Fiberglass Turbo Plenum?

[donpearsall]

Has anyone successfully made a turbo plenum from fiberglass or carbon fiber? I have a ZX-10 that I need to build a custom plenum for and think using fiberglass would be much easier to fabricate to the right shape. I have never seen a fiberglass plenum before and maybe there is a reason. The advantages are ease of making a complex rounded shape. The cons may be failure due to flexing and heat.
Any comments about this?
Thanks
Don

[John Noonan]

Don for a low boost system I am sure it wold be fine however after seeing Aluminum plenums that were made with .100" thick material bulge after a back fire I would not want to see what fiberglass would do in the same situation.

Not to mention many of us riders "lay over the plenum" while making a very fast pass...

Use the force...don't let the force use you.

John

[Stainless1]

Don, I'm sure you have seen carbon fiber high pressure bottles.    So it is possible, shape may affect the max pressure, but I don't think you will get there.  Fiberglass.... I would say probably not, Carbon done right, should work great. 

[Dean Los Angeles]

The composite construction of fiberglass or carbon fiber will withstand pressure pulses better than malleable aluminum.

Fiberglass will work as well as carbon fiber. You need more layers to achieve the same strength.

How thick? As with any pressure vessel you need to look at the total square inches, the pounds per square inch, and the load path through the structure, ie. square shapes don't hold pressure as well as round shapes.

[RansomT]

Don for a low boost system I am sure it wold be fine however after seeing Aluminum plenums that were made with .100" thick material bulge after a back fire I would not want to see what fiberglass would do in the same situation.

Not to mention many of us riders "lay over the plenum" while making a very fast pass...

Use the force...don't let the force use you.

John

Just don't have a back fire.    


What about the intake charge temp causing a problem?

[Peter Jack]

The high pressure bottles that I've worked with have been aluminum wrapped with carbon fibre.

Pete

[JoshH]

Stainless - those high pressure bottles have aluminum inner shell which is wrapped with CF. I wonder if current aluminum plenums could be CF wrapped then vacuum bagged and cured to help support the weld joints though, hummm...

Don - I believe this is possible but with significant learning curve that's probably why its not common practice. There are resins out there which can easily handle the heat but most of these require post curing, which can also make the mold more exotic too. Geometry of the finish part is also key to handling pressure.

[Jonny Hotnuts]

Consider this:

A plenum wall measuring 10"X10" with 10 PSI will have 10 pounds for ever inch....meaning really high internal forces trying to separate the plenum (1000 psi per wall however shape will also have a factor).

http://www.about-air-compressors.com/force-on-a-compressed-air-tank.html

Ransom T also was correct, the polymers used to make CF are affected by high temps.

Basically I would suggest not even considering it.

~JH

[donpearsall]

 Thanks for the comments everyone. John I know very well your point about leaning over the bare plenum for 5 miles and wondering if it will go bang. I already experienced that once. I keep seeing images of that Harley drag racer video who got his arm blown off from an exploding engine. Messy.
Just looking for an easy way to build a plenum, but will probably go with Al or SS with my minimal welding skills.
Don

[Rex Schimmer]

There is some reasoning regarding using low strength and "softer" metals for pressure vessels, which is what a plenum is.  The thinking is to use a material that has a yeild strength a good percentage below its ultimate strength this allows the material to yield (stretch) when over pressured and then when it fails it will typically just stretch until a crack or small hole is formed which relieves the pressure. If you use a high strength material such as 4130 which has a yield strength close to its ultimate strength, especially if you heat treat it, then it just blows up "BANG!" and can generate shrapnel at the same time. I would think that both fiber glass and carbon fiber would act like this. So Don if you are going to build it from stainless be sure to use something in the low 300 area, like 302 or 304. If you do aluminum I highly recommend designing the plenum so that you can back weld most of the joints.

Rex

[johnneilson]

Use 304 or 316 SS, 302-303 SS welds poorly.
416 SS is another option, welds nicely with TIG and then can be heattreated/annealed to a consistant condition.
Gun barrels are made from 416, depending on application pressures up to 45k psi.

A comment on fiberglass and CF, use multiple layers and directions of fibers for strength. Add layers of Kevlar.
The high pressure bottles mentioned are constructed with "tows", CF strands in a string and wound very carefully around the shape for strength.

There is always the option of putting in a burst panel.

John

[Jonny Hotnuts]

And on that note there would be nothing wrong with making an aluminum or SS plenum and then covering it with CF for a wow factor.

It would after all look sweet.

~JH

[johnneilson]

If I had to ride it, the plenum would be titainium with an alum burst panel.
But then, I am not riding or paying for it either!!

John

[Peter Jack]

And when you weld up the plenum be sure you back purge to ensure the structural integrity. If you don't understand the terminology or procedure, don't do the welding.

Pete

[hotrod]

As with all pressure vessels, it would probably be a good idea to proof test the finished plenum but filling it with water, then pressurizing it with compressed air to some reasonable safety factor over its intended peak boost pressure.

By having most of the volume filled with water if it "pops" there is very little volume expansion and pieces parts will not fly as far as if the pressure was entirely compressed air.

Normal engineering practice is for 2x safety factor but given the personal risk for a rider laying on top of the plenum I would test to 3x or 4x design boost pressure.

This will also pre-set any bowing or oil canning of surfaces so that it is mounted in a manner that such flexing will not break the mounting brackets.

Larry