Exhaust system diameters

[Chris_B]

I picked up an R6 pipe for free a while ago and was suprised to see that the mid pipe on the R6 and the GS are the same diameter, which I thought was strange because the R6 obviously needs to flow way more exhaust gases then the GS. So I looked into it a little, and the R6 also has 33mm inside diameter header pipes, which again, I thought was a little strange.

So I got some numbers..
An R6 would move around 599cc's x 7750 = 77371cc/second
A GS, 487cc x 5500 = 44642cc/second
Thats very rough though and it doesn't factor in anything, displacement multiplies by half the redline (exhaust stroke every other revolution).

So it would seem to me the R6 would have a its exhaust gases flowing much faster through the midpipe section but slower, or the same speed because of the extra heat from the higher compression ratio, through the header pipes.

Keep in mind though I'm not even out of highschool and have no idea what i'm talking about.
So what are the benefits of a more restrictive, faster flowing exhaust system?

Does anybody have some exhaust theory for me? Backpressure? It's purpose? And should the GS have a smaller diameter midpipe?

[NiceGuysFinishLast]

Bwahaha.. Paging Dr. GeeP... Or Egaeus... or Mak? Starwalt? DGyver?

[l3uddha]

Keep in mind though I'm not even out of highschool and have no idea what i'm talking about.

[The Buddha]

Yea yea ... flow ... yea ... WTF ...
That mid pipe usually is same for a diesel V8 ... Restriction is in muffler.
Cool.
Srinath.

[Chris_B]

So your telling me its like that just 'cuz? I'm sorry but that answer is just unacceptable, theres gotta be more to it.

[hmmmnz]

did you read sinraths post all exhaust restriction is in the end can on the bike not in the size of the pipe going to it,
as to your mid pipe thing, i have a modified r6 link pipe eg 45mm to 50 mm and then straight into a race can(no baffles) it works better than the standard can, you get enough back pressure from the 2 bends on the header pipe,
so get to it and put on that link pipe and a can so stop wingeing and get to it

[galahs]

if the pipe was too small there could be restriction (back pressure)

but if its too big, the engine could loose low end torque.

Bends in the pipe and welds where the two pipes join could also be restrictive.

Its way too complicated to pull an optimal figure out of the blue without some thourough testing. And even then, pipe diameter would be a trade off between different factors.

[Chris_B]

So but why not get the restriction through the midpipe and then have a more straight through can? I seem to think that a 45mm midpipe on the GS is just to big.

[The Buddha]

What ... then we have do full system and a slip on wont work ... BTW katana 600's have tiny ass header pipes ... and you have to put full systems to get any decent increase.
Cool.
Srinath.