General

Adequate air/fuel mixture is extremely important for turbocharged motors. Stoichiometric mixture is ideal mixture consisting of 14.7 parts by weight of air and 1 part of gasoline. This ideal mixture is good only for fuel economy and low emission requirements. When engine is loaded (under boost) we have to run significantly richer AFR (Air Fuel Ratio). The less efficient engine (poor combustion chamber design, too small turbocharger, not efficient intercooler, less than perfect ignition map) the more fuel we have to dump to cool down combustion chamber and suppress detonation. The person modifying his (her) car has to understand limitations of stock fuel system and act accordingly. Stock fuel systems designed with 15-20% safety margin, it is sufficient only for mild power upgrades like exhaust, intake, IC.
OK, to modify fuel system you have to address following aspects:
1. Fuel tank / cell
2. Fuel pump(s)
3. Fuel lines, fittings
4. Fuel filters
5. Fuel pressure regulator
6. Fuel rail
7. Fuel injectors

                                                                                        Fuel Tank

Most OEM fuel tanks have internal baffles to prevent fuel slosh during cornering and acceleration. For hardcore racing surge tank or fuel cell recommended. With them you can always be sure fuel pump will never loose suction and as a result lean out at high load. For myself I decided to keep thing simple and have at least 1/2 tank of gas when drag racing. Usage of fuel cell offers few significant advantages, like reduced weight and ability to run external fuel pump but I don't like the idea to have fuel tank in the trunk of a daily driver.
Picture on the left copied from the article on the SDS website and slightly edited by myself.
 

                                                                                    Fuel Pump (s)

Now, when you know that you power goal is, let's say, 600 turbocharged horses you have to choose fuel pump. Formula to calculate your fuel requirements is:
                                               Pounds of gasoline per hour = Power * BSFC
BSFC (Brake Specific Fuel Consumption) is how many pounds per hour required to produce 1 horsepower. For naturally aspirated gasoline engines BSFC = 0.48-0.50 lb/hr, for supercharged motors BSFC = 0.55 - 0.60 lb/hr, for turbocharged or NOS assisted motors BSFC = 0.60-0.65 lb/hr.
For our 600hp turbo motor we need 600 * 0.68 = 408 lb/hr of gasoline. Add at least 25% safety margin and result is 510 lb/hr. Specific weight of gasoline is 7.25 lb/gal, so our requirement is 510 / 7.25 = 70.3 gal/hr = 266 ltr/hr. Now you have to look at fuel pump characteristic graph to find out is it up to the job. Say, you are planning to make your 600hp at boost pressure 25psi, your base fuel pressure is 40psi, so pump has to develop 40 + 25 = 65psi of fuel pressure at full load. Below you can find fuel pumps comparison chart taken from www.stealth316.com prepared by Jeff Lucius. All these pumps are in-tank models and only one of them APEXi BNR32 meets our requirements. There are many external pumps like Weldon, Aeromotive and other offering huge production but to use them

with stock fuel tanks is not practical because pump has to be lower than fuel level, in this position it would be exposed to various road hazards. If you want to keep it high and well protected you have to install surge tank in the trunk. Another aspect - high volume external fuel pump will overheat fuel in summer, for street driven cars manufacturers recommend to use voltage controller. Of course using dual or multiple in-tank pumps is most economical solution for high power cars. Though to run single pump is safer, if it fails your car stalls, if one of your multiple pumps fails at high load you will melt pistons. Most popular here is Walbro 255l/hr high pressure pump, it costs only $100-110, less than many OEM pumps. Don't use stock fuel pump wiring for your high performance pump, best solution here to take power from the battery and use stock wiring as a signal to activate relay. Use adequate size power supply and ground wires.

