UA4C for Speeduino

(15 customer reviews)


SKU: N/A Category:


These are currently on back order. Though they have arrived on our doorstep, they will not be marked as in-stock until all back orders have been completed.

Version vC3 White Fang changes include:

-Minor component/placement adjustments
-Further increased voltage spike tolerance and reverse polarity protection
-Still assembled in the USA 🙂

Version vC2 White Fang changes include:

-Integrated stepper idle controller
-Minor component/placement adjustments
-More labeling
-Easier use of external MAP sensor
-Through-holes adjusted for easier soldering of header pins
-Critical solder jumpers now have a default setting (12v tacho, standalone, internal MAP)
-Increased voltage spike tolerance
-Still assembled in the USA 🙂

Version vB3 Sea Fox changes include:

-All boards now ship with 400kPa MAP sensors for no limit boosting 🙂
-Minor component/placement adjustments
-Further improved labeling
-Assembled in the USA

Version vB2 Sea Fox changes include:

-All SMD components including the sensors are now soldered on from the factory
-5 volt output is protected from overload
-Corrected parallel install issue
-Harness connector footprint improved to better hold the connector while soldering
-Further improved labeling
-Assembled in the USA

A new version of the UA4C (vB1 Sea Fox) is available
Changes include:

– Rearranging the serial headers for better fitment in the slim case
– Upgrading the low current outputs, they now support larger loads and are self-protecting
– Changed tachometer circuit to allow 5V, 12V, and high voltage tachometers
– Added indicator LED for 5V power, and improved labeling

The UA4C uses SMD technology to make a 4 ignition/4 injection channel board smaller, with more features, and cheaper. It is a bottom mounted Arduino MEGA shield. The MEGA is placed upside down on top of it.* This makes the total package thickness less than 20mm. All of the outputs (except for stepper idle) include an LED for quick troubleshooting during setup. An externally accessible jumper blocks resetting of the system when a USB cable is connected. Wire housings and 50 (four extra) terminals are included to connect your wiring to the PCB. Will fit in the slim or standard height Hammond case. If you include soldering service the sensors, connectors, etc will be soldered to the board. If you require special provisions you can leave a note on your order use the contact form on the help page.


– 4 ignition channels, logic 5V, 330mA max pulse
– 4 injector channels, ground switching
– 4 high current outputs (idle, idle2, boost, vvt) ground switching
– 8 low current outputs (fuel pump, tachometer, fan, fan2, aux1-4) ground switching
– Accepts DRV8825 module for stepper idle control


– 2 triggers (crank, cam, etc, logic level with socket for conditioner modules)
– MAP (250 or 400kPa) and separate barometer
– Voltage correction
– Throttle position
– Coolant and incoming air temperature
– Oxygen
– Flex fuel
– Launch
– Knock (future code update)
– 2 spare inputs


– Serial3 routed to external connector (optional CAN with future module)
– Bluetooth header with blocking diode to allow use of USB

Extra Stuff

NOTICE: This is an unofficial Speeduino board. Josh Stewart was very kind in adding a definition for this board to the Speeduino code. However, purchases of this board do not directly contribute to his upkeep and updates to the Speeduino software and website. PLEASE consider visiting Speeduino Forum and clicking Support Speeduino at the top.

*In order for the MEGA to fit the unused power jack must be removed. To do this use a pair of side cutters and cut the metal strap on the jack closest to the outside edge of the Arduino board. Then use a pair of slip-joint pliers to twist the jack back and forth while pulling it away from the PCB. It should come off fairly easily, but please take care when doing so. I will assume no responsibility for Arduino, bodily, or other harm. If you order an Arduino MEGA from me this will be done already.


These are the part numbers of official harness tools. While not eBay cheap, they are not as costly as you might think.
Hand Crimp: 10129483-001LF
Terminal Extractor: 10129274-030LF

Awesome User Created Stuff

Cool 3D printed case:


vA3- No known.
vB1- The solder jumper on the bottom for parallel installation does not work as intended. Please contact me for additional steps if you wish to install in parallel with another ECU.

Additional information

Weight 2.5 oz
Dimensions 4 × 4 × 1 in
Include Harness Connections

Yes, No

MAP Sensor

250kPa, 400kPa

Through-hole Soldered

No, Yes

15 reviews for UA4C for Speeduino

  1. cagan

    Hello, I want to buy this for my ca18det. Is it possible to use this with my engine ?
    What else do I need for speeduino setup ? Does this has Wideband in it ?

  2. Jimmy vance. (verified owner)

    Excelente ECU. Fácil de instalar, buenas prestaciones tanto para proyectos complejos como para autos de uso diario.
    Haré mi próximo pedido.
    100% satisfecho.
    Excelente atención de WEAVER.

    • Weaver

      Thank you very much Jimmy!!

  3. takenotakeo

    When using for ca18det
    What should I buy?

    o2 buys wide burn at the same time.
    Crank angle sensor is Nissan 360
    Injector is low voltage
    Audi’s plug-in coil will be used for the world coil

    • Weaver

      Whichever board you like. I would suggest a 0.4 or UA4C. Audi coils are good. You will need to swap the disc in your trigger, the 360 does not work well. Do you mean low-impedance injectors? If so you will need resistors for them if the car does not already have a separate resistor pack. I only have the Tiny WB wideband right now, which has to be soldered on. Normally I would suggest a Spartan 2, but I cannot get them right now. Otherwise I would recommend AEM UEGO which is not something I carry.

