really nice front-end conversion on his bike, with (IIRC) RC51 forks and R1 monoblock brakes, and some really tasty bits he machined himself. Unfortunately, just after he got it all dialled in, he crashed into a car, and broke his VFR in half! Luckily, he wasn't hurt, but he's chucked in street riding and is getting a dirt bike.

[limbimtimwim]

Now if we use the RCV11 or even the latest GSXR 600, you will notice the short stumpy pipework... well this is the return of the megaphone... its were the hp hides.

The GSXR600 is a bad example. The pipe out of the factory on the GSXR600/750K6 onwards isn't that short at all; it snakes around a fair bit under the engine. And it has a exhaust valve that effectively messes with the length.

[Babelfish]

Yeah. A couple of people on VFRD also made some.
Ralph (tok tokkie) also did a really nice front-end conversion on his bike, with (IIRC) RC51 forks and R1 monoblock brakes, and some really tasty bits he machined himself. Unfortunately, just after he got it all dialled in, he crashed into a car, and broke his VFR in half! Luckily, he wasn't hurt, but he's chucked in street riding and is getting a dirt bike.

DIRT BIKE...safer??? All my mates with dirt bikes regularly nail themselve and I'l lost count of hospital visits...admitedly they do seem to get more chances though...however I digress. I'm thinking of doing the front forks too at some point, but before then I need to finish my book "How to negotiate effectively with wife without getting tackle removed during sleep"