UPDATE ON SKUNKWORKS

[Guest captain nemo]

Well, I took the whole exhaust off and apart and did some thinking. I cut the ends off the 'crab' crossover which lead to the back and saw what I suspected - it is just an empty chamber with posts to hold it together and some baffling material welding on the top and bottom sides. Ok, I've decided after my reading that they help the mid range by scarfing off trapped or stagnant exhaust fumes. What this box needs to be is larger - so that it would have more vacuum power. Same reason the race air boxes are huge, for more vacuum power.

 

Next, I purchased a set of Supertraps to weld onto the cut ends of the crossover. BUT, I had a thought that I think I will only place one on and seal the other side shut. 2 into 1 exhaust. This will add more backpressure and ought to give me more bottom end. Plus, since there is now only one exit, that exit will have much more force behind it - creating a bigger vacuum for the other gases to come. Also, the Supertrap does have plates which you can adjust which is a good feature. ALSO, I might even figure out a screw-out device for the 'sealed' end and allow air to come in there at times - simple to experiment and see what happens.

 

It is all the work of a mad scientist and I'm truly in my element again. I will have the parts next week and the welding done for it. Then its all off to Super Hot where it will get a nice ceramic in and out coat of 'airmass blue'. The only Supertrap pod you will see looking at the bike will be behind the swingarm. Interesting.

[al_roethlisberger]

Well, although indeed our OEM crossover is nothing more than an empty expansion chamber(discussed elsewhere in the forum at some point) and is basically nothing more than a simple baffle/muffler itself.... keep in mind that crossovers and headers are generally tuned to time the exhaust pulses to scavenge and/or provide back-pressure pulses that tune the engine output accordingly. Although admittedly our stock ones seem not to be tuned very well )

 

Generally speaking, a particular design will(although not always) sacrifice either top or bottom end, rarely maximizing both.

 

I guess you'll be able to have some success through a degree of "butt dyno" results by just shooting from the hip exhaust design, but finding the correct response by trial and error would best be combined with a dyno and an air-fuel probe to make sure you weren't running overly rich(not the end of the world) or dangerously lean as you made your changes.

 

BTW, when you say

The only Supertrap pod you will see looking at the bike will be behind the swingarm.

.... I don't get it From the rear? From the side?? Where will the exhaust exit?

 

al

[Guest Fonzarelli]

You might find this hard to believe; But the stock exhaust system (with the exception of the mufflers) is about as good as you can get for the standard tune of the engine.

 

Al is correct in saying that the exhaust tubing length, inside diameter, and crossovers/baffels are all designed to tune the exhaust pulses to a certain RPM for maximum torque. When you change or interrupt the pulse timing, you will ultimately put large holes in your powerband. The engineers have carefully calculated everything from the cam profiles to the head flow numbers to arrive at the specific exhaust dimensions.

 

Once you start changing camshaft profiles, porting cyclinder heads, enlarging the displacement, you might want to increase the diameter only of the pipe.

 

As far as mufflers are concerned; the EPA pretty much determines the sound level motorcycle manufacturers must adhere to. Power that is gained by an aftermarket muffler is generally because it is less restrictive than the OE item.

 

Exhaust systems are extremely complex. There is so much going on inside those pipes under a dynamic situation that the only real way to measure improvement is to conduct changes scientifically, one at a time, under controlled situations and environment.

 

As Al also mentioned, a dyno is really the only reliable way to measure increase in performance. The variables in street riding or even at the track are too great to get accurate data.

 

I am not trying to discourage you from your ideas, but letting you know that most of the sweat and blood has already been sacrificed for you.

[Guest Fonzarelli]

Generally speaking, a particular design will(although not always) sacrifice either top or bottom end, rarely maximizing both.

 

You will find that engine changes or modifications will ALWAYS affect one end or the other of the power curve. Usually it decreases low end torque while making more peak horsepower. The catch is, how often do you operate your motorcycle at that "peak" RPM.

 

The only exception you might find to this is an increase in displacement.

[al_roethlisberger]

Generally speaking, a particular design will(although not always) sacrifice either top or bottom end, rarely maximizing both.

 

You will find that engine changes or modifications will ALWAYS affect one end or the other of the power curve. Usually it decreases low end torque while making more peak horsepower. The catch is, how often do you operate your motorcycle at that "peak" RPM.

 

The only exception you might find to this is an increase in displacement.

 

 

...except for dynamically variable exhaust and intake systems like VTEC and EXUP

 

But yes, generally a given static exhaust design will make compromises at one end or the other of the performance curve. So designers of exhaust systems try to tune an exhaust for the type of riding the bike is intended for most often... which certainly makes sense

 

al

[Motomonster]

Now you guys know why I don't let him near my bike when he's got a beer in his hand.

 

+ =

[Guest Fonzarelli]

...except for dynamically variable exhaust and intake systems like VTEC and EXUP

 

Touche, Al!

