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home-made header for the G13B
http://www.teamswift.net/viewtopic.php?f=11&t=55285
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Author:  elbola [ Thu Jan 17, 2013 1:09 pm ]
Post subject:  home-made header for the G13B

I'm about to start making my own headers in a couple of weeks, but I can't find reliable information anywhere about the size and length on the pipes. It's supposed to be a 4-2-1 design, so I don't loose torque at the bottom... I'm not reving past stock limiter either.
I read somewhere in the forum about a possible set-up using 1.25" primary, 1.75" secondary and 2" collector; but I'm a little confused about the length and radius of those pipes.
What do you guys think would be the best set-up for a stock engine?
If you have a book, link or formula I can use to calculate the exhaust, that would be awesome; as I haven't been lucky finding that info yet.

Author:  elbola [ Fri Jan 18, 2013 1:01 am ]
Post subject:  Re: home-made header for the G13B

I've spent hours and hours these days trying several calculators online with no reliable results, as they are all different. Couldn't find any books on torrent-sites either. Can someone point me in the right direction?

Author:  elbola [ Sun Jan 20, 2013 2:40 am ]
Post subject:  Re: home-made header for the G13B

Nobody?

Author:  elbola [ Mon Jan 21, 2013 1:20 pm ]
Post subject:  Re: home-made header for the G13B

Apparently either no one knows or don't want to share that info. I will do it on my own and post the results here, if satisfactory. Thank you sooooooooooo much for your help.

Author:  alpine [ Mon Jan 21, 2013 2:00 pm ]
Post subject:  Re: home-made header for the G13B

http://geometroforum.com/topic/4569879/23/#new

read this thread it might help

Author:  PBC137 [ Tue Jan 22, 2013 4:09 pm ]
Post subject:  Re: home-made header for the G13B

Sorry bud, can't help you....never tried bending pipes nor do I have access to a flow bench.

Author:  crnolic [ Tue Jan 22, 2013 7:37 pm ]
Post subject:  Re: home-made header for the G13B

I've never built a header but...
maybe go with a 1.25" runners to two 1.75" collector then to a 2.25" collector

Author:  elbola [ Tue Jan 22, 2013 7:45 pm ]
Post subject:  Re: home-made header for the G13B

crnolic wrote:
I've never built a header but...
maybe go with a 1.25" runners to two 1.75" collector then to a 2.25" collector

That's kind of what I have in mind. The problem is the length of the pipes. I did find some equations though, I'll post the progress as soon as possible

Author:  alpine [ Tue Jan 22, 2013 9:32 pm ]
Post subject:  Re: home-made header for the G13B

jankoelbola wrote:
crnolic wrote:
I've never built a header but...
maybe go with a 1.25" runners to two 1.75" collector then to a 2.25" collector

That's kind of what I have in mind. The problem is the length of the pipes. I did find some equations though, I'll post the progress as soon as possible

in that geometroforum thread, mwebb, goes on about the calculation you need to find the correct i.d for exhaust pipes

Author:  elbola [ Tue Jan 22, 2013 10:09 pm ]
Post subject:  Re: home-made header for the G13B

alpine wrote:
in that geometroforum thread, mwebb, goes on about the calculation you need to find the correct i.d for exhaust pipes


Yes, he did mentioned something that was helpful..... here http://geometroforum.com/single/?p=659357&t=4569879 but there are too many variables still open, like info about the secondaries, collector and tail-pipe and how the actual design (4:1 or 4:2:1) will change the equation. What I want is to calculate the whole exhaust, or to be more specific: design the proper header for my existing tail-pipe and muffler.

Author:  elbola [ Wed Jan 23, 2013 5:10 pm ]
Post subject:  Re: home-made header for the G13B

I used his formula on the Excel-sheet I'm working on and it's a dead end. Even assuming he's right about the constant gas-speed of 300 feet per second and runner-volume of 1/4*displacement... the most important question is still open, which is the relation between the diameter and length of the runners.

Author:  suprf1y [ Wed Jan 23, 2013 5:48 pm ]
Post subject:  Re: home-made header for the G13B

Take anything posted by that guy with a HUGE grain of salt.

You want a 1 1/2" primary tube.

Author:  t3 ragtop [ Wed Jan 23, 2013 6:29 pm ]
Post subject:  Re: home-made header for the G13B

suprf1y wrote:
Take anything posted by that guy with a HUGE grain of salt.


while wearing hip waders. :-P

Author:  VR4 [ Wed Jan 23, 2013 7:06 pm ]
Post subject:  Re: home-made header for the G13B

suprf1y wrote:
Take anything posted by that guy with a HUGE grain of salt.

You want a 1 1/2" primary tube.



theyre entertaining at least.... :lol:

Author:  Teeth [ Wed Jan 23, 2013 7:11 pm ]
Post subject:  Re: home-made header for the G13B

2" collector sounds a bit large to me if you are trying to preserve bottom end.

