Centrifugal Pumps on an engine are similar to that of a pool pump. Centrifugal air pumps driven by an engine were very popular in the early days of American oval track racing. A Swiss engineer, named Buchi, back in 1909 created the first Turbocharger.

It took a long time for turbochargers to become established, but in the last 40 years they have become universal on most diesel powered engines. Their characteristics are particularly suited to diesel engines. Much has been written about turbo lag, a slight hesitation when extra power is demanded. But in the later designs it has almost been eliminated.

Turbochargers are more complicated than Superchargers, but its purpose is the same as a supercharger which is to increase the density of air entering the combustion chamber. However, a turbo or ‘centrifugal supercharger’ does not rely on engine mechanics to spin its turbines. Instead turbos use exhaust gasses to do this job. For that reason a Turbo has two impellers either end of a common shaft. Exhaust gas which is already at high pressure, is fed into the turbo and spins the turbine at staggering speeds of around an average, 175,000 RPM. On the other end of the drive shaft, the air intake turbine also spins at the same speed and thereby increases the density of air which is forced into the engines combustion chamber. The turbine shaft is supported on a wide supporting bearing, usually in the form of a free-floating bush.

As with Superchargers, a by-product of a turbo is immense heat. This heat needs to be managed effectively in order to increase the efficiency of a Turbo. A Turbocharger requires an intercooler to cool air flow as well as the lubrication of bearings to increase efficiency. On a Turbo, which is more efficient than a Roots Blower, temperature rises of 75 degrees Celcius are common at a boost of 100 kPa or one BAR, which implies manifold temperatures of 110 degrees Celcius.

Although, the Original Equipment Manufacturers (OEM), Turbocharged and Supercharged installation engines are subjected to stringent tests, such as 1000 hours on a dynamometer test bed, at almost full throttle, engines fitted with these high performance additions add levels of stress to the powerplant.

In theory, the life of the engines bottom end should not be affected because the addition of a low-pressure turbo (up to 100kPa boost or one BAR), actually lowers the average bearing loads at higher engine speeds.

When driving a Turbocharged vehicle, avoid accelerating from low engine speeds at large throttle opening in a high gear. These greater torque values load the engine and its drivetrain considerably, especially if it’s a diesel turbo. Any naturally aspirated engine will outlast a modified high performance engine, but compromises performance and fuel economy.

Decreasing temperature is a well known performance tuning trick. In racing terminology and in simple-terms, it means qualifying a racing car on a cold day, and we all know from experience that this works because an engine runs better when ambient temperatures are low.

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Take some time to think what a pump really is and what its functions are. Oil, water and fuel pumps are obvious, but include master cylinders, slave cylinders, clutch operating cylinders and even the pump that operates your window washer. These pumps all work in different ways and can be separated into two categories, namely, displacement pumps or centrifugal pumps.

Displacement Pumps are basically Superchargers. Other similar displacement pumps include the oil pump of a car which is a small version of a Roots Blower. Unlike brake master and slave cylinders which are piston pumps. The Roots Blower, which seems to be the fashion of superchargers today, was first patented by the Roots Brothers in the USA in 1860. Roots Blowers were fitted to famous cars during the ‘50s’ and ‘60s’, such as the racing Alfa Romeos, and supercharged Mercedes-Benz racing and touring cars. This type of blower has recently been revived by Mercedes-Benz and Jaguar due to the designs positive action. A typical boost level of a modern production engine is between 70-100 kPa or one-bar. The maximum boost levels are limited to the fuel quality available as detonation occurs at high boost levels.

Superchargers are devices that force an air/fuel mixture into the cylinders than would usually be drawn in under normal atmospheric conditions, so by definition Turbo Chargers are also Superchargers. However, the way in which they function differentiates them into their respective fields.

Superchargers and Turbo’s are used to force a denser, higher volume of air into the combustion chamber thus giving the engine a huge increase in horsepower.  In a normally aspirated engine (one without a turbo or supercharger fitted to it), air must enter the combustion chamber naturally at atmospheric pressure, which at sea level is around 14,7 Psi. At higher altitudes this pressure is even less and thus a normally aspirated engine will perform better at sea level than higher up, inland.

A Turbo or Supercharger will not only increase the pressure of the air entering the combustion chambers, but also the volume of air. Such a high volume of air into the engine increases the power output so dramatically that a 1500 cc supercharged engine can produce as much power as a 3000cc normally aspirated powerplant.

There are various types of Superchargers, but all are driven mechanically by the engine. The turbines in a Supercharger are driven via a belt there off the engine. These turbines spin extremely fast and thereby increase the density of the air which is then forced down into the engine. Whilst a Turbo Charger makes more peak horsepower, a Supercharger delivers that power more instantly.

