T.O.O. - Manifold Fabrication Questions

Posted by alloy_625 on May 22, 1998 at 00:26:40:

T.O.O., I was wondering what methods you might suggest for fabricating prototype manifolds to try out some of the things you've told us. The following are some methods I was considering...

1) Sheetmetal or tubular plenum with mandrel bends for the runners. Lots of welding, plus it's difficult to form certain shapes including the inlet radii, and long runners with similar wall lengths. Also, aluminum bends are really expensive and typically thin wall.

2) Foam core, sanded and glued, as a form for wet layup using glass or carbon fiber with the foam removed chemically after curing. I'm not sure this is a good idea with regards to fuel resistance and temperature, but it's a nice way to make all sorts of shapes. With a mold, I'd think the runners could also be cast from wax or perhaps just machined.

3) CNC a wooden buck, hammer form aluminum sheet, and weld. I suspect this requires too much skill to do nicely on a first try.

4) CNC each runner as two halves and either weld or furnace braze them together. Do the same with the plenum. Certainly the brute force method, but the results could be very nice. Also leaves plenty of wall thickness for later grinding and experimentation.

Are there any low cost ways to generate a quick and dirty casting? Sand casting looks like it would be difficult for the home tinkerer and investment casting is $$$.

Thanks for the help

Re: T.O.O. - Manifold Fabrication Questions

Posted by The Demon on May 22, 1998 at 01:50:48:
In Reply to: T.O.O. - Manifold Fabrication Questions posted by body on May 22, 1998 at 00:26:40:

Some other options and thoughts:
You can try and make a mold using either wood or hi-density foam and then vacuum-form plastic on it. The problem is that the plastic you'd wanna use to vacuum form probably won't be able to withstand the heat associated with the application you'd use the manifold in.
I don't think that sandcasting is supposed to be that difficult. I think that street rodder or some similar mag just had a very informative article on doing simple sandcasting just 3-4 months back.
Hmmm...lotsa things to think about tho...hmmm...

The Demon

Re: T.O.O. - Manifold Fabrication Questions

Posted by NITRO on May 22, 1998 at 13:17:07:
In Reply to: Re: T.O.O. - Manifold Fabrication Questions posted by body on May 22, 1998 at 01:50:48:

For most racing applications we start by generating a model using one of the SLA machines. Assuming that everything we've calculated comes out correctly we will verify the numbers with extensive static flow testing. Once the piece is deemed acceptable (from a packaging stand point as well), we use a method of "composite coating" to make the SLA piece strong enough to actually test on a dyno engine. If things work well, a determination (based on both #'s, time, and weight) on the method of construction. These methods can include thermoplastic, composite, pressure sand cast, investment cast, a mixture of castings and welding, or total hand fabrication.
For the Honda program we've really gone back to basics, as the ability to package the unit under the hood is very important. As there are many potential customers who don't want to give up their AC, we must keep the alternator in a relatively stock location, and that causes major problems when you're trying to drive the blower from the same source, and we do not want people to "reshape" the inner frame with hammers. We calculate the plenum volume based on experience, and the runner length. Next we introduce an appropriate Honda intake manifold to Mr. Band Saw. We do nice wood work here, so we'll create a plenum shape that will allow correct volume, and locate the runner correctly relative to the blower exit. We bond the wood plenum to the runners and attempt to make it fit the engine compartment. Throttle body location, heater and AC lines, oil filter access, and proper blower support from below are just a few concerns. The way to drive the unit is then studied. Typically the "manifold/blower" will go in the test (vehicles) 40 - 50 times, the reason being that it'll be on an engine on a stand for easier access and point coordination. When we've convinced ourselves that the mock ups are all reasonable (there may end up being as many as four that may work well), we'll fabricate each configuration, usually using the stock Honda flange and runner with a formed "sheet metal" plenum, with a remavable top plate so we can make internal shape changes and also add spacers to increase plenum volume while dyno testing. We often will end up with more than one manifold that does the job well (and fiber glass with epoxy resin works well for prototyping a running manifold), and then it's down to which one fits the car best, and which drive system works best. Once we settle on the unit we agree is best, we make SLA models and SLA patterns for both sand casting core boxes, investment casting, and whatever our plastics specialists want. While waiting on some of the "production" parts, we will wun the fabricated pieces on our "test cars" until we're satisfied that the production components meet or exceed our design specs. T.O.O. likes to run the best prototypes permanently on his cars simply because they hace that "look". And there you have it.
If you're building custom manifolds wood, hot stuff, baking soda, 5 min. epoxy, A B epoxy, aircraft ply wood, maple, oak, and of course fiberglass, Kevlar, and carbon mixes all work well. Making molds using foam core, gator board, modeling clay, etc. all work well. Just remember that if you hang an intake valve, or get any backfire, the maniflod is history, and make sure you can shut off fuel flow immediatly . On the glass manifolds T.O.O. makes us run aluminum straps from the flange to the outside portion of the plenum to prevent the plenum from blowing completely off the engine.
I don't dispute his rational, as I witnessed a pre dyno test where T.O.O. was checking the timing on a ProStock engine with a cast aluminum manifold. Un known to anyone, the rotor had sheared its key and was stuck on # 7 cyl. When the intake calve opened, the spark and ignited mixture traveled up the runner to the plenum, and lit the entire air fuel mixture. The throttles were closed, and the blast balooned the plenum to within about 1" from T.O.O.'s head, and I can assure you that we were all wide awake after that. The fact that the cast plenum didn't explode was a miracle...the Holley 4500 carbs throttle blades were blown into a U shape around the bent throttle shafts...but we were very fortunate. So be careful where you stand, and have a way to kill fuel flow and ignition.