Don't know whether it really performs as good as it looks, but the best looking, 4-2-1 header I've seen is the one on Dominator's Flickr page:

http://www.flickr.com/photos/11473969@N02/

Maybe you could ask him what he thinks of it and to take some measurements.

I only know what others tell me, but I've also heard that the Cultus 4-1 is as good as the 4-2-1 designs at the bottom end if you don't build the rest of the exhaust too big (no bigger than 1 3/4 to the cat anyway). If you want to improve on that you might just weld a better 4-1 collector with a 1 3/4" (or even 1 1/2") restriction on to the Cultus part.

Full disclosure: I don't know what I'm talking about either--if I did I might have been more stubborn about actually getting a Cultus header instead of the Calmini header I picked up instead. And no, I've never seen the inside of the Cultus part to see if the collector could be improved on, but if the one in the stock down tube 2-1 collector is any indication, then there's definitely some room to do better.

Author:  t3 ragtop [ Wed Jan 23, 2013 7:47 pm ]
Post subject:  Re: home-made header for the G13B

you can preserve lower end torque up to a point before you start to lose the ability to breathe at the upper end.

i'm a fan of the cultus tube exhaust manifold, 2.25" exhaust system, and no rev limiter (except the one at the end of my right leg.)

were i to fabricate one of my own i'd probably build a 4-1 that emulated the suzuki cultus header in 409 stainless alloy but without the oem heat shield.

Author:  elbola [ Wed Jan 23, 2013 9:18 pm ]
Post subject:  Re: home-made header for the G13B

I currently have a 2"-pipe, no cat and straight-through muffler. The reason for wanting a 4:2:1 is cuz it's my daily car and also cuz I have a header from a 1.6L Golf that I could partially use for this project (for the collector and stuff). That'll safe me some time and work.

Out of my little "research" has turned out that reduction/increase in primary pipe diameter of 0.125in will move the torque-peak down/up by 650-800 rpm on <2L engines. On the other hand, longer primaries increase low-speed and mid-range power, with reduction in power at maximum rpm but with little change in peak-torque or the engine speed at which it occurs.
So I think upgrading the stock down-pipe would be a good move though, specially to improve the high-end. I'm speculating cuz I haven't made any measurements but those runners are not really long, compared to how they look like on most aftermarket headers, so if the ID's are OK (I assume 1 or 2mm bigger than the exhaust ports) than maybe it's something to think about. Cast-manifolds also perform better keeping the heat in the exhaust system. However I've found plenty information about using long primaries and short secondaries as well, so it gets confusing at some point.

I've been gathering plenty of data and trying several equations over the past few days, that could help in this discussion. Some of the tables or graphs may deviate from the subject a bit, but I think it's good to have it posted somewhere. Anyway here it goes:

First I found flow-bench results of a stock head
Attachment:
FLOW-BENCH RESULTS.tif [599.99 KIB]
Not downloaded yet

Used a dyno-plot(4th gear pull) from redline as a reference for a "stock" G13B, which I believe should be at around high 70's to low 80's at the wheels
Attachment:
neodyno.jpg
neodyno.jpg [ 71.93 KIB | Viewed 6402 times ]

Than I processed that into something I could use. Don't worry about the graph after 7k rpm, I just couldn't find a suitable trend-line for that segment.
Attachment:
stock dyno 2.gif
stock dyno 2.gif [ 187.11 KIB | Viewed 6402 times ]

Attachment:
stock dyno 3.gif
stock dyno 3.gif [ 108.38 KIB | Viewed 6402 times ]

I always wondered about this engine's volumetric efficiency... see how the torque peaks where the VE is the highest?
Than I found a pretty good pdf about exhaust design. Not all pages where available to see, but at least I could find realistic equations and not all the Sh*t that's on the net.
So here are some numbers for a 4:1 design
Attachment:
header 4.1.gif
header 4.1.gif [ 132.21 KIB | Viewed 6402 times ]

And the 4:2:1
Attachment:
header 4.2.1.gif
header 4.2.1.gif [ 172.63 KIB | Viewed 6402 times ]


If I just had a manifold at hand, I could go further and try to emulate the changes in the system. If anyone has good data, please post here.

The idea is to make the whole header myself, but if I can't find the time, I'll at least work on the down-pipe. I chose the ID's based on where the engines VE is the highest and just like Suprf1y said I'll probably go with the 1.5 primaries(peak-performance at 4K rpm). Those are slightly bigger than the exhaust-ports and will probably help with our fight against suction waves :P Than probably 2" secondaries(peak-performance at 6k rpm) and a 2.25" or 2.5" collector (couldn' find good stuff about collectors yet). The big question here is about the relation between the length of the primaries vs the secondaries (I chose 60% of the length for the primaries and 40% for the secondaries but that's not based on any real facts).

Author:  Teeth [ Wed Jan 23, 2013 11:54 pm ]
Post subject:  Re: home-made header for the G13B

What would you use to model?

I'd give you the measurements of my Calmini but that might not help you much. =)

If the best performing Honda headers have anything to teach us they seem to have both long primaries and long secondaries, terminating past the factory cat connection in some cases.

