jikhead Posted August 27, 2005 Share Posted August 27, 2005 Does anyone have information on why Subaru uses the plastic intake manifold on the stock GT? Link to comment Share on other sites More sharing options...
PGT Posted August 27, 2005 Share Posted August 27, 2005 complex shapes, low heat transfer, smooth flow....the same reasons as BMW and other manufacturers. Proper reinforced plastic will hold as much PSI as a cast aluminum unit, yet store less absorbed heat from the motor below. This keeps intake charge temps lower for better control of combustion and more power. Link to comment Share on other sites More sharing options...
John M Posted August 27, 2005 Share Posted August 27, 2005 And the resulting passages are smoother without any honing or machine work. Link to comment Share on other sites More sharing options...
jagcars26 Posted August 27, 2005 Share Posted August 27, 2005 Im sure cost was a factor also. Rudy Link to comment Share on other sites More sharing options...
RobY Posted August 27, 2005 Share Posted August 27, 2005 +1 Cheaper Although nobody has really compared the performance diffrences between the 2 manifolds. Link to comment Share on other sites More sharing options...
jikhead Posted August 27, 2005 Author Share Posted August 27, 2005 So, is this why you must swap to an aluminum manifold if you go with a bigger turbo? Link to comment Share on other sites More sharing options...
highwaydrifter Posted August 27, 2005 Share Posted August 27, 2005 you dont have to, just allows you more options. (market for wrx adn sti turbos is more developed at this point) Link to comment Share on other sites More sharing options...
RobY Posted August 27, 2005 Share Posted August 27, 2005 So, is this why you must swap to an aluminum manifold if you go with a bigger turbo? No, many people choose to swap because there are more WRX style turbos available than LGT style turbos. WRX style turbos are also cheaper. If you want to go into custom fab. PDX plans on running 400hp on thier rotated mount Garrett GT30 kit on the stock manifold. Link to comment Share on other sites More sharing options...
ShaggyGT Posted August 28, 2005 Share Posted August 28, 2005 If your going to go custom why not just swap the manifold to start with. You guys talk like intake manifolds are a costly piece, when infact they are not that expensive($100-150). If you have never seen the stock manifold then you cant say how efficient it is or isnt. I have actually had the manifold off the car and compared it with an STi intake manifold and it is MUCH MUCH more restrictive. The design is absolutely horrible. I guarantee I will have spent as much on my rotated setup with the STi intake manifold as they will making a kit to work with the existing LGT manifold. I am enjoying my 371ft/lbs of torque every single day!!! -Matt Link to comment Share on other sites More sharing options...
RobY Posted August 28, 2005 Share Posted August 28, 2005 PDX tuning claims that the Stock manifold does not appear to be a restriction. They are tuning thier legacy to the same degree as thier STi with a rotated mount to see how the numbers compare... Time will tell. Right now its all kinda speculative. http://www.legacygt.com/forums/showthread.php?t=16190 Link to comment Share on other sites More sharing options...
ShaggyGT Posted August 28, 2005 Share Posted August 28, 2005 I tried to get some pictures of the intake manifold but I cant get good shots of the inside of it. I am considering cutting it in half to find out for sure. Once I get the pictures uploaded I will post what I do have. I also got pictures of the stock TGV housings for those who dont completely understand what they do. -Matt Link to comment Share on other sites More sharing options...
RobY Posted August 28, 2005 Share Posted August 28, 2005 Shaggy, how do the LGT TGV housings compare to the STI housings. I heard they were diffrent and that the STI manifold will not bolt to LGT housings. Link to comment Share on other sites More sharing options...
ShaggyGT Posted August 28, 2005 Share Posted August 28, 2005 The bolt pattern for the intake manifold is the only difference. Otherwise they are EXACTLY the same. -Matt Link to comment Share on other sites More sharing options...
LGT Chris Posted August 28, 2005 Share Posted August 28, 2005 A master Subaru mechanic I know says that it is just as good if not better than the STi intake manifold. It doesn't change shape or lose much strength under high temps (plastic is a very poor conductor of heat) and the flow is much smoother than with cast products. As hard as it is to accept, plastic is much more exact, tons cheaper, lighter, and can be made with marvelous materials these days. If you notice, your radiator is topped (maybe the bottom too) with plastic. I've driven hard at 15-16psi in 105F days with no melt down or gasket failure. I'm sold. :shrug: Just my $0.02 worth. CJ 2005 Subaru Legacy 2.5 GT Luxomissle waGONE Link to comment Share on other sites More sharing options...
mwiener2 Posted August 28, 2005 Share Posted August 28, 2005 plastic is lighter then metal My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
PGT Posted August 28, 2005 Share Posted August 28, 2005 plastic is lighter then metal helium is lighter than air, but you don't tires filled with it. Link to comment Share on other sites More sharing options...
rony Posted August 28, 2005 Share Posted August 28, 2005 helium is lighter than air, but you don't tires filled with it. Omg, sush.... Geez.... My Car vBGarage Link to comment Share on other sites More sharing options...
RobY Posted August 28, 2005 Share Posted August 28, 2005 Lance Armstrong Has his tires filled with it. Link to comment Share on other sites More sharing options...
MarcusDubya77 Posted August 28, 2005 Share Posted August 28, 2005 so what parts and mods are required to swap IM to the STi ones?? Or is it possible to swap the Intake manifold alone?? :woowoo:check out the Diamond Gray Metallic Monster!!! Link to comment Share on other sites More sharing options...
ShaggyGT Posted August 28, 2005 Share Posted August 28, 2005 I wouldnt suggest an intake manifold swap until your ready to upgrade the turbo. Then all you would need is the Intake manifold and an STi TMIC. If your going all out then a FMIC would be a good choice, but would either need to be custom fabricated or an STi type FMIC should work. I will be able to confirm the STi type FMIC fitment here shortly and will do an extensive write up on it as well. -Matt Link to comment Share on other sites More sharing options...
RoundBoy Posted August 29, 2005 Share Posted August 29, 2005 helium is lighter than air, but you don't tires filled with it. Actually.. I have seen this... as well as fill w/ nitrogen. The only reason its not done everywhere is that its easier just to pump air from .. cough.. the air..then it is to store helium, etc for use ... Link to comment Share on other sites More sharing options...
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