For many years Radium has been touting the benefits of a fuel pulse damper (FPD) in fuel injected systems. Formerly only seen on OEM fuel systems, Radium Engineering is the first to introduce the FPD to the high- performance aftermarket.
OEM-grade fuel pulse dampers are specifically designed for the factory fuel system. When modifications are made to the fuel pump, fuel rails, injectors, etc. these dampers are no longer as effective, or they must be removed for modifications.  Radium Engineering fuel pulse dampers are designed for use with high performance fuel systems, so damper benefits can be realized.
An OEM fuel rail with pulse damper

What does a fuel pulse damper do?

An FPD is used in fuel injection systems to attenuate (absorb) pressure pulsations generated by the fuel pump operating and by the injectors opening/closing.
These hydraulic pulses can cause an undesirable noise, which can be transmitted to the passenger compartment.  Under certain circumstances, they can also cause issues with fuel delivery to the engine. These pulsations can be large enough to hear and feel, but are often undetectable with a liquid-filled analog mechanical fuel pressure gauge because they happen so quickly. The fuel pulse damper works by allowing the volume of the fuel system to change slightly to absorb the pulses. This is done with a spring loaded flexible diaphragm inside the damper. 

Below is a graph showing fuel pressure fluctuations on a 4-cylinder engine, with and without a Radium fuel pulse damper installed.

Most OEMs will utilize some method to attenuate the pressure pulsations.  Manufacturers never prefer to add cost to a vehicle. In some cases, instead of a fuel pulse damper, you may find some other methods employed to attenuate the noise. These measures can include rectangular cross-section fuel rails with a carefully tuned width and height, strategic location of the fuel pressure regulator, fuel lines mounted to the body using vibration isolating mounts, etc. For some OEMs, the noise is not an issue and there are no negative effects on fuel delivery, so no measure is taken to address fuel pulsations.

An OEM fuel pulse damper on the return line inside the fuel tank

How do I know if I need a Pulse Damper?

As mentioned earlier, fuel system pulsations can have an undesirable effect on cabin NVH (noise vibration and harshness) by causing fuel line "knocking". They can also contribute to uneven fuel delivery, and mysterious lean spots that are difficult to tune out. These are often the result of the hydraulic pulses acting in harmonic resonance with the injectors opening and closing. This issue can be aggravated by high-flowing aftermarket injectors. In some vehicles, these lean spots can result in stumbling during acceleration, commonly occuring in the 3k-5k RPM range. If you are experiencing any of these issues, a damper could be a good solution.
Furthermore, a fuel system that is plumbed with mostly hard metal tubing will be more susceptible to knocking and pulse issues than a system with a combination of hard tubing and flexible rubber hose.
A dead-end fuel system, with the pressure regulating happening in the fuel tank, may be more prone to fuel line noise and a damper near the fuel rail should be considered.
High-frequency fuel pressure data logging is the best way to see fuel pulses and the impact a damper can have.

Most tuners are not concerned with the noise, but rather with the performance and seek constant, reliable fuel delivery throughout the RPM range in order to optimize the EFI tuning.
If everything is running great, and fuel delivery is spot-on and there is no fuel line knocking noises, then a damper would not provide any benefit to the system. 
A damper IS NOT a magical "cure-all" for any fuel system problem or tuning issue!

Nissan SR20VE Fuel Rail with Radium fuel pulse damper installed in an auxilary port.

Which Damper do I need?
When it comes time to selecting a Radium fuel pulse damper, there are two decision that have to be made: tall or short version and connection type.
Choosing between FPD-XR(tall) and FPD-R(short) is done based on fuel pressure, so it is imperative that the static (base) and maximum fuel pressures are known. Use the guide on the PRODUCT PAGE to select the damper to use. Also make sure you check for room where you plan to mount the damper, as the FPD-XR is quite a bit taller than the FPD-R version.
If fuel pressure and available space allows either damper to be used, Radium recommends the FPD-XR due to it's wider response range.
Connection type will depend on how the damper will be plumbed into the system. Choose a direct mount of the fuel rail has an available (and compatible) threaded port. Choose the in-line version if mounting directly on the fuel rail is not possible.

