Single or Dual Exhaust

Here is what I have and what I want. Have: 990 2008 SD with stock exhaust. Have: 950 2004 KTM Adventure with Dual Akrapovic oval cans.
Want: Lighter, zipper SD. Want: Deeper pockets. Real close on pulling the trigger on a Ti set of Akrapovic cans....but I rode an KTM 950 SE last weekend with single exhaust that kicked ass. So got this idea rolling around in the gray matter to go single exhaust on both bikes with the Akrapovic cans that I have on my Adventure. Win win on the Adventure, more room for luggage/tools or they make a gas tank that fits the missing exhaust void.
I will have to come up with a SM / SE or Adventure Y pipe to mod for single exhaust, not a big deal. Got the ways and means for expert welding / fab.

OK you gloom and doom sayers....why should I not convert over to single exhaust with what I have. I am a function before form kind of guy and spend most of my extra coin on tyres and fuel, not bilig bling orange thingies.

I will have to say the Ti set of Akrapovic cans are really calling me.

Would look the nut's with a single Graves carbon can,,,with no baffle,,,,

I know, I know, i've said this before, a single can, designed as one half of a dual exhaust, will be choking a bike if used as a single exhaust. I would have to see the numbers on air flow and resistance, and then go to school and learn just what those numbers suggest. My gut says can the idea and go buy some gas and tyres.
I have seen an Akra. Evo can designed and installed on an S4RS and it seems bigger than the dual exhaust versions.
The adventure is not the bestest comparison in how and wherefore the power delivery is handled in the same application as the SD and I would venture to guess what works well on the Adventure could stifle horsepower delivery on an SD.
I would love to see the gas savings a single can would afford. Your probably looking at a six pound savings in weight. That would equall +- one pony.
GAS TYRES

For what it's worth I chopped up the standard exhaust to see what was inside. In terms of the bike being
choked by a single exhaust I can't see it - the standard has not only the catalytic converter acting as a choke
but then the holes into each side of the standard can are tiny. From memory they are about 1.5-2.0 cms diameter.
Thus a single straight through Akro has got to be a lot less restrictive that the original.

viewtopic.php?t=6174

What you don't see in these photo's are the holes. The gas goes through the cat converter then through a couple of
holes backwards to the forward chamber (this is the restriction) then through all of the pipes into the sides of
the original cans. Very restricted compared to any sort of straight trough system.

My first responce was made under my selective reading technique, and now, using another technique, reading the whole post, makes it impertnant.
PULL the TRIGGER

I am with ya Jman. I too have taken the abrasive cutting wheel to the stock Adventure exhaust to see the cat and baffle tubes and have see pictures of the guts of the SD. My bud has a stack of the stock Adventure cans with my stock Adventure cans adding to the pile. It is very possible to decat and mod the stockers for refitting, to loose weight and flow restriction while keeping the stock look of the cans, but that another story. The SE I rode was very crisp reving, and sounded great. The mod my bud came up with adds a little boom box, if you will, area to the Y connector pipe right before the single muffler. When I look at his mod, my horse sense tells me this mod flows just fine. It was a lot smaller exhaust can then the one pictured on this post and really fit the dirt bike feel of the SE. I think it was an FMF.

Those frikin' big ol Ti Akrapovic cans are still calling......argggggg....cool factor calling..........

It's simple really, measure the surface area of the holes of the stock exhaust, you need to have at least the same surface area through what ever you use to replace the stocker. When I did mine I believe that I doubled the potential flow compared to stock and ended up about 3/4 the potential flow of the Leo's with decibel eaters.

Sound deadening will suffer if the volume of the muffler is too small. My single Akra is longer than the Leos it replaces and sounds decent noise wise without the baffle.

as a single exhaust expells its gas it creat'es a slight vacum which helps pull a fresh mix into the the barrel it does this more efficiently than a dual system, taper'erd headers also help do this

"I will have to say the Ti set of Akrapovic cans are really calling me."

Called me so hard I e-mailed my bud last Friday and asked him to buy the set that was on e-bay, so he did.
I don't see the set on e-bay today, so I hope they are heading my way.
Looks like I will have a new set of Akrapovic Titanium cans tomorrow.
$800 plus $25 for shipping. New still in box.
Now to make the winter list for the remainder of the mods to this stock bike.
Hope my gas miliage does not take a big hit !

A single outlet muffler design can be better for many reasons like weight and better sound pattern but you cannot have your cake and eat it too. There are many points of tuning from the head flange to the tip of the silencer. Diameter, length, choke at the bifurcation point, taper back up to the final, muffler core size and length all play a part in the exhaust calculations. We work very closely with Burns Stainless in Costa Mesa on many header projects and through our relationship we have built many championship winning exhaust systems. (We are actually next door to them for this reason) See here: http://www.cprfabrications.com/Fabrication.html

The Adventure has "Cheated" it's way to more low end by choking the exhaust right at the port to (US) 1.625". This is a band aid way of doing this as the engine is designed for 1.750 .039 wall tubing as the port is 1.688 at the flange. The stock header is horrible on this bike but accomplishes the goal. (It kills the potential of the engine at the same time) The internals of our 08 Super Duke and 2012 Adventure R are exactly the same, yet the Adventure is gutless compared to our SD, for this reason we are developing a total header and exhaust package that mimics the Super Duke sizing on an Adventure as well as intake and mapping. There will be 4 types, dual slip ons, single sided slip on, full system dual and full system single side. These are coming in the next couple months and are currently being tested.

