Under Engine-Exit Exhaust

[Toast]

I'm wondering if my current Arrow undertail exhaust is the ideal solution for my '03 600RR race bike. Reasons being:
-It seems a waste to have that much weight as far from the bike's CoG as possible; and more importantly to me
-It passes worryingly close to the shock resevoir, which I do not want to be heated up and suffer a loss of damping

I was thinking about getting a custom under-engine exit exhaust to solve both of those problems. However, someone who used to tune bikes on dyno's told me that with such a short exhaust the bike would become very difficult to tune, and likely lose a lot of its mid-range power.

Is this the case? Has anyone tried such an exhaust out on a bike that doesn't normally have one?

[Cajun]

as i aware as a in some lame terms, if not designed for a stubby, you will result in lost of back pressure, which in turn lack of hp,

in theory you can tune the pipe & bike, for certian rpm range, so for track would be possible but trying to tune it for the whole rpm range be a big mission.

[nodrog:Me]

isnt the undertail where the factory pipe was anyway? i'm sure the guys at honda would have put alot of time and research into the pipe weight versus COG etc, and designed the rest of the bike accordingly so i wouldnt worry about too much about the COG.

But a short under engine exhaust would be cool, but they are definitly harder to tune due to lack of back pressure etc, when i fitted the racefit mega to my GSXR it spent all day on the dyno, and the guy actually said that short pipes are a pain in the arse to tune verses the other more standard designed pipes.

[imdying]

will result in lots of back pressure

due to lack of back pressure

Way to confuse him guys

[Cajun]

Way to confuse him guys

sorry mine was spelling mistake

edit, it says lost, and i didn't even correct it

[Toast]

isnt the undertail where the factory pipe was anyway? i'm sure the guys at honda would have put alot of time and research into the pipe weight versus COG etc, and designed the rest of the bike accordingly so i wouldnt worry about too much about the COG.

But a short under engine exhaust would be cool, but they are definitly harder to tune due to lack of back pressure etc, when i fitted the racefit mega to my GSXR it spent all day on the dyno, and the guy actually said that short pipes are a pain in the arse to tune verses the other more standard designed pipes.

Correct, under the seat is where the pipe is on the stock bike. Keep in mind that Honda also had noise and emissions regs to contend with which would have influenced their decision on the pipe's length and location. My main concern is the fact that it passes right next to the shock resevoir. I've got that part of the pipe wrapped with some cloth that's supposed to stop heat transfer, but it's still pretty hot to the touch.

Can an experienced exhaust builder not affect the back pressure on a short pipe by putting a small S-bend in there, or modifying the diameter of the pipe at certain points, or something clever that I don't understand like that?

[Cajun]

anything is possible toast, but might take alot of time which means $$$ to do it correctly.

Have you tread looking at other methods of keeping pipe colder, can't you get that hpc paint stuff on that might help keep it cooler, double, or triple wrap it

[Pwalo]

Can an experienced exhaust builder not affect the back pressure on a short pipe by putting a small S-bend in there, or modifying the diameter of the pipe at certain points, or something clever that I don't understand like that?

I'm pretty sure that they could, but do you want a lump like they have under the Buells, or the later GSXRs?

Not too sure that it would be the cheapest idea either.

[Toast]

anything is possible toast, but might take alot of time which means $$$ to do it correctly.

Have you tread looking at other methods of keeping pipe colder, can't you get that hpc paint stuff on that might help keep it cooler, double, or triple wrap it

What's HPC paint? Where can you get it?

I've got it double-wrapped now. Problem is that if the wrapping gets any thicker it will be rubbing on the shock resevoir.

[nodrog:Me]

Correct, under the seat is where the pipe is on the stock bike. Keep in mind that Honda also had noise and emissions regs to contend with which would have influenced their decision on the pipe's length and location. My main concern is the fact that it passes right next to the shock resevoir. I've got that part of the pipe wrapped with some cloth that's supposed to stop heat transfer, but it's still pretty hot to the touch.

Can an experienced exhaust builder not affect the back pressure on a short pipe by putting a small S-bend in there, or modifying the diameter of the pipe at certain points, or something clever that I don't understand like that?

another option could be to replace the shock with an aftermarket option that has a remote resevoir.

as far as i know the supersport Hondas still run the underseat pipe, so it cant be all that bad.

http://cms.tenkateracingproducts.com/index.php these guys will have all the answers you need.

[Mental Trousers]

It's possible that you can make the pipe go under the engine then do a U turn into a muffler (also under the engine) that exits near the front of the bike rather than the rear. That might give you enough length while still having a muffler (a rather tiny one though).

[Pancakes]

Isn't the undertail exhaust to make the person behind's draughting less efficient? I thought this is why SuperSport bikes did this v.s lower cans more inside the wheelbase? So it doesn't make you faster it makes the person a foot behind you at 200K's slower or use more gas or be less able to slingshot past. (Or the other riders don't like breathing exhaust gas?)

[speedpro]

There will be an optimim header length. The end of the header doesn't need to be the start of the muffler. The end of the header could be well inside the muffler. It would make it a bit trickier to get good gas flow. R6s have a big muffler under the engine with just a little short exit pipe. As far as a lot of things like where the exhausts are, my own cynical view is that it is mostly marketing driven, and that applies to supersport class bikes as well.

[AllanB]

Its probably more fashion than anything else, just like the single side swingarms on the Dukes and Speed/Street triples.

My hornet has the undertails and I too notice that the pipes split in front and either side of the shock - obviously heating it up a bit and the remote damper is above the left muffler.

Most of the high pipe Duke reviews complain of seat heat. Such is fashion.

But I digress - Don't know about your ride but on mine the pipes going to each muffler are very narrow - I've seen a couple of single pipe designs for the Hornet and they use a larger pipe from the main join (4-1 bit) to the single. What I am saying here is if you desire a lower pipe by using a larger diameter mid pipe your muffler may be tucked in closer.

Attached is a Speed Triple single low pipe as an example.

[DEATH_INC.]

Yep, it'll work, but it's gonna take a shiteload of figuring out to get it to fit, without being so low it'll scrape round turns....
The most important part of the exhaust is the four header pipes,before they join into 1 or 2, these affect power more than any other part. On a four > two > one system, the secondary two pipes also have a fairly large effect.
The jury's still out on back pressure, good vs bad. back pressure increases the wave strength in the pipe, but also costs hp to push it out. Only the dyno can tell if you have the right balance.....
I've seen a test on a V8 racecar where they experimented with it, and anytime they introduced any backpressure it lost power.....we also experimented with a vance and hines system on a GSXR1100, which came with different sized restrictors that fitted behind the headers, again it lost power with any one of them fitted.
You also cannot argue the fact that a really free flowing bike engine is a bitch to tune....