Question for Jay...

[Cyclone Joe]

Howdy Jay,

Along the lines of a sheet metal intake and associated costs, would a fiberglass or carbon/kevlar intake be of interest?  The kicker is the heat off the block/heads, but that could be managed if I knew how how it got.  We could always take a baseline epoxy resin and modify it for high temp needs, given the relatively low loads the intake would see.

Joe

[jayb]

I have thought about that Joe, and I actually have a fair amount of experience with fiberglass from my model airplane days.  The appeal would be isolation from engine heat, and of course the appearance if you did a nice job in carbon fiber.  Online I've seen some really beautiful ones, but to be honest I'm at a loss on how I would make something like that for any reasonable price.  To make it look good on the outside, and smooth on the inside, you'd really need forms for both, I think, and probably the form for the inside of the runners and the plenum would have to be sacrificial.  Maybe I've got this wrong?  Enlighten me...

[Cyclone Joe]

Jay,

Here's how I'd make it:

The runners could be made from a sand/glue mixture, (or plaster of paris but you have to chisel that out) which are cast in molds made from wood.  You would then assemble the runners to the top and the base with super-glue and balsa wood.  Your inside surface would come out nice and smooth as you've already stated.  Once you go thru cure, the superglue vaporizes, and the sand/glue mixture is washed out with hot water.  Its like the lost wax method, but I like to refer to it as the lost sand method.  You can dry the sand and reclaim it if you want.  It would allow you to change each runner size as needed, and change the inlet-outlet geometry as needed.  Being able to make the molds from wood is also nice because they're cheap.  If you really are adverse to sand (some folks are) you could do the same process with Woods alloys.

For the outside, you'd want to use a coated Teflon open fiberglass weave, or a plastic film punched with holes to allow the resin/volatiles to bleed out to go right against the wet layup, and pull a vacuum on the assembly.  Once cured, you can then to a light hand sand, shoot it with a high temp semi-gloss and leave as-is.  If you want to make it 'pretty', apply a decorative single ply plain weave or herringbone weave on the outside, and cut the resin with acetone or IPA to make a gel coat.  Let that cure, a little light sanding, a shot of rattle-can gloss and then done.

The biggest question is temperature.  How hot do you think the interface would be from the head to the intake?  That would drive the resin selection.  That in turn would make the project easy, or next to impossible if you had to use a Bismaleimide or polyimide resin.

Joe

[jayb]

I don't know, Joe, sounds like a lot of work.  One thing I like about CNC machining aluminum is that I can load a casting or a billet into the machine, punch the button, head off for a day of work, and have a finished part on the machine when I get home later that evening.  To do a carbon fiber manifold I would have to build the cores, lay up the fiberglass or carbon fiber, cover it with the vacuum bagging materials and pull a vacuum on the whole thing, then after it dries peel it all apart and dissolve the cores, then clean and trim it up.  Seems like it would be pretty labor intensive; I'll bet I'd have 10-12 hours into each intake manifold, and working a full time regular job just wouldn't permit that. 

Here are some pics of some carbon fiber intakes I've looked at in the past:







I always wondered how they got a good joint between the aluminum port sections and the carbon fiber on those manifolds.  Any ideas on how they do that?  I would think that the same kind of epoxy used for the resin, or some variation of that, would crack from temperature cycling.

[Barry_R]

The top one is made locally.
I could ask.

[Cyclone Joe]

Hi Jay,

Indeed it would be a labor of love.  If done right though, you could play with individual runners, making a modular runner intake until you found out what worked best for you while the engine was on the dyno. 

As for bonding to aluminum:
To get good bonding for aluminum, you need to bond to the aluminum itself, not to the aluminum oxide skin.  From when the grit blast is complete you have 4 hours tops to apply the structural primer, otherwise enough of the oxide has developed that you end up with a lousy bond.  Once the primer is on, you can wait months.  Additionally, most folks will put a layer of fiberglass on the inside surface and fill it with carbon black or cabosil to provide a compliance layer.  As for the aluminum prep:
-Grit blast
-Solvent rinse/wipe & air dry
-Structural primer application
-Primer bake

Then you have two options; co-cure with the laminate, or post bond with a structural epoxy.

If its a co-cure with the aluminum, film adhesive is the way to go.  Otherwise a West Marine epoxy filled with one of the two mediums mentioned above will work just fine.  If you had access to the Hysol Loctite commercial products you'd want to go with one of those.

