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Discussion Starter · #1 · (Edited)
OK, ive been working on a custom header project for a few months now. mostly reading, a little math, some measuring and lots of welding practice. I dont have time today to cover everything ive learned to date, but heres' what im currently thinking about:

- on a 4-2-1 header, as part of a whole exhaust system, at what point is the low pressure sonic wave from an exhaust charge reflected back up the pipe?

-is it when it reaches an area of +10x the cylinder volume?

-is it when it merges with it's paired primary?

-is it at the 2-1 collector?

-is it as a square wave (closed pipe), when it hit's the cat's catylist?

-is it at the very end of the tail pipe?

-somewhere else?

currently im trying to figure this out by means of comparing Smith's ideal length formula with actual measurements from the OEM manifold from a 98 typeSH.

according to Smith's "Scientific design of exhaust systems" (i know its old, if you have better reading let me know!) here are some optimal primary lengths for acoustic tuning, according to several estimated volocities of sound in exhaust gas:


estimated ideal length for open pipe primary according to Smith
--------------------------------------------------------------------------------

L = V*T/RPM

L = ideal length in inches
V = velocity of sound in exhaust gas, can range from 1100 - 1900 fps
T = 120' exh port open time in crankshaft degrees (is this correct for h22a4?)
RPM = disired torque peak RPM

-RPM----2k----3k----4k----5k----6k----7k----8k
1100fps-66----44----33----6.4---22----18.8--16.5
1300fps-78----52----39----31.2--26----22.8--19.5
1500fps-90----60----45----36----30----25.7--22.5
1700fps-102---68----51----40.8--34----29.1--25.5
1900fps-114---76----57----45.6--38----32----28.5
2050fps--------------------------41----35----30.75

H22 EGT = 1200-1500f
speed of sound at 1300f = 2050fps

*Smith used 1700fps for his work, and suggested interference pipes (which in a 4-2-1 means the paired primaries) not exceed 18" length (but i dont know where that # came from...?)

OEM exhaust manifold info
---------------------
primary (port to non-sequesncial merge)
length: 32cm (12.5")
dia: 3.8cm (1.5")

2ndary (1st merge to 2nd merge)
length: 51cm
dia: 4.5cm

pipe to cat
length: 44.5cm
dia: 4.8cm

exhaust port dimensions:
4.5x3.5cm oviod
12.85cm^2 area


tottal length (1port to cat): 127.5cm (50")

*lengths include 1cm flages, where appropreate

top, center flange bolt distances 9.5cm, 8.5cm, 9.5cm
flange bolt whole diameter: 8mm
2ndary down segment length:13cm
2ndary post curve to collector length: 38cm
2ndary collector to flex length:5cm
2ndary flex length: 20cm (8")



look at these NASTY transitions:



where is it? LETS TALK!!

ps- if anyone has the equivilant numbers for the mugen header id realy appreciate it, itll save me 4+hrs of camera matching and reverse engereing in 3dsm...
 

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At what lift is that open time for the exh. valve? Is it specified?

You are blazing new ground with this. I don't think anyone has put the effort into it, let alone come up with answers. You would almost be best off to find someone with a dyno and work out some cheap time. :)
 

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That's what I was wondering, how are you gonna be able to test these theories, I mean it looks good on paper, but your never gonna know unless you put in some dyno time. Good luck, and a big :bigthumb: for all the time and effort.
 

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Yes, this is indeed an interesting project. Keep us updated, and make sure you do some dyno testing! :)

I have a couple of automotive engine engineering books, but I have no idea exactly what kind of exhaust theory they discuss. I can get the names of the authors, if I get a chance to look through all the boxes.
 

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hey leptolude, see my suggestions for reading material in the other header post.

Can you share with us what you have been reading? I'm not familiar with any smith's except Carroll Smith.
 

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Discussion Starter · #6 · (Edited)
reading and dyno time

good morning,

heres what ive been reading:
--------------------------------------
Scientific Design of Exhaust and Intake Systems
j. Morrison, P. Smith, 3rd eddition 1972 isbn: 0837603099

Automotive Math Handbook
Aird, 2000,

desktop dyno (read it, havent bought it) by Atherton
check www.mrgasket.com

honda builders...1&2
j. pettit (hire an editor !!!!!)

honda acura engine performance
mike kojima

2 welding books by Peter finch

burns stainless has a some good reading:
http://www.burnsstainless.com/TechArticles/techarticles.html

ive read every smsp post on www.honda-tech.com

my father-in-law was a senior engeneer at Ford, hes teaching me alot, there are a few guys in my welding class that are engeneers also, one of the instructors works for bosal too.. i ask as many question as i can.

-------------------------------

thanks for the link to the sae articles, i work near one of UofMich's large librarys, ill hit the stacks with a list! ive never seen any of Carol Smith's writing, do you have any titles?

