When upgrading or replacing fuel injectors in your Honda, you might encounter discussions about OBD1 and OBD2 injectors. However, the connector type related to OBD1 or OBD2 is not the primary concern when it comes to injector compatibility and potential damage. The real issue lies in understanding injector resistance: whether they are high resistance (saturated) or low resistance (peak & hold). Confusing these two can lead to serious problems, including frying your injectors or engine control unit (ECU).
OBD Connector Types: OBD1 vs OBD2 – Not the Deciding Factor
The terms OBD1 and OBD2 refer to On-Board Diagnostics systems, which evolved over time. OBD1 systems are older and less standardized, while OBD2 is a more modern and standardized system mandated in later vehicles. While OBD1 and OBD2 systems use different types of connectors for diagnostic purposes, this connector difference is irrelevant to injector compatibility. The connector on the injector itself might differ between some OBD1 and OBD2 injectors, but this is easily addressed with adapter harnesses and is not the core issue.
The Critical Factor: Injector Resistance – Peak & Hold vs. Saturated
The crucial distinction lies in whether an injector is designed as peak & hold (low resistance) or saturated (high resistance).
Peak & Hold (Low Resistance) Injectors
Peak & hold injectors are low resistance injectors. They require a different method of control from the ECU. These injectors use a higher current initially to rapidly open the injector (the “peak”) and then reduce the current to hold it open (the “hold”). This allows for precise fuel control, especially at lower engine speeds. However, using peak & hold injectors in a system designed for saturated injectors without proper modification can cause damage due to the higher current draw. This is why, for example, when upgrading to peak & hold injectors on an older Honda originally equipped with saturated injectors, a resistor box is often necessary. The resistor box reduces the current going to the injectors, making them compatible with the saturated injector driver circuitry in the ECU. Examples of Honda OBD1 peak & hold injectors include some Prelude injectors and many aftermarket performance injectors.
Saturated (High Resistance) Injectors
Saturated injectors are high resistance injectors. They are designed to be simply turned on and off by the ECU with a constant current. They are generally more forgiving in terms of compatibility within systems designed for saturated injectors. However, they may not offer the same level of precise fuel control as peak & hold injectors, particularly at lower RPMs. Some OBD2 Honda injectors, like those found in certain Prelude models, are saturated injectors.
Avoiding Injector Damage: Key Takeaways
The key takeaway is to focus on injector resistance and type (peak & hold vs. saturated), not just the OBD1 or OBD2 designation, when considering compatibility.
- Resistance Matters: Always verify the resistance and type of injector (peak & hold or saturated) required for your specific Honda model and ECU.
- Don’t Mix Types Without Modification: Installing low resistance peak & hold injectors in a system designed for high resistance saturated injectors will likely cause damage (frying injectors or ECU) without using a resistor box or ECU modification.
- OBD Connector is Secondary: While injector connectors might differ between some OBD1 and OBD2 injectors, adapters are readily available. The electrical compatibility (resistance) is the primary concern.
- When in Doubt, Check Specs: Consult your vehicle’s repair manual, injector specifications, or a knowledgeable tuner to confirm injector compatibility before installation.
In conclusion, while the terms OBD1 and OBD2 are often mentioned in automotive discussions, when it comes to fuel injectors in Hondas, the crucial factor for compatibility and preventing electrical damage is understanding and correctly matching injector resistance and type (peak & hold vs. saturated) to your vehicle’s system. Focusing on this electrical characteristic, rather than simply the OBD designation, will ensure a successful and safe injector upgrade or replacement.
