The Radium Direct Mount Regulator (DMR) is a high-performance, adjustable EFI fuel pressure regulator designed for high-flow fuel systems.
Its compact design allows for installation in tight spaces while delivering the superior performance required for high-flow fuel systems.
Installation
Using the included union fitting, it can be mounted directly to an 8AN ORB port. It is primarily compatible with the 8AN ORB ports featured on Radium fuel rails.
Conversion adapters for mounting to 6AN ORB and 10AN ORB ports are also available separately.
Compatible Fuels
The RA Series fuel pressure regulator is compatible with the following fuels:
- Unleaded Gasoline
- Leaded Gasoline
- Oxygenated Fuels
- Premix Fuels
It is also compatible with the following alcohol-based fuels:
- Methanol
- Ethanol
- E85
- Other Alcohol Blends
Mounting Instructions
The regulator's main inlet port features 6AN ORB female threads.
By using the included 360° rotating double-ended adapter, it can be mounted to a fuel rail equipped with an 8AN ORB port. It is designed for easy installation onto Radium Engineering fuel rails.
Other swivel adapters are sold separately.
If not mounting directly to a fuel rail, various plumbing layouts can be achieved by installing optional adapters into the main inlet port.
The return port is 6AN ORB. The included 90° 6AN male swivel fitting rotates 360°, allowing for flexible hose routing.
Additionally, this product is equipped with two 1/8" NPT side ports to which you can attach the following options:
- Fuel Pressure Gauge
- Pressure Sensor
- Temperature Sensor
- Other 1/8" NPT Accessories
**Two 1/8" NPT plugs** are also included.
Fuel Pressure Adjustment
The RA Series allows for tool-free fuel pressure adjustment.
Lock nuts and set screws are no longer required; you can easily adjust pressure simply by turning the knob.
The design also prevents air leaks (vacuum/boost leaks) that commonly occur at threaded connections.
1:1 Vacuum Reference
The RA Series features an industry-first 360° rotating vacuum port.
The double O-ring seal ensures high airtightness while allowing the port to be oriented in any direction without tools.
Four types of vacuum fittings are included to suit various applications:
-
5mm Hose Barb
- For 4–6mm vacuum hose
-
3AN Male Fitting
- For 3AN hose ends
-
Push-Connect Fitting
- For 1/4" OD plastic tubing
-
Vacuum Plug
- For use with returnless systems or fixed fuel pressure
The use of medium-strength thread locker is recommended during installation.
Superior Fuel Pressure Stability
Optimized through years of circuit and bench testing.
The newly designed stainless steel return orifice ensures laminar fuel flow, providing stable pressure control even at high flow rates.
- Minimum pressure setting: 18.5 psi (approx. 1.3 bar)
- Maximum pressure: Dependent on fuel pump performance
※Maximum fuel pressure is determined by the fuel pump relief valve and pump controller settings.
Fuel Pressure Drop After Engine Shutdown
It is normal for fuel pressure to drop quickly after the engine or fuel pump stops, and this is normal behavior for aftermarket fuel pressure regulators.
This is because the diaphragm seat and return orifice structures are designed for high flow and may not create a perfect seal.
Please rest assured that this is not a malfunction.
Once the fuel pump restarts, pressure will return to normal promptly.
However, if you experience:
- Long cranking times at startup
- Delayed pressure buildup
the issue may lie with the fuel supply system, such as:
- Internal leak in pump module
- Faulty check valve
- Faulty venturi pump
rather than the regulator itself.
Features
- Supports high-flow EFI systems
- Tool-free adjustment
- 360° rotating vacuum port
- 360° rotating inlet adapter
- Compact design for tight spaces
- Direct mount to 8AN ORB fuel rails
- Supports remote mounting (kit sold separately)
- Two 1/8" NPT accessory ports
What's Included
- DMR regulator unit
- 5mm hose barb vacuum fitting
- Vacuum plug (for returnless)
- 1/4" push-connect vacuum fitting
- 3AN male vacuum fitting
- 6AN male 360° swivel return fitting
- 8AN ORB 360° swivel inlet adapter
- PTFE 1/8" NPT plugs ×2
Before Ordering
〇 About Import Consumption Tax
At Shafutoya, we pay the import consumption tax incurred during customs clearance on your behalf, so you will not be charged any additional fees beyond the total amount paid at checkout.
〇 Compatibility Check
Our product database is based primarily on North American (USDM) vehicles. Please verify compatibility with your Japanese (JDM) vehicle before ordering. (If you are unsure if a listed product is compatible with your vehicle, please feel free to contact us. Our support team will be happy to investigate for you.)
We cannot accept returns due to incompatibility if an order is placed without confirming compatibility first.
Please note that even if items are sorted by selecting the year, make, and model on our top page, this does not guarantee a direct "bolt-on" fit for Japanese-model vehicles.
All products have been translated into Japanese using translation software. If you encounter confusing expressions, please contact us before ordering.
〇 Regarding Shipping
Shipping costs are paid at checkout. Estimates for shipping can be calculated automatically by entering your address on the checkout page. For large items like body parts, there may occasionally be a significant discrepancy between the automatic shipping calculation and the actual shipping cost. In such cases, we will contact you individually via email.
Essentially, all products are shipped internationally from our U.S. warehouse. Unlike domestic shipping in Japan, international shipping takes approximately 7 to 14 days, so please allow sufficient time for your order. If you are in a hurry, please inquire about delivery times in advance. All products are shipped via air freight; they are not shipped by sea.
〇 Regarding Japanese Vehicle Inspection Compliance
All products we handle are designed and manufactured outside of Japan. Please note that they do not comply with "Japanese vehicle inspection standards," and we cannot provide strength evaluation documents or similar paperwork for these standards. Therefore, all parts are sold for "circuit, private property, or off-road use only." Installation and use are at your own risk.
〇 Regarding Warranty
Please inspect the contents of your order immediately upon arrival. Since all products are shipped internationally, packaging or products may occasionally sustain damage during transit. We will only provide returns, refunds, or replacements for damaged, defective, or incorrect items if notified within 7 days of receipt. Furthermore, for products sold through our store, warranty support will be handled exclusively through us. Please note that we do not provide support through other companies or agents located within Japan.