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Aquamist HFS-4 High Flow Water Injection System Red Gauge ( Part Number:AQU 806 084RD)

Aquamist HFS-4 High Flow Water Injection System Red Gauge

Part #: AQU 806 084RD
MSRP: This Item is no longer available.



Brand: Aquamist
Attachment Method: Hardware
Display: Red
Requires Control Unit: Yes (Included)
Tank Included: No
Volts: 12v
Gauge Sending Unit: Electrical
Gauge Size: 52mm

Mfgr. Warranty: 1 Year
Condition: New Product
Return Policy:

RallySport Guarantee - 30 Days

Items that are covered under the RallySport Guarantee offer a 30 day no questions asked return policy.

RallySport Guarantee items may be returned within 30 days of the original invoice date and must include all the original parts and contents for a refund.

The RallySport Guarantee does not apply to products that have been modified, damaged, misused or abused. All returns require an RMA (Return Merchandise Authorization) Number, and freight charges are strictly non-refundable. For more information regarding our freight refund policy, please refer to our return policy page found HERE.


Introducing the Aquamist HFS-4, the newest and most capable water/alcohol injection system in the world! The HFS-4 brings never before seen features to the water alcohol injection market. Some of these features are:

•Auto sensing inputs for conventional and Direct Injection applications
•User adjustable proportioning of IDC to Boost inputs for tuning the injection curve
•New flow sensor hardware and mapping features for the best failsafe and user interface
•Added functionality for interfacing with many standalone EMS and piggy-back systems

Built on the foundation of the rock-solid HFS-3, the new HFS-4 system adds new features to make it the most advanced system Aquamist has ever produced. The most exciting new feature of the HFS-4 is the user adjustable trimming of boost and IDC inputs. This gives the user infinite adjustability of the injection curve.

In conjunction with the new boost input that can be mixed with the IDC signal, the boost input can be scaled with a link on the back of the controller. The options are 2bar, 3bar, and Absolute.

The new HFS-4 also has 3 fixed flow maps with expanded range for one through multiple jets. This expanded range ensures the HFS-4 can handle any flow rate the pump and valve combination can throw at it.

Of course the HFS-4 continues the tradition of PWM valve injection which is unmatched in the industry. The PWM injection provides unmatched control of the injection amount allowing precise mapping of the injection curve with load. The effect on the vehicles AFR are consistent in any gear and load situation providing for optimum drivability and performance.

The HFS-4 also features the best flow sensor in the world for the application, made in-house at Aquamist, capable of flowing ANY water or alcohol mixture or concentration. This unit has been produced and continually developed for over a decade and thousands of units.

Integration with standalone EMS or Piggy-back systems has never been easier. With the variable input, the system can be driven with either a PWM or 0-5V signal. The unit also has 0-5v and raw pulse outputs from the flow sensor for feedback to the control system.
This product has no user uploaded media. You can upload your photo or video of your install by posting a review. Reviews:

  • Q: HFS3 vs HFS 4  KornShaDoW097 3 years ago


    I have a 04 WRX, currently have a shorted out HFS 3v2. I am not DI but am heavily modded. Is there a reason to buy the HFS 4 over the new HFS3v3? Besides the ability to more finely adjust FIDC vs MAP for flow (HFS 3 has a limited version of this behind the board). How does this unit "auto sense" fueling? so I don't need to wire it to the ECU?,,,

    • A: The HFS4 is not needed for your car as it is not DI. We recommend the HFS3v3 for your car. The wiring will be identical on the HFS3v3 compared to your v2.

      Josh P. 3 years ago
  • Q: HFS4 the newest  duroedie26173 4 years ago


    Why in forums are speaking about HFS6 system a you said this is the newest? Please explain, thanks.

    • A: HFS6 is the old system that was discontinued. A higher number does not correlate a newest model

      Kirill C. 4 years ago
  • Q: complete kit  quincy 5 years ago


    other then the tank, is this complete kit ready to use?

    • A: Although universal and install varies greatly to greatly, this kit generally has everything required to install besides the tank.

      Nick S. 5 years ago
  • Q: Comparison  quincy 5 years ago


    How does this compared to the AEM water/meth other then the including the tank? Which one is better?

    • A: Aquamist uses a pulse width modulation pump for better atomization, both pressure and flow sensors, user adjustable proportioning of IDC to boost inputs, direct injection input and proportioning adjustment and advanced failsafe monitoring.

      Zach G. 5 years ago
  • Q: Housing and tank  Sharaf 5 years ago


    Guys, can RSD provide the Twin tank housing for this kit?

    • A: At this current time we do not have any twin tank housings available specific to this kit

      Kirill C. 5 years ago