FAQ's

What do fuel pulse dampers do?

• Fuel pulse dampers act in tandem with the fuel pressure regulator to further control the fuel pressure in an EFI system. They act to smooth out the pressure pulsations caused by the injectors opening and closing as well as the fuel pump operating. These pulsations happen so quickly that in many cases they can’t be identified with an analog gauge but can cause issues with fuel delivery to the engine.

How do you know if you need a damper?

• The fuel pulses created by the injectors opening and closing can cause local, very short, pressure swings. These swings can be made worse by high flowing injectors and low volume fuel rails. Depending on the severity of the pulses, mysterious lean spots that are difficult, if not impossible, to tune out may occur. In some cases, these lean spots can manifest as stumbling during acceleration, most commonly in the 3000 – 5000 RPM range.
• Vehicles that are plumbed with mostly hard metal tubing will be more susceptible to pulsations than ones plumbed with soft line.
• Return-less, "dead head" type systems that are regulated in, or near, the tank will be more susceptible to higher magnitude pulsations since there will be a greater time delay between the start of the pulsation and when the regulator can act to combat them.

Where do I install a damper?

• Ideally the damper should be installed as close to the source of the pulsations (i.e. the fuel rail) as possible. If your fuel rails have an available female ORB port, then a direct mount damper would be ideal. If it does not, and if space allows then you can tee a direct mount damper in by using a combination of an AN Male O-ring to O-ring Swivel and a Female O-ring Tee.
• If using a direct mount damper is not possible then an in-line damper should be used. Again, for best performance, this style damper should be mounted on the feed line as close to the fuel rails as possible. If your engine has two fuel rails, and a crossover line between them, then this would be an ideal location.
• If you do not already have a fuel pressure regulator, and plan on installing one close to the engine, then a regulator/damper combo would be an ideal choice.

Which Damper do I Need?

• There are two heights for the Holley fuel pulse dampers, short and tall; each of which correspond to a different operating pressure range. The short dampers operate in a standard base pressure range of 40 – 70 PSI, where the tall dampers operate in an extended base pressure range of 40 – 100 PSI.
• If space allows it is recommended that a tall, extended base pressure range damper be used due to its added damping ability and wider operating range. If a tall extended base pressure damper will not fit, then a short standard range damper should be used.

How many dampers do I need?

• In most cases only one damper is needed. Some special cases may require more, but they are few and far between.

Should the Dampers Be Vacuum referenced?

• If the total fuel pressure (base+boost/vacuum) will exceed, or go below, the pressure range for the damper you are using then it is mandatory that you reference the damper. Failure to do so would cause the spring to bind, or fully extend, not allowing the damper to perform its function.
• If the total fuel pressure (base+boost/vacuum) will not exceed or go below the rated pressure range, then the damper is not required to be referenced -- it is however highly recommended.