Swapping engines is a popular modification for Honda enthusiasts, especially when looking to boost performance. A common question arises when considering newer, more powerful OBD2 engines for older OBD1 vehicles: how do you make it work? This guide provides a detailed walkthrough on installing an OBD2 B-series engine into a 1992-1995 OBD1 Honda Civic, Del Sol, or Integra. We’ll cover the necessary parts, wiring considerations, and ECU options to ensure a successful swap.
Understanding OBD1 and OBD2 Systems
Before diving into the specifics, it’s crucial to understand the difference between OBD1 (On-Board Diagnostics 1) and OBD2 (On-Board Diagnostics 2) systems. OBD1 was the early standard for vehicle diagnostics, used in Hondas from 1992 to 1995. OBD2 is a more advanced system, becoming standard in 1996, offering enhanced diagnostic capabilities and emissions monitoring. The key challenge in this swap is adapting the different electronic systems to work together.
Essential Parts for the OBD2 to OBD1 Engine Swap
To successfully install an OBD2 B-series engine into your OBD1 chassis, you’ll need specific parts to ensure proper fitment and functionality. Note that ’94-95 Integra owners can reuse some existing parts mentioned below.
Mounting and Brackets:
- Front Transmission Bracket: You’ll need a front transmission bracket from a 1994-2001 Integra or 1999-2000 Civic Si (from any 5-speed model).
- Rear Engine “L” Shaped Bracket: Acquire a rear engine “L” shaped bracket from a 1994-2001 Integra (from any 5-speed model).
- Driver Side 3-Post Mount: This is necessary if you are installing a B18B/C/C5 engine. However, if you’re using an OBD2 B16/B17 engine, this mount is not required. You can reuse your existing Civic/Del Sol driver side dual-post mount when installing an OBD2 B16A.
- A/C Bracket: Use an A/C bracket from a 1994-2001 Integra or 1999-2000 Civic Si.
Drivetrain and Linkage:
- Shift Linkage: A complete shift linkage from a 1994-2001 Integra or 1999-2000 Civic Si is required. Del Sol owners must use a B-series Del Sol specific shift linkage, which can be harder to find used and may be best sourced new from Honda.
- Axles with Half-Shaft: Use complete axles with a half-shaft from a 1994-2001 Integra or 1999-2000 Civic Si.
Wiring Harness – The Key to Compatibility:
- U.S. 1996-2001 Integra Engine Wire Harness: This is arguably the most crucial component. A U.S. OBD2 Integra engine wire harness is designed to be backwards-compatible with OBD1 vehicles, simplifying the wiring process significantly. Honda engineers cleverly designed these harnesses to work with older OBD1 systems. Crucially, avoid using a JDM OBD2 Integra harness as it’s designed for right-hand drive vehicles and the main plugs will be on the wrong side. Similarly, a U.S. OBD2 Civic harness is not suitable due to its one-piece design, unlike the two-piece design of OBD1 and OBD2 Integra harnesses which allows for this type of swap.
For 92-93 DA Integra Owners:
Due to chassis differences, 1992-1993 (DA) Integra owners will reuse their original motor mounts, shift linkage, axles, and cable transmission, all of which are compatible with the OBD2 engine. However, for wiring and ECU, the 1996-2001 US Integra engine wire harness and ECU information below still apply.
ECU and Wiring Explained
The beauty of using a U.S. OBD2 Integra engine harness is that it minimizes the need to convert the OBD2 engine to OBD1 specifications. When installing this harness, you will notice some plugs that don’t connect to your OBD1 shock tower plugs – this is normal and won’t affect engine operation.
VTEC and Additional Wiring:
If you are upgrading to an OBD2 VTEC engine from a non-VTEC OBD1 vehicle, you will need to wire in VTEC, the knock sensor, and IAB (Intake Air Bypass) for GSR/SiR-G engines. This wiring process is similar to wiring these components for an OBD1 engine, using the same ECU pinout locations.
JDM OBD2 Engine Considerations:
JDM OBD2 engines often lack a VTEC Pressure Switch (VTPS). If you are using a JDM OBD2 engine, you will need to perform a minor wiring modification or swap the JDM VTEC Solenoid (VTS) with a U.S. VTS version. The VTPS has a 2-wire plug (power and ground), while the VTS has a single signal wire.
VTPS Wiring Fix for JDM Engines:
To resolve the VTPS issue, splice the power wire of the VTPS into the VTS wire. Then, ground the VTPS ground wire to the body of the VTEC Solenoid. This bypass ensures the ECU doesn’t throw a code 22 (VTPS). If you opt for a JDM OBD2 ECU, this VTPS fix is unnecessary as JDM ECUs do not monitor for a VTPS.
ECU Options: OBD1 vs. OBD2
When it comes to choosing an ECU, you have two main options:
1. OBD1 ECU (Recommended):
This is often the simpler and more straightforward option. Use an OBD1 ECU that is compatible with your OBD2 engine type. For example, for an OBD2 GSR engine, use an OBD1 GSR/P72 ECU. This ECU will plug directly into your existing OBD1 factory ECU plugs and run the engine. If a direct OBD1 equivalent ECU isn’t available for your specific engine (like an OBD1 ITR ECU), you can use a reprogrammable OBD1 ECU such as a chipped P28 ECU.
2. OBD2 ECU (More Complex):
If you prefer to use an OBD2 ECU, it is achievable but requires additional steps. You’ll need an OBD1 to OBD2a/OBD2b jumper harness adapter, depending on the type of OBD2 ECU you choose (a or b).
- U.S. OBD2 ECU: Using a U.S. OBD2 ECU necessitates wiring in a secondary O2 sensor and performing the “CKF (Crankshaft Speed Fluctuation Sensor) Fix”. These ECUs are programmed to monitor these sensors, which are not present in OBD1 vehicles.
- JDM OBD2 ECU: JDM OBD2 ECUs simplify this aspect as they do not require a secondary O2 sensor or CKF sensor, eliminating the need for these modifications.
CKF Fix:
For those using a U.S. OBD2 ECU, the CKF fix is essential to prevent check engine lights and ensure proper engine operation. [Link to CKF Fix Article – Note: In the original article, “HERE” was a placeholder for a link. In a real article, you would link to a detailed guide on performing the CKF Fix.]
Secondary O2 Sensor Wiring:
If using a U.S. OBD2 ECU, you will also need to wire in a secondary O2 sensor, as OBD2 systems monitor catalyst efficiency. [Link to 2nd O2 Wiring Article – Note: Similarly, the original article mentioned a future article. In a real article, you would link to a guide on wiring a secondary O2 sensor.]
Conclusion
Installing an OBD2 engine into an OBD1 Honda is a popular and rewarding upgrade. By using a U.S. OBD2 Integra engine harness and carefully considering your ECU options, this swap becomes significantly more manageable. Whether you choose the simplicity of an OBD1 ECU or opt for an OBD2 ECU, understanding the wiring nuances and necessary components is key to a successful conversion. This guide provides the foundational knowledge to confidently undertake this project and enjoy the benefits of a more modern and powerful engine in your OBD1 Honda.
