Anybody know the main reasons our lower collectors and plenums are made of metal and not plastic? I'd assume plastic ones would be significantly lighter and not heat soak nearly as bad??? I do know the plenum does flow coolant (hot) to the throttle body, but if you don't care about this feature, why not plastic?

I know there are a couple of upper plenums that are made of plastic, but why not the lower (in addition to upper plenums made of plastic with a better design...).

Anybody know? Searched but couldn't come up with anything.

 

The upper part is just a lid. From a design and production standpoint its relatively easy to make, or improve upon the existing one, using information already available from the benefits of plenum spacers, and the downsides of the stock plenum cover. The lower half with the runners is far more complex, theres a lot more design and tuning involved to make it effective.

TK

 

the stock peices are metal cause its way cheaper to get that produced especially at the numbers that they make them. nissan isnt as interested in getting that little bit more HP and less heat soak than they are in saving tens of millions from making it metal

 

5 years ago aluminum was a lot cheaper than it is now. And the tooling to make aluminum parts is a lot, lot cheaper.

Aluminum tooling is made of rubber and sand. Its much easier to sand cast.
The tooling for plastic is made from complicated, multi ton hydraulicly actuated expensive metal parts.

But now with the skyrocket price on aluminum, its getting more advantageous to use plastic.

 

Aaaahhh. That makes perfect sense. I come from owning three LSx motors, which all have plastic intake manifolds and do pretty well with resisting heat soak while weighing next to nothing, and was just wondering if there was actually a functional reason why metal was used on the VQ. It makes sense that it's just all about money, which it always is

 

That's a good question OP, as I have wondered the same~ :-)

 

I know by thumbing through catalogs at work that several companies make metal manifolds for the LS1 now. Not sure what the advantages/disadvantages are or which outweighs the other on either. Must be a decent market for metal manifolds, or they wouldn't make the parts.

 

Plastic would be nice, it may cool down things a bit. Well my Kinetic is one step in the right direction.

 

Simple, Metal is Shiny!

 

Is this why GM is using plastic intakes? Looks cheap - probably why they use these hideous engine covers to cover the whole engine.