How To Choose a Honda K-Series Fuel Rail

At least once a week, we get asked, " Which K-Series fuel rail should I choose? " Because of this, I have decided to put together a list of every brand of fuel rail we deal with and compare each one.

We will compare colours, bore size, fittings, centre feed ports and much more, so read until the end to find the full comparison table!

We have 7 different fuel rail brands here, so I can guarantee you will walk away from this article having narrowed down the options to at least 1 or 2.

There are many more K-Series fuel rails on the market, but these are the most common rails we see daily.

Photo: Instagram @jdkautoworx

What Is A Fuel Rail?

A fuel rail is a hollow, usually metal tube that distributes fuel to the injectors on combustion engines.

In the specific Honda K-Series example, you will have a feed line from the factory, which brings the fuel up to the rail. The fuel pump drives this line, and the pressure is controlled via the fuel pressure regulator in the tank.

The fuel is then evenly distributed across the rail to ensure the injectors never run out of fuel and have the correct supply.

You'll find that most fuel rails are symmetrical to ensure they can evenly distribute fuel to the injectors.

Upgrading your fuel rail in a K-Series application is one of the most common modifications, and we'll explain why in the next section.

Why Should I Buy An Aftermarket Fuel Rail?

There is one massive advantage here to going with an aftermarket fuel rail.

The OEM Honda Civic EP3 or Honda Integra DC5 fuel system is return less, which means there is only one feed line going to the fuel and no return.

This is fine for OEM power, but as soon as you reach around the 300-400bhp mark, you must install a fuel return system.

As you cannot achieve this with the stock fuel rail, you must look at aftermarket options for a feed and return port.

Other important points include that aftermarket fuels are much prettier than the old scabby OEM version.

If you are going for more than 300-400bhp, we have an entire guide to walk you through building an EP3 fuel return system.

Photo: Instagram @david_goldstraw

Best K-Series Fuel Rail Brands

Now, we move on to all of the K-Series fuel rail brands. This is a hefty list with 7 different options. Still, they all offer something unique, such as a specific colour, bore size, or port.

There is something for everyone here, and you can almost guarantee most of the aftermarket fuel rails installed in the UK will include most of these brands.

I will review everything we currently know about each and add product links if you want to learn more about or purchase a specific rail.

The list is in no particular order, but it may be worth reading through each one to see the style and design elements before going to the comparison table at the end.

Hybrid Racing K-Series Fuel Rail

First on the list would be the most popular K20 fuel rail brand we sell, Hybrid Racing.

Hybrid Racing has been manufacturing some of the best K-Series parts on the market since 2001, such as their world-famous short shifters and gear knobs.

There are 2 colour options for the fuel rails here: their famous dust red or dust black, which has a beautiful satin finish.

Every Hybrid Racing fuel rail has a 1/8"NPT port for gauges or pressure sensors, a large ORB08 bore, and threads on either side to quickly adapt to any fuel line size.

If that is your thing, Hybrid Racing also offers tucked fuel lines, which hide the feed line through the central port.

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Skunk2 K-Series Fuel Rail

Next on the list is the Skunk2 composite K-Series fuel rail.

This fuel rail list is for compatibility with OEM intake manifolds, but Skunk2 also makes a specific fuel rail for the Ultra Race series of manifolds, so it would be worth going with that if you're combining with one of their manifolds.

The Skunk2 fuel rail features a 0.625" central bore, larger than the Hybrid Racing fuel rail.

Being manufactured from a carbon composite, it is 33% lighter and 60% stronger than aluminium, making it a good contender for this list.

The downside is that due to the material it is made from, it's only available in black. However, due to their design, they are also compatible with the factory fuel system, which makes this rail very versatile.

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Speedfactory Racing K-Series Fuel Rail

Next on the list is the Speedfactory Racing fuel rail, which differs significantly from the others.

Although it is machined from 6061 aluminium like the others, the design is different. It has a massive internal bore of 0.806" / 20.47mm, the biggest I know of right now.

Speedfactory says that their fuel rail can do 2000+ horsepower, the highest of any K-Series fuel rail on the market!

If you have a full-drag weapon or just like the styling, this is the perfect fuel rail!

The fact that this rail can be used with any fuel is a bonus for street or race cars, and the included ORB10 to AN06 adapters make for an easy installation with the most common fuel line sizing.

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K-Tuned K-Series Fuel Rail

K-Tuned is also a massively popular Honda brand that has been around for years. Its K-tuned fuel rail is very common to see on any build worldwide.

They offer most of the benefits of the other manufacturers, but with the most extensive colour range, which makes them a great option.

The K-Tuned fuel rail is available in black, gold, silver, blue or red to match nearly every style of engine bay.

K-Tuned also redesigned these fuel rails to be more compatible with some of the newer Civics and Rotrex supercharger applications where space became an issue.

Regarding centre bore size, they offer their fuel rails with a 0.70" / 17.9mm, which is the middle of the road compared to the rest on this list. They claim it can handle up to 1000+WHP.

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Acuity K-Series Fuel Rail

Acuity is known for always doing something different; its fuel rails are a perfect example.

Although the bore is in line with the rest, what makes them stand out are the colour finishes they have chosen.

They offer black, red, teal, and purple K-Series fuel rails, and they are the only company I know of that provides teal and purple.

If you're going with a teal or purple theme, this is 100% the option.

They always have sleek designs and beautiful satin finishes, and these rails are no different; see for yourself below!

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Radium K-Series Fuel Rail

Radium is next on the list and is best known for its fuel cell and swirl pot setups.

They now also manufacture a line of fuel rails, specifically for the Honda K-Series.

