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

  1. 4x EV14 injectors
  2. 4x Bottom cushions
  3. 4x Blue top hat fuel rail adapters
  4. 4x Top hat o-rings
  5. 4x Connectors
  6. 3x Fuel rail spacers (yes, 3. FF640 only)
  7. 1x Dielectric grease
  8. 4x Fuel filters (not pictured)
  9. 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

  1. Lubricate critical seals

    • Lightly coat the blue upper O-ring and the two top-hat O-rings with dielectric grease.

  2. Fit the lower components

    • Slide the bottom cushion onto the nozzle (spray) end of the injector.

  3. 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.

  4. 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)

  1. Remove fuel rail per your shop manual. Watch for the tiny black plastic isolators on NA/NB cars—you must reuse them.

  2. Insert injectors straight into the rail. A cocked angle or dry O-ring will slice the seal and create a leak—grease prevents this.

  3. 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.

  1. Re-fit fuel rail, torque per manual, and idle-check for leaks.

  2. Perform an ECU injector-size update / re-tune as required.

5 . Troubleshooting Quick Tips (Injectors)

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 • team@goflowforce.com

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.

 



Flow Rate:

The flow rate for each injector is on the included flow rate card, it will be something near the nominal flow rate for the injector size you have. If you have lost your flow rate card, email me your serial numbers (they start with F3, F6, F7 or F9 and are engraved into the injector body) and I’ll let you know what the flow rates are.

Flow rates are measured at 3 bar (43.5psi) of fuel pressure. If your vehicle has a different fuel pressure, make sure you adjust for this! For example, a 640cc injector in an NB Miata, which has 60psi of fuel pressure, will flow at 752cc. Use the handy calculator below to convert from the average flow rate listed on your flow rate card to the flow at the fuel pressure you are running.

Flow Rate Calculator:
https://www.calconic.com/calculator-widgets/injector-flow-rate-calculator/5c38d7953d0c35001b006ad7?layouts=true

Happy boosting!


Ignition Coil Kits

FlowForce ignition coil kits replace stock NA/NB Miata coil packs with higher-output coils for better spark energy under boost or at high RPM. Two kits available: the R8 Coil Kit (Audi R8 coils) and the LS Coil Kit (D585 LS truck coils).

R8 Coil Kit

Plug-and-play kit for NA and NB Miatas. Audi R8 coils give consistent, high-energy spark with a clean, low-profile install on stock valve cover bolt holes.

What’s included

  • 4x Audi R8 coil packs
  • R8 coil bracket (mounts to valve cover bolts)
  • Wiring harness (year-specific)
  • 1990–1993 cars: requires the 1.6 patch harness (sold separately)

Compatibility

Year Engine Notes
1990–1993 1.6 (B6) Patch harness required (sold separately)
1994–1997 1.8 (BP) Direct fit
1999–2005 1.8 (BP) Direct fit

Wiring: wasted spark vs sequential

The R8 kit defaults to wasted-spark configuration, where two coils fire together per crankshaft rotation. This works on any standalone ECU with no extra wiring.

For sequential ignition (each coil fires only on its cylinder’s compression stroke) you’ll need 4 separate trigger outputs from your ECU. Most modern standalones (MS3 Pro, Haltech, Megasquirt 3) support this with the sequential add-on wires kit.

Dwell values

ECU Dwell @ 13.2V Notes
MS2 / MS3 / MS3 Pro 2.5–3.0 ms Increase 0.1 ms per volt below 13.2V
Haltech Elite/Nexus 2.5–3.0 ms Use the 4-axis dwell table for voltage correction
ME221 / ME442 2.8 ms Adjust based on RPM dwell table
Speeduino 2.5 ms Voltage-corrected automatically if enabled

LS Coil Kit

Plug-and-play kit for NA and NB Miatas. D585 LS truck coils mounted to a stainless steel bracket. Higher dwell time tolerance than R8 coils — good for high-boost builds.

What’s included

  • 4x GM D585 LS coil packs
  • LS coil bracket (stainless steel)
  • Wiring harness (wasted spark by default)
  • Plug wires (for the coil-to-plug runs)
  • 1990–1993 cars: requires the 1.6 patch harness

Wiring

Default kit is wasted-spark. Add the LS Sequential Add-on wires for sequential ignition.

Dwell values

ECU Dwell @ 13.2V
MS2 / MS3 / MS3 Pro 3.5–4.0 ms
Haltech 3.5–4.0 ms
ME221 / ME442 3.8 ms

Plug wires

FlowForce supplies plug wires with both LS and R8 kits, custom-cut for the Miata’s coil-to-plug routing.

