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home-made header for the G13B
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Author:  elbola [ Tue Feb 26, 2013 11:11 pm ]
Post subject:  Re: home-made header for the G13B

_Scratch_ wrote:
"The high speed internal combustion engine" and "calculated intake and exhaust systems" are 2 books off the top of my head.

Couldn't find those ones on the net :( but I did find another book from Graham Bell that goes deeper into these subjects. I only took a global look, but will an update after I fully go through it.

Author:  t3 ragtop [ Wed Feb 27, 2013 9:32 pm ]
Post subject:  Re: home-made header for the G13B

jankoelbola wrote:
_Scratch_ wrote:
"The high speed internal combustion engine" and "calculated intake and exhaust systems" are 2 books off the top of my head.

Couldn't find those ones on the net :( but I did find another book from Graham Bell that goes deeper into these subjects. I only took a global look, but will an update after I fully go through it.


graham bell was a super writer and i always liked his books. his schnurle principle 2 stroke book has the very best and most concise exhaust design chapter of any technical paper i ever read on the subject.

my bailiwick was electronics and as an electrical engineer i realized that electrical engineering and mechanical engineering use mathematical formulae that are very nearly interchangeable as far as transfer functions go so i always replaced rpm with frequency for the math calculations in my exhaust system design work.

the last time i checked, almost all of bell's books were out of print, or should i say between printings. it was like pulling teeth to get hardbound copies of his 2 stroke book 20 years ago. i'd imagine that someone would have to die and leave you a copy of it in their will to get one today. :lol:

Author:  elbola [ Wed Feb 27, 2013 10:57 pm ]
Post subject:  Re: home-made header for the G13B

I go the books on torrents sites. I also have the one about 2-stroke engines, if you or anyone else wants it.

Author:  _Scratch_ [ Thu Feb 28, 2013 11:26 pm ]
Post subject:  Re: home-made header for the G13B

What t3_ragtop said is correct. Exhaust systems mimic the same principals as electric frequencies. But, one must remember that these are not perfect sinusoidal wave forms, nor are they like sound. Pressure waves at high speed and at both high and low densities do some interesting things under different circumstances. For example, a pressure wave will produce a negative pressure wave in the opposite direction when faced with a large change in cross-sectional area. The most fastenating part about this is the fact that it can do this as well to an adjacent pipe causing a phenomena some times refured to as "cross talking (between cylinders)". This can then influence the efficiencies of adjacent cylinders as you now have active pressure waves resonating throughout the system. This is why a Morrison test apparatus is such a useful (but expensive to build) tool for visual representation of pressure wave forms and their time of arrival.

As I said, it takes years of study and failures to really get it right. And even then, your locked in at 1 frequency/rpm that is truly optimal.

Author:  t3 ragtop [ Fri Mar 01, 2013 10:10 pm ]
Post subject:  Re: home-made header for the G13B

back in my old r&d days in the thermal dynamics lab we made a simulacrim of a v2 rocket motor, stretched out, from quartz so that we could get a visual of the flame front when we varied the pulse frequency. along with all the other instrumentation we had on the apparatus, i got a really good handle on the math.

actually, the analog for the morrison test fixture turns out to be audio frequency filters, like crossovers, in bessel and chebychev modes - as far as transfer functions go.

on exhaust systems i have always been keen on anti-reversion designs but sometimes reversion can be your friend when it comes to tuning. i can think of several v8 applications where the crossover pipe and reverse pulses actually help to close exhaust valves and the engines just won't run well without it. i've had more than one chevy v8 that had a "custom" dual exhaust and just ran like crap until i installed that crossover pipe.

in reality, exhaust (and intake) tuning might be equal parts of science and voodoo. =)

Author:  elbola [ Sat Mar 02, 2013 1:33 pm ]
Post subject:  Re: home-made header for the G13B

I wonder if the Suzuki-engineers had to build the engine first and than do a trial and error on the dyno to get the exhaust to perform how they wanted?... I don't think so. One thing I learned at engineering school (as an intern now) is that everything CAN be calculated and predicted nowadays. The equations we use, were indeed a result of lab-tests once, but almost everything is on the books now; it's just a matter of finding them. Except for quantum-mechanics, that's still pretty much only theories.
btw do you guys have a link to that "Morrison apparatus"? All I could find about that guy was a book called "Scientific Design Of Exhaust & Intake Systems"

Author:  _Scratch_ [ Sat Mar 02, 2013 2:39 pm ]
Post subject:  Re: home-made header for the G13B

That's one of the books I was talking about. READ IT!!!!