Where do I install a damper?
It is preferred to mount a damper close to the source of the pulsations as possible. This usually means mounting a damper directly on the fuel rail. If your fuel rail has an available female 8AN ORB or 3/8 NPT port, then you can use a direct mount damper, FOUND HERE.  What is an ORB port? CLICK HERE

Radium Direct-Mount pulse dampers mounted on fuel rails

If the fuel rail does NOT have a compatible port, then an in-line damper should be used, FOUND HERE. The inline damper should be located on the fuel feed line, within the vicinity of the fuel rail, but exact placement is not critical.
If an engine has two fuel rails (V8, V6, H4, etc) it is not always necessary to install a damper on each rail. However, testing will have to be done to verify. In most cases a single damper is sufficient.

In-Line Fuel Pulse Damper

Can I use adapter fittings to fit a Radium fuel pulse damper?
If a fuel rail does not have a compatible port, adapter fittings can be used without sacrificing the function of the pulse damper.

How many dampers do I need?
In most cases, just one. However, special cases may require more. This will take experimenting, as each fuel system is different and pulse damping is complex and not intuitive. For example, OEMs may place a damper near the fuel pump outlet, multiple on the fuel rail(s), and even on the return line in order to make sure that the system is as pulse-free as possible. This is not entirely necessary on a modified high-performance vehicle, as the needs of a performance car are different than a mass produced passenger car. 
If an engine has two fuel rails (V8, V6, H4, etc) it is not always necessary to install a damper on each rail. However, testing will have to be done to verify. In most cases a single damper is sufficient. 

What about the vacuum reference port on the Radium Dampers?
Most boosted engines use a pressure referenced regulator where fuel pressure rises or decreases in a 1:1 ratio as manifold pressure changes. To learn more about pressure referencing and why it is used, CLICK HERE.
If the fuel damper is tuned from the factory for a specific single fuel pressure, then it becomes ineffective as fuel pressure rises outside of the normal range. To address this issue, Radium Engineering has designed the first aftermarket vacuum referenced fuel pulse damper.
A reference line to the intake manifold should be hooked up only if the base + boost pressure exceeds the maximum pressure rating of the damper. This prevents the diaphragm and spring from becoming "pinned" from high pressure, which would make the damper inactive.
Reference the FPD install instructions for more details.

This new FPD design maintains full damping function throughout the range of pressures seen in the fuel system of a boosted engine with a 1:1 vacuum referenced regulator.


We are introducing a pair of new universal direct-mount fuel pulse dampers, the FPD-R and FPD-XR. Each unit comes with different thread options: 3/8NPT or 8AN ORB. These can be mounted to a fuel rail port that has the proper mating female threads. Check your fuel rail for compatibility.

For situations that do not allow mounting of the damper directly to the fuel rail, Radium has also released a version of the dampers for mounting in-line with the fuel delivery line near the fuel rail. The body of the damper features 8AN ORB female ports (3/4-16 O-ring) which accept a wide variety of common adapter fittings. 

FPD-R In-Line version

FPD-XR In-Line version. Available with different -AN adapter fittings. 

Which one do I need, FPD-R or FPD-XR?
The smaller FPD-R is a compact version designed to fit into tight spaces. The only compromise being that it is calibrated for use with 40 to 70 psi base (static) fuel pressure only. If your base fuel pressure is higher than 70 psi, then the larger FPD-XR should be used, which permits base pressures between 40 and 120 psi. More details HERE on the product page.
**Download the installation instructions on the product pages to learn more about measuring base fuel pressure.**

It is imperative that the correct damper is chosen. Email if assistance is needed.

Important note for boosted applications: In order for the FPD to work properly, it must be pressure referenced to the intake manifold, preferably from the same vacuum line that the fuel pressure regulator uses. If the fuel pressure regulator on the engine is NOT vacuum referenced, then do not hook up the vacuum referencing on the FPD. 

Fuel Pulse Dampers are available now through and any Radium Engineering Authorized Dealer.