Will it fit your RX-8?
This unit is built for the first-generation RX-8 only, and a couple of limits matter before you order. Check your car against this list:
| Item | Supported |
|---|---|
| Model years | Series 1, 2003 to 2008 |
| Engines | 13B-MSP Renesis 6-port (Australian, US, Japanese and European market cars) and the Japanese-market 13B 4-port |
| Transmission | Manual only |
| ABS/DSC module | CAN-based modules only. K-line ABS units are not supported |
If you have an automatic or a later Series 2 car, this isn't the right ECU. Talk to us and we'll point you at an option that suits your build.
What comes with it, and what we'd add
In the box you get the Nexus RX-8 Plug-in ECU, mounting brackets and hardware, a USB-C cable, a quick start guide, and a short expansion harness that carries an air temperature plug and a wideband plug. Haltech also includes an 1/8 NPT air temperature sensor with an aluminum weld-on fitting, plus about 8 ft (2.5 m) of vacuum hose and a T-piece for the onboard MAP sensor.
Two add-ons come up on almost every RX-8 we do:
- A wideband sensor. The factory front O2 sensor can't be used (more on that below), so you need the LSU 4.9 Wideband Hardware Pack or the NTK pack. The ECU has its own wideband controller, so the sensor plugs straight into the expansion harness.
- The larger IO harness. The Nexus Plug-in IO Expansion Harness adds ready-made plugs for a flex fuel sensor, fuel and oil pressure sensors, air temperature and a wideband, plus spare pins for extra outputs such as a boost solenoid.
Before it goes in the car: NSP and the setup wizard
Tuning is done in Haltech's NSP software, which runs on Windows. Grab the installer from Haltech's downloads area, run the setup wizard, and open NSP from the Start menu or the desktop shortcut.
Do the first configuration on the bench. Plug the USB-C cable into the front of the ECU and NSP will find it and wake it in low power mode. In that state every input and output is switched off, so nothing can fire while you load a map or build one with the wizard.
The wizard walks you through the whole RX-8 setup in order:
- Name the vehicle. NSP creates a folder on your laptop with that name for maps and logs. Add a description too; it makes it much easier to tell map versions apart later.
- Pick the model and engine from the list of 2003 to 2008 RX-8 variants.
- Choose the auxiliary harness you're running, so the ECU knows which pins your wideband and extra sensors are on.
- Set the engine options: 4-port or 6-port, the porting profile, and injector data for each injection stage.
- Review the summary and correct anything before you finish.
The result is a base tune that should start and run the engine. It is not a finished tune. Plan on proper tuning afterward, and never power the ECU in the car until either the wizard has been completed or a correct map has been loaded.
RX-8 specific things to check
| Area | What you need to know | Our advice |
|---|---|---|
| Drive-by-wire | The throttle body and pedal must be calibrated in NSP before the first start | Do it with the engine off and watch both sensors track smoothly across the full pedal travel |
| MAP sensing | The ECU ignores the factory air flow meter signal and uses its onboard MAP sensor | Tee the supplied hose into the vacuum line that feeds the VDI and SSV solenoids under the intake manifold |
| Air temperature | You can keep the sensor built into the MAF housing or fit the supplied Haltech sensor | If you're going turbo, move to the Haltech sensor after the intercooler |
| Wideband | The factory 4-wire front sensor is not supported | Fit a Bosch LSU 4.9 or NTK sensor through the auxiliary connector |
| Forced induction | Boost control and similar functions use outputs on the auxiliary connector | Set up boost control only once the supporting mods are in place |
ABS light, dead speedo or no odometer
The ECU talks to the ABS/DSC module over CAN, and it currently knows the Australian, US, Japanese and two European addressing schemes. If your module isn't matched, you might see the ABS light on, ABS disabled, and the speedometer and odometer stop working, in any combination.
