Swapping engines in Honda CB7 Accords is a popular modification for enthusiasts looking to boost performance. The compatibility of Honda’s F and H series engines makes these swaps relatively straightforward. This guide, drawing upon common practices and expert knowledge, details the essential information for performing these swaps, with a focus on navigating OBD2 system considerations, particularly for those considering modifications like an EGR delete, commonly discussed in contexts such as the Honda Prelude.
Most F/H series Honda motors share similar layouts and bolt patterns, simplifying the swap process. In many cases, the stock CB mounts and wiring harness can be utilized, minimizing fabrication. However, successful swaps require careful attention to detail, especially when dealing with variations in components and wiring across different engine generations and OBD systems. If you are new to engine swaps, consulting resources like the F22 Removal Guide is highly recommended before starting.
While much of this guide is applicable to H22A/1/4 swaps, the principles extend to other engine swaps like the F22B1/2 or F23Ax. For a broader list of potential engine swaps, refer to resources like http://www.cb7tuner.com/vbb/showthre…=&threadid=523.
Essential Preparation and Resources
Prior to commencing any engine swap, acquiring the correct service manuals is crucial. Obtain manuals for:
- The year of the donor engine vehicle.
- The year of your Honda CB7.
- The year of the ECU you intend to use.
For instance, if you’re installing a 97 H22 engine with a P13 OBD-1 ECU (from a 1994 Vtec Prelude) into a 93 Accord, you will need the service manuals for a 97 Prelude, a 94 Prelude, and a 93 Accord. These manuals are invaluable for wiring diagrams, torque specifications, and troubleshooting. Websites like www.helminc.com are excellent resources for obtaining these manuals.
Wiring Harness and Electrical Considerations
Retaining and modifying your original Accord wiring harness is generally the most effective approach. By carefully unwrapping the tape and loom of your F22 harness, you can gain considerable wire length. This often eliminates the need to cut and extend wires for sensors like the O2 sensor, providing enough slack to reroute wiring as needed for the new engine. After modifications, ensure proper retaping and looming to protect the harness. Soldering and heat shrinking all engine harness connections is highly recommended to ensure reliable connections and prevent future electrical issues.
Small but important sensor differences exist. For example, the oil pressure sensor plug differs between the F22 and H22. You can either swap the Accord sensor onto the H22 or replace the plug on the harness to match the H22 sensor. Similarly, the EGR valve plug may also differ. Reusing your original F22 EGR valve or changing the plug are straightforward solutions. It’s important to note that modifications such as an EGR delete, while sometimes considered in performance contexts, particularly with OBD2 systems like those found in Honda Preludes, may have implications for emissions compliance and should be approached with caution and full understanding of local regulations.
The F22 engine has an additional coolant temperature sensor on the radiator return neck, which the H22 lacks. Simply swapping the radiator return necks between the engines resolves this discrepancy, ensuring proper coolant temperature monitoring.
OBD-1 ECU Pin Locations for Swaps
When using OBD-1 ECUs, common in swaps for simplicity and tuning flexibility, understanding pin locations for essential engine functions is critical. Here are key OBD-1 ECU pin locations:
- VTEC Solenoid: Pin A4
- VTEC Pressure Switch: Pin D6
- Knock Sensor: Pin D3
- Secondary Intake Solenoid: Pin A17 (Connect the Black/Yellow wire on the solenoid to a switched ignition source, and the other wire to pin A17)
- FPR Solenoid: Pin A10 (Connect the Black/Yellow wire on the solenoid to a switched ignition source, and the other wire to pin A10. Note: Not all H22 engines have this solenoid. Its absence will not cause issues if unused, but this is the correct connection method if present and desired.)
Alt text: Wiring diagram illustrating the conversion process between OBD2 and OBD1 distributor wiring systems, crucial for Honda engine swaps.
ECU Compatibility Notes
If utilizing a 94/95 Accord ECU (P0A/P0B), a pin swap is necessary: swap pin A6 with A11 on the ECU harness. This is because the 5th generation Accord wiring for these pins is reversed compared to the 4th generation.
Sourcing ECU Pins
To source ECU pins for modifications or repairs, junkyards are invaluable. Locate any OBD-1 Honda, and carefully extract the ECU harness, providing a ready supply of pins. Cut the desired pin style with sufficient wire length for splicing into your harness.
Plug Identification and Pin Numbering
Honda ECU plugs are identified by letters:
- Plug A: Largest plug.
- Plug B: Middle and smallest plug.
- Plug D: Second largest plug.
- Plug C: Present only on 4WS (4-Wheel Steering) vehicles.
Pins are numbered in a “Zig-Zag” pattern, viewed from the wire side of the plug. Pin 1 is on the top left, pin 2 directly below it, pin 3 to the right of pin 1 on the top row, and so forth. Odd numbers are on the top row, and even numbers on the bottom row.
Mechanical Component Swaps
Axles: For simplicity, use the Accord axles and half shaft. Alternatively, you can use the Prelude half shaft with the Prelude driver’s side inner joint attached to the Accord axle. Avoid using complete Prelude axles as they are too long for the CB7 chassis.
Air Conditioning (H22A): To retain air conditioning functionality, transfer the AC bracket from your F22 engine to the H22. Use the Accord AC compressor, which is compatible with the CB7 system.
Alternator: Prelude and Accord alternators are interchangeable in terms of mounting. However, they may have different pulley sizes. Either alternator will bolt up, but if you use a Prelude alternator with its smaller pulley, you might need a shorter belt or use washers to space out the 10mm tensioner bolt for proper belt tension. Note that Prelude alternators typically have a 6-rib pulley, while Accord alternators use a 5-rib pulley.
