In the previous articles, we introduced Why vehicles need to detect exhaust? and How to test the exhaust of gasoline vehicles? while how to test diesel vehicles exhaust?
1、Free acceleration method
（1）Filter-Type Smokemeters Mode：When the diesel engine is at idle speed, quickly step the accelerator to the bottom for 4 seconds and then release it. Measure the emission of carbon smoke with a Filter-Type Smokemeter.
（2）Opacimeters Mode：When the diesel engine is at idle speed, quickly step the accelerator to the bottom for 4 seconds and then release it. Use opacimeter to measure the light absorption coefficient and calculate the emission degree of carbon smoke.
2、Lugdown cycle：Use chassis dynamometer and engine tachometer to simulate the state of the vehicles under road(load) driving conditions, and measure the exhaust emission of diesel vehicles by opacimeter and NOx analyzer.
3、Ringelman emittance method: Put the Ringerman smoke blackness map at an appropriate position, compare the smoke of diesel vehicle exhaust with the black soil on the map, and determine the blackness of diesel vehicle exhaust plume.
