Benzine
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| posted on 7/12/08 at 06:17 PM |
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Merge collectors
I'm looking at building my own exhaust at the moment, I've got loads of stainless steel pipe and bends and can weld stainless. I
don't know what to do for the collectors though, as it's a straight six I was thinking of using 2 x 3-to-1 collectors. How would you go
about making them? To buy them is expensive (from the quotes I got, £300 for 2)
This chap has made his own:
http://www.honda-tech.com/showthread.php?t=1761667
From that thread: "
Again this is not the best way to do it, I am sure there are easier ways, but this works out for me and I hope it helps you confused guys out!"
Are there other ways of making them?
but I don't have a bandsaw to make such accurate cuts  I'm not sure either about the diameters of the inlets out outlet of the
collectors and what they should be. I've got 2" headers and I'm guessing the outlet should be bigger but I'm not sure by how
much.
Thanks for any info ^__^
[Edited on 7/12/08 by Benzine]
The mental gymnastics a landlord will employ to justify immoral actions is clinically fascinating. Just because something is legal doesn't make
it moral.
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Volvorsport
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| posted on 7/12/08 at 06:21 PM |
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minimum 2.5 inch system , 38mm headers would be about right .
dont demon thieves/jetex have 3into 1 collectors ?
i can maybe help you with some more bits.....
www.dbsmotorsport.co.uk
getting dirty under a bus
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blakep82
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| posted on 7/12/08 at 06:24 PM |
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from memory, my staight 6 BMW has 2 headers like this
 
Description
a bit neater than that though
and then a 2-1 further down
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Benzine
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| posted on 7/12/08 at 06:29 PM |
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quote:
Originally posted by Volvorsport
minimum 2.5 inch system , 38mm headers would be about right .
dont demon thieves/jetex have 3into 1 collectors ?
2.5 after collectors? 2" at the cylinder head covers the exhaust holes very nicely.
Can't see any on demon tweaks and Jetex said they only do 2-to-1.
quote:
Originally posted by Volvorsport
i can maybe help you with some more bits.....
^____^ i'm listening...
blakep82, that does seem a simple design. I'm guessing it wouldn't flow that well if I made it though T_T
[Edited on 7/12/08 by Benzine]
The mental gymnastics a landlord will employ to justify immoral actions is clinically fascinating. Just because something is legal doesn't make
it moral.
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blakep82
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| posted on 7/12/08 at 06:34 PM |
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well, if you were careful in making holes in the sides of the middle tube, with a flap wheel in a grinder for example, took your time, grinding and
checking all the time, making sure the hole is slightly larger than the tube joining it, and made the joins at 45 degrees (or 135, whatever way you
look at it) then you can't go too far wrong surely?
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Volvorsport
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| posted on 7/12/08 at 06:49 PM |
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well for a cheapo collector - you could roll a cone , then shape it .
www.dbsmotorsport.co.uk
getting dirty under a bus
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Fred W B
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| posted on 7/12/08 at 06:58 PM |
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Some more discussion in THIS THREAD
Cheers
Fred W B
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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twybrow
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| posted on 7/12/08 at 07:09 PM |
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Try this.....
I have another couple of links around about making a 3-1 (my Triumph lump is 3 cylinder, so I have done plenty of searching!). I'll see if I can
track them down....
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twybrow
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| posted on 7/12/08 at 07:31 PM |
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And another here.....
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mark chandler
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| posted on 7/12/08 at 07:55 PM |
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Although cutting and blending them like that looks really cool it does drop power, you really need to make a conical collector that all the tubes
enter.
Two advantages
* no bends required to chop about.
* Easier to make/align
All you do is make a back plate that all the tubes will enter in the same plane, drill holes and weld them in place.
Make a cone that will fit so using a bit of the larger exit pipe split it up to make the sides of the cone, and weld up.
Now all you need to do is cut triangles to in fill, hope the diagram makes sense.
Regards Mark
[Edited on 7/12/08 by mark chandler]
 
Rescued attachment tubes.jpg
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Benzine
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| posted on 7/12/08 at 08:03 PM |
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Thanks for all the info, some great ideas ^__^
The mental gymnastics a landlord will employ to justify immoral actions is clinically fascinating. Just because something is legal doesn't make
it moral.
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flibble
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| posted on 7/12/08 at 08:48 PM |
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Theres places like this that sell the bit thats awkward to make:
http://www.coneeng.com/collectors.html
http://www.tailpipes.co.uk/retail/retail_tube_1.php?x=Mandarel%20Bends
Might help, you never know 
Not used them before though..
Kev
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NS Dev
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| posted on 8/12/08 at 10:20 AM |
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The one in your first photo is made hpw they should be made ie. best for flow, but not easiest to make.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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MikeRJ
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| posted on 8/12/08 at 10:29 AM |
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I can remember reading (I think in "Four stroke performance tuning" by A. Graham Bell) that a conical collector was best for power.
I suspect that outright flow would not be as good, but the point of the collector is to create return pulses, and the larger the step change in
diameter, the stronger the return pulse will be.
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