I get more and more questions regarding the topic of NOx catalytic converters. Some askers want to change the exhaust, removing this catalytic converter; some are interested in the normal performance of the engine is possible without the NOx catalytic converter.
I will compile the most popular questions regarding NOx catalytic converters.
1. If the OEM NOx sensor is installed, but the NOx catalytic converter is removed – is the normal performance of the engine possible?
No, it’s not – MSD80 will quickly identify that the performance of the NOx catalytic converter is very low (actually, it’s 0, because the catalytic converter has been removed), it will register error message 30E9, forbid Stratified charge and Homogeneous lean modes – and the problems, which are typical to engines with defect of NOx system, will start.
2. The NOx catalytic converter and NOx sensors of my car are removed, no error message 30E9 is registered. Will the engine of my car perform normally?
No, it will not. The error message 30E9 is not recorded because the engine (due to defect/lack of NOx sensor) doesn’t perform in Stratified charge and doesn’t measure (is not able to measure) the performance of the NOx catalytic converter. Definitely, there are other error messages recorded, for example, 2EAE (no communication with NOx sensor), 2AF2; 2AF4; etc.; error message 30EA also is possible (mathematically calculated poisoning of NOx catalytic converter with sulfur is an above-allowed limit, but due to a defect of NOx sensor the desulfation is not possible). Also, in this case, the engine doesn’t perform and will not perform in Stratified charge and Homogeneous lean modes, it will have all problems, which are typical to engines with a defect of NOx system.
3. The NOx catalytic converter of my car is removed, but the OEM NOx sensor is operational, and there is no error message 30E9. True though, there are error messages regarding the performance of CO catalytic converter. Does the engine of my car perform correctly?
No, it doesn’t. Due to the bad performance of CO catalytic converters, the Stratified charge and Homogeneous lean modes are forbidden, and the low performance of NOx catalytic converters is not even measured. Due to problems with CO catalytic converters, the engine works in emergency mode (even, possibly, in mapped mode, which means – the temperature is lowered to around 80oC) with all problems, which are typical to engines with a defect of NOx system. In this situation, the problems with CO catalytic converters have to be solved firsthand (the typical cause of the problem – is increased oil consumption due to the breakage of the crankcase ventilation membrane).
4. If the NOXEM is installed – will the engine perform correctly without a NOx catalytic converter?
Yes, in this case, the engine will perform as intended by manufacturer: it will turn on the Stratified charge and Homogeneous lean, will perform all adaptations (including test of mechanical and chemical efficiency of cylinder in idle, in low/average/high load conditions), will perform desulfation and regeneration sessions etc.
5. Can the NOx catalytic converter clog because of the impact of the sulfur? Is it necessary to keep the NOx catalytic converter max clean to maintain the maximum performance of the engine?
No, the sulfur does not gives additional resistance to exhaust gasses. The sulfur pollution is measured in several grams, the layer of it – in microns. The exhaust parameters don’t change, when the pollution of the NOx catalytic converter is 0 or 4 grams (4 grams are max allowed value).
Below are listed several recommendations/conclusions from user experience:
- In none of the cases after removing the NOx catalytic converter, an increase in torque/power was observed in the engine. Even in some cases when (due to defective crankcase ventilation membrane) because of increased oil consumption, the CO catalytic converters were damaged, and there were suspicions that the NOx catalytic converter could be clogged with oil residues;
- After removing the NOx catalytic converter, the exhaust became louder, and higher vibrations were observed in idle mode. An increase in vibration can be felt putting the foot on the exhaust pipe;
- The NOx catalytic converter can be replaced with a resonator – also, with this solution (in case of NOXEM installation), the engine will perform as intended by the manufacturer.
Bimmerprofs recommends not disposing of the NOx catalytic converter. It doesn’t decrease the performance of the engine, but (even if the performance is decreased – it’s less than intended by the manufacturer) decreases the amount of nitrites in the exhaust, which, in turn, has a positive impact on ecology. Without the NOx catalytic converter, the amount of NOx in the exhaust reaches high values (1500+ppm) even at low loads.
