Intake manifold fabrication

[shootingsight]

I just ordered a set of exhaust headers for my non-crossflow R16 from RD-Enterprises.  Seems the 'recommended' approach is to split the cast headers I have.  I am a little loathe to do this, both because it is irreversible, and because I was thinking about upgraqding the inlets as well.  Are there success stories people can share?

I noticed the inlet ports for 1-2 are right next to each other, and the ports for 3-4 are adjacent as well.  The cast manifold has four seperate passages.  I'm thinking to make a flange with a single large tube that covers both ports, so the manifold becomes two large tubes with just a 90 degree bend, versus four smaller tubes.  I'd use a vertical pipe as a collector and sit my Weber down-draft on top of it.

This then got me thinking about going to dual carbs.  Especially if I get side-drafts (God forbid, a pair of old Strombergs) but likely something more modern.  Now the inlet manifold would literally be just a straight pipe with a flange at each end.  Or can I even adapt a fuel injection system?

What have people done?

[shootingsight]

Looking at Webers, it appears the DCOE 40 is a dual throat side draft of about the correct size for a 1600cc engine.

[Grumblebuns]

People have separated the stock  cast inlet section from the exhaust side to use headers with downdraft  32/36 DGV type Webers. Like you stated the process is kind of irreversible. The second option is to use a manifold for the single side draft 45 DCOE which is probably the better option. The three makes in the day were Hermes, Warneford and Else and the various clones of each. I have an Else clone on my S2. Since you already have a header this link may not help you but Aardvark International sells an integrated header and intake made from steel tubing.

http://www.talbotco.com/lotus_cat.htm

I don't know if Aardvark is still in business. There is also a fellow member selling a Warneford manifold and 45 DCOE Weber in the Classified section.

http://www.lotuseuropa.org/LotusForum/index.php?topic=3292.0

If you do plan on making your own inlet manifold, good luck with your effort. If it were that easy, there would be more products out there.

[shootingsight]

Wow, the Aardvark integrated system would have been nice if I had asked the question before ordering the header I did.  That said, I own a mill and a TIG welder (which I'm still learning to use), or maybe I use a torch and braze.  I've been looking for an excuse to learn to weld better, so I think I'll make a down-draft manifold and start with my 32/36 DGV, and if that works, a future project can be a side-draft option based on a 40 or 45 DCOE.  If nothing else, you convinced me I was not crazy in my thinking.  On this subject.  Pretty sure I'm crazy on others :-)

[Sandyman]

PM sent.

[shootingsight]

Phooey. I CADed up the head flange and got drawings for the carb flange, and was all ready to start practicing welding when I made the mistake of having lunch with two engineer friends. The first explained thAt he knew someone with a 3D printer that can do wax and there are aluminum foundries that could cast it. The second gave me the name of someone who does direct laser sintering of Alu or stainless or titanium. So now I likely have to make several manifolds just so I can try the techniques.

[gideon]

If you do decide to go ahead and have one or more manifolds cast or printed (sintered) then I might be interested in buying a manifold from you, but more than that I would be interested in hearing more about how you get on, what it comes to when you price out those options, etc.   

FYI, Serge explored a lot of options for making an intake manifold for his car, and wound up 3D printing it from high temp resilient filament.  My guess is that you'll find it costs too much to have cast in small quantities, or to have it printed in aluminum or steel (let alone titanium).

[shootingsight]

So now two people are interested in getting one.  I'll definitely see this to fruition.

I have the great fortune in life that I am retired, so I get to spend time on things that interest me, rather than necessarily what I need to do to earn a salary.  Learning is a passion, and I'm a nerd, so I will definitely look into these and report back.  The beauty is that once I figure out the technology, making a downdraft versus a side draft is purely CAD time, and I drink beer while I do that, so it's not even really work.

