Project GD STI – Improving the Fuel System with Injector Dynamics and Other Details


Since we were going to remove our intake manifold, we decided to use Perrin’s intake to turbo inlet tube.  The Perrin part is so much less restrictive than the twisted and convoluted stock plastic piece.  It is made of 4 ply silicone rubber that is steel wire reinforced to prevent it from collapsing under suction from the turbo.  It is a big part packed into a small space and it really is much easier to install while the intake manifold is off the car.
Did we mention working on Subarus when you are not used to them is a bitch?  There is a lot of stuff packed into a small area around the top of the engine and you have to be patient and careful.  Who thought that bolting the wire harness to the underside of the intake manifold was a good idea?
We removed the stock injectors and pressure regulator.  We will be relocating the stock regulator and reusing it.
We also removed the TGV valves.  The TGV valves help fuel atomization at low rpm and right after cold start by greatly reducing the intake port area by closing this big butterfly valve.  Not only is this a flow restriction but the TGV is also controlled by stepper motors and has sensors that clutter up the tight area under the intake manifold.
Using a die grinder, we ground off the shaft staking and the staking of the TGV valve screws so we could remove them.
Technosquare’s Howard Watanabe machines some aluminum plugs for the TGV shafts.  The plugs will reduce the amount of welding that needs to be done to close up the shaft holes.  This reduces the chances of warping the TGV bodies.

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