building an exhaust.. any guru advice or tips?

[brad black]

ok, so all's not lost...
I was playing around today trying to suss a solution and blew air down the quat d, same as I did to the standard and my fab'd one...
Its actually blowing air back up the other exhaust inlet at about the same thats coming out the outlets...
that cant be a good thing??

so.. if mine's is neutral, IE; is not blowing out the other inlet, it's gotta be better than the quat d??  anyone?   

put some mufflers on the ends of the std headers and try it again.  i'd give both std and aftermarket a go if you have them hanging around.

the quat-d is a complete system (that allegedly doesn't work, from what i've read power wise anyway).  open headers are not.

but if it is pushing air back up the other header it can't be good.  i'd shitcan the idea right there.

[Roaduser]

here's where I'm at ATM. not finished yet, just been ground smooth and soon to be sent off to be ceramic coated on the inside. then ill cc the bent/vert cylinder header and cut the straight/horizontal cylinder to match, weld on my cans and see how it goes!!





as said above, the horizontal cylinder pipe is too long in this pic, i estimate it to be about 14cm too long in this pic, so the can should move to under the rearset. looks much better when moved under the rearset. im still undecided on the cans, i was going to modify these to the style i want but i think ill just put it together as is first and sort that out after


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[pitbull]

well it certainly looks super cool.

[BastrdHK]

That looks awesome  I really like the simplicity and routing of the vertical header/pipe!  Kind of a Sport Classic Zard look.

[Rob Hilding]

 

[Roaduser]

Thanks guys!! 

[brad black]

my thoughts, given in the vein of having my right to express your opinion and you having the right to ignore me without prejudice.

i appreciate the parallel lines you're going for, but given the pipes are quite a long way apart and non symmetrical side to side wise anyway the angle of the bottom one looks a bit odd to me.  how about running it at the angle of the frame rail above the rearset  (50 degrees going by holding the iphone up to the screen)?

or maybe a contrasting colour on the swingarm to help set the muffler off/make it more visual.  it sort of gets lost in the swingarm to me.  perhaps moving the muffler forward when you shorten the header will help keep it more in the bike so the speak.

altho i get the impression the top muffler would look different to how it looks in the photo once you can get a real life perception of depth on it. 

did you do some dyno testing of different pipes?

[Roaduser]

with angles, i did intend on the cans being parallel to each other and the rail under the seat, i have noticed on the zard (after it was pointed out my design is similar ) that they have them nonparallel and contrary to my original thoughts, it doesn't look "off" on their design.

so maybe this is the reason for them being nonparallel on the zards as i agree something does look a little off in that picture, hence the mild disclaimer about lengths. in the above pic the bottom can is hanging by tie wire so it is not set at any angle yet. both cans do also slightly angle out horizontally (equally) which cannot be seen in these pics but looks quite nice in person. ill cut the front header to length, dummy mount the can and take another pic with it in the position i originally intended under the rearset and still parallel, then try and crank it up to a more aggressive angle and see what that looks like then too.

always happy to hear opinions and ideas, cheers brad.

[Roaduser]

oh and as for colours, thats all likely to change soon    i have some new parts to colour/refinish and then the cans/headers should make a little more sence. and yeah that includes a black swingarm

and i did spend a coupla hrs on the dyno with various pipes and have results but not conclusions, hence ive been a little hessitant to put them up on the forum. i believe it mainly comes back to the factory tune not being good with the split headers, then with a less than ideal tune the change in results with the different volume headers wasnt exactly linear.

sooo yeah, i think if i want statistically significant results i would really need to retune individual cylinder maps with atleast one of the sets of split headers if not each, and then observe the changes of afr/hp/tq from there. not something this little black duck has the resources to do unfortunately.  as it was i did keep the room conditions and engine temps consistent atleast but yeah it wasnt really enough.....

[MonsterHPD]

Nice work.
As far as cosmetics go, I think we all design (or sometimes, sort of end up with ...) a design we like. If others like it, nice, if not, well ... nice as well, as long as the creator likes it.
Of course, on the other hand there´s that old aircraft industry saying, "if she looks nice she´ll fly nice"; in my humble view those exhausts look nice, so they could fly well enough  .