Re: T.O.O./NITRO More Manifold Stuff

Posted by alloy_625 on May 22, 1998 at 23:05:58:
In Reply to: Re: T.O.O. - Manifold Fabrication Questions posted by body on May 22, 1998 at 13:17:07:

Hey Nitro, you've raised some more questions with your answer (which is always a good thing). How exactly does baking soda fit into your prototyping scheme. Do you mix it with epoxy as filler, or with water to form some sort of plaster of paris like mix? Something that could be easily molded and removed with "weak" solvents would be great for layup.

With appropriate safety measures, would you feel comfortable running a glass/CF manifold on a daily driver or should the final product be made of aluminum. How about a pop-off plate or engineered stress concentration to act like the pop off valves on older Porsche airboxes?

Also, inside the plenum, T.O.O. mentioned using half donut shapes for air horns. Is this absolutely necessary or is it sufficient to engineer 90 degees of the appropriate radius as a blend from the plenum floor to the runner.


Re: T.O.O./NITRO More Manifold Stuff

Posted by NITRO on May 23, 1998 at 06:20:10:
In Reply to: Re: T.O.O./NITRO More Manifold Stuff posted by body on May 22, 1998 at 23:05:58:

If you want to permanently "weld" two components together prior to covering with resins and, or glass, rub some baking soda between the parts, then flow some Super Jet or thin Hot Stuff on the baking powder and stand back. The two react forming a rock hard material that's strong as hell. The mix will get hot and also give off some "toxic" fumes while reacting, so keep your nose out of the way. You can make parts that have a gap between them into "one" piece by layering the build up, and you can use some masking tape for the backing so the soda dosen't fallout prior to the application of the CA. We couldn't believe some things T.O.O. has made with the stuff, he's literally started with a small part and started layering the "mix" and made a prototype part by addition and careful filing, and sanding. Give it a try. We use it to fix leaks or to change shapes, and replace threads on dyno engines all the time, and all protype manifolds all the time.
Properly supported and with some carbon strips in high stress areas a "composite" manifold works fine. The main reason that NHRA made them illegal years ago was due to other competitors and Edelbrock's complaining. T.O.O. was showing up every week with a different manifold and the competition didn't like the pace. So T.O.O. would test with the composite peices, then weld together an acceptable piece. One thing T.O.O. got out of it was considerable experience TIG welding, because the shops that normally did the welding always screwed up something, so in typical fashion, T.O.O. went out and bought this huge Miller heliarc welding machine and taught himself how to use it. He's certified and he's like an artist with the torch.

Re: T.O.O./NITRO More Manifold Stuff

Posted by The Demon on May 23, 1998 at 01:38:57:
In Reply to: Re: T.O.O./NITRO More Manifold Stuff posted by body on May 22, 1998 at 23:05:58:

Alloy: Just FYI, but when you mix a bit of baking soda with anything containing cyanoacrylate, you'll end up with a rock-hard product. You're another person I think should subscribe to the DIY EFI (do-it-yourself electronic fuel injection) mailing list. There was a big thing a few years back about making custom intake manifolds...and some guys knew quite a bit about which materials to use and not to use. One guy worked for a company that produces injection molded, plastic intake manifolds for OEM applications, and he provided a lot of insight into the discussion...I'm sure you can check the DIY EFI archives for additional information...

The Demon


Posted by alloy_625 on May 23, 1998 at 14:36:34:
In Reply to: Re: T.O.O./NITRO More Manifold Stuff posted by body on May 23, 1998 at 01:38:57:

Hey Demon, actually I've been on DIY-EFI for a couple of years now. I remember that discussion taking place, and apparently one of those guys was/is in So. CA so I should look them up (carbon fiber and Nissan is all I remember). I should probably go look through the archives to see if there's anything applicable for the home practitioner. Thanks for the info on baking soda/CA, learn something new everyday =).


Posted by The Demon on May 23, 1998 at 17:33:54:
In Reply to: Re: DIY-EFI posted by body on May 23, 1998 at 14:36:34:

Alloy: So are you a lurker on the DIY-EFI list?? I gotta admit that 90% of the time I am also...especially when they either talk about something of either no interest to me...or when they talk about things that are just way over my head! And they do tend to do that! :)
As for some more quickie-fabbing ideas, I'd suggest using materials such as ABS and PVC. ABS is more easily attainable in sheet form...so you can make your flanges or what not out of that...then use the PVC in piping form. To join everything together, just put them close together, squirt a liberal amount of CA on, and then just squirt baking soda on the CA (put the baking soda in one of those bottles used for dispensing stuff like acrylic cement; plastic bottles with the needle applicators). You can bend the tubing using localized heating with a heat gun or even a high-powered blow dryer. Hmmm...oh shit, maybe I should give some of this a try myself!! :)

The Demon