This comprehensive guide dives deep into the intricacies of using OBD1 engines in OBD2 Honda vehicles, specifically focusing on the Integra and Civic. We’ll cover engine installation, wiring modifications, and ECU options for various model years, providing detailed instructions and helpful tips to ensure a successful engine swap.
Understanding OBD2 Harness Generations in Integras and Civics
Before diving into the swap details, it’s crucial to understand the different OBD2 generations:
- OBD2a: Found in 1996-98 Civics and 1996-99 Integras.
- OBD2b: Found in 1999-00 Civics and 2000-01 Integras.
These seemingly minor differences significantly impact wiring compatibility. Remember, OBD2a and OBD2b harnesses are not interchangeable.
Engine Swap Guide: Civic (1996-2000)
Engine Installation
Regardless of the B-series engine (B16, B18, B20 VTEC), ensuring you have the correct mounts, shift linkage, and axles is paramount. For 96-98 Civics, using 99-00 Si or JDM EK4/9 engine brackets is recommended for optimal fitment. Axles from 94-01 Integras, 99-00 Si, and 94-97 Del Sols are compatible. 99-00 Si or JDM EK4/9 shift linkage is highly recommended for proper shift lever centering.
Wiring: Part 1 – Engine Wiring Harness (EWH)
You can often reuse your existing EWH or a 96-98 EX 5-speed EWH. Crucially, OBD1 EWHs are incompatible with OBD2 Civics due to their two-piece design. OBD2 Civics utilize a one-piece EWH. Non-VTEC Civic owners swapping to a VTEC engine will need to add VTEC wiring, a knock sensor (KS), and modify the Idle Air Control Valve (IACV) plug from three wires to two. A 96-98 5-speed EX EWH already includes these modifications, simplifying the process. However, you’ll need to manually wire the second O2 sensor if using a USDM OBD2 ECU.
Wiring: Part 2 – Component Modifications
Swapping to an OBD1 engine requires further modifications:
- Distributor: Use an OBD2 B-series VTEC distributor for plug-and-play compatibility.
- Injectors: Use OBD2 injectors for plug-and-play compatibility. Alternatively, modify the OBD2 injector clips to fit OBD1 injectors.
- Alternator: Use an OBD2 B-series alternator for plug-and-play compatibility.
- Intake Air Temperature (IAT) Sensor: Modify the intake arm to accommodate your existing IAT or wire in the OBD1 IAT sensor plug.
- Crankshaft Fluctuation (CKF) Sensor: Implement the CKF bypass trick to avoid needing a USDM OBD2 oil pump.
Engine Swap Guide: Integra (1996-2001)
Engine Installation
Integra swaps are generally simpler, allowing reuse of existing mounts, axles, and shift linkage.
Wiring
You can reuse your Integra’s EWH, following similar modifications as outlined for the Civic, depending on the year. Alternatively, you can use an OBD1 VTEC EWH from a 94-95 Integra GSR, 92-95 Civic Si/EX, or 93-95 Del Sol VTEC. Ensure VTPS, VTS, and KS are wired for non-VTEC Integras. A significant advantage for Integras is that the second O2 sensor is already integrated into the cabin harness.
ECU Options: Civic and Integra
Several ECU options exist, each with pros and cons:
- JDM OBD2 ECU: Easiest installation but limited upgrade options, speed limiter, and smog check incompatibility.
- OBD1 ECU: Offers extensive tuning options but requires a jumper harness, VTPS wiring, and won’t pass smog.
- USDM OBD2 ECU: Allows smog compliance (with CKF bypass) but may require second O2 sensor wiring. Specific ECU choices depend on the chassis and engine. Immobilizer removal or bypass is necessary for 2000-01 Integra ECUs.
Conclusion
Swapping an OBD1 engine into an OBD2 Honda can seem daunting, but with careful planning and execution, it’s achievable. This guide provides the necessary information to navigate the complexities of Integra and Civic swaps, focusing on the critical aspects of OBD2 harness compatibility. Remember to research specific requirements for your particular application and consult reputable resources for further guidance.
