oooo, questions tonight.

Just curious but why has mazda made them out of cast iron it seems? I mean wouldn't it be better if they would have just fabricated it out of a real thin piping to reduce weight and give better airflow?

Are they thick becuase it protects the AF mixture from heat? or are they thick to prevent corrosion?

just curious.

 

They are cast out of aluminum. I believe the reason for casting them so thick is because the casting process is relatively simple, and isn't very perfect at all. Having them thick leaves room for imperfections...?

 

What I was thinking of doing was to fabricate my own manifold thats got a better airflow and is made out of some exhaust piping. That and some flanges on both ends that just bolt on to the block and the TB. Right now its just all thoughts and dreams, but if I think about it enough I'll do it.

thats not what this thread is about though, im just trying to understand the benefits of making the manifolds out of casted aluminum. So far I can see that its an easier fabrication process.

 

Casting is cheap. Super cheap. Steel manifolds would require more on-hand labor. Cast material also handles heat and rapid temperature changes a lot easier. Heavy duty parts will also last longer. Did I mention it's cheap?

 

But in terms of performance between the two (suceptable to heat, or stress, or anything) its pretty much the same?

 

The aluminum shrugs off the heat much much better than steel and is slightly weaker (when comparing density), but is about 1000% easier to fabricate (including any process work needed for mating parts or assembly).

BTW: GM uses Plastic for intake runners on some of their lower reving V6 and V8 cars, but I wouldn't expect it too hold up as well on a rotary engine.

 

Ford uses plastic aswell, I've seen it on Mustang GTs, ZX2s, and Focuses. My dads WS6 even has plastic intake runners.

Its a great idea for non-boosted cars, it shrugs off more heat than aluminum, and is much lighter too.

 

Yeah, I wouldn't be surprised... I generally stay away from domestics... too many bad experiences with crappy built cars.

 

I don't know if this has anything to do with it, but when the FC was being designed, each team had to shave a certain amount of weight off of the parts they were in charge of in order to lighten the car as much as possible. Of course aluminum is lighter than steel, and it may have been made that way in order to shave weight.

-Joe

 

Doesn't the RX-8 use a plastic intake manifold?

 

"Doesn't the RX-8 use a plastic intake manifold?"

YUP, it does indeed.

~Mike.............

 

Ya, you can probably thank ford for that. Probably most of their cars have them, including my dad's '97 crown vic and my mom's '00 mustang gt...

 

Many new(er) cars are using plastic intake manifolds including the RX-8 and 350Z. Benefits are that it is cheap to make, easy to keep clean and light. Downsides are that the material is thin and any porting makes it very weak and more prone to crack. A few companies make aftermarket plastic intake manifolds (they call them plenums) for the 350Z that are new molds that improve flow, they are not modded stock pieces. However, many of these makers have had t re-do their product many many times due to cracking issues (which creates a nice vacuum leak). After a few months, the aftermarket plastic plenums develop small cracks around stress areas from being subjected to heat/engine torque. The companies have taken care of their customers in giving them an exchange for the updated piece or just shipping a new one without the need for a core return.

The path many 350Z owners are now taking to upgrade the plenum is by going with the one company that makes their model out of metal

 

Gee, and here I was thinking that they cast the manifold thick so we could port it...