So, you’re diving into the world of Honda engine swaps and considering putting a more modern OBD2 B-series engine into your trusty OBD1 Civic, Del Sol, or Integra? You’re not alone! This swap is a popular upgrade, especially when looking at engines like the JDM ITR (B18C-R) in an EG Civic or DC Integra. Many enthusiasts explore this path, and understanding how to make it work, particularly when it comes to engine management with an OBD2 ECU in an OBD1 car, is crucial.
This guide breaks down the essentials for getting your OBD2 engine running smoothly in your OBD1 Honda, focusing on using either an OBD1 or OBD2 ECU. We’ll cover the necessary parts, wiring considerations, and ECU options to help you navigate this common modification.
Understanding the OBD1 to OBD2 Swap Basics
First, let’s clarify some fundamental differences. All 1992-1995 Honda Civics, Del Sols, and Integras are OBD1 (On-Board Diagnostics 1). This system is an earlier generation of engine management and diagnostics. OBD1 systems are known for their relative simplicity and ease of modification.
The beauty of OBD1 Hondas is the interchangeability of OBD1 electronic components. You can generally swap OBD1 distributors, injectors, ECUs, and wiring harnesses across various OBD1 Civic and Integra models within the B or D series engine families.
However, when you introduce an OBD2 (On-Board Diagnostics 2) engine – typically from 1996 and later models – into this OBD1 environment, things get a bit more complex. OBD2 is a more advanced system with stricter emissions controls and different sensor configurations.
Essential Parts for OBD2 Engine into OBD1 Chassis
To physically install an OBD2 B-series engine into your 92-95 Civic/Del Sol or 94-95 Integra, you’ll need specific parts. If you own a ’94-95 Integra, you can reuse some of your existing components. Here’s a list of required parts:
- Transmission Bracket (Front): Get one from a 1994-2001 Integra or 1999-2000 Civic Si (any 5-speed model).
- Engine Bracket (Rear “L” shaped): Again, source this from a 1994-2001 Integra (any 5-speed model).
- Driver Side 3-Post Mount: This is needed if you’re installing a B18B/C/C5 engine. If you’re opting for an OBD2 B16/B17, you can actually reuse your existing Civic/Del Sol driver side dual-post mount.
- A/C Bracket: Use the A/C bracket from a 1994-2001 Integra or 1999-2000 Civic Si.
- Shift Linkage (Complete): Get a complete shift linkage from a 1994-2001 Integra or 1999-2000 Civic Si. Important note for Del Sol owners: you MUST use a B-series Del Sol specific shift linkage, which can be harder to find used, so new from Honda might be your best bet.
- Axles with Half-Shaft (Complete): Use axles and half-shaft from a 1994-2001 Integra or 1999-2000 Civic Si.
- U.S. 1996-2001 Integra Engine Wire Harness: This is absolutely essential! This harness is the key to making an OBD2 engine work in your OBD1 car. Honda cleverly designed the US OBD2 Integra/Del Sol engine harnesses to be backwards-compatible with OBD1 vehicles.
- OBD1 ECU or OBD1-to-OBD2 Jumper Harness: You’ll need an OBD1 ECU to directly power the OBD2 engine, or an OBD1-to-JDM OBD2 ECU jumper harness if you intend to use a JDM OBD2 ECU.
Important for 92-93 (DA) Integra Owners: Due to chassis differences, 92-93 Integra owners will need to reuse their original motor mounts, shift linkage, axles, and cable transmission with the OBD2 engine. These parts are compatible. For wiring and ECU, the 96-01 US Integra engine harness information below still applies.
ECU and Wiring: Making the OBD2 Engine Electrically Compatible
The U.S. OBD2 Integra engine harness is the linchpin for simplifying this swap. It saves you significant time and effort compared to converting the OBD2 engine wiring to OBD1 specifications. Crucially, avoid using a JDM OBD2 Integra engine harness as it’s designed for right-hand drive vehicles. The main connectors will be on the wrong side for your engine bay, leading to a wiring headache. Stick with a U.S. OBD2 Integra harness for a smoother installation.