The fix is usually a setting. In NSP go to Connections > CAN > Vehicle CAN System and work through the Vehicle CAN Market options one at a time. After each change, switch the car fully off, start it again and actually drive it so the module can see road speed. Only then decide whether that option worked. See our vehicle CAN system notes for more on how this bus is used.
Hold the DSC OFF button for several seconds before the car goes on the rollers, and confirm the DSC OFF light is showing in the cluster. Press it again afterward to bring stability control back.
Wiring into the auxiliary connector
The 26-pin auxiliary connector is where anything the RX-8 never had from the factory gets wired in: extra sensors, a flex fuel sensor, or custom outputs you define in NSP. The supplied expansion harness plugs into it and can be routed through the engine bay, and it comes with spare pins for your own additions.
To add a pin to the connector, release the bottom locking tabs, push the terminal in from the wire side, then press the top tabs to lock it.
The three switched 12V pins across the CAN and auxiliary connectors share a total of 8A. Add up everything you hang off them before you wire in extra devices.
A few pinout details are worth knowing when you trace wires: pins not listed in the pinout aren't used, some injector functions swap internally depending on whether the wizard was set for 6-port or 4-port staging, and DPO 9 to 23 are fixed functions that can't be reassigned. The 4-port loom has no connector 3, but those ECU pins still work as spare I/O. Need the pinout drawing? Ask us and we'll send it over with advice for your build.
Installing the ECU
The factory ECU lives in a sealed box in the engine bay near the right headlight, with an air duct feeding it cool air from beside the radiator. The swap goes like this:
- Take off the battery cover for access, then remove the three screws on the enclosure lid and unclip it.
- Unplug the factory ECU, remove the three 10 mm bolts on its bracket, and lift the ECU, brackets and air duct out together.
- Split the duct, set the factory ECU aside, and put the lower half of the duct back in the box.
- Fit the Nexus ECU with the supplied brackets.
- Connect the factory plugs, the MAP vacuum hose and the auxiliary harness, then run the setup wizard if you haven't already.
- Leave the upper duct and lid off until the car starts and every added sensor reads correctly. Then close it up.
To get the hose and harness out of the box, you can cut a small half-round notch near the rubber seal at the back of the lid. Make sure the vacuum hose isn't pinched, because a crushed hose gives the ECU a bad MAP reading, and seal the notch with silicone.
Connecting by Wi-Fi and phone
Once it's set up over USB, you can turn on the internal Wi-Fi so you don't need a cable:
- Connect by USB and open Connections in the navigation tree. Enable the Wi-Fi module.
- Under the Wi-Fi item, set an SSID (at least 1 character) and a password (at least 8 characters), then click Apply.
- Turn the ignition on so the ECU is on main power, and join that network from your laptop.
Wi-Fi only works when the ECU is on main power, not USB power. Two laptops can connect over Wi-Fi at the same time as one on USB. When the module is disabled it is fully off. The free Haltech Connect app for Android and iOS uses the same link to show live data, simple gauges, clear trouble codes, assign wiring and change some settings from your phone.
Adding dashes and keypads
There's also an onboard CAN connector for the Haltech CAN system. Add a CAN hub and you can run several devices together, such as a uC-10 dash, a CAN keypad for switching screens or ECU functions, or a Nexus IO16 if you run out of inputs and outputs.
RX-8 Plug-in ECU FAQ
Can I keep my factory wideband sensor?
No. The stock 4-wire front sensor isn't supported. Fit an LSU 4.9 or NTK sensor through the auxiliary connector and the onboard controller runs it.
Does it work with an automatic RX-8?
No, it supports manual transmission cars only.
Will the base map be enough to drive on?
It's meant to get the engine running so it can be tuned. Rotaries are unforgiving, so have it tuned properly before you lean on it. Our free 30-minute consultation is a good place to plan that, and the Honda EP3/DC5 and GM Delco plug-in guides cover the same Nexus workflow on other platforms.
