Understanding ECU compatibility is crucial when converting an automatic Acura NSX to a manual transmission, especially in Canada where OBD2 regulations are in effect. While information is primarily derived from service manuals and online forums, this guide aims to shed light on the complexities of this process for Acura NSX owners. A key question is whether an ECU change is necessary when performing this conversion.
Delving into ECU Compatibility
Early indications suggest that if the vehicle retains its original Engine Control Unit (ECU), replacement might not be required. Transmission control in the NSX is handled by a separate Transmission Control Module (TCM). Service manuals indicate similar external pin connections on both automatic and manual ECUs. Data transfer between the ECU and TCM, and other shared connections, may operate unidirectionally (ECU to TCM). Although manual ECU terminal pins might exist, the corresponding external harness connectors might not be utilized.
Disconnecting the TCM might trigger diagnostic trouble codes (DTCs) and illuminate the Check Engine Light (CEL). To avoid this, keeping the TCM connected to the ECU might be necessary, even without the automatic gearbox. Reconfiguring clutch and neutral switch connections to the ECU is essential; these adjustments are typically external to the ECU.
Drive-by-Wire and Other Considerations
A primary factor in ECU selection is drive-by-wire (DBW) compatibility. Determining the introduction year of DBW in Canadian NSXs (1995 or 1996) is vital, as it narrows down compatible ECU options. The DBW system evolved over the years, potentially involving hardware or firmware revisions. Using an earlier ECU with a later model (e.g., a 2001 NSX) might present compatibility challenges.
Other evolving systems include evaporative emission (evap) and secondary air systems. Later evap systems (potentially finalized in 1999 or 2000) might not function correctly with earlier ECUs. This could lead to emissions non-compliance and fuel vapor smells. Some models (like the 2000 NSX Na2) utilize secondary air injection for rapid catalytic converter warm-up. Early ECUs lack controls for this system, potentially creating further complications. Numerous production changes throughout the NSX’s lifespan could make mixing early ECUs with later models problematic.
Internal Modifications and Alternative Solutions
Anecdotal evidence suggests that while automatic and manual ECUs have distinct part numbers, they might be internally similar. An internal resistor or shunt modification could potentially convert an automatic ECU to a manual configuration, altering fuel maps and potentially ignoring the TCM data line. However, this is not recommended as altering fuel maps is undesirable. This suggests an ECU swap might be unnecessary.
Several NSX enthusiasts have successfully converted early models from automatic to manual. Consulting online resources like NSXPrime forums and project threads can offer valuable insights into ECU compatibility and conversion procedures. For instance, members like “drew” and “McLargeHuge” have documented their experiences, which could help determine the necessity of an ECU change.
Recommended Approach
Before undertaking an ECU swap, thoroughly analyze the 2001 NSX service manual and electrical troubleshooting manual. A detailed pinout comparison can identify key differences between automatic and manual ECU configurations. Prioritize retaining the original ECU whenever possible.
In conclusion, while an automatic to manual conversion in a Canadian Acura NSX may seem daunting, understanding the intricacies of ECU compatibility is essential. Thorough research, consultation with experienced enthusiasts, and careful analysis of wiring diagrams can help determine the optimal approach for a successful conversion while maintaining OBD2 compliance.
