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Perrin Top Feed Fuel Rail & TGV Delete
DISCLAIMER!
Installing fuel rails involves changing the fuel system which, if done improperly, can cause an engine bay fire resulting in damage to the vehicle and / or death. The information on this page is meant to be a GUIDE and in no way should be considered official installation instructions. The fuel rail installation instructions from Perrin are a must for this install. Professional installation is recommended if you do not have experience with automotive fuel systems. JSC Speed in no way assumes responsibility for any damage or injury that may result from improper installation.
The cold weather fuel leak has become a constant nuisance for the 2003 WRX. The raw fuel smell was noticed anytime the car was started in temperatures around 40 degrees Fahrenheit or lower. The leak would seal up once the car came up to operating temperature but any fuel leak is fire hazard. The stock fuel rails feed are set up in series which means there is always one injector that gets the fuel last. The Perrin Fuel Rails were chosen eliminate the cold weather fuel leak and to get even fueling to all fuel injectors. Since the intake manifold needs to be removed this is the perfect opportunity to remove the tumbler generator valves.
wrx intake manifold removed First you need to remove the intake manifold using the instructions from the service manual. There are many vacuum lines, sensors, fuel lines and such that need to be disconnected before you start to pull off the manifold. Make sure you get all of them and it would be wise to make a list of the things you disconnected to ensure you get all of them hooked up correctly when reinstalling the manifold. Be sure to keep the TGV housings attached to the manifold as it will be easier to remove that way. The manifold will need to be worked out gently but firmly as it is a very tight area. Once you have the intake manifold out place it on a clean working service with plenty of room. Make sure you put a towel in the intake ports on the head to ensure nothing gets into the heads.

Now that the intake manifold is out of the car separate the tgv housings from the intake manifold. Remove the stock fuel rails being careful not to damage the fuel injectors. On the right is a picture of the intake manifold in stock form. The TGV is designed to reduce cold start emissions and they do so by closing. When closed air is drawn through the small opening that is about 1/3 of the size of the whole housing. The air moving through this small space causes increased velocity and causes a tumbling effect. This tumbling effect mixes the air and fuel very well before it enters the combustion chamber. Once the car is up to normal operating temperature the valves open and stay that way. The tgv's do not open and close due to throttle input, these are not throttle plates. Even when the tgv's are open they still are a significant restriction. Removing the tgv's will net gains across the rpm band. Tuning is necessary when the tgv's are removed to ensure the air fuel ratios are at a safe level and to remove the check engine lights. The check engine lights associated with the removal of the tgv motors and sensors will put the car into limp mode.

The TGV port process is pretty self explanatory. Remove the motors and sensors; you may want to keep these to sell on ebay. You will have to drill out the screws that hold the flaps in place. Once the flaps are out you can pull the bar out from the side. You may need to tap the end of the bar with a hammer to get it started. Once the bar is out of the way you can seal up the holes where the bar passed through by welding or using a bolt. I choose to tap the holes and thread in bolt, I used some high temperature thread sealant to ensure the bolts wouldn't work there way out.

Once the bolts are in there it is time to remove the lip that the flaps site on as well as the wall left in the middle of the housing. I choose to use a die grinder with a bit designed for steel. The porting process will take a while and you will go through a few different bits but be patient and work slowly. Once you are done with the porting the housing should be smooth. It doesn't need to be perfect as removing the restrictive tgv's provide the gains. Be sure to wrap the tgv sensor and motor wiring plugs with electrical tape to ensure no moisture gets in there. Time to put the tgv housings back on the intake manifold, don't forget to use new gaskets!

stock fuel rails removed

TGV housings in stock form

tgv closed

tgv open

ported tgv housing top feed

items removed from tgv delete
stock fuel line compared to perrin fuel line inner diameter id tgv housing with bolt to seal it up injector wiring harness unclipped injector wiring harness clipped
perrin top feed fuel rail

side of perrin fuel rail

perrin fuel lines routed

fuel lines to firewall

tool

thread sealant

Now it is time to mock up the Perrin Fuel Rails. The top feed fuel rails are being fitted up here so the side feed rails will be slightly different but not by much. The installation instructions from Perrin are very good and should be referenced throughout the install. The injector wiring clips have small tabs that need to be trimmed to fit the Perrin fuel rails properly. Once the tabs are trimmed off mount the fuel rails in there proper place on the tgv housing and the distribution block on the manifold on top of the TMIC mounting bracket. Carefully plan out the way you are going to route the fuel lines. Measure and cut the fuel lines at the proper length. I planned on routing the fuel lines under the manifold but later decided to route them on the top to avoid pinching the lines. At this point it is best to test fit the manifold and ensure that all the lines are not interfering with anything. Once you are 100% sure the lines are at the proper length and routed properly remove the manifold.

Cut the pyro shield at the proper lengths and install it over the fuel lines. Use the Oetiker tool to crimp the lines to the junction block and fuel rails. Make sure you are properly crimping to eliminate any dangerous fuel leaks. Once you are done with the lines its time to put the intake manifold back onto the engine. Don't forget to use new gaskets! Be sure to hook up all of the wiring and hoses you disconnected when you removed the manifold. Put a dab of oil on the fuel pressure regulator and injector o-rings to prevent fuel leaks. Do not over torque the fasteners that hold the fuel pressure regulator to the distribution block. They will strip very easily if you over tighten them! I had a leak from the threads on the brass connector where the fuel enters the distribution block and I was able to cure it using some high temp thread sealant. Be sure not to put thread sealant on the first few threads of the fitting to prevent the thread sealer from clogging up your injectors. Clogged injectors can destroy an engine so be very very careful.

Once all of the connections have been made including the fuel lines and evap lines from the firewall it is time to pressure test the system. MAKE SURE THERE ARE NO OPEN FLAMES, CIGARETTES, HOT SURFACES, OR ANYTHING THAT WILL IGNIGHT FUEL IF THERE IS A LEAK. This part is best when performed with a second person so you can identify any leaks quickly and limit the amount of fuel spill. To prime the system turn the key to the on position but do not start the car! You will hear the fuel pump prime the system and then shut off. You will be able to smell fuel leaks easier then actually seeing them. Once you are absolutely sure there are not fuel leaks its time to start the car.

After performing this modification the car felt stronger across the rpm band. The gains were noticeable from idle to red line and the turbo spools up faster now. It is amazing how much of a difference the tgv's make. A reduction restriction only inches away from the cylinder head really makes a huge difference. The larger the turbo you are running the more gains you will see by removing the tgv's although a stock turbo car will still experience a power increase. The Perrin fuel rails use larger inner diameter fuel lines stock which results in more flow to the injectors. Also, the Perrin fuel rails feed each rail evenly unlike the stock fuel rails. The Perrin fuel rails ensure that all injectors see the same pressure and function properly. Installing the Perrin fuel rail along with removing the tgv's will add more power and ensure equal fueling to your subaru!
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