The Hindu Business Line : Adding turbocharger not possible to existing engine

WHAT is turbo-charging? By what percentage will the power and torque increase? Can it be applied both to diesel and petrol engines? Can it be applied to the newer common rail direct injection (CRD) and multi-point fuel injection (MPFI) engines to improve their performance? Finally, can turbo-charging be applied as an after-market fitment to an old car?

V. S. Rajagopalan

Turbo-charging an engine is a mechanism by which the rated peak power output of the same power train is boosted. Internal combustion engines need a mixture of air and fuel to burn and eventually the energy produced provides the drive force. The turbocharger's technology is quite simple and it achieves its purpose by boosting the flow of one of the two constituents — air — of the combustion process. This, in turn, raises the engine's power output.

Turbo-chargers are generally used in diesel engines to enhance their power and performance. A similar principle is also used for boosting petrol engine performance, usually for high-end cars and for racing applications. All naturally aspirated engines have an air intake mechanism built in that helps kick-start the combustion process. So, when the intake valves open in the engine, the piston's downward movement immediately creates a vacuum which forces air into the combustion chamber. With the simultaneous delivery of fuel into the chamber and the sparking from the plugs, combustion takes place.

The turbo-charger consists of a turbine (almost like a wind turbine), which is connected to the engine's exhaust line. Along the same line, a compressor that is powered by the turbine follows. The engine exhaust gases are re-routed and caught by the turbo-charger's turbine blades, spinning the same to speeds as high as 250,000 rpm in some cases.

The turbine then cranks and powers the shaft on which it is mounted. The spinning shaft, in turn, powers the compressor on the other end of the whole system.

Since the compressor is located on the engine's air-intake path, this device actually speeds up the process of flow of air into the engine. So, instead of the usual flow of air into the chamber due to the vacuum created by the pistons, air is actually force fed into the engine by the turbocharger's compressor. This leads to a sudden jump in the amount of air inside the combustion chamber, to a level which in is excess of what is required for combustion under the regular (non-turbo) cycle.

To balance the air-fuel mixture, electronic sensors on board the car pump more fuel into each of the engine's combustion cycles; thus leading to an increase in the amount of fuel burnt for each injection. This results in higher engine power and performance. A five to ten per cent jump in rated peak power output is achievable by introducing a turbo-charger to the engine

Turbo-chargers have been applied to boost the power of both diesel and petrol engines, but while petrol engines have to necessarily be multi-point fuel injected for inducting superchargers (as they are called for petrol applications), the diesel engines that feature turbos need not necessarily be the common rail injection type.

It is not possible to add on a turbo-charger to a diesel engine in the after-market. Considerable changes need to be made to the engine and intake components and more on-board electronics is required for enabling the introduction of an efficient turbo-charging system for the car.

Recently I bought a used Bajaj Pulsar 150cc, which had done about 1,500 km. After the buy, one paid service was done. The problems that I am able to perceive now are, the bike's pickup has reduced and also there is a lot of smoke coming out of the exhaust accompanied by burning smell every time I stop the bike after trying to race past the 80 kmph speed level. I rarely do more than 60 kmph within the city and I observe that whenever I try to accelerate to speeds above 100 kmph, these problems crop up. What could be the reason?

Rajshekher

Various factors together may be contributing to the lower pick-up and increased emission. You have not mentioned whether this Pulsar 150cc is the older version or the newer DTS-i. Either way, the most common reason for the increase in smoke/emission from the exhaust are increased carbon deposition, which usually happens because of the use of poor quality fuels over an extended period.

The other reason for increased smoking and burning smell emanating from the silencer could be the mixing of engine oil with fuel in the combustion chamber or elsewhere. Often, this kind of mixing happens because of piston damage or damaged oil seal. Oil entering the combustion chamber could lead increased engine heat owing to poor combustion characteristics after the oil mixes with injected fuel. This would also lead to damage to the engine and components, including pistons.

The lower pick-up can be attributed to the leakage of oil into the engine. This apart, it could also be due to poor engine tuning, air lagging at the intake point or clutch plate wear and tear. Extended and improper use of the clutch will speed up the wearing process and this, in turn, can lead to lower pick-up.

That is another reason (extended improper use of the clutch) why you will also need to take the bike to a company-authorised mechanic for a thorough check of the vehicle. The issues that we have mentioned are not exhaustive and are only suggestive of the most probable problem areas that will have to be examined. But going by your description of the bike and its problems, the other possibility is that the bike's speedo has been tampered with to show a lower reading.

So, have your bike checked for tampering, which may be the principal source of all your problems.

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