Fiberglass inlet manifold

[30psi 4agte]

Fibreglass may bbe ok if done correctly but i guess it depends on how much boost you plan to run ?

I have managed to split straight through 3mm alloy on my plenumn!!!!
But that is with excessive boost!

[Ben Wilson]

I made all sorts of one-off intake pipes air boxes intake runners and ducts etc.

the best way is to make it from foam then paint it with plaster of paris... costs a few dollers for a big bag of it, you can build up as many coats as you need mix detergent and talk in to make it easier to sand and quicker to set just have a play with quantities

once its all sanded smooth and ready then paint it with acrylic house paint followed by a good coat of PVA (the wood glue works fine) and your ready to lay your glass or carbon straight over the whole thing. I just use polystyrene and polyester both cheep and easy

best is a thin layer of glass and 2 layers of carbon with the weave at 45 degrees. scrape out the foam, soak it in water to soften the pva and a high pressure hose helps to lift the plaster etc

it really is good stuff to play with ...have fun!!!

So, you the plaster to the foam from the polyester and to get a decent surface finish? How hard is it to get the plaster out of a complex shape?

[thechuckster]

The PVA on the plaster provides the smooth finish.

Difficulty of removal will be dependant on how much plaster soaks into the foam turning the foam into an armature instead of a crushable support for the plaster.

[1jzracing]

itsd not hard to remove if you use plenty of PVA

soak it in water and the pva disolves, otherwise i think weak hydrochloric acid will soften the plaster also, i found the high pressure hose works the best it just lifts the plaster off

you must seal it with water based acrylic house paint on the plaster to keep the pva from soaking through the plaster

dont use acrylic car primer or anything like that the thinners soak through the plaster and melts the foam.... total disaster it chushes like an egg shell when you handle it

[myne]

theres a nissan boy getting around with a custom carbon fibre plenum... 20 psi is not alot of pressure when u come to think of it, pump your bike tyre upto 20 psi and see what it feels like

plasticine can hold 10psi for a while.

[jimmy19650]

Some of these ideas sound good. I have made Manifolds, sumps, rocker covers, even a phlenum for an old Group A commodore out of Glass or carbon over the years.

As a few have mentioned, glass, carbon or kevlar is fine, however, it is the resins and curing processes used that cause the problems.

In my opinion, forget about Polyester resin completely for anything that even gets warm. The deformation due to temp will eventually crack the resin (matrix) and cause air to be drawn in - lean mixtures.

The only resins that even have a chance, if you are wet laying up, are vinyl ester or epoxy resins. Make sure that these resins can handle reasonable temperature. Not all can.

The best ways to make manifolds from my experience, and I am not suggesting this is textbook are:-

1) For making several identical manifolds, take a mould off an existing manifold, timber plug or anything that you want to use as a manifold. This mould needs to have a thick gelcoat surface to allow for polishing as well as enough thickness so it stays rigid. The resin used needs to be selected to handle temperature if you will later heat the mould during the curing process. Be sure to allow draw in the mould around joins so it separates, and locate all mounting bosses and fixtures accurately if you wish to put metal inserts in for things like injectors, bearing etc. A good mould can be very, very complicated, have lots of joining flanges, and often in more than 5 parts.

2) To make a 1 off manifold, make your manifold sample out of Polystyrene, and seal with a slurry of epoxy and Q cell. This is like a very runny putty that you can later sand to a very good finish. Remember the external finish of your sample manifold will be the inside of finished manifold. Wax and PVA this sample, or plug as it is commonly called. Lay up your reinforcement, whether it is carbon, kevlar or glass, with whatever resin you are using onto the surface of the plug. Remember to lay up thicker sections around mounting bosses and flanges for strength.You will then need to seal and fill the weave of the cloth with a few layers of resin, and later sand and polish. If you are using polyester resin, you need to mix in between 2-5% wax in styrene so it can be sanded. If you dont seal and sand the weave, you will end up with the weave texture on the out side if the manifold. I then use acetone to dissolve the polystyrene core, then compressed air to blow out epoxy and Q-cell seal. A one off manifold is complete, with a smooth inside surface

3) There is a carbon product called pre-prep which the military and Boeing use in the production of aircraft components. This is a carbon layer with a semi cured epoxy matrix, which needs to be completely cured with heat and pressure. Pre-preg has the consistency of those breakfast rollup bars that are made by uncle tobys. Most prepregs need temperatures of over 80 degrees for many hours to cure, as well as pressure or vaccum applied to the laminate. There is however, a new low temperature pre-preg available that cures at temperatures as low as 60 degrees. The only problem is that this temperature needs to be maintained for 14 hours. There are others available with varying combinations of temperatures and time. These low temp pre-pregs can be cured with simply a temperature controlled fan heater and an insulated box. I have even seen card board boxes used. The good thing about pre-pregs is that they can be shaped easily, the resin ration is perfect, and as long as the correct temperature and duration is used, you will have a mechanically and structurally sound component.

