04) Petrol 2 speed idle emission test
04.1) Test Stage 1
04.2) Test Stage 2
04.3) Test Stage 3
04.4) Outside testing limits
04.5) Petrol 2 speed idle emission test with OBD compliant vehicle
4) Petrol 2 speed idle emission test
The following presentation will be based around the AVL DiGas 480 series emission tester as used in for example the DiX 650 tower as pictured. It is meant to give you a good insight into the current European emission testing protocol, and how the equipment deals with the tests.
Emission testing on petrol power vehicles in all European countries and many countries outside the European union is done using a two speed idle test.
The two speed idle test is simulating congested urban traffic, idling in traffic jam and low load (<20% throttle) running as what would happen in build up areas.
Urban areas have the highest density polulation, so pose the greatest health cost risks to society.
Detailed view of DIX 650 Diagnostic Station with the DiGas 480
The test is described on the following pages in great detail, this to achieve a full understanding of the process for the operator.
You should be aware that most of the screens are only visible for mere seconds, as the process is fullly automatic*).
E- OBD vehicles
E-OBD vehicles where build from Jan 2000 new models and Jan 2001 existing models. E-OBD vehicles are NOT fail safe. An E-OBD vehicle has more closed loop systems and check functions, not much more has changed.
On E-OBD vehicles if something goes wrong in the mixture preperation process within the programmed parameters the up and down stream oxygen sensors will be happy and letting high emissions through.
There seems to be a misconception that E-OBD vehicles do not need to be emission tested. This is largely based on the fact that in some European countries (Germany in 2008 more countries will follow) an EOBD scantool needs to poll the ECU for emission related fault codes (readyness test) during the emission test.
Also these vehicles have during the emissions test their engine temperature and RPM measured via the E-OBD connector, which is a great time saver.
Non OBD vehicles
- Temperature measurement
For non OBD Petrol vehicles which includes vehicles up to 2000 or some even newer, like Australian sourched vehicles the temperature of the engine needs to be measured with an oil temperature probe inserted into the dip stick. The oil temperature needs to be greater than 70° C before the test can comence. A cold piston will have high HC's and high CO's as result. The combustion will not extend into the fringes (cold areas) of the cold combustion chamber. Therefor a large number of vehicles could fail the test.
- RPM measurement
The engine speed needs to be measured during an emission test.
In many early to late 90's engine management system the mixture control will go into open loop at idle. Also every engine management system will enter into a different mixture/ emission control cycle as soon as the accelerator is released (idle). As stated before most urban vehicle emissions are emitted during idle and low part load.
The emission tester needs to recognise the operating status of the engine, so that it can produce an objective two speed idle emission test result.
The tester will indicate to hold the engine speed between 2500 and 3500 RPM and will wait until it senses that the engine is between those two speeds, this is called high idle. The high idle emission values are being stored if the engine speed is between those two values for a period of time.
After the high idle test is finished an idle test has to be performed. The emission tester will sense that the RPM are low, between 500 and 1000 RPM and that the idle speed is stable for a period of time. The emission tester will store the idle speed emission results.
On vehicles which are in a poor state of repair it is some times impossible to hold the RPM at a stable level. A slow responding (worn) oxygen sensor, incorrect adjusted TPS, or seized idle control motor are just a few examples that will cause unstable engine speeds. These vehicles inevitably will fail the emission test.
*) The process is fully automatic except that the vehicle needs to be connected to the machine and the vehicle type needs to be selected from a menu.