Plastic Intake Manifolds in new cars...

[al_motor]

I've noticed that several new cars like the new Civic and the Mazda3 seem to be running what look like plastic intake manifolds?

Are they completely made of plastic?

Is it because they repel heat? Or is it because they're "lightweight"? Or is it yet another cost-cutting measure?

[ghosthunter]

I've noticed that several new cars like the new Civic and the Mazda3 seem to be running what look like plastic intake manifolds?

Are they completely made of plastic?

yup... completely made out of plastic. But not ordinary plastic. Heat resistant so they won't melt/deform from the heat under the hood.

Is it because they repel heat? Or is it because they're "lightweight"? Or is it yet another cost-cutting measure?

Both lightweight & cost cutting. Its also faster (and cheaper) to manufacture plastic parts than the same parts from metal.