Joe

[Cyclone Joe]

Jay,

If the 'bond and assembly' approach is an option, the runners, as long as they have a draft, and can have their cores removed, can be made from aluminum and reused if coated with a mold release.  To avoid vacuum bagging, industrial shrink tubing, similar to what you'd use on wiring, can be used as well.  You'd wrap the a-stage laminate on the aluminum mold, slide the shrink tube over it, warm it so it starts to contract, and then during cure it will continue to de-bulk and give a nice outside finish.

You could make  a bunch of runners, set the oven, go to work, and come home and they're done.  Then its a matter of bonding the runners to existing aluminum adapters, letting that ambient cure, then they're ready to go.

I guess in my head I was thinking of a monolithic assembly, but a 'bond and assembly' approach would make more sense given limited time.

Joe

[jayb]

That's an interesting idea, especially since I have some West Systems epoxy and a big tub of cabosil "in stock".  I could machine the plenum and the "feet" of the runners, and then just do the runners themselves in carbon fiber.  All the runners would have draft, so aluminum forms could be made, and laying up the runners would be much less time intensive than trying to lay up the runners plus the plenum.  The runners would be easy to vacuum bag, too.  Are you pretty sure that there wouldn't be any thermal expansion issues with gluing the runners to the aluminum?  I've never heard of that aluminum primer that you mentioned, maybe that's the secret...

I don't know if the temperature at the face of the intake adapter will be a problem or not.  The only point of reference I have is with my clear valve covers.  The polycarbonate those are made of is supposedly good to 275F, and there has been no evidence of melting or warping on the dyno, so I know it hasn't gotten that hot at the valve cover rail.  If I had to guess, I doubt that the temperature on the flange of my intake adapter would ever exceed 220F.

[jayb]

The top one is made locally.
I could ask.

If you get the chance, Barry, please do.  No big rush...

[Barry_R]

Dalquist could check too - - same guy made the intake for his EMC Pontiac this year.

[Cyclone Joe]

Jay,

The aluminum wont be a problem as its going to 'grow' into the composite, which isnt going to move with temperature (well it does, but relative to the aluminum it doesn't).  If you order some 50 micron nickel powder, and add 5% by weight, the nickel powder will act as 'teeth' and it will stick.  I did this by accident once, and it wouldn't come off of a Teflon coated mandrel; bad day then, but a neat trick now.  Keep the laminate only as thick as needed to let it deflect during thermal cycling to keep the stress out of the bond-line.

You could double-check that it wouldnt crack based on the CTE, the dimensions, and the shear strength of the epoxy.  Keep in mind the composite wont really grow thermally relative to the aluminum. 

Stick with an ambient cure on the west systems epoxy and no vacuum (made that mistake ONCE) and you should be good to go for a while.  If it does crack, you can always drill/tap from the outside to secure it, and then put the 'right stuff' on the OD to seal it up.

[fairlanegt427]

i am slightly off the subject of carbon intake that you guys are talking about, but does or is their just a coating that the aluminum intake  could be dipped in that wouldnt retain heat for that cooler charge?  i have tried to google this and i really do not find anything.

[482supersnake]

 http://www.youtube.com/watch?v=-UR6IrfPdFs

Skip to 12:56 they show the process for making a composite intake.

[Cyclone Joe]

i am slightly off the subject of carbon intake that you guys are talking about, but does or is their just a coating that the aluminum intake  could be dipped in that wouldn't retain heat for that cooler charge?  i have tried to google this and i really do not find anything.

There are coatings that minimize or eliminate the conduction through the aluminum, but are application specific (rocket engine turbomachinery, for example) and are not typically available to the public.  In fact, I don't know of one that could be purchased by an individual; they're all ITAR controlled.

Joe

[rockittsled]

CYLINDER HEADS
TBC is applied to the combustion chamber to improve combustion temperatures while reducing overall head temperature. When the combustion chamber is coated, the valve faces are set in place and coated at the same time. Often, the exhaust ports and even the back side of the exhaust valves will be coated to further manage the heat of combustion. All heads benefit from TBC, but these gains are heightened with aluminum heads.

From http://swaintech.com/coatings-get-technical/

I have read articles where it is applied to the ports also to protect the intake charge from heating up and to the exhaust ports to keep the heat from soaking into the head and slowing down the velocity of the exhaust, thereby dropping scavenging and slowing down the next exhaust pulse

[fairlanegt427]

that is all I have found also is for aircraft/ industrial purposes,  I guess ill have to just stick with the old faithful fan plugged into generator.