building an exhaust.. any guru advice or tips?

[MonsterHPD]

I had to search my memory in order to remember roughly how the dyno session went. All the runs were made on the same day; the mapping with the complete system was made first, then the header length runs were made with the same mapping.

I forgot to mention the complete system run was made with the, well, complete system, meaning the headers are 700 mm long. I could not run that version with the bare headers since that would have roasted the rear tire. This means that that run reflects the effects of the shortest headers as well as the collector / silencer.
I would like to repeat this test with a really large-diameter collector I could slip over the header ends on all versions, but I don´t have access to the dyno any more (the operator / friend has gone to another company).  
 
We had some problems with the lambda equipment, but I don´t remember how we eventually did it. We also ran into the dreaded "Nemesis misfire", even if we did not know what it was at the time, so the testing was not quite as systematic as it could have been.
As an interesting side; when we did the header runs I was standing beside the rear wheel (stupidly), holding the exhaust extractor cone against the headers. The pressure on the cone from the exhaust at full throttle and 8000 rpm was amazing, making me understand why the F1 guys are (were) so hot on blown diffusors.  

Anyway, here is the same graph, with AFR. Some of the AFR numbers I do not really believe.



With this result in mind, I have settled for 800 mm headers for any 2-1 system I might make in the future.
I do not have any explanation exactly why the full-system graph is so different, but there clearly would be some potential here.

On the stock-with-slip-on vs. 2-1 /PCIII/Open lid comparo, the slip-on is clearly quite lean, I don´t know how much that would affect torque. Maybe Brad could give us a hint here, I don´t know anyone with more Duc mapping experience than him.  



The last graph compares a 2-1/PCIII/Open lid Monster run with the Rain bike 800 mm header 2-1 with no-snorkels airbox and some unknown rather rich chip in it. (it has the old 1.5 or 1.6 ECU, so it´s not so easily mapped as the Nemesis). The different runs are just repeat runs to make sure the reults were reasonable; AFR is pretty OK.



I´m also pretty impressed with the stock X collector, as it seems to work very well; I think most of the improvement on a stock bike with a full system is due to lower back pressure. However, they do ground easily and I wanted a 2-1 as tight as possible on the bike along with the tucked-in rear-sets.
 
Your bike looks very nice with the split headers and megaphone silencers, I think it will work just OK  

Nice also to hear you have an XS650. I had one for may years before getting the Monster, 860 cc, Mikuni 36´s, re-profiled cams and (you guessed it) a home-made 2-1. Since this is a Duc forum, send me a mail if there´s anything I can help you with.  

And oh yea, Duc forum or not, a nice Commando is a very handsome bike. A pity they are no longer around    :'(

(not counting the new version....)

[MonsterHPD]

No action on this thread for a while, so I figured I´d give the hose vs. water header length measurement methods a go.

The only header I had available is the stock Monster 800 rear header.

Hose method first:

Hose in header, mark with a few turns of plastic tape:



Pull out, and measure (the hose is stubbornly opposing staying straight, and I only have 2 hands):



Measured this way, the header is a shade over 400 mm, including the part that will go into the "X" collector.

Next, the water:



The header took 432 ml (or cc) to fill. With an outside diameter of 40 mm, and a wall thickness of 1.5 mm resulting in an inner diameter of 37 mm, the length works out as L= 4*432 /(Pi*4*iD*iD) = 40.178 cm, or 402 mm.

In other words, in this specific case both methods give essentially the same results. For my personal use, I´ll use the hose method since it allows me to measure individual pieces as well as partially or fully assembled headers, push-jointed, tack-welded or finished. I will check the water method on a longer piece of header whan I have them off the bike, lets see what that might show.      

[monsta]

Back again...    been awhile, but I've still been chipping away when I get a bit of time. (havn't been getting to much of that)
Anyhow, I've set up a system that I use to test the flow. Its far from perfect because there are many variables.
I'm doing the same as before with the a blower jammed into exhaust , but using a bit of paper held over inlet/outlet to observe what it does.







What I've found is that the standard header has a good suction from opposite exhaust(less with exhaust can fitted), but the cut down X section is fairly neutral.
When I fit a bit of tube to the cut off X section it draw's much better, showing that it needs a bit of length on the exit to make it work.

With the tight radius donut bends on the outlet it actually pushes air back up the other exhaust (like the quat d) showing (to me) that the bends create a bit of restriction.
Because I dont have the room to add a straight or large radius tube on the outet, I thought I might go down another path.

So, I cobbled up a Y peice that will fit inside the box and tested that.



It had similar results, also needing a bit of extra tubing on the exit to make it work, but probably not quiet as good as the X section.
I think there are other factors involved as well such as the angle they join at. But I'm not sure, I'm just bumbling around...
 
The other thing to factor is that I cant have the exit to close to the wall of the box, as that also creates a restriction send air back up the opposite exhaust.

Anyhow, I think I may go back to plan A and just button it up and hope for the best. I really would like to get it done and clean up my work bench! 
Maybe the extra pressure the engine creates will make it work better than the low flow air blower I'm using?   

[monsta]

well after about 18 months with this thing sitting on my bench at home I finally found some time to finish it off!   

In the end I did 4 different configurations to try and get the air to flow. The one that I ended up with seemed to flow 'nearly' as good as the stock manifold.
Getting the pipe to create a vacume at the other cylinder was  definately not as easy as I thought it would be!

I'm guessing it will be WAY better than the xbox but maybe not as good as stock!

I wont know for a while because I havn't put it on the bike and its getting ceramic coated at the moment, then I'll be away for about 5 weeks.
(cant wait tho!  )

heres a pic of the nearly finished job, just had to clean up the welds...

[MonsterHPD]

Great job, I´m so pleased to see this one go live again
Enjoy your 5 weeks away, but keep us posted when you get the system installed, and up and running. That will be SOO interesting.  

[monsta]

well, finally got it on! 
Mostly pretty happy with it, though it kinda loud! 
Makes the power that I expected, a lot better than the X Box! second gear wheelies no problem and 3rd if I get the rev just right...

heres some pics,
in this one you can see the standard header and cut-off pipes that I originally had on it. The paper is neutral. doesn't really suck in or blow out. ( I've got a blower pumping air down the opposite exhaust)

 

this is the one I made, pretty similar, paper is neutral...



this is the Quat D,  Blows out hard!  that would be going back up the opposite exhaust. I'm no guru, but I don't think that's a good thing!
Hence the power loss.



And here's how the finished product looks...  I may try packing it with stainless gauze and see if I can quieten it a bit, but I think it will be a balance between noise and power because its so small? you can see I have put an inspection cover on it so that I can still play around with it...

[MonsterHPD]

Cool, looks great, exhaust, bike, all 

I think that´s a great bike you have there.