Our Guide to Fuel Systems

As with building any performance vehicle or high level tuning; Fuelling is one of the key elements, get it wrong and it could lead to immense disappointment on the rollers. Alternatively, a rod could pop out of the side of the engine to say hello (Yes, this also depends on the mapping, but we’ll cover this in another article). The level of build or the power target in mind will have a steer on how advanced a fuel system you’ll require. Within this article we look to cover the components and fundamentals required to design a system for your build.  As a basic guide, we have categorised three stages of Fuel system – Below.

Up to 450HP

If you’re aiming for a punchy, but road useable power from your build, you will most likely get away with the following component upgrades. to compliment the existing OEM system. This tends to be the cheapest route as you’re utilising what’s already in place. 

  • Aftermarket In-Tank Fuel Pump
  • Aftermarket Injectors
  • Adjustable Fuel Pressure Regulator
  • Aftermarket Fuel Rail (If Required). 
  • ECU Mapping


For those looking to mix it up with big-power cars a more advanced system upgrade is required than for lower power builds. With stepping up the power the higher you go the more likely you are to implement a Motorsport based fuel system. 

  • Aftermarket In-Tank Fuel Pump
  • Aftermarket External Fuel Pump(s)
  • Adjustable Fuel Regulator
  • Aftermarket Fuel Rail
  • Aftermarket Injectors
  • Aftermarket Fuel Filter
  • Uprated Braided Lines / Fitments
  • Fuel Swirl Pot (If Required)
  • ECU Mapping

Motorsport Applications

Motorsport systems can be a whole different ball game, as for each race discipline there will be a set requirement or specification that needs to be met in order for the vehicle to race. The fuel system is less focussed on power and more at adhering to the set regulations. 

  • Aftermarket Baffled Fuel Cell
  • Aftermarket In-Tank Fuel Pump
  • Aftermarket External Fuel Pump(s)
  • Aftermarket Fuel Rail
  • Aftermarket Injectors
  • Aftermarket Fuel Filters
  • Uprated Lines / Fittings
  • Fuel Swirl Pot
  • Fuel Regulators
  • Fuel Temp Sensors
  • ECU Mapping

Fuel System Components

Aftermarket Injectors

Injectors control the amount of fuel entering the cylinder. Ever wondered what that annoying ticking noise is, coming from the top of your engine? That’s the injectors spraying fuel into the cylinder ready to combust. Injectors come in two different forms (top feed & side feed) different Top-hat sizes and injector sizes. 

The Top-hat size indicates the size of the top of the injector that mounts within fuel rail, some injectors will feature larger top hats than OEM and may require an aftermarket fuel rail to suit. The injector size relates to the amount of fuel that can pass through the injector nozzle, this is measured in ‘CC/Minute’ and is indicated by different colours (Colour/CC matrix are manufacturer specifc). 

Unfortunately selecting the correct injector size isn’t as simple as selecting a target power from a catalogue. The injector size will depend on the fuel quality used, the amount of cylinders and how the engine is powered (e.g. NA, Super-charged or Turbo-charged). To put this into perspective; Our project R32 GTR is running an RB26 with 1000cc injectors, using RON95 fuel this would happily see the injectors capable of circa 1000bhp. However, the same car using E85 would actually require 1300cc injectors to see the same sort of power. For more information and support on this, we highly advise doing your homework and speaking with tuners that specialise in your vehicle. 

It’s worth noting that by changing the injectors, your vehicle may require harness adaptors to be fitted and will most definitely require a remap of the ECU.

Aftermarket Fuel Rail

Often made from billet aluminium, a high-flow aftermarket fuel rail serves two purposes. The first being to allow a greater flow of fuel supply to the injectors, the second to accomodate aftermarket injectors where the top hat is larger than OEM. 

Nearly all aftermarket fuel rails that we have come across will require AN adaptors or fittings in order to install. The use of AN fittings is covered within a seperate article. 

Aftermarket Fuel Regulator

These allow for the adjustment of fuel pressure when using high-flow performance fuel pumps and uprated injectors; Too much pressure and you risk blowing the injector seals or force the injectors to fail by allowing fuel to pass the squirter; Too little pressure and the injectors maybe starved of fuel when the engine is under load.

Every vehicle is equiped with a regulator, but OEM tend to be fixed pressure or vacuum operated. This works well for standard power which the engine was designed for, but by tuning the engine, you are increasing the fuel system requirement.  