Anyway, s lot of what "design" work I do is based on what I think might work, so I have a few questions concerning these exhausts:

Are the megaphones in the pictures empty; i.e. "real" megaphones?
Why will you have them ceramic coated on the inside?
I´m a bit confused abouth header length and volume; do you use header volume as a way to measure length, or is header volume itself the design criteria?
If volume is the criteria, what is the theory concerning header volume?
Even if you won´t publish the dyno results, were there any trends that could be of interest?

I have a theory of my own concerning the stock "X" header configuration:
Since the "X" piece splits 2 different-length headers into 2 mufflers, with each header splitting into 2 roughly half-diameter branches, I think the "X" piece is designed to kill off any wave / resonance activity that might take place in the exhaust.
This would render the motor pretty insensitive to any exhaust modifications (excepting back pressure due to silencer flow resistance), enabling Ducati (and anyone else) to sell any style slip-on exhausts they could dream up, with tolerable effects on engine behaviour, especially considering the improved sound compared to the dull-sounding stock mufflers.

After all, some exhaust are slip-on in the original position, others are under-seat (or beside-the-seat), adding maybe 50 cm of header length. Normally, this would affect an engine noticeably, but I think a Monster will run at least reasonably with any of the Ducati aftermarket slip-on exhausts even if you do not change the mapping? Or am I just beeing paranoid...?

       


     


     

[brad black]

please publish the results.  this thread is more tech than idiotic petty pointer out of non perfection as some can be, and there's enough serious people contributing to make the info very worthwhile.

did the exhaust formula from the mv forum reach here?  i forget now.  haven't been there for ages.  http://www.mvagusta.net/forum/showthread.php?t=43891

here it is, been around for a long time
the formula;
Length= 850 x Exhaust opening [degrees BBDC+180]/rpm[power peak] 
the Exhaust opening is effective opening ie; 0.040-0.050"  exhaust valve opening point, i used 1mm lift.

Diameter, the pipe must hold, from the valve to the end of the head pipe twice the cylinder volume.
D = 2x the square root of swept cylinder volume[in cc]/8.2/L/Pi

[Roaduser]

yeah it did brad, by you, here was my reasoning

his formula for length is
850x [exh bbdc+180] / rpm @peak power
850x [57+180] / 8500 = 23.7 in long

that seems fair....

for diameter of pipe
2x the square root of swept cylinder volume[in cc]/8.2/L/Pi
2x square root of 400/8.2/23.7/3.14
2x square root of 0.655
2x 0.809
1.618 inch

and yeah, i will post up the results i have. I'm off for the weekend so ill aim at getting it organised on monday.
but basically the rear cylinder appeared to be running lean on the oem tune with split headers and this was a bigger negative than the various lengths of pipe. because i can't do split maps with a power commander i have since brought the ingijet u sent me and will use that to tune my bike to suit the split equal headers. i think this will give me the best results

[Roaduser]

MonsterHPD, these are not really megaphones by your definition, they are glass packed with a perforated inner tube and thus i wouldn't say the effective volume really increases much.
i want to have the headers (not the cans) ceramic coated on the inside to try and reduce the heat/browning of the pipes while keeping the brushed stainless look on the outside, just a theory, may not work but ehh worth a shot...
and as for volume, yeah I'm basically using it as a more accurate measure to maintain equal headers, the length is an easier way for some to measure but with the various bends i find the volume easier. I've tried to explain my thoughts on volumes/length in the quote below but from my dyno time i decided that the volume isn't near as important as matching the headers to each other and then tuning accordingly. so i made the rear cylinder to look good and will cut the front to match its volume, and being the same diameter pipe they should then be equal length.

from the above formulae and link i believe the volume and length are both the determining factors in tuning pipes and the diameter is a by product. once you have done the theory and start building the diameter becomes a constant and the length becomes the variable. as for wether the volume or length is more important, i don't know, but it matters little now for my setup anyway. Equality is my goal

when one header has a pressure force that passes the merge it creates a negative pressure in the non firing header and helps remove waste and, depending on cam profiles, possibly suck more inlet gases into the non firing cylinder. that theory prevailing, your scavenging is happening at the merge and dependant on the header pipes before the merge and the characteristics of the merge itself.

