KB
30-03-2005, 01:16 AM
"What is known to the tuning world from dyno plots and tuning is that the ECU on OBD2- equipped vehicles will eventually "detune" modifications that alter cam timing, ignition timing, and air/fuel delivery. This includes common breathing modifications (intake/header/exhaust and port work). What this means for the average tuner is that when you bolt on i/h/e, do manifold or head (port) work, change injectors or fuel pressure, or just about any other engine-related mod, the ECU will detect the change in emissions and alter the timing and fuel maps to compensate. This has been dyno proven on multiple occasions with multiple different performance mods. It also happens that this is especially true for air/fuel controllers (AFCs).
The purpose of the EPA-mandated OBD standard was to provide a means for which factory engine controls could diagnose engine control malfunctions and identify to the driver (and subsequently the repair shop) that there was a problem. The OBD2 standard, mandated for all 1996 and up vehicles, required that the OBD interface be standardized across all makes and models, as well as monitoring emissions components performance and proper operation. This means that for 1996 and newer vehicles with OBD2 that if you remove the catalytic converter or EGR valve that the ECU will eventually identify that these components are no longer working and flag a check engine light (CEL) and OBD2 code.
Aside from OBD2 (including original OBD vehicles), Honda ECUs (from the factory) run rich at WOT and in VTEC. This is likely for safety's sake, to help reduce the chance of detonation and allow for wide variances in climate, altitude, temperatures, etc. This can have a drastic effect on power. Honda ECUs also don't deal very well with bolt-on mods due to the MAP-based system of determining airflow into the engine. What this boils down to is that whether you are stock or modified, you are probably running too rich at WOT and in VTEC. At part throttle, it is debatable that an AFC gains much if anything at all- the engine is running "closed loop" (using the O2 sensor to trim the fuel mixture) and Hondas are tuned to run lean at part throttle for clean emissions."
Taken from: http://www.ntpog.org
(http://www.ntpog.org/)
The purpose of the EPA-mandated OBD standard was to provide a means for which factory engine controls could diagnose engine control malfunctions and identify to the driver (and subsequently the repair shop) that there was a problem. The OBD2 standard, mandated for all 1996 and up vehicles, required that the OBD interface be standardized across all makes and models, as well as monitoring emissions components performance and proper operation. This means that for 1996 and newer vehicles with OBD2 that if you remove the catalytic converter or EGR valve that the ECU will eventually identify that these components are no longer working and flag a check engine light (CEL) and OBD2 code.
Aside from OBD2 (including original OBD vehicles), Honda ECUs (from the factory) run rich at WOT and in VTEC. This is likely for safety's sake, to help reduce the chance of detonation and allow for wide variances in climate, altitude, temperatures, etc. This can have a drastic effect on power. Honda ECUs also don't deal very well with bolt-on mods due to the MAP-based system of determining airflow into the engine. What this boils down to is that whether you are stock or modified, you are probably running too rich at WOT and in VTEC. At part throttle, it is debatable that an AFC gains much if anything at all- the engine is running "closed loop" (using the O2 sensor to trim the fuel mixture) and Hondas are tuned to run lean at part throttle for clean emissions."
Taken from: http://www.ntpog.org
(http://www.ntpog.org/)