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Exoracing | What is a swirl pot and how do they work?

Exoracing | What is a swirl pot and how do they work?

Posted by Kym Allen on 9th Feb 2021

What is a swirl pot and how do they work?

Before we go into detail about what a swirl pot is, we first need to understand the benefits of using one, and the best ways to go about installing one. We installed a full swirl pot system in our turbo civic a few weeks back, so if you need the see the installation visually head over to our youtube, or click this link to head straight there.

What is fuel surge (starvation)?

First off, we need to understand what fuel surge is and the negative effects it can have on your car.

The main cause of fuel surge or starvation is when a car is accelerating, braking, or cornering hard where the fuel in the tank can be shifted away from the fuel pickup. This in turn pulls air into the fuel system. When a fuel injected engine is starved of fuel, even for limited amount of time, it will at the very least slow you down by causing the engine to “splutter”, however the worst-case example of this would be damage to your engine and fuel pump, especially if this was happening on a regular basis like fast cornering on track.

If you just drive a factory standard car to work and back abiding all traffic laws, then it is likely you would never experience this. However, if you have added forced induction to a car or increased the power excessively then it might be time invest in your fuel system.

If you are running high power carburettors, then it is likely they have a big enough float chamber to compensate for fuel surge.

What is a swirl pot/surge tank?

Exoracing swirl pot

A surge tank or commonly known as a swirl pot is usually a small one or two litre pot located near the fuel tank that

acts a supporting fuel tank between your main tank and the engine.

The idea behind the name ‘swirl pot’ is because when the fuel enters the pot it is forced in at an angle that spins the fuel around the pot, the same way water goes down the bathplug.

Because the fuel is swirling around the pot it does not matter which direction the car is going or how fast it is doing it, the fuel is always being forced around the pot to them bottom where the main pump will pickup the fuel and send it to the fuel rail.

How does it work?

In a fuel system with a swirl pot the fuel is taken from the main tank via lifter pumps. This always keeps the swirl pot full of fuel. Fuel is then drawn along the system by the main pump to the fuel pressure regulator which dictates how much fuel goes into the rail and how much is returned. The swirl pot has a return feed back into the main tank that keeps the fuel in the swirl pot at the correct level, without this the swirl pot could become massively over pressured which could result in the tank bursting and leaking fuel into the car.

What are the benefits?

The main benefit of a swirl pot system is ensuring that you never encounter fuel starvation. If, however you are planning to run an aluminium fuel cell, then you are even more likely to encounter fuel starvation as they generally are not baffled, and the fuel can move around the tank very easily. If you are planning on removing the original fuel tank and replacing it with a fuel cell and swirl pot, you might also save yourself some weight in the process. A lot of older fuel tanks especially are very heavy and weigh a lot compared to modern aluminium tanks. Moving the fuel system to the boot of the car also may work in your favour for distributing weight around the car. Many cars come out of the factory front heavy, and evening this out can help with pulling some weight back and balancing the car.

Is there any reason to not run a swirl pot?

aem inline fuel pump

In some cases, a swirl pot will have the pump inside, but if it does not then you will have fit an external lifter pump and main pump somewhere inside your car. These can be very loud! If you do plan on daily driving the car in tank pumps may be the way to go.

Safety is also a thing to think about when fitting a fuel system inside your car with a fuel cell and swirl pot. Usually, the fuel system is added into the boot where there is a lot of room to fit everything that is needed. However, in the event of a being rear ended by another car (which could happen on the road or on track) it would be very possible for the fuel system to be compromised in the impact which would result in fuel inside the car with the driver. This is a massive safety risk and if you plan on doing such an install it would be wise to add a rear crash bar and a firewall to protect yourself.

Could I fit my own fuel system?

Fitting a fuel system is something that should be done with great caution. The physical installation of a fuel cell, swirl pot and pumps are straight forward where mounting holes need to be drilled then everything can be bolted in. The challenges come with getting the new fuel lines made with AN fittings ensuring that no leaks are going to occur. Fuel inside the car is very dangerous as you can probably imagine! It would be possible to use rubber hose with push on fittings, however if you are running these lines through the car there is a strong chance that they will leak fuel vapour in the cabin. Rubber hose is also delicate and can be easily damaged, it is possible to get rubber hose with a stainless steel braiding around it to protect the line.

swirl pot setup

The best option though would to be go with a Teflon (PTFE) line. With modern fuels having an increasing amount of ethanol in them, the rubber hose would perish with time if using anything with more ethanol than UK pump fuel and need replacing more often. Teflon line however is resistant to ethanol, meaning it can be used with most fuel, even race fuel, plus you do not get any fuel vapour inside the car! On each fuel line you run, both ends are going to need a fitting of some type. The safest for this application would be AN fittings. These are forced over the line and then tightened with an AN spanner ensuring a solid seal and to not damage to fitting.

If this is something you have no experience with, it is best to get a professional to help prepare the lines. When choosing what swirl pot to go with you need to consider how much fuel you are going to need. For some applications you would only need one lifter pump, which means less ports on the swirl port. For this reason, it is best to choose which pumps are going to be the best for your application. Choosing the correct fuel pump and lifter pumps is again more complicated. You would need to work out how much LPH you need (litres per hour), then match the lifter pumps to the main fuel pump to ensure even fuel delivery. After all of this has been installed the wiring still would need to be done. This is for some people the most complicated bit of all. Most fuel cells have sender units that tell you how much fuel is in the tank; these can be wired into the old fuel gauge in the car. Each pump also needs to be wired in, including the correct relays if needed.

If you are interested in building your own fuel system, we can supply everything that is needed and offer advice on choosing the right hardware for your individual needs.