When you need replacements

  • Visible crimp damage or arcing at the plug end
  • Misfires that follow a specific cylinder after a coil swap
  • Wire broke at the crimp during install (common; we’ll send a replacement set, no charge in the warranty window)

Spark plug recommendations

  • NGK BKR7E or BKR7EIX (NA/NB stock-displacement turbo builds)
  • Gap: 0.028″ – 0.030″ for boost; 0.032″ – 0.035″ for NA
  • Step colder for >300whp

Troubleshooting — won’t fire when cranking

If you’ve installed the coil kit and the engine cranks but won’t catch:

  1. Confirm spark visually. Pull a coil, ground it, crank — you should see a strong blue spark across the gap. If no spark on any coil, it’s a trigger / wiring issue.
  2. Check the crank sensor. A bad signal from the crank sensor will stop spark on a standalone ECU. Use your tuning software’s logging to confirm RPM is registering during cranking.
  3. Verify ignition wiring polarity. Each coil has a 12V supply, a trigger (negative), and a ground. Reversed trigger / supply prevents firing.
  4. Check the patch harness (90–93 only). If you’re on a 1.6 without the patch harness, the connector pinout won’t match — coils won’t get a clean trigger signal.
  5. Dwell too low. If dwell is set to 1.5 ms instead of 3.0 ms, you’ll see weak spark or none at idle. Bump dwell up.

Engine Swaps & Standalone ECU Compatibility

Common scenario: 1.6 → 1.8 engine swap

If you’re swapping a 1.6 NA chassis to a 1.8 BP engine, here’s what changes with respect to FlowForce parts:

  • Injector kit: the 1.8 motor uses a different fuel pressure spec (4.0 BAR vs the 1.6’s 3.0 BAR). If your kit was bought for a 1.6, flow rate effectively changes. Use the flow rate calculator above to confirm.
  • Coil kit: the R8 and LS kits are valve-cover-mounted, so they fit either engine. The 1.6 patch harness is no longer required if you’ve installed a 1.8 engine and rewired the ignition section.
  • Plug wires: length is the same. Reuse.
  • Fuel pump: if you’re going to higher horsepower, upgrade to the DW200 (covers stock through ~500whp).

Reach out to team@goflowforce.com if your swap scenario is unusual.

Standalone ECU compatibility matrix

FlowForce injectors and coil kits work with any standalone or piggyback ECU that supports independent injector and ignition control. Per-ECU notes:

ECU Notes
Megasquirt 2 (MS2) Use base dead time (13.2V) + voltage correction (offset per volt) from injector chart. No microsecond dead time table.
Megasquirt 3 / MS3 Pro Use the μs dead time table directly (firmware 1.6.xx+). Supports sequential ignition.
Haltech Elite / Nexus Use μs dead time table. Sequential and wasted spark supported.
ME221 / ME442 Use μs dead time table. Both wasted and sequential ignition supported.
Speeduino Use μs dead time. Voltage correction automatic if enabled in settings.
SquirtForce MS2-based. Use base dead time + voltage correction (not the μs table). Install-wise compatible with MS2 patterns.
Link / AEM EMS / other standalone Use whichever dead time format your ECU supports. Contact FlowForce for the data sheet if your ECU isn’t listed.

Where to find the right dead time chart

Each injector page on goflowforce.com has its dead time chart in the product images. This page also includes them in the Dead Times section above. If you’ve lost the printed chart that shipped with your kit, email team@goflowforce.com with the serial numbers (engraved into the injector body, format F3xxx / F6xxx / F7xxx / F9xxx) and we’ll send a fresh copy.

Common pre-purchase questions

Which injector size do I need?

Roughly: 380cc good for ~200hp, 640cc good for ~300–350hp, 725cc Denso ~350–400hp, 900cc good for ~450hp, 960cc good for 500+whp. These are guidelines — the final call is your tuner’s based on your specific build (fuel type, boost level, target safety margin).

What’s the difference between FF640 and FF960?

Flow rate. The FF640 is good for around 300–350hp; the FF960 supports 500+whp. The FF960 still idles cleanly thanks to flow-matching at both idle and WOT — bigger isn’t always rougher with our matched sets.

Do I need a fuel pump upgrade?

For most NA/NB builds with FF640 or smaller, the stock pump is fine. For FF725+ on a turbo build, the DW200 is the right pairing — stock-wired, no tune changes, supports up to ~500whp. We sell it as a discounted bundle option on each injector kit page.

Will FlowForce injectors fit my year?

NA/NB (1990–2005) Miatas — all our standard kits are plug-and-play. NC (2006–2015) — use the FF640-NC kit. ND2/ND3 (2019+) — use the ND2 Stage 1 kit. Other applications (non-Miata) are not officially supported.

Will the R8 or LS coil kit fit my NB?

Yes. Both kits are designed for NA and NB. The 1990–1993 1.6 patch harness is required for that year range; 1994–2005 cars use the standard kit directly.

Do I need plug wires with the R8 kit?

Plug wires are bundled with the LS kit and with the R8 kit — different routing for each, but both include the wires you need to get from coil to spark plug.

Can I use FlowForce parts with a Speeduino / Megasquirt 1 / SquirtForce?

Yes. Any standalone with independent injector and ignition control works. For dead times, use the base-and-offset values from the injector chart (not the μs table) — MS2-family ECUs (which include Speeduino and SquirtForce) need the older dead time format.

How long does shipping take?

Standard US orders ship in 1–3 business days once produced. We sometimes run behind during product launches or volume spikes — if your order is more than a week out without an update, email team@goflowforce.com and we’ll check the queue.

What’s your return policy?

30 days for unused product in original packaging. Defective products are covered under warranty (we ship replacements, no return required for plug wires / connectors). For more on returns or exchanges, email team@goflowforce.com.