Short answer: Autosports Engineering stocks Haltech's full Plug 'n' Play ECU lineup for a range of platforms — Toyota Supra JZA80, Honda B-series/DC5/EP3/S2000, Mazda RX7 FD, Ford Falcon Barra, and GM LS swaps via the Rebel LS — plus Haltech's racing-grade Nexus R3/R5 standalone VCUs. The confusing part for most builders isn't which platform kit to buy, it's which ECU tier actually fits their engine and goals — and cylinder count alone doesn't tell the whole story. This guide breaks down real I/O specs and, just as important, which functions (drive-by-wire, flex fuel, wideband) are genuinely independent versus which ones eat into your general input/output count.
Which Haltech ECU tier is right for you?
| ECU / VCU | Engine support | Injector / ignition outputs | Onboard wideband? | Typical price |
|---|---|---|---|---|
| Nexus S2 | Up to 4-cyl / 2-rotor | 4 / 4 | Yes, 1 channel | ~$2,365 |
| Nexus S3 | Up to 8-cyl | 8 / 8 | Yes, 1 channel | ~$2,800 |
| Elite 1500 | 1–12-cyl / 2-rotor (via CAN expansion) | 4 / 4 native | No — external CAN kit required | ~$2,120 w/ harness |
| Elite 2500 | 1–12-cyl / 4-rotor | 8 / 8 native | No — external CAN kit required | ~$2,490–$2,772 w/ harness |
| Rebel LS | GM LS platform only (turnkey) | Full LS-specific harness kit included | Yes (sensor pack included) | ~$1,695 ECU |
| Nexus R3 VCU | Up to 8-cyl / 4-rotor | 8 / 8 | Yes, 1 channel | ~$2,585 |
| Nexus R5 VCU | Up to 12-cyl / 6-rotor | 18 / 12 | Yes, 2 channels | ~$4,415 |
Full I/O comparison — analog, digital, and pulsed
Cylinder count is only part of the picture. Here's the complete input/output breakdown for each model, since this is what actually determines how many sensors, solenoids, and accessories you can run without needing CAN expansion hardware:
| ECU / VCU | Analog inputs (0-5V) | Sync pulsed inputs | Low-side DPOs | Push-pull / DBW-capable outputs | CAN ports |
|---|---|---|---|---|---|
| Nexus S2 | 11 | 6 | 6 | 4 (8A, PWM) | 2 |
| Nexus S3 | 11 | 6 | 6 | 4 (8A, PWM) | 2 |
| Elite 1500 | 10 | 4 | 12 digital outputs (combined) | Shares general I/O — no dedicated bank | Up to 45 channels via CAN expansion |
| Elite 2500 | 10 | 4 | 12 digital outputs (combined) | Shares general I/O — no dedicated bank | Up to 45 channels via CAN expansion |
| Nexus R3 VCU | 11 | 6 | 6 | 6 (8A, PWM) | 2 |
| Nexus R5 VCU | 23 | 10 | 8 | 4 (8A, PWM) | 3 |
Note: the S2 and S3 share identical general I/O counts — the only difference between them is injector/ignition driver count (4/4 vs. 8/8). Rebel LS is built as a turnkey GM LS harness system rather than a raw I/O platform, so it isn't directly comparable on this table — confirm exact I/O with Haltech's spec sheet if you're planning heavy accessory integration on an LS swap.
Independent functions: what's actually dedicated vs. what eats your I/O
This is the part that trips people up. A few marquee features sound "built-in," but whether they draw from your general input/output pool depends on the ECU tier. Confirmed directly against Haltech's own published specifications:
Drive-by-wire (DBW)
- Nexus (S2/S3/R3/R5): Supports up to 2 independent DBW throttle bodies per Haltech's official spec sheet. Motor control runs off the dedicated push-pull/half-bridge output bank (4 outputs on S2/S3/R5, 6 on R3) — purpose-built for electronic throttle, not shared with your low-side DPOs. Throttle position feedback sensors (TPS) still draw from the shared analog input pool — typically 2 of your 11 (or 23 on R5) analog inputs, with built-in redundancy support.