However, there are downfalls to Supercharging. As with Turbo Charging, heat is a big problem. The speed of the turbines create heat as they collide with and hit air molecules added to the heat created by the mechanical operation itself. This heat is absorbed by the air which the Supercharger is compressing which in turn expands and thereby reduces its density. Thus there is always an objective to increase the efficiency of Superchargers.

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THE DUAL-MASS FLYWHEEL has successfully reduced the vibration that an engine will normally transmit through into the gearbox and drivetrain. A dual mass flywheel is basically constructed from two discs or flywheels roughly the same diameter as a standard run of the mill single plenum flywheel would be. Each disc of the dual mass flywheel would share about one half the mass of a single flywheel. The first flywheel is attached to the crankshaft and with the spigot shaft driving through the second flywheel oscillating in harmony in respect to each other.

An engine and its flywheel that is harmonically balanced still gives off vibrations in a number of different ways. These vibrationms are caused by the combustion forces acting on the pistons and connecting rods, whether it is a two-cycle engine or four-cycle engine. The foremost vibration given off is known as 'torsional vibration transverse' and the effect it has on engine and gearboxes is far worse at lower engine RPM than at mid and high engine speeds. Diesel engine vibrations can be up to five times more severe under operating conditions than that of most petrol driven engines and this is why harmonic balancing plays such an important role in any rotating engine part, with special attention being paid to the flywheel..

Movement is controlled by circumferential springs working against stops or buffers so that the first flywheel is able to vibrate with the crankshaft while the springs ensure that very little of this vibration gets transferred through to the second flywheel. A normal clutch unit, but without springs in the hub of the driven plate, is bolted to the second flywheel and the gearbox input shaft is splined to the driven plate of this clutch. The result is that very little torsional vibration gets transmitted to the rest of the vehicles drivetrain thus ensuring a more harmonious transfer of vibrations as the per the old saying, ‘two is better than one’, which is key to vibration dampening.

The amount of oscillation that takes place is directly related to engine speed and the load bearing capacity of the vehicle. This means that when you combine a large throttle opening with a low engine speed the oscillation will be severe, but as the engine speed climbs, or the throttle opening is reduced, the oscillation will die down. In other words when driving try and refrain from harsh throttle openings and heavy clutching as the modern dual mass flywheel can not take aggressive clutching as the older more conventional clutch and flywheel combinations.

Repairs for a dual mass flywheel in particular can be extremely expensive. For example, a Mercedes-Benz Vito clutch repair costs in the region of R15000.00. An alternative and much cheaper repair method is to replace the unit with a single disc flywheel and clutch assembly at half the price.

This conversion process is being done in South Africa in a number of cases where the flywheel is far too expensive or unavailable from the agents or scrapyards.

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Piston manufacturing has been the result of continuous research and development of unique materials, engine and piston designs and technologies through time. The forged pistons manufacturing process begins from the raw materials to a skirt coating finished part. Racing conditions demand the strength that only forged pistons can offer the engine builder and vehicle manufacturer. When compared to cast pistons, forged pistons are by far tougher and proven to be extremely durable in abusive racing conditions of all types. The forgings are designed to stand up to the any abuse that high performance motorsport applications require without failing, typically before any other part of the engine breaks.

Cast pistons are often found to be on the brittle side and are absent from the grain structure found in forgings of any kind. It is cast pistons that will inevitably fail catastrophically when the inertia levels are exceeded. Forgings have tightly condensed grain that is aligned to the basic shape of the piston or in other forgings the shape of the part. This produces higher mechanical properties and a better resistance to stress and fatigue within an engines harsh environment thus maximizing performance.

Skirt shapes and profiles are very specific to each piston application. The shape of the pistons skirt is one of the most functional areas on the piston besides the piston rings and gudgeon pin. It is the skirts that provide stability and smooth operation the cylinder sleeves bores. The pistons stability within the bore is of paramount importance for a proper piston ring seal and which also reduces levels of friction. Some forging alloys expand more than casting alloys to produce the most power, least wear, and best seal at optimum running temperature. Some pistons manufacturers offer a skirt coating, which ultimately ads to the toughness of the piston working together to minimize friction and produce more horsepower, and provide improved wear resistance. This process allows the piston to be fitted to the bore with a finer tolerance of bore to piston clearance, allowing a better ring seal, without compromising the reliability of the engine. Design work is very detailed to insure the latest piston skirt profiles for minimal rock, tight clearances, and long skirt life.

Engineers specialize in building custom forged or cast pistons to your exact specifications. Light weight forgings and extra strength forgings, skirt coatings, offset pins, and a variety of other features are available from manufacturers. Custom pistons for drag racing, oval track, rally cars, modified saloon racing and moto-X amongst many other forms of racing and are able to manufacture just about any piston required.

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