Note. The visual and function test is not applicable from 1st January 2010 in the emissions test. It will be performed in future as part of the main test!
The visual check is one of the most important points of the exhaust emissions test. This should be performed carefully, since it can exclude many incorrect evaluations.
Special instructions are listed as follows:
- Visual check of all exhaust emission-relevant components for presence, completeness, absence of leaks and damage, provided that this is possible without removal.
- Check catalytic converter for mechanical damage by tapping.
- Visual check catalytic converter housing for over-heating (red/violet discoloration).
Pre-condition for effective minimising of pollutant emissions, apart from correct engine adjustment, is the general engine condition, such as:
- Air cleaner element
- Spark plugs / glowplugs
- Absence of leaks in the intake and exhaust muffler systems
Leaks in the intake and exhaust system as well as defective oxygen sensors are the most common cause of failure of the EGE (exhaust gas emissions) test.
Check pollutant-related components including exhaust system for presence, completeness, leaks and damage as far as is possible without dismantling. This includes, in particular, the catalytic converter, oxygen sensor and, if necessary, fuel vapour retention system, exhaust gas recirculation systems, secondary air systems and sensors and actuator lines.
On Opel vehicles, the visual inspection of the fuel filler flap and its securing device includes checking the presence and operation of the fuel filler flap retainer and the presence and operation of the overflow-prevention device in the filler neck. The overflow-prevention device consists of a spring-loaded flap at the end of the filler neck. It is always closed, apart from when refuelling. The test involves using a suitable tool (e.g. a pencil) to see if the flap opens and automatically closes. The Agila and Astra-H have a fuel filler flap with loss-prevention device. On these vehicles, the loss-prevention device must be checked (see "Visual and functional check - fuel system, fuel filler flap and securing device").
Result of visual check, components, – not satisfactory / – satisfactory.
Diesel Particulate Filter (DPF)
The cleaning system is designed such that all exhaust emissions can be efficiently reduced in combination with a primary and an underfloor catalytic converter close to the engine. As well as soot particles, these are hydrocarbons (HC) and carbon monoxide (CO).
Opel commenced mass-production of the innovative diesel particulate filter technology at the beginning of 2004 in the Vectra series and in the Signum with the newly developed 1.9 CDTI ECOTEC engine, which is also described in the "New Technical Features MY 2004.5".
The new diesel particulate filter consists of a solid ceramic honeycomb made of silicon carbide through which microscopically small channels pass. The flow of exhaust gas passes through the walls of the channels and the soot particles collect on their surfaces. The particles deposited must be burnt off regularly to prevent the filter becoming blocked. The so-called regeneration phase relies on a precious metal coating on the filter substrate and targeted multiple injection which raises the exhaust gas temperature of the diesel engine to the ignition temperature of 600 degrees Celsius which is required for the combustion process in the filter. An injection system which can make the requisite flexibility available in every engine load range is a pre-condition for this. Thus the system should work at its optimum not only when under full load but also when "cold", for example in short urban journeys when working as a taxi.
To be able to fulfil these requirements, Opel favours direct injection using the latest generation common rail system for its diesel models. This technology enables the quantity injected and its pressure to be controlled in accordance with need, as can the injection pattern for the fuel in the cylinder.
A further advantage of the intelligent Opel solution: the regeneration takes place in non-continuous intervals, adjusted to the respective style of driving. That means that the combustion of the soot particles deposited and therefore the subsequent injection of fuel only takes place when back-pressure occurs in the filter because of deposits. This process is controlled by pressure and temperature sensors in the area surrounding the DPF unit – the driver does not notice this process at all.
In addition to the "start cat" close to the engine, an oxidizing catalytic converter is located upstream of the particulate filter which oxidizes the HC- and CO-emissions with the aid of the atmospheric oxygen in the diesel exhaust gas. The nitrogen oxide emissions are reduced below the EURO 4-limit value by internal measures in the engine. This configuration guarantees that the engines will meet future exhaust gas regulations.