Article from the Telegraaf Newspaper on the workings of the Turbo - will be translated soon |
The exact starting point for the use of Turbos is a bit of a grey area, but I believe the idea was born in Europe, as this continent craved for V8 performance, without the fuel consumption of these cubic beasts due to the sheer astronomic cost of fuel in this part of the world.
It was Formula 1 that eventually paved the way for the development and uptake of the turbo into mainstream production. Although F1 regulations allowed for turbos and superchargers (the latter of which date back to the early 1930's with the likes of the beautiful 12 cylinder Bentley's and later in the second world war fighter planes) to be used in the mid 1960's. It was thought though by F1's regulators that no team would actually make use of this rule due to the requirement of the engines having to have smaller capacities if these 'gadgets' were to be used.
Renault fancying its self as an innovative manufacture, took up the challenge and were the first to use a turbocharger on their 1.5 litter, V6 engine in the RS01 Formula 1 car chassis, which debuted at the British Grand Prix in 1977.
The engine was a revolution, as even though it only had a capacity of 1.5 liters, it was able to pump out something in the region of 580 bhp (all be it for a short while), whilst normally aspirated competitors of the time were 'only' able to develop something in the region of 500 bhp.
After this introduction into F1, the first 'civil' application of the turbo came under the bonnet of the Saab 900 in 1978. This company has incidentally been the only manufacturer in the world (to my knowledge anyway) to have at least one turbo model in its line-up right up to now.
In the truck sector, it was the Mack Truck company who were the first to plumb a turbo onto a diesel engine. As many of you will know, the turbo has come of age with the diesel engine, with nearly every truck, ship and heavy earthmoving machine having one of these compressors bolted onto the side of it. In addition to this, I believe that the turbo has been singularly responsible for creating a complete new car segment - namely the diesel car. It is responsible for transforming the once lethargic 'Noddy'esq' cars to serious 'must have' cars. Now making up something in the region of 30% of total European car sales.
THANK YOU MR.TURBO!
We Salute You
The principals of turbocharging and supercharging are essentially the same, with the exception that a supercharger is belt driven directly off the crankshaft (like the way your water pump, power steering pump and alternator are driven). Whilst a turbocharger is driven by the exhaust gasses of a car. I know that there are also 'hybrid' versions on the market that use a combination of both turbo and supercharger systems, (an example of this is the Rotrex system, made by Scanpower Tuning ApS in Valby Denmark), but I will only delve into the workings of the turbocharger. If you want to know more about the Rotrex, drop me a line and I will mail you the article.
In its simplest form, an engine works by "sucking in cold (good) air, mixing this with vapourised fuel, igniting it, to then blow the hot (bad) air out" as demonstrated below.
Cold Air Hot Air In Out
Workings Of An Internal Combustion Engine Diagram
The problem with this, is that it relies on the compression of the pistons in the bores to 'pull' and 'push' the air in and out of the engine. This in its self takes (costs) energy and thus horsepower. Because of this, there is a 'ceiling' to how much and how well the engine is able to 'breath'.
The fuel that an internal combustion engine burns requires air to complete the combustion cycle. Once the air/fuel ratio reaches a certain point, the addition of more fuel will not produce more power, only black smoke or unburned fuel into the atmosphere.
So, if it was possible to 'force feed' an engine (i.e. ram air down the engine's throat), it may be possible to get more power from the engine. The way a turbocharger is able to do this, is by increasing the volume of air being forced into the engine (by compressing the air), allowing more fuel to be delivered to produce more horsepower from a given size engine. A turbocharger may be able to increase the power of an engine by some 40% or more, compared to its normally aspirated cousin.
However, even though compressing air and forcing it into the engine will be better than a normally aspirated engine, there is a drawback, namely that when air is compressed, it also heats up. Again, I refer you to your bicycle hose,and ask you to feel the hose when you have spent some time pumping up your tyre, it will be hot. And as aleady mentioned, it is cold air that is desired as this can 'hold' more oxygen particles!
The way that the clever engineers solved this, was by using an intercooler. This is an air to air radiator (much like the radiator of your car except that instead of water flowing through it, it is compressed air). This intercooler cools the compressed air before it is sent into the block. The picture below shows the air's routing through the engine including its temperature, indicated by the colouring.
Now that I have explained the basic principals of the system to you, it is rather simpel to understand what a turbo is and how it works. Below I have added a section diagram of a turbo.
The twin red arrows on the right are the exhaust gasses coming from the exhaust manifold into the so-called hot air passage of the compressor housing. The hot air then pushes against the blades of the turbine wheel and exit on the right of the diagram. By turning the turbine wheel, the connecting shaft is rotated, which in-turn rotates the compressor wheel on the other side of the compressor housing. This compressor wheel then sucks in (cold) air through the so-called cold air passage which is then blown out the top to the inlet manifold of the engine.
There is just one additional bit of information that you need. This system can be seen as being an ever increasing spiral of speed (of the turbo). The reason for this, is that as the turbo has more exhaust gasses flow through it, it sucks more air in, which in-turn provides more exhaust gasses and so forth. To avoid the engine from over revving, over boosting (turbo pressure) and ultimately destroying its self, a bypass-valve is added.
This vent is connected to the exhaust gas side of the turbohousing,(before the turbine blades) and is controlled by another valve through a connector shaft. (see the pictures below).
This second valve works through a chambered diaphragm system (illustrated below and seen in the picture above as the goldish cylinder at the top of the shaft running in the middle of the picture). On the one side of the diaphragm is a chamber with a spring inside it pushing against the diaphragm. On this side, there is also a shaft running from the diaphragm through the middle of the spring and out of the chamber to the by-pass vent. On the other side of the diaphragm there is a chamber that is connected to the inlet manifold by means of a hose.
The spring has a pre-calculated compression rate so that when the pressure of the cold air being blown into the block reaches a certain level, the diaphragm is pushed back, which in-turn (through the connecting shaft) opens the by-pass valve.
There you go, now you know how a turbo works.
In addition to this, the turbochargers increased air pressure in the engine means that the engine can be run at altitude without adverse effects. Something that cannot be said for normally aspirated engines which will lose horsepower with increases in altitude.
Extra care in operation - need to give the turbo more time than normal to get up to operating temperature and cool off subsequently after a drive
The engine working picture was kindly donated by my friend Stephan from Squadra Tuning (click for contact details), whilst the section diagram of the turbo and the routing of the intercooler picture were donated by my friend Casper at C&E Turbochargers (click for contact details) who rebuilt my turbo and took the pictures of the process, found on the previous page, for me. I also Want to thank Teri Olcott from the Vintage Cars Web-site for his review of the turbo, ideas from which I have weaved into this page