Open pipes??

[Pasta Bobber]

Ok, so i'm the idiot chopping up my S2R 1K into a bobber/chopper style bike. Naturally I want the pipes to fit the look of the bike......short and LOUD, possibly straight pipes, maybe a little baffle stashed inside. I'm curious as to everyones opinions as to the effects this will have on the motor.

I know I'll need to map for this (monstermash chime in anytime please)

Valves are mechanical, so do they really need the back pressure?? sorry to sound like such a newb 

[needtorque]

Actually backpressure is not a big deal at all on 4 stroke engines. That is really a concern on the 2 strokers.  Core em and enjoy.  If you change the intake side you may need to remap or it may require a remap or some added fuel in some way or another just with the exhaust but there are many options for this.

[psycledelic]

I rode mine a couple of times with just the headers while I was situating things to get my exhaust modified by motocreations.  With just the DP headers, the bike was very, very loud.  It sounded pretty good, but at idle, it tended to have a funny noise to it. (The bike was loud enough to get the Harley guys looking, just a matter of time before I would have been pulled over).  I ran with just the udder after I sent my headers to MotoCreations.  Honestly, the udder, while not as loud, sounded better.  But looked ugly.   Mark pretty much took my headers and made some short extentions with baffling.  That was the ticket.  Killer sound and loud.  More along the lines of what "straight pipes" should sound like.  I took the bike back to the shop and had them tune it to the exhaust (no need for a PowerCommander).  I assume the baffling helped the performance, cause the bike runs smoother.  There is less popping and more growl on decel.   It definitely helped the sound.  

[ProTeal55]

I ran my 07 S2R1K around for most of it's life with the udder open (no mufflers).
Loved the sound, but as said above just couldnt take the look of the udder itself, which eventually led me to get a set of BoomTubes from Mark over at MotoCreations. Since the bike is basically stock I had him put somekinda baffeling in the pipes to help keep the stock ECU happy. Great sound, custom look you dont see on most other bikes (people are always asking where I got the pipes), keep the back wheel completely open, etc...

[angler]

S2R 800 with boomtubes.  Stock ECU. Open airbox. CO is right on without need for re-flash or a power commander, but it needed some adjustment to get back there after the install.  The decrement to bottom end power was obvious instantly - until the re-tune.  Now it runs like a scalded dog.

I had Motocreations minimal baffle on my first iteration with the boomtubes. Too loud for my tastes.  More than too loud, it was very "blatty" - produced a real sharp sound instead of the bass tones you get out of Termi's or cored stock, which makes sense since they have no place to resonate.  I like the sharpness, but loud and sharp is hard.

Mark shipped me more restrictive baffles, gratis, and made them quite a bit quieter and the sharpness went down.  Both good things.  Boomtubes are a great product if you go the commercial route.

My point? You can do A LOT sound-wise and perfomance-wise with stock ecu, interior only baffles and what amounts to very short pipes with a crossover.  I'm sure you could do better with a re-flash or a power commander, but mine runs great now.

[psycledelic]

S2R 800 with boomtubes.  Stock ECU. Open airbox. CO is right on without need for re-flash or a power commander, but it needed some adjustment to get back there after the install.  The decrement to bottom end power was obvious instantly - until the re-tune.  Now it runs like a scalded dog.

I had Motocreations minimal baffle on my first iteration with the boomtubes. Too loud for my tastes.  More than too loud, it was very "blatty" - produced a real sharp sound instead of the bass tones you get out of Termi's or cored stock, which makes sense since they have no place to resonate.  I like the sharpness, but loud and sharp is hard.

Mark shipped me more restrictive baffles, gratis, and made them quite a bit quieter and the sharpness went down.  Both good things.  Boomtubes are a great product if you go the commercial route.
My point? You can do A LOT sound-wise and perfomance-wise with stock ecu, interior only baffles and what amounts to very short pipes with a crossover.  I'm sure you could do better with a re-flash or a power commander, but mine runs great now.

Same here.  I don't see the need for PC or anything else.  Probably could get a little more out of my bike with one, but I just don't see the need.  If I was that hellbent on performance, I doubt I would have bought the S2R800. 

[NorDog]

Actually backpressure is not a big deal at all on 4 stroke engines. That is really a concern on the 2 strokers.  Core em and enjoy.  If you change the intake side you may need to remap or it may require a remap or some added fuel in some way or another just with the exhaust but there are many options for this.

This is not exactly true.  Backpressure in a 4 stroke is nowhere near as critical as it is in a 2 stroke, but even the four stroke, expecially a performance 4 stroke, uses backpressue in scavaging, which maintains higher exhaust gas inertia, and thus facilitates intake inertia during valve overlap (that's why there is valve overalp).

Scavaging is all lost with completely open pipes.  This is not considered a problem with drag bikes because of the flow dynamics of running an engine with full open throttle.  But for street riding and road tracks backpressure is important.  After all, ever see pro-racers running 4 stroke bikes with straight open pipes?

[Keld]

Same here.  I don't see the need for PC or anything else.  Probably could get a little more out of my bike with one, but I just don't see the need.  If I was that hellbent on performance, I doubt I would have bought the S2R800.  

"A little more maybe", on my bike I got +21% HP and +11% torque with a new ECU  
And open pipes are best at high revs and full throttle like dragracing
 Exhaust are science even with a 4 stroke.