Aftermarket In-Tank Pump

In tank fuel pumps are direct replacements for the current OEM pump within your fuel tank. These types of pump are high flowing and can serve either as your primary fuel pump or where larger power applications are being specified, they can be used as a ‘lift’, ‘scavenge’ or ‘feed’ pump to external swirl port/fuel pump setups. 

Fuel pumps are measured using ‘Litres Per Hour’ (L/PH) or by CC/minute. Most in tank pumps range from 200 – 450 LPH and can be suitable upto 500hp on some vehicle applications, without the need for external pumps. 

Aftermarket External Fuel Pump

External fuel pumps are often used when a Motorsport fuel cell has replaced the OEM fuel tank or alternatively, with a swirl pot/lift pump combination to provide an increased flow over the use of just an in-tank pump. External pumps come in a variety of sizes and just like the in-tank pumps, are measured in L/PH or CC. The use of an external fuel pump will require aftermarket fuel filters to be installed before the pumps within the sytem design.  

Aftermarket High Flow Filter

High-flow fuel filters are required either as a direct replacement of the OEM filter or alternatively used to protect any external fuel filters from any foreign bodies that reside within the fuel tank or swirl pot. 

Similar to an OEM filter the aftermarket variants comprise  a cartridge design and require the replacement of a high flow filter element. The majority of aftermarket high-flow filters require AN fittings. 

Motorsport Fuel Cell

Cells are aftermarket fuel tanks designed to meet strict motorsport requirements. As a part of these requirements some cells are designed to be used with baffle foam. This has the benefit of reducing fuel starvation whilst under intense G force within the bends. However should the cell become damaged; The fuel will be contained within the foam like a ‘fuel sponge’ and as a result reduces the splash of fuel over the inside of the car. By using a cell, you have the ability to move it within the car to aid in weight distribution. 

Aftermarket Swirl Pot

Swirl pots are used as means to store a ‘buffer’ amount of fuel when using both a lift pump and external fuel pump. The key advantages to using a swirl pot is that it provides a means to reduce fuel starvation by isolating a portion of fuel within a cyclinder that doesnt allow for the fuel to move around. Swirl pots can come in various sizes measured mainly by their litre capacity. 

Uprated Fuel Lines / Fittings

There becomes a point when the OEM fuel lines become a restriction or bottle-neck when using high-flow high-performance fuel components. It is advisable to replace all lines with braided high pressure variants with the necessary AN fittings to suit. 

Motorsport requirements will often stipulate that uprated, high pressure, shielded lines need to be used. As seen in the title image, hardlines can be used, however these are a specialist product that require tooling.

Fuel System Design

No matter if you’re a theoretical mastermind or a wing it on the fly type of person, there are still some key basics that need to be thought about when piecing together your fuel system in order to make it work. Below we have provided a low-level overview of how a basic fuel system should look, by using this as a starter you can then advance the system as required by simply mutliplying the core components. 

Diagram A - Use of an In-Tank Fuel Pump/Swirl Pot

Components (C#)

C1 – Fuel Rail (Engine Bay)

C1A – Injectors (Engine Bay)

C2 – Fuel Pressure Regulator (Engine Bay)

C3 – External Fuel Pump (Near Tank)

C4 – Fuel Filter (Connected to Ext Pump)

C5 – Fuel Swirl Pot (Near Tank)

C6 – Fuel Tank / Cell

C6A – In-Tank Fuel Pump (If Applicable)

Optional Sensors (S)

S – Fuel Rail (Fuel Pressure)

S – Fuel Regulator (Fuel Pressure)

Flows (F#)

F1 – (High Pressure) Feed from the in-tank fuel pump to the top ports on the swirl pot. This is the feed that will take the fuel being sucked up by the pump and feeds it into the swirl pot. 

F2 – This is the lowest feed on the swirl pot that will feed fuel into the filter. The reason for the lowest port being used is that unless run dry, the fuel will always be fed into this port by gravity. 

F3 – (High Pressure) This is the feed from the external fuel pump to the Fuel Rail.  

F4 – (High PRessure) This is the feed between the Fuel Rail and the Fuel Pressure Regulator

F5 – (Low Pressure) The return feed of any unused fuel back into the Swir Pot. This will connect to one of the top ports on the Swirl Pot. 

F6 – (Low Pressure) This is the Swirl Pot over flow, should the Swirl Pot become full the excess fuel flows back into the Fuel Tank/Cell. 

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