  4. Mohamad zamri

    how to register account

    • Weaver

      Sorry, accounts can only be created if an order is placed. This is to prevent bots and scammers from creating accounts.
      Thank you, Weaver

  5. Kritsada Khaokrue (verified owner)

    i kidda need additional steps because I wish to install in parallel with another ECU.
    2008 Volkswagen GTI

    • Weaver

      You will need to either not add solder to JP14 or on on vCx and higher cut the bridges on JP14 as they are jumped by default. Some OEM ECU vary the coolant bias as the engine warms to increase resolution in the operating range, if yours does this then you will likely have to install separate sensors or find a way to tune around it.
      Also if trigger signal is hall (direct digital) do not use pull-ups, if it is VR then make sure to use a MAX conditioner others will affect the signal too much.
      Thanks, Weaver

  6. Erwin

    In my opinion the best speeduino HW available at beginning of 2021.
    Only the connectors makes me not so happy….
    Wish it would be compatible to Cinch Modice case to get a real connector and even an Antenna for the wifi module I added ….
    Might be dreams come true with the Teensy verison :-).
    Thank You very much

    • Weaver

      So glad you like it!

  7. Garcia Wallace (verified owner)

    Thanks Weaver ,
    Got my new UA4C to upgrade b1 last week,
    Assembled and working great.
    Shipping was very fast & great price I love this new b3 board the marking on it makes it so much easier to follow.
    Am kinda mad because I wanted to order more map line barb for the front and DSC . I forget to ,only when the board arrived I realized I didn’t add them. Lol
    Thank you.

    • wmarkel

      I’m very glad to hear it! I know the feeling, I’m always forgetting some little thing when I order. 🙁

      Thanks! Weaver

  8. Victor Rodriguez (verified owner)

    So far an excellent board, easy to put together and quality is awesome. I did have some trouble getting the correct trigger but that was on me. Hands down to the best board available and awesome price.

    • wmarkel

      You’re too kind. Thank you, glad to hear it.

  9. Haikal (verified owner)

    when cranking the injector led not flashing.. can somebody tell me how to fix it?

    • wmarkel

      Hi Haikal,
      Sorry you are having trouble. There is no simple answer. A number of things must be correct to have it work. I will contact you directly.

  10. Jose

    At the moment the board seems to not function properly. Connected everything according to the diagram and pinouts but when I connect the board to tuner studio the map sensor becomes the tps (when I move the throttle the map readout changes). Also the map output does not seem to be represented in the sensor screen. Is there something I’m missing. Or maybe I need to open the Arduino config file to change the pins…

    • wmarkel

      Hi Jose,
      This is a classic symptom of not having the correct board type selected in Tuner Studio. Please go to Engine Constraints and check/correct your board type setting.

      Thanks, Weaver

  11. Ryan S. (verified owner)

    Great Speeduino compatible board. I’m using it for a 1980 CB750 fuel injection swap and it has all I need to run full sequential injection. I do wish the board had a few extra inputs though, I’d like to run a few more sensors for logging. More than enough outputs for a motorcycle. Only issue I really have had was getting a vacuum line connected to the MAP inside the slim case from Hammond, I had to drill a hole through the top. The hose couldn’t make the sharp turn inside the case. Wish it was 90 degree/parallel to the board and more of a hose barb style sensor.

  12. Blake Tchida (verified owner)

    Just purchased my second UA4C because the first project went so well and runs amazingly. Best speeduino based ecu out there with all the great features of a good standalone (4 ignition and injector channels, fuel pump and rad fan control, variable valve timing control, FLEX INPUT for E85, and much more!!!

    Thank you for providing such a great product at an incredible price for the performance!! Will definitely purchase another one as soon as I find a good excuse for another speeduino project lol

  13. yingste

    Great product, been running in my car for several months now. Slimmer and cheaper than the .4 and also includes a baro sensor. Almost definitely buying one again for the next project. Just wish you guys sold a premade loom/connectors with 8ft of wire since I’m bad at making nicely crimped connectors.

    • wmarkel

      Thanks so much. Sorry no harnesses here, but the nice guys over at SpeedyEFI do make them up.

  14. SMA Save Money Auto ltd (verified owner)

    Hi how are you,

    We purchase a UA4C board and cannot find no wiring diagram on Speeduino Wiki to support it can you kindly provide us with information on the wiring diagram we have a this is our second request thanks for your favorable response.

    • wmarkel

      As I have told you before, sorry if you do not receive my emails, there are no wiring diagrams specific to the UA4C. The Speeduino wiki and forum are full of diagrams on how to properly connect injectors, coils, sensors, etc to virtually any ECU. Descriptions of every pin on the UA4C including the circuit schematics can be found here:
      Thank you, Weaver

  15. DCwerx

    Without a doubt the best speeduino PCB to date. Super high quality and loaded with inputs and outputs.

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