Plastic Intake Manifold?

I finally popped the plastic engine cover off my LGT last night, and I noticed that the Intake Manifold is plastic. I did a search, and found a little information, but not really what I was looking for. Also noticed that the throttle body is down on the right rather then sitting right on top of the intake manifold.

What are the positives of this design (less engine noise?)? Any negatives? Has anyone done extensive tests?

The plastic feels almost sturdy as alumnium (from my extensive rapping on the plastic test ), so I don't think strength is an issue.

I'm also curious what the flow is like compared to the FXT or STi manifold.

Obviously you'd have to replace the intercooler and intake manifold at the same time, but I was just wondering if anyone knew what gains/trade-offs are to be expected.

plastic = less heat soak, easier to make, less top-weight, no need for welding and the shape is more flexible to manage vs. metal.

throttle location = it's ETC, they can put it anywhere since it's drive-by-wire. It doesn't have to be in a place where it use to be a mechanical challenge to make sure the throttle cable wouldn't have a problem with it's routing.

Keefe

Is that credited to the Manifold? Hmmmmm

Wait... Ive drivin STI'sand they are way more torqy! Smoother tq band maby...

The Ford 4.6 intake manifolds cracked because they also ran a coolant line through the plastic section. When they realized this breaks things, they re-designed the intake to use an aluminum section for the water passage and the rest is still plastic.

We won't have that issue on these cars.

Anyway, I would say it's the design of a manifold that decides tq and hp characteristics, not the material. Being plastic also means the runners are perfectly smooth - no boring or extrude honing required.

Being plastic also means the runners are perfectly smooth - no boring or extrude honing required.

WERD!!

Plastic intakes have been around long enough that we shouldn't have any problems :crossesfingers:

The Ford ones, were, well, from Ford

i would also point out the high torque numbers that the stage 2 LGTS are making as evidence that the manafold makes better torque too

I don't know that you can draw much from that. Both the Cobb and PDXtuning stage 2 setups make less torque on a Legacy than an STi. Unfortunately the Cobb setups aren't exactly the same as their Legacy stage 2 dyno plots seem to leave the up-pipe cat in place but I doubt that the up-pipe is lowering peak torque by 30 ft/lb at the wheels. The Legacy appears to be making a lot of torque because the peak torque is a good deal higher than the peak HP but I think that this just shows that something (possibly the turbo's hotside) is really restricting flow at high rpms.

that, to me, would be more likely...

I cant wait to see more options like turbo kits for the LGT!

I don't know that you can draw much from that. Both the Cobb and PDXtuning stage 2 setups make less torque on a Legacy than an STi. Unfortunately the Cobb setups aren't exactly the same as their Legacy stage 2 dyno plots seem to leave the up-pipe cat in place but I doubt that the up-pipe is lowering peak torque by 30 ft/lb at the wheels. The Legacy appears to be making a lot of torque because the peak torque is a good deal higher than the peak HP but I think that this just shows that something (possibly the turbo's hotside) is really restricting flow at high rpms.

That's more to do with the size of the turbo. You can get a plastic manifold to flow good because you can make them to very particular standards. Easier to make than traditional metal ones.