I actually have 5 technologies of interest:

1.  Direct Laser Sintering.  Pile of metal powder, laser melts it layer by layer, so it makes your part.
2.  Binder printing.  You 3D print a mixture of plastic and metal powder by extruding the molten plastic with high density powder in it.  It prints nicely because the powder is carried in the liquid plastic binder.  After printing, you put it in an oven, and the plastic burns off and the metal powder particles eventually fuse.  Does not need a high power laser like #1, because you are just melting the plastic, not fusing metal on the printer, but you do get about a 20% shrink as the binder burns off, so on odd shaped parts warpage can be an issue.  Might work, since I was planning on putting these on a mill and facing off the flange surfaces anyhow.  For the rest of it, slight warp is no issue.
3.  3D print in wax, then make a lost wax casting.
4.  3D print in sand, and make a direct casting.
5.  Laser cut the flanges, then TIG weld stainless tubing.  I think this is a simple design for a side draft, slightly more complex for down draft.

Several of these can be done in various metals.  For #1 I know someone with ability to do Titanium, Stainless, and Aluminum.  For the others I do not know, but aluminum casting is not difficult.  Luckily I live in Cincinnati, an old machine tool city, so I know there are several casting places in town.

If I trade-mark these, I'm going to mess with people's minds.  I think the company name will be 'Lucas Electric'.

[Grumblebuns]

I've already gone down this road of looking at commercial casting of intake manifolds. Unless you have a special relationship with a casting company, be prepared for sticker shock on the cost of low production casting. For a hobby, the upfront costs forced me to put my project on the shelf for now.
 
http://www.lotuseuropa.org/LotusForum/index.php?topic=3177.0

[jbcollier]

If you are going to build your own manifold, do some research on manifold design.  You’ll also want to be careful about selling them.  What fits on your car may not on another.  Some exhaust headers curl upwards and reduce available clearance quite a bit.

[shootingsight]

OK, I made progress.  I got the downdraft manifold drawn in CAD.  I learned a lot about working with lofted elements in SolidWorks too.  Attached are a few renderings, and sectional views.  I can print the flanges on a regular printer in 100% size and physically lay them on the block to assure fit.  So this should be enough to get the quotation process started.  I did find an on-line 3D printing company that allows you to upload STL files and gives an instant quote .... in aluminum it was $2,200.  So that's a non-starter, though I have a buddy who has a 3D printing company that does metal.  I might be able to get a better price.

Plastic 2D options were in the $250 range, and this company was in Belgium, so I'm hoping there is a wax printing company in the US that will be cheaper ... or I can figure out how I can get my own printer to print wax so I can look at investment casting.

The other option is to get a bunch of tubing and cut bits and get some flat stock, then learn to weld....

[Sandyman]

Shooting, great 3D cad. Lots of promise. The carb on my car is a Weber 32DIR37 replacement. I will do more research to see if the manifold on  the 1.5 is the same as a 1.6.
Sandy

[shootingsight]

Found an on-line quote for binder printing: they print it in plastic that has high density 420 stainless parts in it.  Then they fire it in an oven to burn off the polymer and get the powder to sinter, then they dunk it in liquid bronze which flows into the voids.  That is $870, so still high.

I also found that I can buy wax filament for my 3D printer, but have not yet understood how they manage internal supports.  Someone suggested there are low temperature wax, so you can heat it and melt out the supports, but I have not found a source yet.

Next investigation is into printable sand, to see if the mold can be 3D printed.

[jbcollier]

It would be better to have separate runners to each cylinder.  This helps to isolate individual intake pulses and allow some ram effect.  Ideally the runners would start larger and gently taper down to the port’s size.  I’m not an expert in these matters.  But there are books and websites on this.

[shootingsight]

I did some reading on it.  There are advocates of a Helmholz design, where you want the resonant frequency of the air inside to match the frequency of the valves opening.  However, it only optimizes at one RPM, and indeed and half that RPM would actually hurt.

I'll try to take my existing manifold and block all openings but one, and see if I can measure it.  I have an oscilloscope and a microphone, so by slapping the last opening with my hand, it will ring the inside volume and I can measure the frequency.

The other theory out there is to make everything as big as possible and reducing drag, which would suggest combining runners so when one cylinder opens, it can suck from a bigger pipe, and flow restriction goes with the 4th power of diameter, so doubling the cross sectional area will give 1/4 the drag in the pipe.  I'll read more and see where it goes.