# Composite intake manifold

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#### slociviccoupe

##### Well-Known Member
just like title says. Ideas and thoughts on composite intake manifold. For intake runners use the carbon sock over a foam plug? Or do a 2 piece mold and lay carbon in conventionally.
Next is how to bond to aluminum hrad flanges? Do you create a flange and sandwich them with epoxy between 2 aluminum pieces mechanically fastened together?

Its for a subaru engine and it will be turbocharged and intercooled but shat epoxy to withstand the temperatures.

The stock manifold is just way too heavy. Way too tall. Ive seen others do simple mild stedl and it works , same with fabricated aluminum. But seems a composite manifold can be made and work. Just which way to aproach it.

#### Toobuilder

##### Well-Known Member
HBA Supporter
Log Member
Assuming its the typical individual runner layout, then a two piece layup (top and bottom) with a male or female mold could work. Flanges would probably be best with phenolic.

That said, an aluminum fabricated unit would probably be lighter and a LOT easier to build as a one off.

#### slociviccoupe

##### Well-Known Member
I agree on aluminum as i can tig.
Plenums, runner material and velocity stacks readily available. Just no machined head flanges with the exception of maybe re machining a set of billet tgv deletes and making them into head flanges with the injector pockets and transition from round to port shape. Then just weld to those. Last resort chop up stock manifold for its flanges or chop the runners to lower it and sheetmetal plenum with stock cast runners.

#### Geraldc

##### Well-Known Member
I used carbon sock over foam runners that I made out of flat foam and rounded off. For the flanges a few layers of carbon formed on a flat sheet of plastic or similar and then drill holes and cut outline.

#### slociviccoupe

##### Well-Known Member
Epoxy used? Im very used to west systems. What was used to attatch your flanges to the runners or plenum? And asuming used acetone or gas to dissolve the foam after. How many layers did you use and what was total weight.

#### pictsidhe

##### Banned
Epoxy used? Im very used to west systems. What was used to attatch your flanges to the runners or plenum? And asuming used acetone or gas to dissolve the foam after. How many layers did you use and what was total weight.
Get as much foam out mechanically as you can. I'd be tempted to try a pressure washer. Once you add solvent, you have a nasty messy goo.

#### radfordc

##### Well-Known Member
Even better would be to 3D print the mold for the intake. There are filaments that can be dissolved out of the finished parts.

#### Hephaestus

##### Well-Known Member
Even better would be to 3D print the mold for the intake. Àyàaaaaàahere are filaments that can be dissolved out of the finished parts.

I wouldn't... PVA dissolves in water sure - but it swells with humidity so it can be particularly fun to use as a mold - maybe if you live in the desert...

ABS dissolves in acetone, but foam would dissolve faster/easier so less messy. You need the intake to be resistant to acetone /petroleum anyway so...

#### rv7charlie

##### Well-Known Member
If 'composite' is a must, instead of printing a mold, just print the manifold. Our local community college has a 'fab lab' that's open to the public, and they have multiple printers that will print carbon/nylon. Should be able to find similar printers at a local 'maker space'.

If hand-layup, the coolest trick I've seen was by a friend building a manifold for a rotary. He wanted long, convoluted runners, so he started with PVC pipe with approx the right inside dia. Split it lengthwise, and strapped it back together. Inserted a bicycle inner tube, blocked on one end. Filled inner tube with packed sand & tied it off. Removed the PVC, and was able to bend the 'sausage' into the shape he needed. Then wrapped with fiberglass, let cure, dumped the sand and pulled out the tube. Flanges and plenum were 'conventional' construction.

For the flange, what's the stock manifold made of? A lot of rotary guys start with the stock manifold, and mill off everything but the stub tubes leaving the flange, and build off that. Should work with a factory composite manifold, if you're building composite, and aluminum can be tig'd to an aluminum manifold.

Charlie

#### radfordc

##### Well-Known Member
There is a thread somewhere on the net showing how a guy 3D printed his intake manifold/plenum. He did use structural nylon to print. He found out that the parts were too porous as printed and leaked air. He coated everything with epoxy and I think it finally worked.

