Mnifolds do not see the same stress as internal parts, but who knows? Chemistry is always moving things forward.

I do remember back about 20 years though when I would see random articles about ceramic blocks or heads and I don't remember one ever being put into production.

 

[QUOTE=JonBoy,Dec 1 2009, 09:59 AM] Virtually every manufacturer is using plastic intake manifolds on some or all of their cars.

 

Thats ballin' a man chasing a dream for 40 years.

 

As long as they're normally aspirated, they only see atmospheric pressure and a lot of heat. Heat is easily managed and plastic weighs a LOT less than cast iron or aluminum or steel. So, it makes sense to use it. It doesn't tend to be as strong, though, so the design is arguably more critical.

GM and Ford had issues in the 90's with their plastic IMs but I think those issues have pretty much died on today's cars.

 

I happened across this article about a week ago.

Plasteel

Anyone can get access to this article for free, but it's basically talking about a composite material with properties similar to steel.

EDIT: Also, did anyone see that MacGyver episode?

 

While I agree that I would be moderately skeptical of an all plastic or composite engine, you guys have to consider that you could feasibly make a combination metal/ plastic engine that I think it is easy to not worry about.

Think of closed deck vs. open deck blocks. Obviously, open deck blocks lack some of the inherent rigidity that closed deck blocks do, but to a degree that is insignificant even in high power applications, so long as certain steps are taken.

What I think we can gather from this is that it is not necessarily to have a couple inches of solid metal around a cylinder to keep it from falling apart. In other words, if the cylinders themselves are sufficiently rigid, even open air (actually coolant passages) around the block is sufficient to reinforce the part that sees tremendous abuse.

It seems to me that if you were to add some additional reinforcements to the cylinders and crank journal areas, that you could then have "prongs" or other such extensions that protrude from that center section (for the purpose of anchoring and load spreading). You then place the cylinder section into a mold and encase it all in a plastic material. The prongs acts as a sort of rebar for the plastic to mold onto and they connect the cylinders, through the water jackets, to the external structure of the block, without all of the negative effects that a closed deck metal block has inherent.

You still have metal to do your heavy lifting and to withstand your serious loads, and the plastic is more or less there just to hold it all together.

To ask a plastic to do ALL of the work seems like a bit of a stretch, but to ask it to perform a much more simplistic function seems reasonable to me.

Just think of the plastic or composite vehicle ramps that you can buy at the autoparts store. You can park a 5,000 lb SUV on them and they are pretty low tech. Imagine a more complex structure and what it would be capable of.

Which brings up another point. Metal, used in a simple shape like an engine block, gets much of its strength from a simple structure but an abundance of material. Plastic can be shaped into virtually any shape you want. Just imagine how strong a complex lattice work or triangulated structure could be.

What we may see from the outside of the block as a rectangular plastic shape (assuming it's a four cylinder) could actually be different layers and types of plastic with special properties that buttress the other materials weaknesses, all of which could be over a complex triangulated internal framework. With the ability to shape and form plastic, the possibilities would be endless. With metal, you can create external webbing for the block and whatnot, but inside the metal that makes up the block, it's pretty much just an abundance of material with not much going on in the way of structure. It is rigid the way that a rock is rigid.

 

Where I live I have seen 50 degrees below zero, and 110+. If they can make it to work in those extremes, great.

 

the 03 honda civic ex i have with a D17 uses a plastic intake manifold. anything over 200hp on that and it pops, literally.

 

[QUOTE=JonBoy,Dec 1 2009, 10:59 AM] Virtually every manufacturer is using plastic intake manifolds on some or all of their cars.

 

I agree with your points as delivered but question the feasibility of complex internal latticework in a motor. If you're molding and have complex shapes like that, cores are almost absolutely required and they are both expensive and a pain in the neck to use. If you can do simple lattices, it wouldn't be as bad but there's a lot more to it than just saying "Do lattices and triangulated structures".

I work with a lot of castings for gearboxes and internal features are a royal pain to deal with. Easy to design in but much more difficult to reproduce in a foundry or forge.

Also remember that you'll have dissimilar expansion rates so it may be difficult to keep the materials bonded when heat cycling them.

I think it's a neat idea but the actual implementation isn't going to be that easy, especially if you want 150K+ miles out of it in all kinds of environments.