You can always tell a Radium product from a mile away because of its distinct laser etching and design elements, and its Radium fuel rail is no different!

They have a 0.69" internal bore, one of the largest on the list. They are also E85 safe and will fit OEM and aftermarket injectors.

Nuke Performance K-Series Fuel Rail

Nuke Performance is a Swedish fuelling specialist that manufactures some of the world's best fuel cell and swirl pot setups.

We've dealt with their products for several years, and the quality is outstanding, just like the Nuke Performance fuel rail.

They make a wide range, including a specific option for the Honda K-Series. In classic Nuke style, it has a gel plaque in Swedish colours!

Like many other rails on this list, they offer an OEM fit and E85 compatibility, but they uniquely use a 3/8"NPT thread at the end of the rail.

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Honda K-Series Fuel Rail Comparison Table

Now that we've reviewed the fuel rails, it's time to merge them into a single, simple table.

From here, you can easily decide which one is right for you.

While comparing fuel rails for this article, I was shocked to discover that bore sizes differ so much between manufacturers and that there isn't a standard size. However, many of them hover around the same point.

Also, as you can see below, most manufacturers use the same or similar aluminium grade, apart from Skunk2, which has broken the mould and used a carbon composite for their design.

How Do I Choose Which K-Series Fuel Rail To Buy?

There are a few factors here that will help to determine which fuel rail you should buy.

First, look at all the design choices. There is a wide range of design elements here that you might like the look of.

Secondly, the colour choices generally play a big part in your decision. Black is the most popular and common choice choice as it will fit with virtually every engine bay colour. Still, if you want to go for something different, something such as the Acuity teal fuel rail would be the best option.

Next, although it only applies once the higher horsepower bracket (over 800bhp), the bore size may be something to consider.

For example, if you were running a 1500bhp drag build, the Speedfactory fuel rail would be the best option, as it is the only rail rated for over this.

Other than the points above, the choice is mainly about what you like. There isn't a "best" or "worst" option here; they are all good quality rails, so pick the one you like most.

Photo: Instagram @flawless_culture

Frequently Asked Questions

I've compiled a list of the most commonly asked questions to answer anything I haven't already covered.

If there is anything else you want to add or know, please message us below or on our contact form, and we can help.

When should I upgrade my OEM K-Series fuel rail?

If you were looking to go with a turbocharged setup and run more than around the 400-500bhp mark, you would need to upgrade the fuel system to a return-style one.

The fuel rail wouldn't be the restriction here, as it is generally known to hold a maximum of 500-600bhp.

Upgrading the entire fuel system to a return style would be the turning point, as you would have to go with an aftermarket K-Series fuel rail regardless.

Does fuel rail bore size make a difference?

Unless you were going over 1000bhp, which fuel rail you choose should be fine in terms of power.

Even the smallest bore on the list, the Hybrid Racing fuel rail at 0.5" / 12.7mm, is still bigger than the factory bore size and should be able to flow up to 1000bhp without a problem.

The only difference in bore size that would matter here is to dampen pressure pulses from the larger injectors on the market.

How do I go about adding a fuel return system?

You need multiple parts when creating a DIY fuel return system, but we've written an article to guide you through this process and include all the required parts.

This includes every fitting you need with a rough cost estimation and links to buy everything.

Check out our how to build an ep3 fuel return system guide here.

Is a centre feed port necessary?

The short answer is no. The main advantage of using the centre port is that you can tuck your feed line and have a neater, tucked engine bay.

There is an argument that it helps to evenly disburse fuel and keep the rail fed, but I have found no evidence.

Should I install a fuel pressure gauge?

Fuel pressure gauges are convenient tools for tuning or fault finding in the fuel system.

If you are having fuel issues and the fuel pressure gauge is showing lower than expected, then you know there is an issue somewhere in the system.

Also, being able to tell what fuel pressure you are set to is very handy when trying to get the most out of your engine.

I would advise against fitting it directly to your fuel rail, even though most manufacturers offer a 1/8"Npt port on the fuel rail. The vibrations can kill the fuel pressure gauge once you go with more rigid engine mounts than stock.

Always fit them to a fuel pressure regulator mounted on the bulkhead or somewhere not directly connected to the engine mounts.

Does a fuel rail add more power?

No, an aftermarket K-Series fuel rail will not add more power, but when paired with a fuel return system, it will allow you to run more than 450-500bhp.

Will my OEM injectors fit an aftermarket fuel rail?

Yes, every fuel rail on this list will allow you to use your OEM injectors, and many of them, such as the Nuke Performance fuel rail, allow for the use of specific OEM retaining clips.

Is installing an aftermarket fuel rail a straight swap?

The only rail on this list that would directly fit the OEM system is the Skunk2 composite fuel rail. For every other rail, you must swap out fittings or adapters to fit the OEM system.

As mentioned a few times, most people will only upgrade when needed, and a fuel return system using AN lines and fittings solves the fitment issues here.

Photo: Instagram @ep3_max

Conclusion

So there we have it: my list of aftermarket K-Series fuel rails and the specifications of each one side by side.

Hopefully, this has made your decision easier when it comes to choosing and comparing each one.

For most people, myself included, it comes down to styling and which fuel rail you like the look of the most. Unless you're going for over 1000bhp, you won't see any huge performance differences.

If you're thinking of purchasing any of the fuel rails in this article, then use our specific blog reader discount code for 5% off of our website:

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And if you want to learn anything else about the ep3, or regarding fuel systems then check out some of our other previous articles below:

• How to build an EP3 fuel return system
• The ultimate K-Series clutch guide
• The best K-Series clutch for daily driving
• The ultimate EP3 engine tuning guide
• How to install Honda detent springs