-------------------------------

billy, yeah that honda builders test was a little funny... the thing that got me was that the tottal difference between the 3 headers was within +/-4 hp/ftlbs or so.... ive been at the dyno and had similar differences pull to pull... i dont know what to think of that test. yeah more dyno time is deffinately in my future. once i get to the actual fabrication (research is slowing, just made fitment jig, 1st design is next THEN ill actauly make one.. plus, its cold as $#!7 up here these days)

-------------------------------
as for the primary merges...

it seems that as far as the gas flow itself is concerned, so long as the transitions are smooth as near paralell as possible and in equal length pipes, it doesnt matter. But the pressure (sonic) energy does care.

if you want to use a merged primary for scavenging, your basicaly making an interference pipe (read Smith). to do that you want the paired primary's exh. valve to be closed when the pressure wave hits the 1st merge and partialy goes UP the paired primary and partialy DOWN to the 2nd merge etc etc (where this wave gets reflected in a full exhaust system is what the original post is about). After the pressure (sonic) wave gets reflected a low pressure pulse travels in the oposite dirrection, its this low pressure (slight vacume) pulse that you want to reach back to the open exhaust valve before it closes, to help pull the remaing gas out and to reduce pumping friction. From what ive read in Smith/Morrison its this sound driven energy that does most of the scavenging, not the gass itself (but that info is from the 50-70s...).

so given all of that, it seems that it only matters if you pair primaries that have exhaust valves closed in opposition, regardless of what cycle the 2nd paired piston is in. heres a good link with a snipet from Dave at smsp:

http://www.hadamotorsport.com/tech/review/dsemc/index.htm


.. at work, time for a staff meetng, so now the questions are:

- where does the presure wave from the exhasuting cylinder get reflected (other than it's paired primary's closed exh. valve, ie original post)?

- if you have a 4-2-1 design, so long as 2 paired primary exh. valves are not open at the same time does it matter which cylinders are pared, and if so why (does the gas slug actualy help scavenge or is it just pressure waves?)?

glad others find this as interesting as i do. started mig wleding last night, ITS SOOOOOO EASY compared to TIG.. geez. but i have to say i like TIG's controll and pace a little better.
 

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Discussion Starter · #7 ·
from the other thread:

from the other thread, just bringing over hear for the sake of linear conversation.. :laugh:

-------marcucci-----
So any comments on sequencing the exhaust?

1&4, 3&2: pulses evenly distributed across time in secondaries
1&2, 3&4: pulses unevenly distributed across time but sequential
1&3, 4&2: pulses unevenly distributed across time but sequential

I'm not sure if evening the pulses over time provides more gain with "continuous" scavenging, or if sequencing them right after one another (but then a dead time between the next) provides better scavenging in a system where the secondaries meet soon (better overall scavenging). In that case, I would think a 1&3 + 4&2 arrangement would be best as the pulse from 1 would scavenge 3, then 4 scavenge 2, and 2, 1, and so on.

-------marcucci-----
No, but I think it is more a logistical thing (routing primaries). Can you share with us what you have read that would indicate this to be ideal? Everything I have read states that header staging doesn't matter as much power-wise as thought, and even says that the primary length isn't as much of an issue.

When it comes to scavenging I would think that staging them 1-4 and 3-2 would be best to spread out the exhaust pulses so that they are evenly distributed. Meaning, with an order of 1 - 3 - 4 - 2 you would have 1 flowing and 4 flowing with the same length of time across the firing order. If you ganged 1 and 2, 1 would flow... then a long dead time, then 2, then 1 again real quick... dead time... follow my logic?

----paulyg----
All auto manufacturers and prob the good aftermarket designers are all using CFD (computational fluid dynamics) software such as STAR-CD and FLUENT to do any modeling of intakes or exhuasts. They then back up the modeling with real world testing. Also of good use is "WAVE" simulation which is a way to model gas flow as 1-d compresable simulations. Check out Optimim Power's Virtual 4-stroke for an application of this.

For some really serious reading, try some SAE tech papers. You have to pay for them, but alot of these papers are written by detroit, japan, and germany's best engineers.

http://www.sae.org/servlets/product...V&TECH_CD=ECOMP

http://www.sae.org/servlets/product...V&TECH_CD=ENGIN
 

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Well, then, with Smith's logic I would think that anything other than 1&4 primaries merging and 2&3 primaries merging that you would still have both valves opening at the same time in the "sequential" method of combining them. I would have to sit down and map things out, though, to be sure. I would also think the length of the pipe would have something to do with it since it would effectively be a delay line, though I'm not sure if the speed would change enough to matter. Might be way equal length primaries aren't as big a deal as some people say.
 

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Discussion Starter · #9 ·
speed of sound

yeah, this seems to fit in the "the more you learn, the more confused you get, till one day it all makes sense" catagory.

