Hello everyone, i'm here at work and was kinda bored so i thought i would do a write up on various things that seem to trip everyone up when it comes to modifying cars. Hope you enjoy and learn a couple of things.
On-board Diagnostic system(or OBD2), is a protocol standard for all cars manufactured after 1996. Its purpose is to let you know if anything is wrong with the engine(like faulty sensors, misfires, detonation, etc). Since it is a protocol standard, all ECUs transmit their error codes in the same way(thats why the ODB2 scanners work for any OBD2 car). Back in the days of ODB1 each manufacturer had its own protocol, so unless you had the manufacturers code reader, getting the error codes from the ECU was difficult.
The purpose of aftermarket ECUs like AEM, Motec, Hydra is to control the engine. Tuning a car means programming the ECU in the car to support the modifications to the engine. Basically this means telling the ECU to apply X amount of fuel and Y amount ignition timing for a each amount of load(manifold pressure) and RPM that the engine will see.When you turbo a naturally aspirated motor you surpass the capabilities of the ECU. Honda programmed the ECU(pretty much perfectly) to function below 0 psi (from the MAP sensor). Once you hit positive manifold absolute pressure the ECU has no idea what to do. It does not know how much fuel to add or how much ignition timing to apply for engine load/engine speed.
When it comes to emissions (at least in CT), if their emissions computer can not communicate with your OBD2 port you fail automatically. What this means is that if you run an aftermarket ECU(AEM, Motec, Hydra, Hondata, Crome, etc) you will fail because none of these comply to the ODB2 standard. Their purpose is for engine control, not diagnosing problems. In other words after-market ECU = fail emissions. If your engine is boosted, chances are, you are not running a stock ECU. The reason being that the stock ECU will not know how to control your bigger injectors, or understand how to deal with positive pressure from the turbo, or read in additional sensor data like EGT or wideband sensor(s).
As far as passing emissions is concerned it depends on where you are and who you know. Some states are more lax than others and getting a friend that works at a shop to pass you will work in some places but not others. Once again, i can only comment on CT's rules and regulations, but the computer they have at the testing facility checks the VIN number from the ECU to make sure that the ECU is for that specific car. What this means is that the whole testing process is automated and getting a friend to pass you will not work(at least in CT). This leaves you with only 1 option to pass; Revert the car back to stock(as far as engine electrical and catalytic converter if you don't have one on) and run the stock ECU. In other words, change out all the ECU controlled/reading parts like injectors, EPM, wideband or EGT sensor(s), and run your wastegate wide open(so you don't hit boost and the ECU will know how to control the engine). As long as your engine is functioning properly(no trouble codes) you will pass emissions. This method has proven to work seeing as i did it 2 years ago for my emissions test and my engine was boosted back then too. If you have changed to dynamics of the engine (Pistons, cams, valves) your stock ECU will not be able to control the engine, and chances are you will damage it. Risking engine damage for emissions testing is not worth it.
For those that have modified their engine internals past the control of the stock ECU or swapped the engine, there is another way to pass. I'm still working out the design of my ECU hack, but rest assured this hack will be done by the end of the month (cause thats when i have to pass
) and i will share the knowledge with my fellow 6geners.
I hope this clears up a couple of things for everyone. Feel free to comment or ask questions.
On-board Diagnostic system(or OBD2), is a protocol standard for all cars manufactured after 1996. Its purpose is to let you know if anything is wrong with the engine(like faulty sensors, misfires, detonation, etc). Since it is a protocol standard, all ECUs transmit their error codes in the same way(thats why the ODB2 scanners work for any OBD2 car). Back in the days of ODB1 each manufacturer had its own protocol, so unless you had the manufacturers code reader, getting the error codes from the ECU was difficult.
The purpose of aftermarket ECUs like AEM, Motec, Hydra is to control the engine. Tuning a car means programming the ECU in the car to support the modifications to the engine. Basically this means telling the ECU to apply X amount of fuel and Y amount ignition timing for a each amount of load(manifold pressure) and RPM that the engine will see.When you turbo a naturally aspirated motor you surpass the capabilities of the ECU. Honda programmed the ECU(pretty much perfectly) to function below 0 psi (from the MAP sensor). Once you hit positive manifold absolute pressure the ECU has no idea what to do. It does not know how much fuel to add or how much ignition timing to apply for engine load/engine speed.
When it comes to emissions (at least in CT), if their emissions computer can not communicate with your OBD2 port you fail automatically. What this means is that if you run an aftermarket ECU(AEM, Motec, Hydra, Hondata, Crome, etc) you will fail because none of these comply to the ODB2 standard. Their purpose is for engine control, not diagnosing problems. In other words after-market ECU = fail emissions. If your engine is boosted, chances are, you are not running a stock ECU. The reason being that the stock ECU will not know how to control your bigger injectors, or understand how to deal with positive pressure from the turbo, or read in additional sensor data like EGT or wideband sensor(s).
As far as passing emissions is concerned it depends on where you are and who you know. Some states are more lax than others and getting a friend that works at a shop to pass you will work in some places but not others. Once again, i can only comment on CT's rules and regulations, but the computer they have at the testing facility checks the VIN number from the ECU to make sure that the ECU is for that specific car. What this means is that the whole testing process is automated and getting a friend to pass you will not work(at least in CT). This leaves you with only 1 option to pass; Revert the car back to stock(as far as engine electrical and catalytic converter if you don't have one on) and run the stock ECU. In other words, change out all the ECU controlled/reading parts like injectors, EPM, wideband or EGT sensor(s), and run your wastegate wide open(so you don't hit boost and the ECU will know how to control the engine). As long as your engine is functioning properly(no trouble codes) you will pass emissions. This method has proven to work seeing as i did it 2 years ago for my emissions test and my engine was boosted back then too. If you have changed to dynamics of the engine (Pistons, cams, valves) your stock ECU will not be able to control the engine, and chances are you will damage it. Risking engine damage for emissions testing is not worth it.
For those that have modified their engine internals past the control of the stock ECU or swapped the engine, there is another way to pass. I'm still working out the design of my ECU hack, but rest assured this hack will be done by the end of the month (cause thats when i have to pass
) and i will share the knowledge with my fellow 6geners.I hope this clears up a couple of things for everyone. Feel free to comment or ask questions.
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.. Luckily I don't need to pass emissions or inspections in Oklahoma, but if I ever move it may help!
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