Do Diesels Have Catalytic Converters?

Catalytic converters are an indispensable ingredient of contemporary autos, aiding to handle emissions and restrict the influence of every single auto on the world. But even though we take them for granted in cars in general, diesel automobiles ought to elevate some interesting questions for emissions-minded buyers.

Following all, the combustion mechanisms don’t perform the exact same way, and the distinctions amongst fuel and diesel gasoline will demolish your automobile if you use the mistaken 1. So why would not the exhaust also be various?

Diesel automobiles have catalytic converters, but it ought to be no shock that they really do not share many similarities with their gasoline counterparts. There is far more to think about, and if the thought of diesel presents you visions of billowing black smoke from a roaring exhaust, you possibly feel they aren’t as effective at their positions.

But diesels have appear a long way in environmental friendliness. With developments in diesel fuel and the following-treatment method programs that all set exhaust for the outside the house air, diesels are making only a fraction of the hazardous byproducts of prior generations.

What Is a Catalytic Converter?

Magnaflow catalytic converter
Magnaflow catalytic converter (Image Credit: Kim2480, Wikimedia Commons CC BY-SA 3.0)

Diesels generate far more hazardous emissions than regular fuel engines, but the two catalytic converters eliminate the same byproducts. These include:

  • Carbon monoxide
  • Hydrocarbons (HCs)
  • Nitrogen oxides (NOx)

A normal gasoline-run car makes use of catalysts to change these hazardous pollutants into much less harmful emissions. After the gasses go away the motor via the exhaust manifold, they vacation to the catalytic converter, in which three critical metals— platinum, palladium, and rhodium—make the conversion.

The gasses go by means of the “filter” of the catalytic converter, a ceramic honeycomb composition with a coating of the all-important precious metals. The metals need to warmth up to activate, so they are most successful following the car has been managing for several minutes. The ceramic design aids it get sizzling more quickly and keep the warmth, and an insulating wrap additional speeds up the process to avert too many pollutants from escaping.

The metals in the heated catalytic converter adjust the chemistry of the passing exhaust via reduction and oxidation. The major processes that take place incorporate:

  • Platinum and rhodium pull oxygen off nitrogen oxides to release harmless nitrogen
  • Platinum and palladium add oxygen to carbon monoxide to create CO2
  • Platinum and palladium add oxygen to hydrocarbons to form H2O and CO2

Do Diesels Have Catalytic Converters?

Diesels are much a lot more fuel-productive than gasoline-run autos and therefore have some emissions advantages. But they also create up to ten times far more nitrogen oxides than gas automobiles and significantly much more soot. Soot is particulate issue (PM) consisting mainly of unburned hydrocarbons. Modern day diesel engines deal with these dangerous byproducts by making use of far more levels to filter the exhaust.

Diesel Oxidation Catalyst

Close-up of automotive torque converter
Image Credit: jeffy11390, Shutterstock

The diesel oxidation catalyst (DOC) was the first phase of diesel catalytic converters that arrived in the late eighties. In more complicated contemporary diesel engines, it is nevertheless the very first phase of emission reductions.

Most of the system’s platinum and palladium sits right here, changing HCs and CO to H2O and CO2. Since it lacks rhodium, it functions equally to more mature two-way catalytic converters that did not get rid of NOx. Modern day DOCs oxidize passing nitric oxide (NO) to create nitric dioxide (NO2), which aids the later on catalytic converter levels in eliminating NOx.

Diesel Particulate Filter

The diesel particulate filter (DPF) is the main weapon in PM reduction. Companies released DPFs to their diesel vehicles in the early 2000s. They turned necessary by the end of the decade.

A DPF is a wall-circulation monolith, a tubular composition composed of hundreds of parallel channels with alternating plugs at the finishes. Exhaust gasses can permeate by way of the walls to proceed on by way of the tailpipe, but the PM stays trapped in the filter. A purposeful DPF can trap up to ninety nine% of PM, eliminating the visible black soot that you’ll see coming out of more mature diesel tailpipes.

As the DPF works, it collects soot and can end up clogging. It have to usually regenerate to stay obvious and practical, or the automobile will ultimately crack down. Diesels have a DPF indicator light in their cluster to warn of a regeneration problem.

Filters regenerate by burning away the trapped soot. They do this by way of energetic or passive regeneration:

  • Active regeneration: Exhaust heats up to over 1,000°F to burn off soot
  • Passive regeneration: Introduction of NO2 oxidizes soot at lower temperatures

Passive regeneration, the a lot more productive strategy, operates with regular exhaust temperatures, usually taking place with lengthy drives on the freeway.

Energetic regeneration needs an extra heating component to get to the needed combustion temperatures, so it employs much more vitality. If the Eu senses the DPF is blocked, it will increase the temperature to combust the soot. It is much more typical for energetic regeneration to occur on shorter drives the place the exhaust does not have time to heat up.

In worst-scenario situations, you could need a pressured regeneration in a shop when the blockage helps make the automobile inoperable. No make a difference how it regenerates, a DPF will also need occasional cleaning as it builds up ash from burned soot.

Selective Catalytic Reduction

catalytic converter in modern car
Image Credit: Ulianenko Dmitrii, Shutterstock

The DPF is the very last phase in modern day diesel catalytic converters, subsequent the selective catalytic reduction (SCR). The SCR was the most well-liked remedy for new rules in 2010 that tightened NOx emission expectations for hefty-obligation vehicles.

Rhodium is not sufficient to deal with the massive oxygen load the ample NOx in diesel exhaust presents. But an SCR can minimize NOx emissions by up to 90%. The huge chamber sits between the DOC and the DPF, using an open up-loop method of expendable diesel exhaust fluid (DEF).

DEF is composed of ammonia or, much more typically, an aqueous mix of around one-third urea and two-thirds deionized water. Small quantities of DEF spray into the SCR toward a catalyst. Urea will crack down into ammonia (NH3) and carbon dioxide under the exhaust’s warmth. As these interact with the NOx in the catalyst, they generate harmless nitrogen and h2o.

How to Tell If a Diesel Catalytic Converter Is Failing

The cluster in your diesel will generally warn you of dire scenarios with your exhaust. Oxygen sensors positioned in the exhaust soon after the catalytic converter can feeling changes indicating an obstruction or breakdown in the converter. A scan tool should notify you what is going on.

Your auto has other methods of speaking difficulties with the catalytic converter, however they are not as subtle as a flashing light-weight powering the steering wheel. Frequent indicators of a issue contain:

  • Poor motor performance
  • Sulfur smell
  • Dark exhaust smoke
  • Overheating engine
  • Sluggish acceleration

Keeping on leading of regular provider and cleaning your catalytic converter at regular intervals for each your vehicle’s guidelines will make sure you get the most use out of your catalytic converter. At $one,000–$three,000 or even more, replacements are not low cost, but your catalytic converter must previous 10 or a lot more several years when given appropriate treatment.

Final Thoughts

Diesels have come a lengthy way in producing much less emissions, and the catalytic converter’s evolution will only keep on. But more than the prolonged phrase, the industry’s programs show up to be focused on other technologies, most of which are far far more eco-pleasant and much less dangerous to human health.

The infrastructure isn’t all set to assistance EVs across the board, particularly in the trucking industry, so diesels will have their area for the foreseeable future. But as restrictions grow to be more rigid and technology enhances, the shift away from diesel will continue to select up the tempo.


Featured Picture Credit rating: Ulianenko Dmitrii, Shutterstock