Power Steering (H22A): Use the 4th generation Accord power steering bracket and pump with a custom-sized belt. Only two bolt holes will align, requiring shimming of the lower hole. Alternatively, use the complete H22A power steering bracket and pump assembly, which necessitates using the Prelude high-pressure power steering line for proper fitment.
Engine Mounts: For H22A swaps, reuse all of the Accord engine mounts. The F22A and H22A engine block dimensions are virtually identical, allowing for direct bolt-on compatibility with the original mounts and brackets. This ensures straightforward engine installation back into the CB7 chassis.
For other engines like the F22B1, utilize the F22Ax driver’s side inner mount and bracket (the mount that passes through the timing covers and bolts to the block side). Transfer this mount from the F22Ax to the F22B1. All bolt holes should align except for one.
Transmission Mounts: For 5-speed manual transmissions, you will need to tap two unused holes on the Prelude transmission case using a 10×1.25mm tap. First, enlarge these holes with an 11/32″ drill bit suitable for metal. Remove the two studs from their original location on the Accord transmission mount and install them into the newly drilled and tapped holes on the Prelude transmission. This allows the Accord transmission mount to properly attach to the Prelude transmission.
For automatic transmissions, no modifications are typically needed; the transmission should bolt up without issue.
Fuel Rail and Exhaust Systems
Fuel Rail: Use whichever fuel rail configuration best fits your setup. USDM F22 and H22 fuel rails are generally similar, while JDM H22 fuel rails often have the fuel fitting on the opposite side. Select the fuel rail that provides the most convenient fuel line routing. It’s recommended to use the H22A injectors and sensors. If your new engine is JDM, you may need to reuse your original F22 fuel rail for compatibility with your fuel lines.
Exhaust: For H22A swaps, the USDM 93-96 Vtec Prelude exhaust manifold will bolt directly to the CB7 exhaust system. However, the JDM H22A downpipe flange is often larger and may not directly bolt to the CB7 catalytic converter. Solutions include cutting and welding a new flange, purchasing an aftermarket header designed for a 93-96 Vtec Prelude, or redrilling three holes in the larger JDM downpipe flange to match the CB7 bolt pattern.
For H22A4 (97+ USDM H22A) installations, some users have reported header clearance issues with the front crossmember. Grinding down the crossmember may be necessary in these instances to ensure proper clearance.
For swaps involving other engines like the F22B1, use a header and downpipe specific to that engine. However, the downpipe will likely be too long to properly connect to the CB7 catalytic converter, necessitating custom exhaust work.
OBD2 Engine Considerations (97+ H22A4 or Type-S H22A)
Integrating OBD2 engines, such as the 97+ H22A4 or Type-S H22A, into an OBD1 CB7 chassis requires careful planning. The simplest approach is often to revert to OBD-1 management by using an OBD-1 distributor, injectors, and ECU. Converting a CB7 to full OBD-2a is complex and rarely undertaken due to the extensive wiring and sensor integration required. When dealing with OBD2 engines, considerations around components like the EGR system become more prominent due to the increased diagnostic capabilities of OBD2. While OBD2 EGR delete might be discussed in performance circles, particularly concerning Honda Preludes which often utilize these systems, it’s critical to understand the implications for emissions testing and legality.
Distributor and Ignition System
Internal/External Coil Issues: If your CB7 originally had an internal coil distributor, a JDM H22 distributor should plug in directly without modification. However, if your car had an external coil, a minor modification is needed to the external coil plug. Splice together the yellow and yellow/black wires on the plug that originally connected to the external coil. The black/white wire is not needed and can be disregarded. Alternatively, instead of splicing, a 30 amp fuse can be jammed into the plug to bridge the yellow and yellow/black wires.
To retain an external coil setup with a JDM distributor (which typically has an internal coil), you must open the JDM distributor and remove the internal coil. Route the wire from the igniter that originally connected to the internal coil out of the distributor and into the blank spot on the distributor plug. Use a 93-95 Prelude Vtec distributor cap and rotor for external coil configurations.
Distributor Cap Compatibility:
- Internal coil: Use a CB7 internal coil cap/rotor or a 00 Civic SI cap/rotor.
- External coil: Use a 93-95 Prelude Vtec cap/rotor.
Aftermarket Ignition Amplifier Installation (MSD/Crane): For CB7s originally equipped with an external coil, to install an aftermarket ignition amplifier like MSD or Crane, cut off the plug that went to the stock coil. Splice the yellow and yellow/black wires together and connect this combined wire to the ignition-on input of your aftermarket amplifier (typically red for MSD). Connect the black/white wire to the trigger input of the aftermarket amplifier (typically white on MSD).
ApexI VAFC Settings (Baseline)
These ApexI VAFC (Variable Air Flow Converter) settings are starting points and require dyno tuning for optimization based on your specific engine setup:
- 0-4800 RPM Wide Throttle: -2% fuel adjustment
- 4300-8000 RPM Wide Throttle: -5% fuel adjustment
- VTEC Engagement (Low to High): 4700 RPM
- VTEC Disengagement (High to Low): 4600 RPM
- Throttle Point Low: 10%
- Throttle Point High: 50%
Conclusion
Successfully performing an engine swap on a Honda CB7 requires meticulous planning, attention to detail, and a solid understanding of both mechanical and electrical systems. While this guide provides comprehensive information, always consult official service manuals and seek expert advice when needed. Remember to address OBD2 system considerations thoughtfully, especially if contemplating modifications like EGR deletes, to ensure both performance gains and legal compliance.
Special Thanks to Wadzii and poison for their contributions to the original information and diagrams.
