30 DAY AVG. PRICE$276.77/each
DESCRIPTION / USES
Taken from a diesel engine.
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Diesel catalytic converters come from diesel engines. A lot of times the diesel engine cats are not worth too much money due to the lack of precious metals inside like platinum, palladium, and rhodium. However, there are some diesel cats that are worth a decent amount of money. You can send pictures of your diesel cats to our team for an accurate quote.
Since the diesel engine is more durable than its gasoline counterpart, the required life expectancy for diesel catalytic converters is also longer than that for gasoline converters. For example, since 2004 the US EPA durability requirement for emission control systems on heavy-duty diesel engines is 10 years/22,000 hours/435,000 miles (700,000 km), whichever occurs first (previously, the requirements were 8 years/290,000 miles or 467,000 km).
In situations where thermal losses from the converter are important, they have to be modeled during the converter design. Double walled designs with either air gaps or ceramic fiber insulation are commonly used on gasoline converters in the close-coupled location, which are optimized for cold start hydrocarbon performance. Since diesel cold start emissions are much less critical, such designs have not been used for diesel converters. However, due to the low temperature of diesel exhaust gases, diesel converters should be placed close to the exhaust manifold or exhaust pipe insulation should be applied to assure satisfactory catalyst performance. The low temperature performance, including cold start, is becoming increasingly important for diesel catalytic converters, especially in light-duty applications.
The geometry of converter headers, especially that of the inlet header, can influence the exhaust gas flow distribution in the catalyst. It is believed that flow maldistribution negatively affects catalyst performance and/or durability. That opinion, although not supported by convincing experimental data, became a widely accepted consensus. Even if the emission performance is not improved, a skillful design of the headers can certainly decrease the total catalytic converter pressure loss.
Catalyst canning technologies have evolved since the 1990s, driven by the demands of California LEV, ULEV and SULEV gasoline applications. Still more development will be needed to satisfy the demands of future exhaust systems, especially for diesel engines. The major factors responsible for the evolution in catalytic converter technology can be summarized as follows:
- In gasoline applications, the converter was either moved to a close-coupled location, or a second close-coupled pre-converter was introduced in addition to the underfloor converter. The close-coupled converter, installed very close to the exhaust port of the engine, is exposed to high temperatures, high thermal shock conditions, and increased vibration, thus calling for more robust canning.
- Ultra-thin wall ceramic substrates for gasoline engines have wall thickness on the order of 0.002-0.003″ (0.050-0.075 mm). Example commercial configurations introduced in the late 1990s include 600/3 and 900/2 substrates. These parts are weaker than the older, thicker wall substrates (e.g., 400/6.5, of 0.0065″ or 0.17 mm wall thickness). New materials and/or packaging methods were necessary to accommodate these parts.
- Widespread use of catalytic converters on diesel vehicles, such as on Euro 3/4 cars, created specific challenges related to the low temperature operation.
- Exhaust systems on heavy-duty engines, especially those incorporating diesel particulate filters (DPF), require very robust packaging. While monolithic DPF substrates are packaged using essentially the same methods as catalytic converters, they are much heavier and larger, thus creating new challenges.
The first thing to say about diesel engines is that they always run ‘lean’.
For this reason, a catalytic converter used on a diesel engine is often known as a ‘diesel oxidation catalytic converter’.
Another important characteristic of diesel engines is that the exhaust gas is cooler than that of spark-ignition engines, in some cases falling to a temperature of barely 100 C at idle.
Since catalytic reactions are temperature dependant, it is a good idea to find out the exhaust gas temperature for a particular application at an early stage.
Coatings on diesel catalytic converters can be varied to give ‘light-off’ at different temperatures, as illustrated on the following graph: