BS6 diesel-engined cars: How to escape the DPF problem?

When BS6 emission norms came into effect, many manufacturers launched diesel engines with DPF or diesel particulate filters to meet the norms. While these filters make car emissions cleaner, they have caused diesel vehicles to shut down. We find out what is causing the problem and how to avoid it?

Diesel, as you know, is the most energy-dense hydrocarbon fuel commercially available. This means that when it is mixed with air and ignited, it combines with available oxygen molecules to release water, carbon dioxide and a lot, lot more energy. This is in theory, however, and inside a physical engine, never does perfect combustion occur.

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What can go wrong?

Loads on the engine vary and sometimes there’s less oxygen-rich air like when the turbo isn’t pushing in more air at low RPMs, such as during rush hour driving, or when driving at higher altitudes where the air is less dense. Additives, accelerants, engine oil present inside the combustion chamber, etc. create a bunch of other byproducts including soot.

This soot is harmful, and increasingly stringent emission norms, such as the Bharat Stage 6, dictate that these particulates must not be allowed to enter the atmosphere and be dealt with to reduce the impact on the environment and our health. One solution is to capture these tiny particles by taking the exhaust through a microscopic sieve in-line with the exhaust system. Excess heat from the exhaust gasses under heavy engine loads would help burn these off.

How to get rid of it?

This sieve is called the Diesel Particulate Filter, of DPF. Most modern diesel-powered cars have this system. If you drive on the highway regularly, you might not even know your car has one, because the conditions required for the DPF to clean itself are more than likely met. For those who only do short commutes, lug the engine, or drive at higher altitudes, the DPF makes its presence felt. An error code shows up on the MID as an engine check light or a dedicated telltale, and the vehicle enters a limp-home mode or could even refuse to start. This is to protect the engine and exhaust parts from damage.

But, you can avoid it too!

Prevention is better than cure, applies here too. There are two ways this is taken care of. The first and the most common way is to go for a long highway drive. Consistently heavy engine loads, high-RPM for 20min-30min, are generally sufficient for the exhaust gasses to turn hot enough to burn off the collected soot and clear the DPF. On the upside, some fun times.

Another way is built into modern cars. Some cars will passively raise the idle speed to heat the exhaust and introduce excess fuel into it. Others indicate that DPF needs to be regenerated and a procedure needs to be followed while the car is parked for it to do this on its own. This is best for owners who live inside city limits and can’t just hop onto a highway regularly.

If these procedures are followed regularly and diligently, they help protect the engine and exhaust parts. Sometimes despite following the procedures, the vehicle throws up warnings very often, and this means that something else is wrong with it, and it’s time to visit the car doctors.

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