Author:  elbola [ Thu May 02, 2013 10:18 pm ]
Post subject:  Re: home-made header for the G13B

Haven't had time to work on this... hope to have some time next month. This is the header I'll modify to fit the GTi, or at least take some parts of it; specially the Y-piece where the primaries connect to the secondaries.
image_id: 22782

I took the measurements (not have them with me now), but it's seems like the sizes I'll be needing. Does anyone know the inside diameters of the primary and secondary pipes of the stock header? So I can compare...

Author:  suprf1y [ Fri May 03, 2013 11:26 am ]
Post subject:  Re: home-made header for the G13B

ID of the stock manifold runners is 35 mm

Author:  elbola [ Sun May 05, 2013 2:04 am ]
Post subject:  Re: home-made header for the G13B

suprf1y wrote:
ID of the stock manifold runners is 35 mm

Thanks for the info :) The primaries on the VW-header seem to be about the same ID, but the secondaries have greater OD's. I hope I can still use the Y-pieces though.

Author:  elbola [ Thu Jul 04, 2013 7:12 pm ]
Post subject:  Re: home-made header for the G13B

Update: I've been really busy, so I've not been able to put time into the car. Once I get the time, there are also a couple of things of higher priority in my to-do-list. However there's something worth mentioning: I got lucky today and found pieces of a Gti-header at a friends backyard, so I'll probably use the upper part of that one and the collectors of the VW-header to make my own...

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Author:  elbola [ Sat Oct 26, 2013 8:08 pm ]
Post subject:  Re: home-made header for the G13B

I finally started building the header... I copied the dimensions of the stock manifold, so I could make something that's plug and play =). One thing that's really interesting is how restrictive the secondary runners are on the stocker... they are like 37mm OD while the primaries are 35mm ID. I'm still trying to get the right size pipes to make something that's worth the effort, if not I'll at least upgrade the secondaries. I'm against the clock cuz I need to have this finished this week, before the new clutch kit arrives...

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Author:  suprf1y [ Sat Oct 26, 2013 8:13 pm ]
Post subject:  Re: home-made header for the G13B

Quote:
One thing that's really interesting is how restrictive the secondary runners are on the stocker... they are like 37mm OD while the primaries are 35mm ID.


There's a good reason for that.

Author:  elbola [ Sat Oct 26, 2013 8:28 pm ]
Post subject:  Re: home-made header for the G13B

suprf1y wrote:
Quote:
One thing that's really interesting is how restrictive the secondary runners are on the stocker... they are like 37mm OD while the primaries are 35mm ID.


There's a good reason for that.

Not according to the formulas posted above...

Author:  suprf1y [ Sun Oct 27, 2013 8:40 am ]
Post subject:  Re: home-made header for the G13B

What formulas?

Author:  elbola [ Sun Oct 27, 2013 10:43 am ]
Post subject:  Re: home-made header for the G13B

suprf1y wrote:
What formulas?

First page... I even posted an Excel-sheet.

Author:  Mr.Pipe [ Sun Oct 27, 2013 11:24 am ]
Post subject:  Re: home-made header for the G13B

Are those formula from Pipe MAX?

Author:  elbola [ Tue Nov 05, 2013 9:15 pm ]
Post subject:  Re: home-made header for the G13B

Update: I couldn't get any elbows or parts to make the collectors, so I had to work with what I could find. Fortunately I do have a pipe-bender so that helped a lot. This is my first header and I'm not a professional welder either, so I'm actually pretty happy with this result.
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These are the specs:
Primaries: 37mm ID
Secondaries: 40mm ID
Collector: 45mm ID

According to Graham Bell's book the primaries should be 15 inch long and I respected that norm. However I found the diameter for the secondaries and total length of the header not realistic or suitable for my goals. The header was supposed to be "plug and play", so I could change back to the stock manifold if needed... all aftermarket headers are a drop-in too and considerably shorter that they are supposed to be (according to Bell) , so I've started to question this book's formulas.
Anyway at some point, I started to make choices based on what "seems" right by comparing my work to the stock manifold and aftermarket headers out there (in pictures); hence my choice for 40mm ID for the secondaries.

I'll let the paint cure for a few days and install this weekend. Really excited =) ...

