Fuel Pressure Regulator Modification
These are the materials and instructions on an easy way to add an adjustable fuel pressure regulator to the system.
Here are some simplified directions that I thought of really quickly so I could have missed a step but I am sure when you do it you will see how easy it is. There is a parts list below of what is needed.
Note-When installing the swivel connectors to the FPR fittings on the fuel rail a little bit of oil should be on threads and that will make a good seal. No sealer is needed on the swivel fittings except a little bit of oil.
Note- Stock MR2 fuel pressure with the 440cc
injectors is around 36psi. Stock fuel pressure on the supra twin turbo with
550cc injectors is 43psi. Now if put in the 440cc injectors and raise the fuel
pressure to 43psi it will basically make them 480cc. (Some have had them cleaned
at 43psi and it showed 480cc because of this amount and claimed to have had
overbalanced stock injectors. That is not possible and a down right LIE at stock
pressure. There is not such thing as overbalancing the stock injectors). Now if
you just installed the supra injectors with the stock regulator you would only
have like 510cc injectors instead of 550cc, which can be enough if you like with
your application. On that same note, if you take the supra injectors that are
550cc at 43psi and put them at 50psi you will have around 600cc. Now also
take into consideration that you do not want to go too high on the initial fuel
pressure because for each 1psi of boost you add 1psi of pressure in the rail. So
if you start out with 50psi and then boost to 20psi then you have around 70psi
of fuel pressure, which should be around the limit you want to go to. This is
due to the fact that the more pressure you run the less fuel your fuel pump can
pump at that pressure. There is a direct correlation between the amount of
pressure a pump can hold at a certain amount of fuel flow. So the more pressure
the less amount of fuel it will allow and vise versa. At the higher pressures
and amounts needed a supra pump may be needed or a drop in replacement that is
even stronger. I know the supra guys use a drop in replacement for the supra
pump that is a bit better and should be cheaper than a supra fuel pump. The
Walbro pump for a Supra upgrade should be GCA3334
Directions
1-Take off stock regular. You will need to take off the vacuum hose and return line. Take off return line all the way to the metal return line that is next to the fire wall. When taking off the regular there is a lock nut that is basically flush with the fuel rail. Just crack this nut loose then you will be able to spin the regulator off.
2- Take out Fuel pressure regulator and put on these fittings to it. Put on 6an plug on right inlet. Put on 6an male to 4an male on bottom. Put on 6an male to 6an male on left side. Put on 1/8npt fuel pressure gauge. I put all these on with some pipe thread sealer just to make sure there are not any leaks. You can also use O-rings of the correct size which should work better, but I did not have any at the time when I did it. You can get a different fuel pressure gauge if you want to have one in the car, just make sure you get an electrical one.
3-Install the 90 degree 12mmx1.25thread to 6an fitting, but do not make it tight yet because you will just have to take it off anyway in a minute.
5- Install the fuel pressure regulator where you want to. I put one on one car on the rear fire wall and that worked out nice. On my own car I attached it to the water radiator cap in the back of the engine. Just find a place that you like and make sure to consider where the lines are coming in, going out and where the fuel pressure gauge will be. You will need to see this.
6-This is the only hard part of the install. On the left side of the FPR (fuel pressure regulator) with the 6an male fitting you will put on a 6 an straight swivel fitting. Now after ordering the parts and putting it in the car I think a 90 degree 6an swivel fitting would work better but it does cost about twice as much so it is up to you what one you will use. Now install the an line into the fitting. Here is how I do it. I cut the an hose by putting electrical tape rapping around it tightly and then use a cutting stone in my air grinder. Not everyone has one but you should be able to do the same thing with a dremel tool and a cutting stone. You can order only one foot of 6an hose and that should be ok. It should come cut nice on both ends so do not frey the stainless steel ends or it will be almost impossible to get the fitting on. You need to take the 6an fitting apart and put the hose in the one end and then screw the make part onto that I take the 6an fitting apart and put the end cap in the vise. I then take the 6an hose, (with no tape on it) and put it onto the fitting on one side. On the other side I take a small screwdriver and work the hose into the cap. When doing it you will see what I am talking about. When on you push the hose into the fitting all the way down. now you can take the fitting out of the vice and turn it around. I then put the main part of the fitting into the hose. I spit on the end a little bit so it will slid on real nice. You know how good the universal lubricant of spit it. You will need to push down on the fitting and turn it at the same time to get the threads to start. If you can not do this you and you are really close you can actually pull the hose down a tiny bit to get the threads close and start. Once it is started it will go on easy until the end when it gets tight. If it gets tight they you have done it right. If you are tightening up the fitting and the hose moves out that means that the center piece on the main fitting did not go into the center of the hose inside the end cap. Stop and pull it out and start over. If it is not on there good in the center it will just push out and not work at all. Just to let you know the 6an and 4an fittings are the hardest part. The 8-10-12 an fittings are much easier to do.
7-Now that the hard part is done put the straight (or optional 90 degree fitting) on the FPR but do not tighten it down. Put the other end up to the 90 degree fitting on the fuel rail to see how you want to route the fuel line and how long you need it. When you find what you want cut the line (see above) or just use how ever long the piece is if you like. Now take off the 90 degree 12mmx1.25 thread fitting on the fuel rail and install the 6an line into the fitting (see above for how to do it).
8-Now install the 4an hose into the 4an straight fitting (see above on how to do it). Then attach that to the bottom of the FPR but do not tighten. Now route your 4an return line to the metal line fitting next to the fire wall that you took off. Measure how long you want it. Take off the 4an line and fitting and cut the hose to the length you want. Now install the fitting and hose. What I did was use a torch to heat up the line so it will fit on because it is really tight. I also used the stock clamp to hold the return line onto the metal hose but a good hose clamp would not be a bad idea on this line.
9- Turn the key to on but do not start the car. The pump should run for a few seconds and you will be able to see what the pressure is at. You can adjust the pressure on the top fitting, just losen the lock nut and use an allen to tighten or losen the fitting to make the pressure go up or down. Once set to where you want it lock it down and don't touch if. If you do tuning and base you tuning on this amount of fuel and change the fuel pressure afterwords all your tuning will be wasted since it is based on fuel pressure. Now you are done. Wasn't that easy?
Parts required. I got all this from Summit racing and will include summit part numbers.
1-Aeromotive Fuel pressure regulator. AEI-13109 129.95
2-6an to 6an male to male AER-FCM2052 4.25
3-4an to 6an male to male AER-FCM2156 4.95
4-6an plug EAR-580606 2.95 (these come two in a pack so you will have an extra one)
5-6an 90 degree to 12mmx1.25 EAR-849091 28.39
6-6an straight fitting EAR-300106 5.95 (Or optional 90 degree an fitting EAR-309106 14.95)
7-4an straight fitting EAR-300104 5.95
8-6an hose 3ft AER-FCA0603 15.95
9-4an hose 3ft AER-FCA0403 12.95
10-Fuel pressure gauge ATM-2171 29.39 (Optional for gauge in car ATM-4309 84.95)
Total will be 236.43, if no optional parts are used.