Where we see everyone go wrong is when they choke the exhaust into one side that is already choked for dual outlets. Now you have room for tools and less power to drag them around. Previously mentioned was that a single straight through would theoretically flow like a dual "CAT'ed" exhaust. Possibly, but why choke it again when the goal is weight and power? Without giving up our formulas, going 2 into one does not mean double the size diameter of the outlet, but there is much more science to it than that. The "Choke" points are probably the most critical area of tuning exhausts and the expansion thereafter is secondary. This being said, we are speaking in terms of getting ultimate power. A proper exhaust diagram that we ran on an Adventure finished at a 3 inch core! The problem is, this is not realistic because like mentioned above, you can't have your cake and eat it too. Cake being power and eating it would be the obnoxious noise that would make.

We can say that a proper 2 into one on a Super Duke should end at a 2.25 core and the choke, well that's our little secret... We are in development and can't say too much. The taper on the collector should be no more than 25 degrees. 15 is optimal merge angle but some bikes don't have the room for a long 2 into 1 like that. The choke would be the diameter at the end of the merge collector right before the transition. Bottom line is that if your going from stock to single side, probably fine if done right. If going from aftermarket dual to single and using the same size cores, no good and will mess up your tuning. Dual aftermarket to single larger core of previously mentioned size, good if done right. Or, if there is enough demand, we will add them to our line of properly tuned exhausts. What do you think?

Upsides:
Weight
Sound (loud but more "Indy" car'ish)
Looks (If you wanna be different)
Room for tools on an Adventure
Cost compared to buying a dual

Downsides:
Loud
Packing burns out quicker
Done wrong will hurt power

Ok. I am all ears. ^ ^

WOW ! Thanks for all that Fab Guy. Will have to re-read and think about all of that.
Thank you very much.

I'm probably the only one but, I would like a 2 into 1 for the Superduke with the front head pipe running high rather than under the engine. No passenger accommodations required. I'll figure out where to put the rear master cylinder. Proper diameter headpipes and Ti can please

Thanks,
Will

Beringer discs, master cylinders and I think calipers to

I like my single better.

First Post. Thought I'd add my run at a single exhaust set up. Being a cheap azz I counldn't see spending over a grand on exhaust. Went on the hunt at clist and found a cheap carbon R77 slip on from some random litre bike (2.25 ID). Mitered up some stainless, welded on a ball flange. Dropped 21lbs off the bike.

Thanks. It was 150 for the pipe and 47 bucks for the tube.

Just be careful with the full carbon cans on twins!

I've tested several carbon cans on twins when I was working as a motorcycle exhaust developer and big twins tend to overheat the cans (even titaniums!) if you don't take precautions. Make sure you have a double layer of stainless steel wool around the perforated tube, if possible wrapped in a fine steel mesh. This will prevent the damper wool from burning and blowout and leaving a less thermally insulated section towards the outer shell. DO NOT underestimate this effect, we had carbon cans burned within 5 minutes on the dyno!

If you're early you can recognize burned out sections by knocking on the outer shell and hearing a more hollow sound compared to the rest of the damper. Later, the carbon will look dryer in some sections of the pipe (usually the part where the exhaust gasses enter the damper) and might even turn a little green. This means the carbon will be more likely to crack or blow a hole in it.

With the single damper setup this is a bit more likely to happen than with a double damper setup because of less heat distribution. Adding a DB-killer causes more back pressure and therefor higher exhaust gas temperatures.

Jermo,
You're 100% correct. Too late for this can, I think. The twin makes this thing huff like a lung. To the point that the carbon has started to fray at the seams. I will likely move (at some point) to the stainless sleeve with the carbon end cap. It looks great in all carbon but not going to work long term. There are some can out there that are stainless with a carbon cover. Not nearly as cool but they would list on the twin. I sure sounds great, was cheap and took a HUGE amount of weight off the bike.

I have made a single exhaust for mine (photo's in the hello thread. "Hi from NZ"). The can is made by AdrenalinR, a local company. I cut the original header and welded a 4 bolt flange to it. 2 identical flanges are mated to both the original pipe so they can be refitted easily and the new pipe/muffler. Its a really good muffler so its not that loud but it soumds mean as. I cut the black ugly thing in such a way that it can be easily re-joined. I also made the tail tidy to hold the # plate, tail light and indicators.

Have you got a pick of the join to the headers

Yeah I'll have a go at posting some for you tonight.

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The Carbon can already had the larger baffle in it as it slipped on the outside of the 2.25" inlet and widened in a cone, so I used the larger half.
Turned out OK though I think.

Agree...very cool. Nice job.

Yea man

I like this.

So.... Had the bike on the Dyno today...

Lost 2.6kg from the FMF (lighter than leos and akras)

Scans of dyno run to follow
fookin AWESOME!!!

You got access to a sound meter?

Really like the looks of this!

Great job man.

I love the emoticons!!! Can we get this one?