New GT Manifold

[RallyDRock]

it is the manifold. the plastic is lighter and does not hold the heat(heat soak) like cast aluminum. better performance and cheaper but cool factor= 0
i wish i had a polished turbo manifold it really looks awesome [^]

[bigtommy83]

i'd rather have the plastic intake manifold as opposed to my hot metal intake. As soon as it becomes available, I may have to order one.

[wsd0836]

Thermodynamics 101:
A metal manifold is conductive to heat. It is hot because it is sinking (absorbing) the heat out of the air flowing through it. Thus making the air cooler. A plastic manifold does not get as hot because it does not sink as much heat from the air inside it.

[RallyDRock]

have to disagree with ya on that one. the air coming from around the engine on the outside of the intake is hotter than the air inside the tubes. the manifold sinks the heat from outside and heats up the intake charge.

[wsd0836]

Yes...that might be true if, in fact, the engine bay ambient air temp is greater that the air temp inside the manifold. Fourier Law of Heat Conduction would apply: "When there exists a temperature gradient within a body, heat energy will flow from the region of high temperature to the region of low temperature." Do we know for a fact that the engine bay temperature is greater?

[RallyDRock]

yes.
using a thermocouple i measured the intake air charge temperature to be only a few degrees greater than the ambient air temperature outside the vehicle. the intake charge is drawn from outside the engine compartment through the drivers side fenderwell. The intake air has such a high velocity passing through the manifold that it doesnt have the opportunity to absorb much heat from the manifold. if i had an IR thermometer i could measure the surface temps of the engine parts after some highway operation but i can say from experience that it is hot enough to give a second degree burn.

for more info you can look here
http://www.bstockum.com/toohot.html

[tangerinedream1845]

well the new is nice BUT you can't do this to it !

[wsd0836]

Nice article. You also made a good point: "...intake air has such a high velocity passing through the manifold that it doesnt have the opportunity to absorb much heat from the manifold." The air velocity would have to be rather slow to transfer a significant amount of heat from the manifold. In that case it wouldn't matter if the manifold was exothermic or endothermic since the transfer of heat from the manifold to the flowing air or the transfer of heat from the flowing air to the manifold would be minimal either way. That being the case the material the manifold is constructed of would not matter from a thermodynamics standpoint. Do you agree?

However, in theory, by removing the metal manifold and replacing it with a plasic one, they have essentially removed a large heatsink from the engine block. Thus, concentrating heat in other areas of the bay, and possibly raising the overall temp of the bay. Since now there is less metal to absorb and dissipate the heat...in theory.

By the way, I've meationed this before, but not all '05 GTs have the plastic manifold. My '05 GT convertable has the metal manifold. It's exactly the same as the one in my wife's '03 GT.