- Elite (1500/2500): DBW is explicitly listed as requiring 2 user-defined outputs and 4 user-defined inputs from the general pool — meaning it directly reduces how many I/O channels you have left for other sensors and accessories. Budget for this when planning an Elite-based DBW conversion.
Built-in wideband O2
- Nexus (S2/S3/R3): 1 onboard wideband controller (supports NTK and LSU4.9 sensors) — fully independent, doesn't consume an analog input or CAN channel.
- Nexus R5: 2 onboard wideband controllers — same independence, doubled for dual-bank tuning.
- Elite (1500/2500): No onboard wideband. Closed-loop O2 control requires an external CAN-connected wideband controller kit (sold separately), which uses one of your CAN expansion channels rather than an analog input — an additional purchase and setup step the Nexus range doesn't need.
Flex fuel
- Confirmed on both Nexus S2 and Nexus S3 — flex fuel is a listed "YES" feature on Haltech's official Nexus S2/S3 specification sheet, not a functionality gap between the two tiers.
- How it connects: per Haltech's own documentation on the shared Nexus platform architecture, flex fuel sensors are frequency-type devices that connect through one of the synchronized pulsed inputs (SPIs) — the same input bank used for cam/speed sensors — rather than a fully separate dedicated channel. That means it counts against your 6 available SPIs on S2/S3/R3 (10 on R5), alongside cam sensors and anything else frequency-based you're running.
- Elite (1500/2500): Same mechanism — flex fuel uses a direct sensor input from the shared 4-input SPI bank, so it counts against a smaller pool than the Nexus range offers.
Platform Plug 'n' Play kits ASE stocks
Nexus S3 — Supra JZA80
Nexus S2 — Honda OBD-I
| Platform | ECU options | Starting price | Shop |
|---|---|---|---|
| Toyota Supra JZA80 (2JZ non-VVTi, manual) | Nexus S3 only | $2,800 | View kit |
| Honda OBD-I B-series (Civic/Integra/Prelude 92-95, Accord 90-95) | Nexus S2, Nexus S3, or Elite 1500 | $2,120–$2,800 | View kit |
| Honda Integra DC5 / Acura RSX (05-06) | Nexus S2, Nexus S3, or Elite 1500 | $2,120–$2,800 | View kit |
| Honda Civic EP3 (02-05) | Nexus S2, Nexus S3, or Elite 1500 | $2,120–$2,800 | View kit |
| Honda S2000 AP1/AP2 (non-DBW) | Nexus S2, Nexus S3, or Elite 1500 | $2,120–$2,800 | View kit |
| Mazda RX7 FD3S-S6 (92-95) | Nexus S2, Nexus S3, or Elite 1500 | $2,120–$2,800 | View kit |
| Mazda RX7 FD3S-S7&8 (96-02) | Nexus S3 or Elite 1500 | $2,120–$2,800 | View kit |
| Ford Falcon BA/BF/FG (Barra I6) | Elite 2500 (terminated harness) | $2,712–$2,772 | View kit |
| GM LS swap (Gen III/IV, cable or DBW throttle) | Rebel LS (turnkey harness system) | from $1,695 | View kit |
Not seeing your exact platform? Reach out — Haltech's PnP catalog covers more vehicles than we can list here, and we can source what you need.
Don't need the ECU? Harness-only options
If you already own a Haltech Nexus S2/S3 ECU (from a previous build, for example) and just need the vehicle-specific adapter harness, standalone harnesses are available separately — typically $535, versus $2,120+ for the full ECU + harness kit.