Author:  t3 ragtop [ Tue Nov 05, 2013 11:56 pm ]
Post subject:  Re: home-made header for the G13B

a. graham bell has been a respected authority on exhaust design for a long, long time. i used his many books on the subject to design 2 stroke schnurle principle engine exhausts 25 years ago. i have a couple of his hard bound books that have been out of print for 25 years. he had a really concise and well written chapter on exhaust tuning in 'the design and tuning of the schnurle principle 2 stroke engine' which was what turned me on to bell more than 30 years ago. see if your library has anything by mike moss, too. he wrote more from a 4 stroke perspective but a lot of his writing was taken from graham bell's work.

if anything, bell's books are written from the stand point that anyone who attempts to use his data is already knowledgeable in all the intricacies of sectioning pipe and bends, welding, flow dynamics, and lots of metal working basics. because of all that, building pipes is as much voodoo and artistry as it is science and mathematical calculations.

believe me when i tell you that i used bell's ideas and math to build expansion chambers incorporating some complicated forward and reverse cone designs and dimensions that tuned up true to his math. practical applications of exhaust systems based on formulae gleaned from his book have worked out great for me but i had to be able to translate the math into real steel.

having been educated in electrical engineering, i have always used math and equations whose functions are applicable in both electrical and mechanical engineering. that usually means that i translate rpm into frequency and solve the mathematic problems from that angle. it just makes it easier for me to wrap my head around.

you can find a lot of good fabrication guidelines in the machinist's bible and the bosch automotive engineering handbook. i can also think of 2 or 3 welding digests that have the specifics needed to fabricate cone sections, tapered bends, and tricks on pipe sectioning.

a couple texts for 100 and 200 series flow dynamics come to mind, too. google laminar flow and read that until it clicks for you.

there's some good data and applications that can be found in texts from the sheet metal tradesmen, especially where round duct work is being featured.

i used to build some pretty ugly, quick and dirty stuff to see how it worked out. when i found something that worked i would clean it up and refine it. a lot of prototype work i turned out worked great but was uglier than sin. i have the highest respect for guys like jardamuth who take the craft to the point of being fine art, beautiful to behold along with solid engineering and advanced design.

bolt that header on and give it a whirl. :wink:

Author:  Teeth [ Wed Nov 06, 2013 9:39 am ]
Post subject:  Re: home-made header for the G13B

I am not surprised that building to the formula results in a very long header--if you look at modern competitive designs for cars with aftermarket support (Hondas) the best headers require a custom exhaust and deletion or relocation of the cat rearward in order to run a longer one.

I am going to guess that what you built is going to work very well for you in spite of that compromise, however. It isn't very pretty, but that's ok too--form follows function and you may have inspired me to build my own, at some point.

Author:  elbola [ Wed Nov 06, 2013 11:28 am ]
Post subject:  Re: home-made header for the G13B

Than if Graham Bell is right, that means the stock manifold was calculated following totally different principles; because nothing adds up. Something that really kept me thinking is that according to Bell, 1.5" primaries go with 2" secondaries (for our engines @ 4k rpm)... 2" seems like a lot to me, but maybe I'm wrong. I'll go through the math again to see if I made any mistakes.
On another note, I would like to know the specs of the aftermarket headers for the G13B out there (can someone share that info?), so I could review them using Graham bell's approach. The fact that they bolt on to the rest of the stock exhaust system, making them really short compared to the expected length at say 4k rpm, makes me wonder what diameters those runners have.

PS: Yeah my work isn't the prettiest, but the lack of tools and materials didn't help much. I suppose my welding/fab-work will get better with time.

Author:  t3 ragtop [ Wed Nov 06, 2013 7:32 pm ]
Post subject:  Re: home-made header for the G13B

just for comparison, here's a cultus 4 to 1 design header.
Image
Image

i particularly like the stylized heat shield on these pipes.
Image

Author:  elbola [ Wed Nov 06, 2013 7:55 pm ]
Post subject:  Re: home-made header for the G13B

t3 ragtop wrote:
just for comparison, here's a cultus 4 to 1 design header.
Image
Image

i particularly like the stylized heat shield on these pipes.
Image

Could you post the diameter and length of the runners?

Author:  t3 ragtop [ Thu Nov 07, 2013 5:56 am ]
Post subject:  Re: home-made header for the G13B

next to impossible right now as the header is on my red vert and it's put up for the winter.

i'm going to guess that the tubes are 1.5" and 30" in length. the single pipe downstream of the collector is 2" in diameter and 10" - 12" long.

Author:  elbola [ Thu Nov 07, 2013 5:01 pm ]
Post subject:  Re: home-made header for the G13B

t3 ragtop wrote:
next to impossible right now as the header is on my red vert and it's put up for the winter.

i'm going to guess that the tubes are 1.5" and 30" in length. the single pipe downstream of the collector is 2" in diameter and 10" - 12" long.

According to Bell's book, 1.5" tubes work the best at almost 4k rpm for our engines, although the runners should be 40" long (with a 4:1 set-up) in that scenario.
What would you say is the rpm-range at which the cultus header works the best?

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