N43/N53 and Technical Inspection

Not without a reason, BMW AG in their instruction how to perform their engine exhaust test highlights the specifics of N43/N53 engines.


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Test instructions for the exhaust-gas (emissions) test on BMW vehicles with petrol engines

BMW vehicles as from model year 1968, MINI as from R50 and Rolls-Royce as from RR01


I have read, that some owners of vehicles with these engines are taking the printed copies of this document with them, because the inspectors of Technical Inspection are considering the data, displayed by gas analyzer, as incorrect.


When one year ago I passed the Technical Inspection and the exhaust gases for my N53B30 were done, the engine performed in Stratified charge and CO/CH indications were very low. For example, HC has displayed around 10 .. 17 ppm. Only after passing the inspection, I noticed, that the inspector has recorded in the protocol 100 ppm. Then I didn’t understand, why he did that. But now I am smarter. If you want to know, why the inspector did that – read this entry! But when I asked, if he is not confused, for example, by Lambda value, he answered – let’s check the holes in the exhaust system… Needless to say, that no holes in the exhaust systems were found.


CO/CH allowed values in Latvia for a vehicle of the current generation is:

CO idle: 0.3 %

CO by 2000 .. 3000 RPM: 0.2 %

HC: 100 ppm

Lambda: 1.00 +/-0.03


This year, as usual, I passed Technical Inspection, which includes measuring of the exhaust gases.

When measuring in idle, the engine performed Homogeneous mode, CO was displayed at 0.000 %, HC was within a range from 3 .. 8 ppm

Measuring with increased RPM displayed Lambda around 1.90, CO still was 0.000 %, HC dropped to several ppm.


At this moment inspector started to check measuring equipment for the exhaust gases – he disconnected the measuring gauge from the filter, restarted the measuring equipment. Nothing of this helped – the results were still the same. Then the inspector checked log files of the measuring equipment and found the moment when the engine switched from Homogeneous moisture to Stratified charge and recorded in the protocol highest values found in the log file:

CO: 0.000 % idle

CO: 0.010 % with increased RPM

HC: 11 ppm

Lambda 1.04


And now I know, why the inspector in previous year’s Technical Inspection recorder 100 ppm – he didn’t believe to the data, displayed by the measuring equipment!


It is possible, that this story sounds funny, unfortunately, the situation can change, if the inspector considers, that the exhaust gases don’t meet the standards. Then you have to print the regulation from BMW AG and it should be presented to the inspector of the TI.