Turbochargers Ltd

First developed for the comercial sector in 1924, the turbocharger uses the engine's exhaust gases to power a turbine, which drives a compressor, and pushes more air into the engine. This allows the engine to produce more power without any increase in size. Turbochargers have provided such significant improvements in engine efficiency that they are now fitted to almost all new diesel engines.

All of the engine exhaust gases pass through the exhaust manifold and into the turbine housing (unless diverted through the wastegate). The expansion of these gases, acting on the turbine wheel, causes it to turn. After passing through the turbine, the exhaust gases are routed to the atmosphere. In many cases, the turbine muffles the exhaust sound, so lillte to no noise muffling is needed.

The turbine also functions as a spark arrester. For example, it is recognised by the U.S. Department of Agriculture as providing a spark arrester function adequate for forestry operations. The compressor is directly connected to the turbine by a shaft. The only power loss from the turbine to the compressor is the slight friction of the journal bearings.

Also called Twin Flow, Twin Scroll Twin Port or Dual Port Turbochargers, this refers to the turbine (exhaust) hous design with 2 exhaust entry ports. To better utilise these impulses, one design has an internal division in the turbine housing and the exhaust manifold which directs these exhaust gases to the turbine wheel. There is a separate passage for each half of the engine cylinder exhaust.
On a six-cylinder engine, there is a separate passage for the front three cylinders and another passage for the rear three cylinders.
By using a fully divided exhaust system combined with a dual scroll turbine housing, the result is a highly effective nozzle velocity. This produces higher turbine speeds and manifold pressures than can be obtained with an undivided exhaust system.

Also called Twin Flow, Twin Scroll Twin Port or Dual Port Turbochargers, this refers to the turbine (exhaust) hous design with 2 exhaust entry ports. This type of turbine housing design matched to a split pulse exhaust manifold design lifts low engine speed performance but making the turbine side of the turbo up to approx 15% more efficient. The benefit of this is that you can still use a relitivly unrestrictive large A/R housing but still maintain good boost responce. This consept has been used in Diesel applications for a sevceral decades but is only begining to gain popularity in the performance tuning scene.  

The turbocharger offers a distinct advantage to an engine operating at high altitudes. The turbocharger automatically compensates for the normal loss of air density and power as the altitude increases.The appearance, construction, and operation of the altitude compensator is the same as that of a turbocharger. However, the purpose is different.
The purpose of a turbocharger is to increase the power output of an engine by supplying compressed air to the engine intake manifold so increased fuel can be utilised for combustion.
The purpose of the altitude compensator is to maintain consistent power output and efficiency of an engine operating at all altitudes. This is done by supplying compressed air to the engine intake manifold at a pressure about equal to that at sea level.
There is no increase of fuel for combustion and consequently no increase in basic horsepower of the engine. However, the extra air provided by the altitude compensator normally increases combustion efficiency, which generally will improve fuel economy and reduce smoke level.

With a naturally aspirated engine, horsepower drops off 3 percent per 1000 ft (300m) because of the 3 percent decrease in air density per 1000 ft (300 m). If fuel delivery is not reduced, smoke level and fuel dilution will increase with altitude.

With a turbocharged engine, an increase in altitude also increases the pressure drop across the turbine. Inlet turbine pressure remains the same, but the outlet pressure decreases as the altitude increases. Turbine speed also increases as the pressure differential increases. The compressor wheel turns faster, providing approximately the same inlet manifold pressure as at sea level, even though the incoming air is less dense.

However, there are limitations to the actual amount of altitude compensation a turbocharged engine has. This is primarily determined by the amount of turbocharger boost and the turbocharger-to-engine match.

All turbochargers operate at a very high speed. This can range from 40,000 to over 300,000 rpm.

There are four basic ways of using multiple turbochargers on an engine:
1. Twin Turbo. This is where you have 2 turbos being fed exhaust gas from half of the engine each. This is popular in a "V" type engine where one banks exhaust gas feeds each turbo. This is still single stage turbocharging, but using more than one turbo to achieve the desired boost pressure. Common on petrol/gasoline engines.  
2. 2 Stage compounding Turbochargers. This is where you have a small High pressure (HP) turbo mounted close to the engines exhaust ports and a larger Low Pressure (LP) turbo being fed from the waste gasses the are coming from the HP turbo without any valving. Sometimes this system uses a wastegate to control the peak pressure. Usually found on hip powered diesel engines where high boost pressures are required. This system offers good throttle response while still achieving high engine performance and very high boost levels by way of compounding the boost pressure.   
3. Staged Turbocharging. This is where you have 2 turbos, one larger than the other in a staged setup using valving to bring the 2nd (usually larger) turbo into play at a desired engine speed or load. This system offers good throttle responce as well as high volumens of air flow. Typically yhr boost pressure is not compounded in this setup.
4. Regulated 2 Stage Turbocharging. This system is complex with valving used to control both the airflow and the exhaust gasses. it provides a seamless transition into high boost with amazing response and can offer very high performance. This system can be used with 2, 3 or more turbos for great effect. Also commonly used with VNT style variable geometry  turbochargers.