Forget about using a U.S. OBD2 Civic engine harness altogether. OBD2 Civic harnesses are one-piece designs, running from the engine through the firewall and directly to the ECU plugs. OBD1 Civics/Del Sols/Integras, and OBD2 Integras, utilize a 2-piece design where the harness separates at the shock towers. This 2-piece design is what allows for the backwards compatibility we leverage with the Integra harness.
When you install the OBD2 Integra harness, you’ll notice some plugs that won’t connect to your OBD1 shock tower plugs. This is normal and doesn’t affect engine operation.
Wiring for VTEC, Knock Sensor, and IAB
If you’re upgrading to an OBD2 VTEC engine in a non-VTEC OBD1 vehicle, you’ll need to wire in VTEC, the knock sensor, and IAB (Intake Air Bypass) for GSR/SiR-G engines. Wire these components just as you would if you were installing an OBD1 engine – the ECU pinout locations are the same.
Addressing the VTEC Pressure Switch (VTPS) on JDM OBD2 Engines
JDM OBD2 engines often lack a VTEC Pressure Switch (VTPS). If you’re using a JDM OBD2 engine, you’ll need to address this. You have two options: perform a simple wiring fix or swap the JDM VTEC Solenoid (VTS) for a U.S. VTS. The VTPS has a 2-wire plug (power and ground), while the VTS has a single signal wire.
VTPS Wiring Fix:
- Splice the power wire for the VTPS into the VTS wire.
- Ground the VTPS ground wire to the body of the VTEC Solenoid.
This fix prevents a check engine light (code 22 for VTPS) when using a USDM OBD1 or OBD2 ECU that expects a VTPS signal. If you use a JDM OBD2 ECU, this fix is unnecessary as JDM OBD2 ECUs don’t monitor for a VTPS.
Choosing Your ECU: OBD1 vs. OBD2 for Your Swap
Now, let’s discuss the ECU choices for your OBD2 engine in an OBD1 chassis. You have two main paths:
Option 1: Using an OBD1 ECU (Recommended)
This is often the simpler and “best” option. Use an OBD1 ECU that corresponds to your OBD2 engine type. For example, if you’re using an OBD2 GSR engine, use an OBD1 GSR (P72) ECU. This ECU will plug directly into your OBD1 factory ECU plugs and power the engine.
If an equivalent OBD1 ECU for your specific OBD2 engine doesn’t exist (like an OBD1 ITR ECU), use a reprogrammable OBD1 ECU like a chipped P28 ECU. These can be tuned to properly manage your OBD2 engine.
Option 2: Using an OBD2 ECU (More Complex but Doable)
If you prefer to use an OBD2 ECU, it’s achievable but requires additional steps.
- OBD1-to-OBD2 Jumper Harness: You’ll need to purchase an OBD1-to-OBD2a or OBD2b jumper harness adapter (depending on whether you’re using an OBD2a or OBD2b ECU). These adapters bridge the wiring differences between the OBD1 car and the OBD2 ECU.
- USDM OBD2 ECU Considerations: If you choose a U.S. OBD2 ECU, you’ll need to wire in a secondary O2 sensor and perform the “CKF Fix” (Crankshaft Speed Fluctuation Sensor Fix). USDM OBD2 ECUs expect these components, which are not present in OBD1 cars.
JDM OBD2 ECU Advantage: If you opt for a JDM OBD2 ECU, you bypass the need for a secondary O2 sensor and the CKF sensor fix. JDM OBD2 ECUs are not programmed to look for these sensors, simplifying the wiring process when using an OBD2 ECU in an OBD1 car.
Conclusion: Successfully Running an OBD2 ECU in Your OBD1 Car
By understanding the parts needed, wiring nuances, and ECU options, you can confidently install an OBD2 engine into your OBD1 Honda. Choosing the right approach, whether it’s utilizing an OBD1 ECU for simplicity or navigating the complexities of an OBD2 ECU in an OBD1 car with jumper harnesses and wiring adjustments, will ensure a successful and powerful engine swap. Remember to prioritize a U.S. OBD2 Integra engine harness for a smoother process and consider your ECU options carefully based on your engine and desired level of complexity.