another theory is that where the pipe area increases dramatically (commonly the merge area, or in zoomies/split pipes the end of the pipe) there is a wave that returns back up the firing cylinders header till it hits the valve or cylinder, then returns again out the header and that can aid in scavenging of a firing cylinders own wastes/aid inlet gases. this theory is the tuning of a header pipe and thus the timing of the return wave is effected by the length and volume of the header pipe before the merge/termination of the pipe. this is thought to then only have a positive effect at one point in the rev-range and thus a different length of header can increase performance in a different area of the rev-range and have a negligible or negative effect at others. as the wave will be at a constant speed and timing from when the valve opens, it depends on the engine speed/valve timing as to when and wether the wave is synchronised and having a positive effect on the cylinder.

[MonsterHPD]

Roaduser,
thanks for the info.

I´ve used header length and id as the design parameters, altho different sources quote different formulaes or otherwise to determine the correct values. I´ve found some different formulaes over the years, and I´ve made a compilation as per below (hope the document comes out OK ...):

Edit: Did not come out that great, but at least marginally decipherable.... 



M&S is Morrison and Smith, who wrote the book "Scientific design of intake and exhaust systems" long ago; their formula give a length that is not engine speed dependant. CW is a formula I found in an old issue of Cycle World.
I have basically used the orange "medel" (meaning average in swedish).

Whatever formula is used, the result is very dependant on the exhaust gas temperature, since the sonic wave speed is dependant on the temperature, values between 1400 fps and 1700 fps beeing quoted in different sources. Since exhaust temperature will vary with load, there is a further uncertainty here.

Several other sources I have found also recommend to aim for an engine speed approx. 1000 rpm below peak engine speed, since the scavenging effect will have effect maybe 1000 rpm each side of the "best" effect.

I do think that header diameter is important, and from all I have seen the 2V duc motors do not like too big headers. I have used 38 mm id tubing for the bikes with stock valve diameters, I would have liked to have 40mm or 41 mm for the big-valve ST2 engine but could only find 43 mm id.

The length and diameters you have chosen seem to be right in the rule-of-thumb ballpark ( 23.7" <=>602 mm; 1.618" <=> 41mm) . As you noted, getting better than that requires testing for which we as ordinary people do not hve the resources. I don´t think the results would justify the effort anyway, unless we´re dealing with heavily tuned engines.

To determine length of the headers I´ve used a piece of as-big-diameter-as-possible hose that I push through the header and mark up the ends of the header on the hose, pull it out again, and measure. Not exact down to the last mm, but easy to use and also easy to determine the length of each section before they are welded together, and assembled sections only tack-welded together.

The result of the ceramic coating will be interesting. I probably cn not use it even if it works, since I´ve never heard of anyone providing that in Sweden.....  

[Roaduser]

seems you have done some research on the topic!!   so if I'm reading right, basically that graph is showing the ideal header length for max performance (hp or tq?) at a particular rpm assuming everything else is constant. supports the theory we have been discussing nicely. so theoretically i am in the right area, but as with my tests its everything else that is making more of an influence on the outcome than the actual header length/volume. so the conclusion I'm coming too is keep the diameter around the 38-40 mm range and the length anywhere between 1000 and 600 as long as the headers are equal and looking cool!!  

here is the raw graphs from my testing, feel free to analyse and draw your own conclusions. And yes i realise how lean this engine is running, lets think of it as a calculated risk that i took when i decided to continue on with the testing...  

my basic conclusions from this is that my tune is crap, split headers make the std tune even less suiting, the length of headers is not significant in this test especially when compared to the effects of a bad oem tune, and i think/hope that when i finish my pipes and tune the individual cylinders to suit that i will be able to overcome the power loss shown in these graphs and possibly even improve on it a little..... but i dunno about the low end torque, there is a LOT being lost here..  :'(

Base run with shortened Remus DP highmounts, TPO beast inlet,


alltogether hp vs AFR


altogether torque


600ml headers front vs rear cylinder


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