Upgrading or swapping engines in your Honda Integra often involves navigating the complexities of different OBD (On-Board Diagnostics) systems. One common challenge arises when installing an OBD1 engine into an OBD2 Integra chassis, particularly concerning the distributor. This guide provides a detailed walkthrough on how to successfully convert your Integra’s OBD2 system to accommodate an OBD1 distributor, ensuring your engine runs smoothly and efficiently.
Understanding OBD2 to OBD1 Distributor Conversion
Before diving into the specifics, it’s crucial to understand the fundamental differences between OBD2 and OBD1 distributors and why this conversion might be necessary. OBD2 systems are more advanced, offering enhanced diagnostics and emissions control compared to their OBD1 predecessors. However, when swapping in older, but potentially more performance-oriented OBD1 engines (like certain B-series VTEC engines), compatibility issues arise, especially with the distributor wiring and connections.
This conversion typically involves adapting the wiring harness to match the OBD1 distributor’s plug, as they are not directly compatible with the OBD2 harness. While seemingly intricate, with the right guidance and careful execution, this conversion is a manageable task for the determined DIYer or any competent mechanic.
Step-by-Step Guide: OBD2 to OBD1 Distributor Conversion for Integra
This guide focuses on the distributor conversion aspect, assuming you are already in the process of an engine swap and have addressed other necessary modifications like engine mounts and axles, as outlined in the original article.
1. Identify Your Vehicle and Engine Type
First, confirm whether you have an OBD2a (96-99 Integra) or OBD2b (00-01 Integra) chassis. Knowing your specific Integra model year is essential because wiring nuances can differ slightly. Similarly, identify the OBD1 engine you are installing. This guide generally applies to B-series VTEC OBD1 engines.
2. Gather Necessary Parts and Tools
For this conversion, you will primarily need:
- OBD1 Distributor: The distributor unit from your OBD1 engine.
- OBD1 Distributor Plug(s): These can be sourced from an OBD1 engine harness. Having the pigtails with some wire length will make splicing easier.
- Wiring Tools:
- Wire strippers and crimpers
- Soldering iron and solder (optional, but recommended for robust connections)
- Electrical tape or heat shrink tubing
- Multimeter (for testing continuity, optional but helpful)
- OBD2 Engine Wire Harness (EWH): You will be modifying your existing OBD2 Integra engine harness.
3. Distributor Plug Conversion: Wiring is Key
The core of this conversion lies in adapting the wiring between your Integra’s OBD2 engine harness and the OBD1 distributor. There are two main approaches:
Option A: OBD1 Distributor Plug Splicing
This method involves cutting the OBD2 distributor plug from your Integra’s engine harness and splicing in an OBD1 distributor plug.
- Locate Distributor Plugs: Identify the distributor plug on both your OBD2 Integra harness and the OBD1 distributor you’ll be using.
- Wire Diagram Reference: Crucially, you’ll need wiring diagrams for both OBD2 and OBD1 distributor systems. These diagrams will show the function and color-coding of each wire. (Refer to reliable online resources or repair manuals for accurate wiring diagrams for your specific Integra and OBD1 engine type.)
- Cut and Splice Wires: Carefully cut the OBD2 distributor plug from your Integra’s engine harness, leaving enough wire length on the harness side for splicing. Then, using the wiring diagrams, match each wire from the OBD1 distributor plug to the corresponding wire on your OBD2 harness, based on their function. Color-matching wires is important but always verify function with wiring diagrams as wire colors can sometimes vary.
- Secure Connections: Connect the wires using your preferred method – soldering and heat shrinking provides the most durable and weather-resistant connection, while crimped connectors with electrical tape are a quicker alternative. Ensure each connection is well-insulated to prevent shorts.
Option B: OBD2 to OBD1 Distributor Adapter Harness (If Available)
While less common for this specific distributor conversion alone, check if there are any commercially available adapter harnesses that simplify this process. If a reputable adapter harness exists for “OBD2 Integra to OBD1 Distributor,” it can eliminate the need for manual splicing, offering a more plug-and-play solution. However, verify its quality and compatibility before use.
4. Injector, Alternator, and IAT Considerations (As Needed)
While focusing on the distributor, remember that converting to an OBD1 engine might necessitate changes to other components’ wiring as well, as mentioned in the original article. Specifically:
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Injectors: OBD1 and OBD2 injectors may have different plug types. You might need to splice injector plugs or use OBD2 injectors compatible with your harness. The article also mentions a clever trick of modifying the OBD2 injector clip for OBD1 injectors as a temporary solution.
Alt text: Close-up of an OBD2 injector clip modified to fit an OBD1 injector, secured with a zip tie, illustrating a wiring modification technique for engine swaps.
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Alternator: OBD1 and OBD2 alternators often use different plug styles (round vs. square). You might need to swap alternator plugs or use an OBD2 alternator compatible with your harness.
Alt text: Comparison image showing the round plug of an OBD1 alternator and the square plug of an OBD2 alternator, highlighting the difference in connector types for engine conversion wiring.
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IAT (Intake Air Temperature) Sensor: OBD1 and OBD2 IAT sensors have different plugs. Adapt the wiring or relocate/adapt your IAT sensor as needed.
5. ECU Compatibility and Wiring
The ECU (Engine Control Unit) is the brain of your engine management system. When converting to OBD1, you have ECU options to consider:
- OBD1 ECU: This is a common choice when converting to an OBD1 engine. You will likely need an OBD2 to OBD1 jumper harness to connect an OBD1 ECU to your OBD2 Integra chassis harness. OBD1 ECUs are generally easier to tune but may have emissions implications.
- OBD2 ECU Options: You might be able to use certain OBD2 ECUs (like those from specific Integra or Civic models mentioned in the original article) with the OBD1 engine, potentially requiring the CKF bypass trick (for US OBD2 ECUs) and wiring for the secondary O2 sensor if needed.
Choose your ECU strategy based on your goals (performance, emissions, ease of tuning) and wire accordingly. The original article provides detailed ECU options and their pros and cons.
6. Testing and Verification
After completing the wiring modifications, meticulously double-check all connections. Ensure wires are securely spliced, insulated, and correctly matched according to the wiring diagrams.
Before starting the engine, it’s wise to:
- Check for Shorts: Use a multimeter to check for any shorts in your wiring.
- Verify Continuity: Confirm continuity in your newly spliced distributor wiring.
Once you are confident in your wiring, attempt to start the engine. If it doesn’t start or runs erratically, re-examine your wiring, ECU setup, and consult troubleshooting resources.
Conclusion: Successful OBD2 to OBD1 Distributor Conversion
Converting your Integra from OBD2 to OBD1 distributor, while requiring careful wiring work, is a crucial step when installing an OBD1 engine. By understanding the wiring differences, meticulously following this guide, and utilizing accurate wiring diagrams, you can successfully complete this conversion. Remember to address all related wiring aspects like injectors, alternator, IAT, and ECU compatibility for a fully functional and optimized engine swap.
Disclaimer: Automotive wiring modifications should be performed with caution and a solid understanding of electrical systems. If you are not comfortable with these procedures, it is highly recommended to seek professional assistance from a qualified mechanic experienced in Honda engine swaps.
Reference:
- Original Article:
