Swapping engines in your Honda Integra or converting from OBD1 to OBD2 engine management can seem daunting. This detailed guide breaks down the Integra Obd1 To Obd2 Conversion process, offering updated and more in-depth information for enthusiasts and DIY mechanics alike. Whether you’re upgrading for performance, emissions compliance, or simply modernizing your Integra, understanding the nuances of this conversion is crucial. This article focuses primarily on 5-speed manual conversions, as automatic to manual swaps involve additional complexities not extensively covered here.
Before diving in, let’s clarify some common acronyms you’ll encounter throughout this guide:
- OBD2a – 1996-1998 Civic / 1996-1999 Integra
- OBD2b – 1999-2000 Civic / 2000-2001 Integra
- EWH – Engine Wire Harness
- VTS – VTEC Solenoid
- VTPS – VTEC Pressure Switch
- KS – Knock Sensor
- IACV – Idle Air Control Valve
- Dizzy – Distributor
- PnP – Plug n’ Play
Integra Engine Installation and Mounting Considerations
Whether you’re installing a B16, B18, or B20 VTEC engine into your Integra, ensure you have the correct components for a seamless fit.
Engine Mounts and Brackets:
For Integras, you can generally reuse your existing engine mounts and brackets. However, if you are sourcing parts or need replacements, consider these points:
- Front Transmission Bracket: Integra brackets are typically compatible.
- Rear Engine “T” Bracket: Integra “T” brackets are suitable for maintaining engine position.
- A/C Bracket: If retaining air conditioning, use your existing Integra A/C bracket. Alternatively, a “P54” 1994-1997 Del Sol DOHC VTEC A/C bracket or a CRV A/C bracket can be used if you need to adapt to a smaller Civic A/C compressor.
Shift Linkage and Axles:
- Shift Linkage: Integra shift linkages are designed for the Integra chassis and should be reused.
- Axles: Axles from 1994-2001 Integra (JDM or US models, all 5-speed), 1999-2000 Civic Si, and 1994-1997 DOHC Del Sol are compatible with Integra chassis for B-series swaps.
Once the engine is physically installed, the next critical step in your Integra OBD1 to OBD2 conversion is the wiring.
Integra OBD1 to OBD2 Wiring: Part 1 – Harness Basics
For 1996-2001 Integras, you have options regarding your engine wire harness (EWH) when performing an OBD1 to OBD2 conversion. A key advantage for Integra owners is the 2-piece harness design, which offers more flexibility compared to Civics.
Harness Compatibility:
- OBD2 Integra Harness: You can reuse your existing OBD2a (1996-1999) or OBD2b (2000-2001) Integra EWH.
- OBD1 Engine Wire Harness in OBD2 Integra: Yes, you can use a US OBD1 engine wire harness in a 1996-2001 Integra! Integra’s 2-piece harness design maintains backwards compatibility with OBD1 EWH connectors at the shock tower. Compatible OBD1 VTEC EWH options include:
- 1994-1995 Integra GSR
- 1992-1995 Civic Si/EX
- 1993-1995 DOHC Del Sol
This compatibility simplifies the wiring for an Integra OBD1 to OBD2 conversion, especially when using an OBD1 ECU. If you have a non-VTEC Integra and opt for an OBD1 EWH, ensure you wire in the VTEC Pressure Switch (VTPS), VTEC Solenoid (VTS), and Knock Sensor (KS) from the ECU plugs to the shock tower connector.
IACV Modification:
Regardless of whether you use an OBD1 or OBD2 harness, if you are using an OBD1 engine, you’ll likely need to address the Idle Air Control Valve (IACV) wiring. OBD1 engines and some OBD2 models (like 96-00 5-speed EX Civics and 99-00 Si) use a 2-wire IACV. Many OBD2 Integras and Civics use a 3-wire IACV. The IACV mod involves converting your 3-wire IACV plug to a 2-wire plug.
Integra OBD1 to OBD2 Wiring: Part 2 – Sensor and Component Adapters
To fully integrate an OBD1 engine into your OBD2 Integra, you’ll need to address wiring differences for several key engine components:
(1) Distributor Plug:
- Option 1: OBD1 Distributor Conversion: Cut and splice OBD1 distributor plugs onto your OBD2 EWH, matching wire colors.
- Option 2: OBD2 Distributor (Plug n’ Play): The easiest solution is to use an OBD2 B-series VTEC distributor (from any 1996-2000 B-series VTEC engine). These distributors are plug-and-play with 1996-1998 (OBD2a) EWHs.
(2) Injector Clips:
- Option 1: OBD1 Injector Clip Conversion: Cut and splice OBD1 injector plugs onto your OBD2 EWH, matching wire colors.
- Option 2: OBD2 Injectors (Plug n’ Play): Use OBD2 injectors (from any 1996-2000 B-series or even D-series engine). These are plug-and-play with OBD2a EWHs.
- Option 3: OBD2 Clip Modification (Budget-Friendly): A clever trick is to remove the blue cap inside your OBD2 injector clip. You can then wiggle the clip onto the OBD1 injector. Secure it tightly with a zip tie to prevent vibration-induced disconnection.
(3) Alternator Plug:
OBD1 alternators use a round plug, while OBD2 alternators use a square plug.