My second Walbro activated from LS driver of my AEM EMS at boost pressure 1bar. Inserting double Walbros into the mk3 fuel tank is not easy, but possible. I connected one pump with -6AN hose to stock fuel supply line, another pump - to tube welded into the evaporative canister outlet line cover. One more thing to remember about multiple fuel pumps is: if you run in parallel 2 same fuel pumps their production will be at best 1.4 - 1.6 times production of one pump. Twin 255 lph Walbros flow 380 - 400 ltrs or less. Provided fuel lines routed properly and good fittings used. It will be discussed later. Also it is not recommended to run in parallel 2 different pumps unless they have very similar characteristic flow vs. pressure

                                                                            Fuel Lines, Fittings

There are following recommendations for the delivery fuel line sizes:
up to 500hp  -6AN hose (ID = 8.6mm)
up to 800hp  -8AN hose (ID = 11.2mm)
up to 1100hp  -10AN hose (ID = 17.5mm)
Return line should be 1 size smaller
If you run popular twin Walbro setup pumps delivery side lines should be connected through the Y-merger fitting into the one bigger size line and then in engine bay big line goes into the Y-fitting and feed fuel rail from 2 sides. Never ever use banjo connections, T-fittings and similar OEM style stuff, with similar success you can install restrictor washer into your -8AN line. Twin 255 lph Walbros if ran through the T-fitting will hardly produce 300lph.

 I used -6AN lines from dual Walbros through the Y-block into the -8AN line, then in the engine bay -8AN through the Y-block into the two -6AN lines and into the fuel rail.

                                                                                        Fuel Filters


For fuel filter use either double OEM filters or better yet aftermarket high performance filter. I choose Aeromotive p/n 12301 filter with disposable 10mic fabric element. It flows 2000lb/hr at less than 1psi pressure drop. I will never need even half of that flow.
Don't use for EFI cars washable stainless mesh elements 40mic or worse 100mic filters
In fact 100mic filters belong to the suction side of the pump and used mostly for externally mounted fuel pumps as suction strainer.

     

 

                              Fuel Pressure Regulator and Fuel Rail

Most OEM FPR are qiute reliable, just don't try to modify them by fitting something like custom adjustment screw or punching the top of it to increase spring pressure. If regulator fails it can cost you a motor. Better buy reputable name adjustable pressure regulator. Only
make sure it meets your system flow requirements. I use Aeromotive 13101 adjustable FPR, it flows enough for 1000hp and as a nice touch has port where I fitted sensor of my fuel pressure gauge
Fuel rail should be at least the same size as fuel delivery line or bigger to ensure proper flow and dampening of pulsations caused by fuel injectors. ID of 7M fuel rail is 12mm AFAIR and sufficient for at least 700-800hp. Though there are some higher flowing fuel rails on the marked offered by Suprasport and Powerhouse Racing. Fuel rail has to be fed from two opposite sides, again for better flow distribution and pulsation dampening.
I did it on my motor as you can see on the picture - double -6AN feed lines and return -6AN in the middle.
Stock banjo fittings and restrictive fuel pressure dampener were scrapped and replaced by better flowing Earl fittings

                                                                                            
                                                                                   Fuel Injectors

There are two types of injectors - low impendance (peak-and-hold) injectors and high impendance (saturated) injectors. Resistance of low impendance injector coil winding is 1.5 - 2.7ohm, for high impendance injectors this figure is 10-16ohm. Low impendance injectors are more responsive and desirable for high power cars running 1000cc or higher injectors. It is easier to achieve good idle quality with them. Their biggest disadvantage is necessity to use ballast resistors and more heat generated in drivers circuit.
There are 3 main nozzle types of injectors - pintle type, disc type and ball type. Every type has it's own advantages and disadvantages. There are few injectors manufacturers on the market - Lucas, Bosch, Denso, Rochester. When you buy HKS or Blitz or Greddy injectors you pay extra $$$ for rebadged items. Neither of above tuners make their own injectors, they just stick their name on Denso or other makers products.
7MGTE uses peak-and-hold (a.k.a. low impendance) 440cc injectors. They max out at around 300whp at 85% duty cycle. Generally it is not recommended to exceed 80-85% duty cycle, injectors go static open without significant increase in fuel flow. If you see 85% or higher numbers on your datalog you definitely need bigger size injectors. To calculate injectors size for your power goal use this formula:
                                         Injector size (in cc) = Horsepower*BSFC*10.5 / no. of injectors used*0.80
(where 0.80 is maximum desirable duty cycle of 80%)
Very handy calculator can be found here
I use 780cc injectors from Titan Motorsports, they are Lucas injectors AFAIK and should be just enough for my 650hp turbo with MW50 injection