[dlaing]

If you compare the power curves of the stock crossover, compared to the stucchi and fbf crossovers, the stock is not so well thought out in that it has a big hole just above 4000RPM.

Granted it is quieter, and it is an improvement on crossover used on the V1100Sports.

Whatever Captain's results are, is probably a luck of the draw.

He could get more or less power anywhere along the RPMs.

Choosing one muffler over two is more likely to boost Low RPM power, as he suggested.

I suspect he may lose a little power elsewhere, but he'll probably still have more peak power than a Jackal and alot more peak power than a Quota, and he will have one of the lightest exhaust systems available on any V11.

But because the change is so dramatic, I think he should get the bike to a tuning link for a custom map.

My Quat-D gained almost 4HP and air to fuel ratios as bad as 18:1 were corrected, after the tuning link.

[al_roethlisberger]

If you compare the power curves of the stock crossover, compared to the stucchi and fbf crossovers, the stock is not so well thought out in that it has a big hole just above 4000RPM.

Granted it is quieter, and it is an improvement on crossover used on the V1100Sports.

Whatever Captain's results are, is probably a luck of the draw.

He could get more or less power anywhere along the RPMs.

Choosing one muffler over two is more likely to boost Low RPM power, as he suggested.

I suspect he may lose a little power elsewhere, but he'll probably still have more peak power than a Jackal and alot more peak power than a Quota, and he will have one of the lightest exhaust systems available on any V11.

But because the change is so dramatic, I think he should get the bike to a tuning link for a custom map.

My Quat-D gained almost 4HP and air to fuel ratios as bad as 18:1 were corrected, after the tuning link.

 

 

hrmm, maybe, maybe, and maybe... that is, especially on the "lightest exhaust issue"

 

As you say, it will be something of a game of "hit and miss"

 

 

Depending on the stock steel he uses for can, it could be quite heavy to get a durable design Comparably, my Leo Vince exhausts are super light. I can easily hold one straight out with one hand while holding the end of the lead-in tube... which would have been impossible with the OEM LaFranconis. And the Stucchi isn't too terribly bad either.

 

Sure, if well executed, the under-slung exhaust is bound to be lighter, but it might not be so much as one might think once it's all said and done, as it's bound to be a good bit larger than the crossover.

 

 

And you are also right to continue to stress getting the mixture analyzed as he modifies the exhaust, especially to avoid any lean issues.

 

...because as he is doing this "seat of the pants" and apparently being driven more from an aesthetic perspective, there indeed will be a lot of "maybes" that probably won't be realized until after measuring the results

 

But it's very likely he'll get unpredictable and inconsistent results on the initial attempts, as mentioned before, exhaust design is actually relatively complicated to get correct(unless just terribly lucky )

 

It'll be interesting to see how it goes

 

al

[Baldini]

Go to it Captain...just don't blow up the lab!!

[Guest captain nemo]

Excellent comments. The other option is to go for top end. In this case I would weld the Supertrap pods directly onto the headers! I could still adjust for back pressure for around town and open them up for out in the country - for higher speeds. It would be loud, but not as loud as straight pipes, plus I could fit them pointing down toward the ground. Here, I think I would lose some low end, but the pods still allow for SOME adjustment. It would be clean and elegant.

 

What should it be? Crossover or no crossover?

 

Al, my first idea would be to keep the crossover and weld the pod right to one of the cut off pipe openinings - this would have the pod sticking straight out beside the tire and the swing arm (so from the side you would not see it).

[dlaing]

I prefer a no crossover design because if you are not concerned about legal decibels, you can probably get a cleaner running bike if the left and right exhaust flows do not interfere with each other.

However, it may be difficult to place a pair of supertrapps under the transmission in such a way that they do not reduce ground clearance.

 

And Al, you may be right about the weight.

I am not sure how much Supertrapps weigh, and the weight added from welding could be significant, otherwise it is one less muffler, which could be lighter.

I hope he plans to exit the one muffler on the left side because it can be closer to the tire.

 

Captain, which Supertrapps are you thinking of?

[gthyni]

Attach a picture of a couple of Supertrapp,

the Megaphone (from a Buell) is 2" intake and 4" discs/outlet.

I plan to use that and a custom made 2into1 on my Nuda.

It is considerely lighter than the stock silencers.

 

The smaller is on old IDS (now called IDS2) 2" in 4" out,

it is extremly light.

 

The lenghts are 18" and 16" respectively.

Edited December 13, 2003 by gthyni

[Guest captain nemo]

I'm not sure the type. They are only about 7 inches long. They ordered the discs for them, so I'll see them Wednesday or so - the day I'm seeing LORD OF THE RINGS!!

[Baldini]

What should it be? Crossover or no crossover?

I don't know much about this but I did run my 950 tonti w/o any balance pipe for a while & it killed the top end. I think it's about scavenging. they were wide diameter headers too which probably didn't help...

 

Captain, I still think you were good on the white ....blue???

 

KB, Cymru