I personally have found that a hand laid up manifold made out of a carbon/kevlar twill weave, about 350 grams per square inch, using a good temperature rated epoxy resin, is more than adequate for all the applications I have used them in. Just be aware that if you put aluminium bosses or flange plates into a carbon laminate, the eletrolytic reaction between these two materials will cause problems. Best to separate these with a thick barrier of resin.

There are too many combinations of resins, reinforcements, waxes, gelcoates, plug materials, laminating methods, catalyst ratios and types,vaccum bagging methods, kilns, heaters, autoclaves and the effects of different lengths of heat to the properties of a laminate for all to be answered here. Best to research the topic well before you attempt anything, messing up what could be a great project, then spend the rest of you life bagging composite materials.

[ae10]

Sprayed or whatever , theres still a chance of the glass delaminating at some point , as you would,nt use a single layer of glass would you ....

Have had lots of experience making glass , carbon and kevlar bodies and various parts and unless you know what your at its frighteningly easy to get an air pocket .

Besides just glass loooks plain ugly and might be ok for a grass tracker but not your pride and joy motor

this may be way off the mark, but would it be possible to elctro-plate the finished product, thus giving a smooth and uninterrupted coating? would that prevent delamination, or am i overestimating the strength of elctro-plating (assuming its even possible to elctro-plate fibreglass)? would a heat resistant enamal coating like used on exhaust manifolds be better? these would also solve the problem of 'plain ugly glass' in your engine bay

[Ben Wilson]

Well I started on the plug for the inlet runners on the weekend.

Bare plaster:


Primed:


Painted (first coat):


I need to get some more paint on there, then I'll give it a week or so to seal before sanding it back (I'm not looking forward to this bit...)

This has been a great thread so far, thank for all the advice and ideas.

[MWP]

How did you shape the plaster.... its been a looong time since ive played with the stuff (primary school).

Put the plug in an oven at low heat.... ~70degC is enough to greatly speed up the curing time of the paint (a few hours will be enough).

[Ben Wilson]

I built up a 'mould' using a trumpet and a sheet of melamine. I cut a hole in the malamine big enough that the base of the trumpet would fit through, but the top wouldn't.

I bolted a plate to the flange the trumpet, then built up a fence on the top to create the base of the part you see above.

I coated the surfaces in vasoline, then just poured the plaster in.

Either the draft angle of the trumet was too small, or there is some damage in there because it didn't want to seperate. I had to use a 3 jaw puller to get the trumpet off in the end..

My housemate is very understanding, but I think even she would draw the line at an oven which stinks of automotive paint

[takai]

Ben: Just wait for hard rubbish and then go pick up an old electric oven for the garage. Either that or go to Revolve. Double win, as you can heat party pies in winter with it too.

[Ben Wilson]

LOL - You've seen my shed, how on earth am I supposed to fit an oven in there?

[takai]

True, true, you do have a very good point. Although the little corner between the door out back and the aircompressors could work

[Ben Wilson]

Yeah, but I'd wind up piling stuff on it, then it would get turned on and bad things would happen....

Bear in mind that I only do fiberglass work every few years - it takes me that long to forget how much I hate the stuff

[oldcorollas]

this may be way off the mark, but would it be possible to elctro-plate the finished product, thus giving a smooth and uninterrupted coating? would that prevent delamination, or am i overestimating the strength of elctro-plating (assuming its even possible to elctro-plate fibreglass)? would a heat resistant enamal coating like used on exhaust manifolds be better? these would also solve the problem of 'plain ugly glass' in your engine bay

just to answer this.... electroplating onto insulators is not easy. first you need to put some kind of metal coating on the fibreglass, on which to electroplate further material.
unless you had a sputter coater or evap coater, or some other PVD, then i would not recommend even trying.

strength of electroplating?? electroplated layers have no strength as such. perhaps a chrome coating would resist wear a bit, but .... the manifold is not subject to wear?

meh, paint with fibreglass suitable paint....