New Delhi: How can we forget the old diesel engines that were heavy, sluggish and noisy, emitting choking clouds of black smoke to pollute the atmosphere? We are also not allowed to forget them because many old diesel engined vehicles still clutter our streets. It is therefore not surprising that many people condemn all diesel engines without knowing how much the technology has changed.

Murad Ali Baig, Auto expert & columnist

Since February 1897, when Rudolph Diesel made the first successful diesel engine , technologies have evolved every decade. Today, diesel engines, despite diesel costing as much as petrol, account for 49% of engines in passenger cars sold in a highly pollution conscious Europe with 69% in France.

Many buyers of prestige cars like the Audi, BMW and Mercedes are not bothered about the price of fuel want diesel engines so there has to be something good about modern diesels.

The torque and efficiencies of diesel engines had been good from the beginning but many improvements were made to improve combustion with better fuel pumps, injectors and nozzles to create a finer spray, etc.

In 1976, Daimler-Benz introduced turbo chargers that used exhaust gasses to push more fuel into the cylinders for better combustion while simultaneously capturing waste energy. This increased power and lowered emissions. But the revolutionary common rail technology introduced in the late 90’s was the most important improvement generating 30% more power, nearly double the torque, much lower vibration and greatly lowered engine emissions.

In the old diesel engines, each cylinder had fuel pumped into it one by one. Now a common rail or tube containing compressed fuel to very high pressure, feeds all the cylinders of an engine and an electronically controlled injector releases the fuel into the cylinders at very precise intervals.

So more fuel is pumped into each engine and the fine spray gives better combustion for more power with lower emissions. Preheating of the fuel also results in lower vibration with the result that new diesel cars are peppy and fun to drive.

The biggest benefit of the new diesels is the huge savings in fuel. As the new diesel engines deliver high torque at low engine speeds you can drive in higher gears at lower speeds and save about 30% fuel with plenty of power for acceleration.

Emission levels are lowered both through better burning of the fuel inside the engines as well as from the post combustion exhaust treatment. Catalytic converters, better mufflers and particulate filters scrub the exhaust gasses to improve emission levels. But better engines also need better fuel. Now that India has low sulphur diesel the SOX levels have gone down dramatically but some of the diesel is still adulterated.

Diesel engines have proven to be a great success among Indian passenger cars but small diesels have not been very successfully since they have not been developed suitably for India’s huge hatchback market. However, we may see some small diesels from Toyota’s Daihatsu subsidiary when they launch their small car in the not so distant future.

India’s industry leader Maruti has recently introduced their new 75 hp 1300 cc common rail diesel in Swift and we are sure to see it later in other models too. Hyundai has an excellent 110 hp 1500 cc CRDi diesel in its powerful Verna.

Almost all Tata motors cars are fitted with a 1405 cc workhorse ranging from 54 to 68 hp. Most Ford Fiesta’s are fitted with a 68 hp, 1400 cc turbo diesel common rail engine. The Skoda Octavia owes its success to a 91 hp 1900 cc TDi engine. The new Chevrolet Optra has 120 hp 2000 cc diesel. They are also found among most of India’s luxury imports. Mercedes alone offers seven different cars with the most advanced diesel engines.

Most of India’s SUV’s have diesel engines because most of them have to travel long distances especially if they are used as inter city taxis. Both the M&M Scorpio and Tata Safari have graduated to excellent common rail diesel engines. Daimler-Benz all sport modern diesel plants. And, they all meet mandated pollution norms.

With these improvements in engine technologies and fuels the impact has been huge and the Government has been able to move from Bharat Stage I to Bharat Stage IV where the carbon monoxide (CO) emission levels have declined 81%, the HC and NOX levels are down 69% and particulate matter, or soot, is 82% lower. These improvements are due to government pressures as well as response by the highly competitive auto industry.

Industry has done its bit and the Government must now move to urgently phase out the old diesel vehicles cluttering the roads including many owned by numerous government departments. They must also immediately curb the malpractice of the overloading of trucks. With their big engines that do heavy mileage every month an average bus or truck uses over ten times the fuel of a car and are therefore big contributors to India’s pollution.

Murad Ali Baig is one of India’s foremost auto experts. Feedback to his column can be sent at