----- lets think about this some more ---

ive read estimates for the speed of sound and exhaust slug in modern engines ranging from 1100fps-1900fps for sound and 100-300fps for the gas slug. the gas speed is dependant on piston speed, cylDia/portDia and id imaging exhaust valve timing (blow down), and combustion pressure too.

to determine simple open pipe length estimate, for the pressure wave, you can use the math above (l=v*t/rpm), but i havent figured gas slug travel time vs pipe length and valve timing yet. i dont even know if it realy has any affect though (within reason), itd be pretty simple to do, just havent done it yet.

At what lift is that open time for the exh. valve? Is it specified?
oh yeah, the lift amount/crank degrees isnt specified, but im sure it has influence, i think that simple math assumes a "time in degrees with mean lift..." thats why i was asking about detailed, stock, type sh cam timing specs the other day. thanks for the crower link.

...Well, then, with Smith's logic I would think that anything other than 1&4 primaries merging and 2&3 primaries...

i was reading yesterday (i forget where) that some racing people (didnt say who, when etc) found that the drag on the gas slug outwheighed the benifits of exactily identical primary lengths. with pressure wave speeds of 1700fps, in 1-4' pipe lengths i could see that being the case. but then again we are talking about valve timings of.... what..

7600rpm / 4 (exh cycle only, 1 cyl) = 1900/1min = 31/1sec = .032 sec assuming uniform valve timing

so with a .032 seccond "window" a pressure wave needs to travel (lets say in the stock manifold) 4 feet (down p1, up p2, down p2, up p1 to port, and who knows where else...) at 1700fps. a pressure wave moveing at 1700fps goes 54.4 feet in .03 secconds... and now we get see how simple math fails in exhaust tunning... :confused:

back to work now..
 

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Discussion Starter · #10 ·
interfearence

read a little more last night, still cant find any answers regarding cylinder pairing logic, but i did find a few pressure experiment charts that, on an interference type system (eg 4-2-1), the pressure waves reflecting off from the closed end and the open end returned back to the port at intervals relative to the pipe lengths (duh) and were relatively semetrical. Also, Smith talks alot about the benifits of megaphone additions to the end of an exhaust pipe.

from this and from looking at m. kojimas book's header pics it seems that the "down the pipe" pressure wave will reflect once it hits a space of, lets geuss at 2x the pipe volume, per even length.
somthing like this:

http://www.burnsstainless.com/Megaphones/megaphones.html

-i wonder how megaphones act when the back end is welded to a large diameter, cat-pipe-sillencer exhaust?
 

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I think it would be easiest to fab/modify a stock manifold and dyno it rather than try to approach it scientifically. As David Vizard's "No Loss Exhaust" article points out, it's easier to experiementally derive values than it is to try and take into account ALL factors to do it mathematically.
 

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Wow lepto, I have been mig welding for about six years now, as I am a autobody tech, and have just started tig welding. I think you will never get as clean of a weld with mig as you woud with a tig, especially if you are practiced at tig. I have only a few tig sessions and I would much rather tig something now then mig. You don't get splatter with tig as well, that's a big plus man. I would definately tig your header system. Just my opinion.
 

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Discussion Starter · #13 · (Edited)
yup, i suc kat mig on 16gauge...

oh my... i burnt through $20 worth of mild steel pipe on thursday... just couldnt move fast enough for the wire... ill take slp's advice and go back to tig... what about back purging the welds with tig, do you have to do that on mild steel or only stainless steel? i was considdering gas welding it... ideas?

built the fitment jig tonight, ill post pics. It should help experiment with lengths, etc. ill post #s with the pics, they wouldnt make much sence without images.

EDIT: removed the "so far" design, im waiting to get my info-pack from headersbyed.com , Ed seems to think that the whole steped tube diameter design "isnt all that..." so im going to see what he has to say before i think about design anymore. Ed happens to drive a 5thgen base too :) arent preludes great...

i dont think any more math is going to help, your right todd...
 

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Re: yup, i suc kat mig on 16gauge...

leptolude said:
oh my... i burnt through $20 worth of mild steel pipe on thursday... just couldnt move fast enough for the wire...
What setings did you have it on? The cheap Lincoln we used in FSAE had an adjustable wire feed rate and adjustable voltage. For a thin steel you should only need a "B" or "C" voltage. And if the wire is feeding too fast, slow it down. Maybe your mig doesn't have adjustments but I think most do.


EDIT: I just read that you are taking a welding class, so you prob know what I just said above. Sorry.

I never answered your question about Carol Smith. He wrote Tune to Win, Drive to Win, Prepare to Win, and a few others. Essential motorsports reading IMO.
 