- Option 1: OBD1 Alternator Plug Conversion: Cut and splice an OBD1 alternator plug onto your OBD2 EWH.
- Option 2: OBD2 Alternator (Plug n’ Play): Use an OBD2 B-series alternator (from any 1996-2001 B-series engine). This is a direct plug-and-play solution for OBD2a/OBD2b harnesses.
- Option 3: Hybrid Alternator Plug Swap: Disassemble your OBD1 alternator and swap in the inner plug from an OBD2 alternator. It’s believed a D-series alternator plug might also be compatible, but this requires further verification.
(4) IAT Sensor (Intake Air Temperature):
OBD1 and OBD2 IAT sensor plugs differ.
- Option 1: Retain OBD2 IAT Sensor: Keep your OBD2 IAT sensor and drill a hole in your intake arm to mount it.
- Option 2: OBD1 IAT Sensor Conversion: Cut and splice an OBD1 IAT plug onto your EWH to use the OBD1 IAT sensor located on the intake manifold runner.
(5) CKF Sensor (Crankshaft Fluctuation Sensor):
The CKF sensor is a crucial consideration for Integra OBD1 to OBD2 conversion, especially when using a US OBD2 ECU. US OBD2 ECUs (but not OBD1 or JDM OBD2 ECUs) expect input from the CKF sensor, which is integrated into the oil pump on US OBD2 engines. OBD1 and JDM OBD2 engines lack this sensor.
- CKF Bypass Trick: Fortunately, a CKF bypass trick eliminates the need to physically install a US OBD2 oil pump. This bypass allows you to use an OBD1 engine with a US OBD2 ECU without a CKF sensor. This is particularly beneficial for passing emissions testing in some regions if your Integra is BAR’d for a B-series engine or you’re running an OBD1 engine in an OBD2 chassis. Learn more about the CKF BYPASS TRICK.
ECU Options for Integra OBD1 to OBD2 Conversion
Choosing the right ECU is paramount for your Integra OBD1 to OBD2 conversion. You have several options, ranging in complexity and features:
(Option 1) JDM OBD2 ECU (Easiest):
- Pros: Direct plug-and-play with Integra harnesses. JDM OBD2 ECUs do not require a VTPS.
- Cons: Limited ECU upgrades available. JDM OBD2 ECUs will likely not pass US smog tests as they don’t communicate with US OBD2 scanners. Speed limiter around 115-120mph.
(Option 2) OBD1 ECU Conversion (Popular for Tuning):
- Process: Use an OBD2a to OBD1 jumper harness (for 1996-1999 Integras) or an OBD2b to OBD1 jumper harness (for 2000-2001 Integras) and an OBD1 ECU (like a reprogrammable P28).
- Pros: OBD1 ECUs are highly tunable and widely supported. They do not require a 2nd O2 sensor or CKF sensor, simplifying wiring and diagnostics. OBD1 ECUs are generally more forgiving than sensitive US OBD2 ECUs.
- Cons: Will not pass smog tests in regions with OBD2 emissions checks. Requires wiring in the VTPS.
(Option 3) US OBD2 ECU (Smog Legal Options):
- (Option 3a) OBD2a US ECU (1996-1999 Integra):
- ECUs: 1996-1997 Del Sol DOHC VTEC P30 ECU, 1996-1999 Integra P72/GSR ECU, or 1996-1998 Integra P73/ITR ECU.
- Pros: Can pass smog if the CKF bypass trick is successfully implemented.
- Cons: Requires wiring in the 2nd O2 sensor.
- (Option 3b) OBD2b US ECU (2000-2001 Integra):
- Process: Use an OBD2a to OBD2b jumper harness (for 1996-1999 Integras) or remain OBD2b for 2000-2001 models. Use a 1999-2000 Civic Si ECU or a 2000-2001 Integra GSR/ITR ECU (note: 2000-2001 Integra ECUs require immobilizer removal).
- Pros: Can pass smog if CKF bypass trick is successful.
- Cons: Requires a 2nd O2 sensor to be wired and functional. 2000-2001 Integra ECUs need immobilizer attention.
(Option 4) JDM OBD2 ECU with OBD2b to OBD2a Jumper (For 2000-2001 Integra in OBD2a Spec):
- (For 2000-2001 Integra converting to OBD2a): Use an OBD2b to OBD2a jumper harness with a JDM OBD2 ECU or a JDM CTR (PCT) ECU (which is OBD2b spec and plug-and-play in OBD2b cars but requires a jumper for OBD2a).
- Pros: Potentially easier wiring than US OBD2 ECU options in some scenarios.
- Cons: Requires OBD2b to OBD2a jumper harness. Will not pass smog. Speed limiter at 115-120mph.
ECU Notes for 2000-2001 Integras: 2000-2001 Integra ECUs are equipped with immobilizers. Swapping these ECUs requires immobilizer removal or bypass for the car to run. Aftermarket immobilizer bypass chips are available to address this and prevent check engine lights related to immobilizer removal.
This comprehensive guide should provide a solid foundation for your Integra OBD1 to OBD2 conversion. Remember to double-check wiring diagrams and component compatibility specific to your Integra model year and engine choice. With careful planning and execution, you can successfully navigate this conversion and enjoy the benefits of your upgraded engine management system.
