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 Post subject: Excellent method for creating merge collectors!
PostPosted: Thu Apr 26, 2012 12:30 pm 
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Location: Pennsylvania, USA
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I found this over on a Honda forum. I do not wish to take credit what so ever, but I found it extremely interesting and useful. Very simple to make, all in all. You can see the watermark in the images to visit the site of the original creator.

Anyone who wishes to fabricate manifolds of any kind will need to purchase (sometimes upwards of $400 each) or build collectors. They are very expensive for quality pieces, with the right tools and time anyone can make their own quality merge collectors.

Tools you will need:
Welder
Cutting device
Protractor
Scribe and or pens
Measuring instruments
files
Safety gear consisting of at least eye protection (I wear a mask and ear protection when cutting)
Supporting tools for your equipment

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First you must select your material, for every turbo manifold I build; I use 304 stainless steel sch 10 which is readily available from many places. I get mine from Ace Stainless, I highly recommend them. For basically all Audi/VW applications I use 1.5" primaries. As this material is a nice match to exhaust port sizes at hand. You will need approx. 6 inches of material for each individual runner, so for two 3-1 collectors you will need at least 3 feet. Get yourself double that, you will screw up and you will need a bunch for other stuff anyway. ** tip, go get some sch 10 1.5” pvc as it shares dimensions, good for practicing at a fraction of the cost.

Choose your cutting method, I have used chop saws, band saws, mills and even seen them cut out with a cnc plasma. I use a chop saw because it is cheap, easy and discs are always available. The concept of all of this is the same on any machine. Now you need a jig/clamp of some sort, no saw of this type will have a clamp that can reach the extreme angles needed here. This is mine, it technically isn’t a jig because you still have to measure length and set angle for each cut, but I like it, I am use to it and it works.

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Materials are simple, 2” sch 10 pipe (I used ss because I had it at the time, I suggest cheaper mild steel for this) with a piece of angle iron welded on and bolted to the saw bed. You can also see I utilized an existing hole on the saws bracket for further strength, welded a bolt from the inside and ground down. To clamp I just welded a nut to the top after drilling the proper size hole and run a bolt in. It is set at 11.5 degrees for my intersection angle. I make all my collectors at that, the less angle, the more flow, but also more length. You can make a more compact collector by going to higher angles, but that takes away smoothness. It’s all a trade off. Adjust for your application and needs. I make things geared towards max power, not always ease of install or practicality.

In these pictures you can see I threw some tacks into the lower sections of the tube, this allows the piece being cut to always center to the same position horizontally as the bolt tightens. Do not make them so big as they keep the tube from going flat on the bottom of the clamp, you can fine tune this with a file.

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Set the depth, I use 6 inches as that’s what works perfect on this setup. Since I have not said this yet in this article, Measure twice, cut once. Save yourself the hassle in life, always measure twice, cut once. **edit: I noticed I forgot to mention a key thing here, your two cuts have to be at the exact same depth, not exactly my depth of 6 inches, just the same depth for each set of two cuts. Otherwise they will be off and wont mate up to other collectors. This is one of the most important measurements in the process.

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Then you need to mark a reference point, I like to blacken an area with a sharpie, then scribe over that, makes it highly visible with glasses and all that.

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Now you must get your base angle off your blade, all cuts are based off the actual thing doing the cutting. Do not make the easy mistake of just marking out X amount of degrees on the tube and removing everything else thinking it will make a circle. Due to the fact the angled cuts are what eventually need to come back to 360 degrees you will be way off. I am lucky and my garage is flat, bench is square and my saw is true. My blade sits at dead nuts 90. If yours is off that is okay, just adjust everything to match or shim your saw base accordingly.

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Then you need to dial your tube in to the same spot which is now 0. On this simple magnetic protractor I modified it a little, I made a slug of hot glue on the back to make it stick into tubes easily and stay. I can run a long stick through and cut out 6 collectors without it ever budging. They probably make one like that, I have had this one forever and it was like 10 bucks so I just made it better.

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Now you are ready to cut, you have some options here. You can go +/- 30 degrees from 0, or you can cut there and then roll a full 60 degrees to the right. I do it both ways, I don’t know why. It’s not easier or harder either way. I will detail going +/-30 as it is more accurate for most beginners I think. On my saw I actually go to +/-31 degrees, every setup will vary ever so slightly from many factors such as blade deflection so I will always make reference to it as a flat 30. The 30 is for doing 3-1 collectors. Other styles such as 4-1, 5-1, 6-1 and so on will each need different amounts removed. The 30 stays the same regardless of that intersection angle from earlier.

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Make that first cut, I pulse the blade slowly until I make my first little groove to lock into as chop saw blade likes to flop around a bit. I have found this works with a very high level of precision compared to just squeezing the trigger and hammering down. When finished it should look something like that. You can run the saw up and down a bunch after finishing the cut to face the piece and reduce finish work you will need to perform.

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Now roll back past 0 and go 30 the other way for your second cut. I should mention you can reverse the order to suit your preference; you don’t have to do either cut first. I like making the ghost cut as it is a flat surface. Face this cut just like the last to reduce hand finishing.

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The clamp setup works well for finish work, just spin it around, grab some files and go to town. The concept is obvious I hope, just get rid of all the crap. You can really shape the points here also. Look at these pictures close and then the fresh cuts; you will see how much was just hanging there. I have some coarse files for the bad stuff; the 5-1 collectors are really chunky. This is where you can choose to expend as much or as little effort as you wish. The results speak for themselves when you clean them up well.

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Clamp still spins to 90 after removal of a bolt to cut off the nearly finished piece. Here are some extra pictures of probably the most boring step just because they look cool.
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Repeat as many times as needed (probably 6)

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5-1 piece compared to a 3-1

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Here your care in measuring and finish work pays off. Your Exhaust gases will be nice and happy flowing through here.

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I wire wheel them and then wipe down with acetone. Always clean your metal very well before welding, even tacking.

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You could weld these up now, or just tack them up. I personally prefer to finish fabricating a manifold 100% tacked up, even the collectors and then break them apart and finish weld all at once. I have screwed myself on tight stuff and not been able to get to the inside of a primary to merge connection.

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No gaps are what you are going for here.

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Last but not least you can trim up the cone, these transition to 2” so I just slip that over, mark and then cut.

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I hope this has been informative for all, if any questions exist, please do not hesitate to ask. These are not the easiest things to build, in my opinion they are actually one of the hardest parts of all this for people. I have seen many highly skilled people waste hundreds of dollars in material figuring this all out.

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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Thu Apr 26, 2012 1:22 pm 
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simple and effective, excellent!

Drew


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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Thu Apr 26, 2012 1:30 pm 
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Location: Pennsylvania, USA
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I agree - I have ordered some tubing as I am making some parts. I am anxious to give this a try!

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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 4:49 am 
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Can anyone recommend a good MIG welder for novices? Mainly for welding stainless exhausts.


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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 6:10 am 
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There is a UK MIG welding forum.

IMO as long as you dont buy the cheapest out there, most will be good for that kind of stuff.

Ive had a 150A Murex machine now for must be near 20 years.

Was tempted recently though buy the Thermaklarc Fabricator 181A machine. It's an invertor based unit and can do MIG and TIG ( DC only )

I dont need a TIG as I already have one, but it could be handy to have the MIG in the same machine for stainless work if you were so inclined.
Plus being an inverter, it runs down to very low amperage which would be great for thin metal.

Most wound machines dont go much lower than 30A, I think the inverter goes to half that

Whatever you do, dont just buy a cheapie. my 150A has done me anything Ive ever needed, although recently some stuff could have done with a more powerful unit.
No matter how little you might think you will use it, buy a god one anyway. It will give years of service, and you've no idea how handy it is when making silly little things. I wouldnt be without one.
And regardless of what anyone says, it is far far better to have in a workshop than a TIG. It's fast and easy to use, versatile and can weld single handed which is invaluable when making stuff.

When I bought I wanted a decent machine that would take a full 15kg roll and carry the bottle.

With hindsight, I really didnt need the 15kg roll, as they are huge. The Thermalarc above only takes a 5kg roll, and has no built in trolley. But trolleys are available.


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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 7:07 am 
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I use a Hobart Handler 140 - its been more than enough for MIG work. I never find myself welding big plates together. Just exhaust or schedule pipe like in this thread. I recently picked up a Miller Diversion 180 so now I have a Hobart MIG and Miller TIG. The Hobart is more than enough. Just remember that if you MIG weld stainless steel you need stainless wire but you also need tri-mix gas (helium, co2, argon). If you use regular 75/25 argon/co2 your welds will not come out right. You also need to bump the wire speed up quite a bit from what you might be used to welding.

Was up until 3:30 - 4:00 AM this morning finishing this up:

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Collector Design 2 by Jon Kensy, on Flickr

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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 8:40 am 
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Cheers for the advice guys. Much appreciated.

This seems to get some good comments on the welding forums - http://www.machinemart.co.uk/shop/produ ... mig-welder

Seems a reasonable price too. The only gotcha being the 15amp requirement. Does that mean I will need a 15 amp breaker in the consumer unit, or just a 15amp fuse in the plug?


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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 9:20 am 
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VR6Turbo wrote:
Cheers for the advice guys. Much appreciated.

This seems to get some good comments on the welding forums - http://www.machinemart.co.uk/shop/produ ... mig-welder

Seems a reasonable price too. The only gotcha being the 15amp requirement. Does that mean I will need a 15 amp breaker in the consumer unit, or just a 15amp fuse in the plug?


Generally a 15A machine will recommend a 20A socket, breaker, and wiring.

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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 9:44 am 
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Thanks Jon

I'd better stick to 13 amp welders then!


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 Post subject: Re: Excellent method for creating merge collectors!
PostPosted: Fri Apr 27, 2012 12:01 pm 
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VR6Turbo wrote:
Thanks Jon

I'd better stick to 13 amp welders then!


Check the manual - most welders will specify input requirements. Int he US I think code is 20% over rated on cabling and sockets. Breakers are find because they'll just trip, just don't over-break the circuit.

We got a kiln for my mothers jewelry making and its a 15A requirement, 20A box required.

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