Hello, I was browsing through the web seeking for ways to remove CEL after blocking off EGR passage and have seen people doing it on other cars using a resistor plug. Would it work on a first gen NSX and did anyone try it before?
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EGR delete resistor plug
- Thread starter Abmax
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- cel egr delete egr valve resistor
First gen NSX as in NA1/NA2 versus NC1 or do you mean pre versus post OBDII?
On a pre OBDII car there are probably ways that you can block the ECU from generating an error code when you delete the EGR valve. Later OBDII cars have a lift / position pot and that might be harder to fake. However, that might be the least of your issues. When the engine is in the EGR operating range it admits exhaust gas to the intake manifold which reduces the available O2 for mixing with the fuel. The fuel maps in the EGR range are adjusted to reduce fuel PW to keep the AFR at the target value. When the ECU gets the message that the EGR is not working I expect (but am not 100% sure) that it switches to a back up fuel map based upon no EGR so that the engine is safe and generates a CEL saying that there is a problem. If the ECU does not detect an EGR failure because you have tricked the EGR monitoring circuit it may not map switch leaving you with a lean AFR engine condition which is undesirable.
If you are prepared to rewrite the fuel map to adjust the fuel PW values in the EGR region you can eliminate the lean fuel problem and do the trick to avoid the CEL. @Honcho has remapped his NA1 ECU and I believe is running with the EGR deleted so he can probably give you better advice on the complete solution.
On a pre OBDII car there are probably ways that you can block the ECU from generating an error code when you delete the EGR valve. Later OBDII cars have a lift / position pot and that might be harder to fake. However, that might be the least of your issues. When the engine is in the EGR operating range it admits exhaust gas to the intake manifold which reduces the available O2 for mixing with the fuel. The fuel maps in the EGR range are adjusted to reduce fuel PW to keep the AFR at the target value. When the ECU gets the message that the EGR is not working I expect (but am not 100% sure) that it switches to a back up fuel map based upon no EGR so that the engine is safe and generates a CEL saying that there is a problem. If the ECU does not detect an EGR failure because you have tricked the EGR monitoring circuit it may not map switch leaving you with a lean AFR engine condition which is undesirable.
If you are prepared to rewrite the fuel map to adjust the fuel PW values in the EGR region you can eliminate the lean fuel problem and do the trick to avoid the CEL. @Honcho has remapped his NA1 ECU and I believe is running with the EGR deleted so he can probably give you better advice on the complete solution.
Do not trick the ECU into thinking the EGR is present if its not, that creates a dangerous situation where the ECU is running advanced timing maps and reduced fuel (to account for the inert exhaust gasses that are no longer present in the combustion chamber).
@Old Guy there is a single ROM bit that disables the entire EGR system in the 91-94 ECUs, no modifying of the fuel tables is needed. There are separate EGR fuel and timing maps that are no longer used once the system is disabled like this, I've actually repurposed those memory regions for my code patches and additional features I've programmed in.
This is the proper way to disable EGR: make a custom chip with the EGR bit disabled.
@Old Guy there is a single ROM bit that disables the entire EGR system in the 91-94 ECUs, no modifying of the fuel tables is needed. There are separate EGR fuel and timing maps that are no longer used once the system is disabled like this, I've actually repurposed those memory regions for my code patches and additional features I've programmed in.
This is the proper way to disable EGR: make a custom chip with the EGR bit disabled.
I agree with John. The only way to safely disable EGR is to turn off the bit. I do it via the Demon II system.