Author:  elbola [ Thu Jan 24, 2013 12:38 am ]
Post subject:  Re: home-made header for the G13B

Teeth wrote:
What would you use to model?

I'd give you the measurements of my Calmini but that might not help you much. =)

If the best performing Honda headers have anything to teach us they seem to have both long primaries and long secondaries, terminating past the factory cat connection in some cases.


If we knew the specs of the stock system, we could theoretically calculate how the exhaust-gases behave through the different volumes, in order to achieve hp and air-flow from the charts. Than we could simulate how the system is affected with the changes we make. I've been looking for 3d-modeling and dyno-simulation software, but all we need is pure math. Oh and a better dyno-plot to start with! The one I used is a guide only, you can see the x-axis wasn't even on a decent scale :P
If there's one thing certain, is that the equations for exhaust-calculation are not 100% reliable, specially the ones found on the net. Too many factors are left out of the picture and average values are used, which is why some engines may react different than others to modification. Like the air-flow through the head, thermal efficiency, turbulence, etc
By example I used a value of 1200°f for temp in one of the tables, but that's just an average value for all gasoline engines. and that input is actually really important in order to get reliable results.
I think the equations I'm looking for, can only be found at engineering books. There are out there, it's just a matter of time before I find them =) But I'm happy with the progress so far, at least we have an idea of how our system flow.

Author:  elbola [ Mon Jan 28, 2013 10:50 pm ]
Post subject:  Re: home-made header for the G13B

btw does anyone know the inside diameter of the stock down-pipe?

Author:  elbola [ Thu Feb 21, 2013 1:56 am ]
Post subject:  Re: home-made header for the G13B

update: I've been really busy with studies/work so I couldn't work on this. The book I used for the calculations above is called "Four-Stroke Performance Tuning by Graham Bell" and can be found here http://books.google.com/books?id=OTOYHR ... ns&f=false. It's only a preview so you can't see every page, but it gives you an idea. This is also the second edition, which has been really hard to find on the net; but I did manage to find the first edition. Here's the chapter about exhaust systems:
image_id: 22557 image_id: 22558 image_id: 22559 image_id: 22560 image_id: 22561 image_id: 22562 image_id: 22563 image_id: 22564 image_id: 22565

If someone wants the whole book, let me know. The file is too big so it won't work through e-mail, but drop-box is also an option.

Author:  _Scratch_ [ Sun Feb 24, 2013 12:06 am ]
Post subject:  Re: home-made header for the G13B

I have researched intake and exhaust manifold design for the last 8 years roughly. I have built numerous headers and full systems. What I'm going to tell you, your not going to like. There is no such thing as an equation that will give you the perfect primary or secondary lengths. There are far too many variables to take into account. What you can do however is experiment. Without the appropriate test equipment (like a Morrison test apparatus) you really have no idea what is actually happening. so did the equation work? Are the gains I'm see just a result of less restriction or timed scavenging? Is it all in your head?
unless you want to spend the kind of time i have researching things like the effects of temperature on gas density and its influence on column inertia, take my advise. Buy an aftermarket header if you want reasonable power first crack, and leave it. Or, Build one, (longer than you would expect) give it a shot. Run it, figure out where your torque curve lands and what you need to do to correct its shortcomings. Learn from it and build another, and so on.
There is no such thing as a perfect header. you are always trying to work out a good compromise.
Have fun with it and take pride in your work.

Author:  elbola [ Sun Feb 24, 2013 12:44 am ]
Post subject:  Re: home-made header for the G13B

_Scratch_ wrote:
I have researched intake and exhaust manifold design for the last 8 years roughly. I have built numerous headers and full systems. What I'm going to tell you, your not going to like. There is no such thing as an equation that will give you the perfect primary or secondary lengths. There are far too many variables to take into account. What you can do however is experiment. Without the appropriate test equipment (like a Morrison test apparatus) you really have no idea what is actually happening. so did the equation work? Are the gains I'm see just a result of less restriction or timed scavenging? Is it all in your head?
unless you want to spend the kind of time i have researching things like the effects of temperature on gas density and its influence on column inertia, take my advise. Buy an aftermarket header if you want reasonable power first crack, and leave it. Or, Build one, (longer than you would expect) give it a shot. Run it, figure out where your torque curve lands and what you need to do to correct its shortcomings. Learn from it and build another, and so on.
There is no such thing as a perfect header. you are always trying to work out a good compromise.
Have fun with it and take pride in your work.

Thank you for your post. I do want to spend time on it.... just point me in the right direction. Maybe a book or site that could provide the right concepts and equations to bring this to the next level? I love physics, so I wouldn't mind spending my free time on this.

Author:  _Scratch_ [ Sun Feb 24, 2013 12:59 am ]
Post subject:  Re: home-made header for the G13B

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

Author:  yummybacon [ Sun Feb 24, 2013 10:01 pm ]
Post subject:  Re: home-made header for the G13B

http://www.pt2w.com/srd/index.php?main_ ... cts_id=100

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