The question of OBD2 oil pump compatibility with an OBD1 GSR engine often arises during engine swaps or builds. This article clarifies the differences between OBD1 and OBD2 oil pumps for Acura Integra GSRs and addresses whether using an OBD2 pump on an OBD1 engine is feasible.
Understanding OBD1 and OBD2 Oil Pumps in GSRs
A common misconception is that significant differences exist between OBD1 (94-95 Integra GSR) and OBD2 (96+ Integra GSR) oil pumps. Historically, the primary difference was the gear diameter, with OBD1 pumps having larger gears. However, modern oil pumps generally use the smaller diameter gear regardless of OBD generation. The main distinction now lies in the housing.
Why Change the Oil Pump?
Given the minimal internal differences, changing the oil pump during a build or swap isn’t always necessary. A functioning OBD1 oil pump is typically sufficient for a stock or mildly modified GSR engine. Unnecessary replacement adds cost without significant performance gains. If rebuilding or refreshing the engine, inspection and potential resealing of the existing pump are often sufficient.
OBD1 vs. OBD2: Compatibility Concerns
Using an OBD2 oil pump on an OBD1 GSR engine is possible with the correct lower timing belt cover. The timing belt cover is the primary point of interference, as the OBD2 cover is designed for the slightly different housing of the OBD2 pump. Using the corresponding OBD2 lower timing cover will ensure proper fit and function.
It’s crucial to understand that the oil pump itself doesn’t directly interact with the ECU. Compatibility concerns primarily relate to physical fitment with the engine block and timing components.
Choosing the Right Oil Pump
If replacing the oil pump is deemed necessary, using a GSR OBD1 (94-95) oil pump is the most straightforward option. It eliminates compatibility concerns and ensures proper fitment without requiring additional modifications.
While a VTEC oil pump might seem logical for a VTEC engine, both VTEC and non-VTEC B-series engines (in this context) utilize the same fundamental oil pump design. The “VTEC” designation on some pumps often refers to the application rather than significant internal differences.
Conclusion
Using an OBD2 oil pump on an OBD1 GSR engine is possible with the corresponding OBD2 lower timing cover. However, replacing a functioning OBD1 pump is often unnecessary. If replacement is required, sticking with an OBD1 GSR oil pump simplifies the process and ensures compatibility. Always consult with experienced mechanics or tuners for guidance specific to your build.