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Discussion Starter · #15 · (Edited)
mugen camera matched

ok this weekend:

i completed my welding fit jig (ill post pic and measure #s tomarow)

put my work skills to work:


via 3dsm5.1's camera mathcing utility, and known bolt hole measures, i came up with the following measurement estimate. If anyone has a Mugen header for h22, and would dontate 5 minutes to my cause id apprecaite it, send me any measurement numbers that you have, or can get!!

EDIT: [### is actual measure, thanks koollude]

primary
-------
length: 35cm (14") [43cm 17.25" aprox, assuming 45' rad...prob 15-16" on the center line]
diameter: 4.45cm (1.75") [4.49cm, 1.77"]

seccondary
----------
length: 88cm (34.6") [44cm 17.5" aprox....]

EDIT: oops, notice 88/2 = 44.... i made a mistake in 3dsm with the measure utility and mirror modifyer...... i was right, on this one at least

diameter: 5.0cm (2") [4.7cm, 1.85"]

collector
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length: 14cm (5.5") [6cm, 2.36", measured from BASE MODEL HEADER, this may be where the size difference is]...
diameter: 6.3cm (2.5") [5.7cm 2.25"]

mugel tottals
-----------------
L: 79cm, 31"
D: 1.77 - 1.85
COL L: 6-14cm 2.36 - 5.5"
COL D: 5.7cm, 2.25"

am i close, someone tell me (maybe i should just call king and ask)... [to far of on lengths and dia to be able to recreate this exactly, but i was in the ball park, not bad for knowing only bolt hole distances. good thing i got actual #s... ]

this was a fun excersize, i dont plan on just recreating this header though, first ill try somthing completely different :)


--------------

The best find of the weekend was this though:
http://www.headersbyed.com

Its been hard to find a source for mild steel bends around here. Burnsstainless has "california sponsored race team" prices, and they dont seem very interested in individual DIY'ers, and all the local steel places are more plumbing oriented, ironic considering Detroit (aka MOTOWN, the MOTORCITY) is nearby. This company seems to be focused on domestic V engine stuff, but pipe is pipe and flow is flow... there are some good articles etc too. I placed my first order today, hope it goes well.

---------------

paul, it was a miller mig machine, it was adjustible, i just need more practice... ever try thin wall tube but joints... :( im going to try and find a pipe beveler and do small slip fits, with lap welds...
 

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damn can't wait for the finish product, so technical someone AQ this **** and also if its good will you mass it for our memebrs?
 

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Discussion Starter · #18 ·
more port pairing...

Yeah todd, i did notice the primary pairings... one thing that make sense is pulling the #1 over to the #4. the alternator, PS pump make the driver's side a little tight. I still dont know what to think about sequencial vs non sequencial pairing...... AHHH TOO MUCH CONFLICTING INFO!!!!!!! :confused:

not suprising considering Mugen is the child of Honda, but this manifold seems to be a refinement of the OEM version. different dimensions on the primaries, clean merges and lighter materials.. (not to mention the bling and the braging rights for spending a G on a production header, if you into that kinda stuff, im not).

------
thanks dragon... its a fun project. my wifes' been hella busy with grad school too so it keaps me out of her way... and ive been learning tons, multifunction projects are great.
 

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Discussion Starter · #19 · (Edited)
..JIGaa who you rolln wit...

.... uh betta get it right .... uh betta get it right.....

sorry couldnt resist, heres a pic and # for my welding JIG



fitment jig dimensions
----------------------

base section (cat flange to outside edge of secondary curve)
------------
L: 31 1/2" (80cm)
W: 5" (12.7cm)
H: 3 - 2 5/8" (7.62 - 6.66cm)

up section (seccondary curve to bottom of flange)
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L: 7 - 4 1/2" (17.8 - 11.4cm)
W: 5 - 14 1/4" (12.7 - 36.2cm)
H: 16" (40.64cm)

flange section (from base to top of flange and out to edge of primarys)
-------------
L: 7" (17.8cm)
W: 14 1/4" (36.2cm)
H: 3 1/4 (8.25cm)

this area is visualy represented in the mugenRevEng image, by the red box like object.

i put the transpierent image of the oe manifold in there to better describe how this think works, even thought the angles are wrong in the photos. the verticle section slides out, i assembles this with the manifold inside, so i know it fits. It is a very conservative fit, as there is probably more room to play with.

i know the end product will have to be fit on engine to get good alignment but this jig will let me play with layouts without having to disasemble my car (its still transportation for me). anyone have #s for the mugen header, id like to see how accurate i was....
 

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Re: mugen camera matched

leptolude said:
paul, it was a miller mig machine, it was adjustible, i just need more practice... ever try thin wall tube but joints... :( im going to try and find a pipe beveler and do small slip fits, with lap welds...
I learned to weld on 1.25 X .063 chrome-moly tube with a Lincoln MIG. You'll get better! If I can produce decent welds, so can you.

EDIT: Spelling mistake.
 
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