#### Hephaestus

##### Well-Known Member
There is a thread somewhere on the net showing how a guy 3D printed his intake manifold/plenum. He did use structural nylon to print. He found out that the parts were too porous as printed and leaked air. He coated everything with epoxy and I think it finally worked.
But imagine the fun chasing leaks down the road at temperatures take their toll...

In an airplane - print a mold.

There's that new metal filament, you print it at home, then ship it off to be kiln fired. It's still got porosity issues, but one might be able to electroplate to fill... It's been theorized for a year+ not sure anyone's tried it...

#### Steve C

##### Well-Known Member
Layer to layer bond isn't so great with 3d printing. I wouldn't want to subject it to all the vibration of an engine. I like the idea of using it as a plug though.

The metal stuff you can print is very expensive and it shrinks when they cook it. It doesn't shrink the same in all directions either, so you'd probably throw a couple away before you ended up with one that fit. Neat idea though.

#### Hephaestus

##### Well-Known Member
The metal stuff you can print is very expensive and it shrinks when they cook it. It doesn't shrink the same in all directions either, so you'd probably throw a couple away before you ended up with one that fit. Neat idea though.
It's actually not terrible, I ran 250g through the printer for some test pieces for my own curiosity. It's pretty linear in shrinkage - not much different than abs really in that sense. Easier than SLA to get accurate pieces. I think one manufacturer offered a plug-in for SolidWorks to get it pretty **** close.

Large format SLA does exist as does castable resin. Print it in SLA sand cast in aluminum? It is an option.

#### Steve C

Some have done cast aluminum with fdm. I don't recall what filament they used that was able to be melted out of the sand, but what an amazing capability. I find that sort of thing very interesting. People get a lot out of a $300 printer! #### Hephaestus ##### Well-Known Member Some have done cast aluminum with fdm. I don't recall what filament they used that was able to be melted out of the sand, but what an amazing capability. I find that sort of thing very interesting. People get a lot out of a$300 printer!
PLA can be straight up used for lost casting, played with it a few times still can't find a good use.

#### Geraldc

##### Well-Known Member
Epoxy used? Im very used to west systems. What was used to attatch your flanges to the runners or plenum? And asuming used acetone or gas to dissolve the foam after. How many layers did you use and what was total weight.
I used West systems. The plenum and the runners were made of foam with 3 layers of carbon socking. Runners joined to the flange by overlapping 1/2 inch then joint filleted with Wests and glue powder.3 layers of cloth for plenum.Flanges in contact with motor and throttle covered with one layer fibreglass. Foam cleans out with acetone.

#### Steve C

##### Well-Known Member
West has a low tg of 140F or so. That means it gets soft at engine temperatures. I'd consider mgs, ez-poxy or Aeropoxy which can be post cured to at least 180. Had some bad luck with Aeropoxy, so that would be my last choice.

I've been trying a resin from a so-cal company called BJB Enterprises. They have a resin that has low viscosity and can be cured to 300F if needed. I can only get it to 200 for post, but that's enough for me. I really like it.

#### Russell

##### Active Member
I made a foam mold that was a bit undersized of the desired finished size. I then coated the mold with about 1/8 inch of “Liteweight Spackling”. S-Glass and West System epoxy was uses to cover the entire mold. After curing everything was dunked in a tub of water overnight. The dunking allowed the water to eat away at the spackling. This made mechanically removing the foam without worry of goo being left behind. The interior of the manifold came out very smooth.

The below photo shows the foam in early stages of forming. The second photo is of the finished manifold.

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#### BoKu

##### Pundit
HBA Supporter
West has a low tg of 140F or so. That means it gets soft at engine temperatures. I'd consider mgs, ez-poxy or Aeropoxy which can be post cured to at least 180...
Even that is a bit low for an intake manifold, especially with turbocharging. I'd recommend PTM&W 2080, which post-cures to a Tg of about 260F.

#### Royal

##### Well-Known Member
If I can find an 3d model of that intake ill see if I can 3d print a mold. I'd love to try. I have a printer and I usually print with petg. Doesn't melt with acetone or thinner. I can prime it with mold surfacing primer. Just haven't tried it yet on petg.