Rebel LS: what's actually in the box
Rebel LS ECU (Gen III / Gen IV)
The Rebel LS base kit includes the ECU, main harness, cable-throttle + IAC sub-harness, LS EV1 injector sub-harness, T56 transmission harness, three alternator harness options (Bosch/Delco/Yazaki), a knock sensor adapter, and a full wideband sensor pack (Bosch LSU 4.9 sensor + weld-on bung). Depending on your specific LS variant — EV1 vs. EV6 injectors, cable vs. DBW throttle, Gen III vs. Gen IV — you may need a different sub-harness than what's bundled; those are sold separately for exactly this reason.
Racing-grade: Nexus R3 & R5 VCUs
Nexus R3 VCU
Nexus R5 VCU (flagship)
Common questions
What's the real difference between Nexus S2 and S3?
Output count. The S2 has 4 injector drivers and 4 ignition outputs — enough for a 4-cylinder or 2-rotor engine. The S3 doubles that to 8 and 8, which is why it's the only option offered for the 2JZ-powered Supra (an inline-6 needs more outputs than the S2 provides). General I/O — analog inputs, pulsed inputs, DPOs, DBW outputs — is identical between the two; only the injector/ignition driver count changes.
Should I get a Nexus tier or an Elite tier ECU?
The main practical difference is the onboard wideband controller and integrated WiFi/datalogging — Nexus (S2/S3/R3/R5) has these built in; Elite (1500/2500) doesn't, and needs an external CAN wideband controller kit if you want closed-loop O2 control. DBW also behaves differently: Nexus has a dedicated push-pull output bank for it (supporting up to 2 independent throttle bodies), while Elite's DBW draws 2 outputs and 4 inputs directly from your general I/O pool. If you're deciding between comparable tiers, Nexus is generally the more complete package unless you have a specific reason to prefer Elite.
Does drive-by-wire use up my other inputs and outputs?
On Nexus ECUs, the DBW motor itself runs off a dedicated push-pull output bank that doesn't compete with your other outputs (supports up to 2 independent throttle bodies) — but throttle position feedback sensors still use 2 of your shared analog inputs. On Elite ECUs, DBW takes 2 outputs and 4 inputs directly from the general pool, so budget accordingly if you're running a lot of other sensors and accessories.
Does flex fuel work on the Nexus S2/S3, and does it use up other inputs?
Yes — flex fuel is confirmed on Haltech's official Nexus S2/S3 spec sheet as a supported feature on both tiers. It connects through one of the shared synchronized pulsed inputs (the same bank used for cam and speed sensors), so it counts against your 6 available SPIs on S2/S3 rather than using a fully separate dedicated input.
Do I need the full ECU + harness kit, or just the harness?
Only buy the harness-only option if you already own a compatible Haltech Nexus S2 or S3 ECU. If this is your first Haltech ECU, you need the full kit — the harness alone doesn't include the ECU itself.
What if I'm building a full standalone race car, not a street PnP swap?
That's where the Nexus R3 and R5 VCUs come in — these aren't Plug 'n' Play adapters, they're standalone Vehicle Control Units combining engine management, power distribution, and data logging in one unit, built for serious racing applications. R3 supports up to 8-cylinder/4-rotor engines with 11 analog inputs and 6 pulsed inputs; R5 is Haltech's flagship, supporting up to 12-cylinder/6-rotor with 23 analog inputs, 10 pulsed inputs, and dual onboard wideband controllers.
Does the Rebel LS include everything I need for my specific LS swap?
The base kit covers the most common Gen III/IV LS configuration, but injector style (EV1 vs. EV6), throttle type (cable vs. DBW), and alternator style vary by exact engine source. Check the sub-harness options — they're sold individually so you only pay for what your specific engine needs.
Still not sure which ECU fits your build?
Between platform compatibility, ECU tier, and I/O headroom, Haltech's catalog has a lot of combinations. Browse the full parts catalog, or reach out with your engine, chassis, and goals (street swap vs. race build, plus any accessories you're planning to run) and we'll help you land on the right kit.