Injector Instructions

Thanks for buying a set of Flow Force Injectors! There are only a few things that stand between you and the power and performance of EV14 awesomeness. If any of these steps are confusing, or if you run into issues, please email me at team at goflowforce dot com so I can help, and so I can improve this documentation for others.

If you are the type to wait for the movie to come out rather than reading the book, some customers have created some top-notch videos on youtube. Check out the videos by supercarmio, OGPedXing, and Beavis Motorsport. If you see any other great videos, or if you made one yourself please let me know so I can add it to this list.

Assembly

The following are instructions for a 640cc kit for a 1990-2005 Mazda Miata. Other kits are largely similar.

What's included

4x EV14 injectors
4x Bottom cushions
4x Blue top hat fuel rail adapters
4x Top hat o-rings
4x Connectors
3x Fuel rail spacers (yes, 3. FF640 only)
1x Dielectric grease
4x Fuel filters (not pictured)
4x Grey bottom cup adapters (FF740, FF900, and FF960 only)

1 . Kit Contents

Qty	Part	Notes
1	Injector, pre-flowed & coded	Size varies by kit (380 cc, 640 cc-NC, 725 cc – Denso, 740 cc, 900 cc, 960 cc)
1	Bottom cushion (rubber “donut”)	Not supplied in NC kits
1	Top-hat (aluminum spacer)	Grey on tip, blue on top (except 640 cc-NC)
2 – 4	O-rings	Extra set included for 380 cc kits (easy to pinch)
1	Plastic fuel filter “basket”	Pre-installed on 380 cc kit
—	Cup adapters & rail spacers	See size-specific notes below
—	Adapter harnesses	Not required for 725 cc Flyin’ Miata injectors (Denso connector)

2 . Pre-Assembly Steps

Lubricate critical seals
- Lightly coat the blue upper O-ring and the two top-hat O-rings with dielectric grease.
Fit the lower components
- Slide the bottom cushion onto the nozzle (spray) end of the injector.
Prepare the top-hat
- Seat a lubricated O-ring into the machined groove on the top-hat.
- Drop the fuel filter basket-side first into the bore; the internal taper will hold it in place.
Fit the top-hat
- Slide the top-hat over the electrical end of the injector until fully seated.

At this point, the injector’s overall height should match the OE unit. If it doesn’t, re-check each step.

3 . Size-Specific Notes

Kit	Connector / Adapter	Special Parts
380 cc	Bosch EV14	Filter pre-installed; two full sets of O-rings; spacers supplied.
725 cc – Denso	Direct plug-in (no adapter harnesses)	Follow standard assembly.
740 / 900 / 960 cc	Grey cup adapter on tip, blue cup on top	Bottom cushion installs on grey cup; no fuel-rail spacers.
640 cc-NC	Denso NC style	No bottom cushions or electrical connectors; grey cup uses a green O-ring.

4 . Installation (Vehicle)

Remove fuel rail per your shop manual. Watch for the tiny black plastic isolators on NA/NB cars—you must reuse them.
Insert injectors straight into the rail. A cocked angle or dry O-ring will slice the seal and create a leak—grease prevents this.
Clean and prep connectors (especially on high-mileage cars):

Flush female terminals with contact cleaner or gently scrape with a suitable pick.
Apply a pea-sized smear of dielectric grease inside each cavity before reconnecting.
725 cc kits: use the existing Denso plugs—no adapter harnesses needed.

Re-fit fuel rail, torque per manual, and idle-check for leaks.
Perform an ECU injector-size update / re-tune as required.

5 . Troubleshooting Quick Tips

Symptom	Likely Cause	Fix
Fuel leak at rail	Pinched upper O-ring	Remove, inspect, replace (spares in 380 cc kit)
Rough idle after swap	Connector corrosion	Repeat cleaning + dielectric grease
Injector sits high	Missing bottom cushion or cup adapter	Confirm size-specific parts list

Questions?
Flow Force Tech Support • support@goflowforce.com
Flyin’ Miata Customer Support • (970) 464-5600

Document rev. 2025-07-10 – incorporates clarification that Flyin’ Miata 725 cc Denso injectors do not ship with, or require, adapter harnesses.

A programmable or standalone ECU such as Megasquirt (MS2/MS3), Haltech, AEM EMS, or ME221/ME442 is required to run these injectors. Tuning injectors correctly is critical to drivability, so we strongly recommend having an experienced tuner handle this setup. If you’re confident in your tuning abilities—read on.

Simply adjusting required fuel and dead time values is not enough to make the car run well. If you’re upgrading from stock Miata injectors or similar, your entire fuel table must be re-tuned. This is because EV14 injectors use a completely different internal design, and their flow characteristics vary non-linearly across different pulse widths. It's not just that 640cc injectors flow ~3x more—they also behave very differently at low duty cycles and transient conditions. Be prepared to fully retune your VE/fuel table from scratch.

Dead Times

MS2 users should use only the base dead time (at 13.2V) and the voltage correction (offset per volt) directly from the chart.

MS3 users, Haltech ECUs, and ME221/ME442 (ME2x) systems running modern dead time models (e.g., Megasquirt 1.6.xx firmware) should instead use the calculated dead time in microseconds (µs), derived from the injector’s voltage offset percentage using the following formula:

Dead Time (µs) = Base Dead Time × (Voltage Offset % / 100)

Each injector chart (e.g., FF380, FF640, FF725, etc.) includes both:

The base dead time at 13.2V
The voltage offset %
And the calculated µs dead time per voltage level (11V–16V)

Use these µs values directly in your dead time table if you're using:

MS3 (with firmware 1.6.xx or later)
Haltech Elite/Nexus
ME221 / ME442 (ME2x)
Any ECU that supports voltage-based dead time mapping

Fuel Pressure Reference

Unless your fuel system is modified:

1990–1997 NA Miata's use 3.0 BAR fuel pressure
1999–2015 NB/NC Miata's use 4.0 BAR fuel pressure

Be sure to reference the correct column (3.0 BAR or 4.0 BAR) in your injector chart.

Happy boosting!