An in depth look at the turbochargers

An in depth look at the turbochargers  
Filed under:
on 06/10/2008

The word 'turbo' sends a shrill through the auto enthusiast's spine. They immediately tend to get related to Bugatti's and Porsche's. With that kind of a response a turbocharger evokes, they should have been popular right from the time they entered the Auto industry, right?... hmm... in fact No!

One of the most remarkable inventions to aid the Internal combustion engine, turbochargers had to struggle and were up against the wall for about twelve years after they debuted on the first production car. Auto manufacturers either ignored them or were unsatisfied after they tried bolting them on to their cars.

In this Automotoportal featured, we discuss the birth, development, merits and demerits of turbochargers. So wear your seatbelt, and get ready for the extra excitement!

A turbocharger is a device which uses a turbine run by exhaust gases to drive a compressor to force more air into the engine at a higher pressure. The result of this is increased efficiency. As simple as that!

The turbocharger was invented by Swiss engineer Alfred Buchi in the year 1905. But its first application was during World War II to help aircraft engines perform better. It is an example which is pretty rare in the world of engineering of 'something for nothing.'

Turbo's first appeared in cars in the year 1962 on the Chevrolet Corvair Monza Spyder. The engine was a flat-6, air cooled and rear-mounted.

All turbo's in modern engines are bolted on to the exhaust port but this particular turbo was placed between the carburettor and the intake manifold. The turbo helped the power to leap from 95 to 150 bhp, a direct gain of 50%!

Unfortunately, the Corvair had to be discontinued within sometime, not because of turbocharger problems, but due to the car's dreadful handling. This meant trouble for the turbo right at the beginning of its life in the Auto Industry.

The turbo's stint with GM was not yet over. After being a part of an unsuccessful package in Chevrolet, it moved on to another wing of GM- Oldsmobile. A V8, 3+ liters engine was the chosen candidate. Similar to the Corvair, the turbo was mounted between the carbs and the manifold. A considerable jump in power was the effect as the engine churned out 215 bhp compared to 155 previously, at 6 psi boost (Boost refers to the increase in manifold pressure generated by the turbocharger in the intake manifold that exceeds normal atmospheric pressure.)

The usage of certain grades of fuel resulted in the deadly formation of carbon deposits in the cylinders. Engineers tried getting around the problem by injecting a 50-50 mixture of water and methyl alcohol but due to reliability issues, that plan was dropped and so was the turbo. Frustration mounted on the turbo. One brand, two attempts, still no avail.

German Auto giant BMW was the turbo's next destination. In the 60's, BMW had a major role to play in races and was very actively involved in motorsports. In the 1969 edition of the European Touring Car Championships, for the first time, BMW contested with turbocharged 2002 saloons and eventually went on to win in the 2-litre category. Prompted by the success, BMW decided to throw in a turbocharger on the street legal version of the track bred saloon four years later.

Working alongside a Kugelfischer fuel injection system, the KKK turbocharger helped the road car reach speeds as high as 130 mph which was regarded phenomenal for a 2-door car at that time, all this when the engine measured 2000 cc. The main drawback of this engine was turbo lag. Turbo lag is the feeling of nil-response when the accelerator is depressed and sudden-response moments later.

This meant that the turbo was useless on the 2002 until 4,000 rpm was reached and even when it did, the turbo kicked in vigorously. This did not go down well with BMW, with reliability issues and dreadful fuel-consumption figures adding fuel to the fire, that too at a time when the world was witnessing an oil crisis and crude oil prices were at an all-time high.

By this time, turbochargers had spent a frustrating period of twelve years in the Auto industry. It was a case in which it always found itself at the wrong place and at the wrong time.

One German sports car maker named Porsche was set to change all that. It would give turbo's a new meaning and the way the world looked at them was going to change. Porsche's successful and popular rear-engined 911 was the turbo's proving ground and didn't it do well!

A similar KKK turbocharged was employed to do the work and the output of the 3-liter raised from 200 to 260 bhp. The only difference compared to its earlier applications was the use of an intercooler, a device that functions like a radiator in cooling the charge, so that higher amounts could be forced into the engine. The Porsche 911 Turbo went on to win fans and received a lot of positive feedback. It suddenly became the car people thought of when the word 'turbo' was raised.

After witnessing the success and potential of a turbocharger on the Porsche 911, other Auto makers soon followed suit. Saab, a brand today considered as pioneers in turbocharging, was the first to take the plunge and offered a family saloon with a turbocharger in 1977. The purpose was not to extract more power, but to meet the harsh emission standards. The 99 turbo was a success not only to Saab but also to turbocharger as it proved its worth in mass-produced passenger cars. By the end of the 1980's, turbo's found themselves helping out engines that ranged from a mere 548 cc on a Mitsubishi to the 6750 cc engine on a Bentley. Turbochargers played an important role in pushing up Bentley's sales and by 1989, 49% of the cars Rolls Royce sold were Bentleys compared to 6% in 1981.

After it failed to impress the automakers stateside, turbo's returned in 1978 on the Buick Le Sabre. It wasn't long until that model was discontinued and Pontiac tried their hand with the turbo by installing them on the 1981 Firebird and Trans Am models. The turbo achieved wide spread success on US soil through the 80's and manufacturers found them as convenient devices that could boost power without any major modification to the engines.

Listed below are the merits and demerits of using a turbocharger:

1) Higher power output
2) Better atomization of fuel (translates into better combustion, smoother operation maximizing fuel-efficiency)
3) Better torque characteristics (can be used to achieve better acceleration and the gearbox can be designed for reducing downshifts when acceleration is required during cruising)
4) Reduced exhaust smoke

1) Engine components need to be made of thermally inactive materials due to excess heat build up
2) Turbochargers are costly and are seldom repaired when damaged.
3) Turbo lag - The one big disadvantage of using a turbocharger.

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