A turbocharger is a turbine-driven, forced induction unit that increases an engine’s efficiency by forcing extra compressed air into the combustion chamber, liberating more power and torque. The key difference between a naturally aspirated engine is the presence and functionality of a compressor. This forces more air, mixing with more fuel, facilitating a greater pressure and hence generating more power.
How does a turbocharger work?
In naturally aspirated (N/A) engines, intake gases are sucked into the engine via atmospheric pressure, filling the void of the downward stroke of the piston. The volume of air, compared with the theoretical volume, if the engine could maintain atmospheric pressure, is called volumetric efficiency. A turbocharger optimises an engine’s volumetric efficiency by increasing density of the intake gas facilitating an increase of power on each engine cycle.
The turbocharger compresses ambient air from which it enters the intake manifold at a heightened pressure. This results in a greater mass of air entering the cylinders, per intake stroke. The energy required to spin the centrifugal compressor is derived from the kinetic energy of the recycled exhaust gases.
Boost is the term by which the manifold pressure exceeds atmospheric pressure. The control of a turbocharger can be by the use of a waste-gate, blow-off valves and variable geometry.
Can a turbocharger damage the engine?
In petrol engine turbocharger applications, boost pressure is limited to keep the engine system within its thermal and mechanical design. Over-boosting an engine causes damage through pre-ignition, overheating, and over-stressing the engine’s internals. For example, to avoid engine knocking or detonation, the intake manifold pressure must not get too high, thus the pressure at the intake manifold of the engine must be controlled. Opening the wastegate allows excess energy to bypass it directly to the exhaust pipe, thus moderating boost pressure. The wastegate can be either controlled manually or by an actuator, via the ECU.
What is turbo lag?
Lag is the time required to change power output in response to a throttle change, noticed as a hesitation when accelerating. The exhaust system and turbocharger has to generate the required boost, spooling, which is not instantaneous. Inertia, friction, and compressor load are the primary contributors to turbocharger lag.
Do superchargers suffer from lag?
Superchargers do not suffer from turbo lag, as the compressor is being driven by the engine.
Turbocharger applications can be categorised into those that require changes in output power (such as automotive) and those that do not (such as marine, aircraft, commercial automotive, industrial, engine-generators, and locomotives). While important to varying degrees, turbocharger lag is most problematic in applications that require rapid changes in power output. Engine designs reduce lag in a number of ways:
- Lowering the rotational inertia of the turbocharger by using lower radius parts and lighter materials
- Changing the turbine’s aspect ratio
- Increasing upper-deck air pressure and improving wastegate response
- Reducing bearing frictional losses, e.g., using a foil bearing rather than a conventional oil bearing
- Using variable-nozzle or twin-scroll turbochargers
- Using multiple turbochargers sequentially or in parallel
- Using an anti-lag system
Petrol powered turbocharged cars
The first turbocharged passenger car was the Oldsmobile Jetfire option on the 1962–1963 F85/Cutlass. Also in 1962, Chevrolet introduced a special run of turbocharged Corvairs, initially called the Monza Spyder (1962–1964). Later, Porsche added the technology to the 911/930 from 1975 and Saab followed with the famous 1978–1984 Saab 99 Turbo.
Today, turbocharging is common on both diesel and petrol-powered cars. Turbocharging can increase fuel efficiency by allowing a smaller displacement engine.
The first turbocharged cars in F1
In F1 a 1,500cc turbo engine was equivalent to 3,000cc N/A engine. Jean-Pierre Jabouille gave the turbo-engined Renault RS01 its debut at Silverstone in 1977, retiring with turbo failure. 7 races later, he achieved his first finish. The twin-turbo setup came into play in 1979 and within 2 years, Jabouille gained the first victory in the French GP. BMW, Alfa Romeo and McLaren /TAG/Porsche, in 1983, experimented with the forced induction route and applied various configurations, aimed at gaining a competitive advantage. The BMW’s turbo, a truck turbo, was gigantic and the delivery was explosive. The lag was also significant. In later years, this was addressed but always remained a feature with the combination of huge turbo units and relatively tiny engine capacities.
BMW turbo F1 cars – extreme qualifying specification
In 1985, 1,300 bhp was extracted from as little as 1,500cc in qualifying specification. Porsche/TAG’s engine powered McLaren to titles in 1984, 1985 and 1986. The most extreme turbocharged F1 car was arguably the Benetton BMW. In 1986 the entire grid had utilised turbochargers. In 1986, a rule restricted to 195 litres of fuel on race day, but in 1987, when a pop-off valve – set to 4 bar, limited turbocharger pressures. The demise culminated in 1989 when the FIA announced a move to a 3.5 litre normally aspirated engine.
Diesel-powered turbocharged cars
The first production turbocharger diesel passenger car was the Mercedes 300SD, produced from 1978. Most diesels are now turbocharged, due to improved efficiency and performance of diesel engines. The concept Audi R10, complete with a diesel engine, famously won the 24 hours race of Le Mans, for three consecutive years, in 2006, 2007 and 2008.
The first example of a turbocharged bike is the 1978 Kawasaki Z1R TC. Several Japanese companies produced turbocharged high-performance motorcycles in the early 1980s, such as the CX500 Turbo from Honda- a transversely mounted, liquid cooled V-Twin also available in naturally aspirated form. The Dutch manufacturer EVA motorcycles builds a small series of turbocharged diesel motorcycle with an 800cc smart CDI engine.
Experimental installations within aircraft started in the 1920’s. As an aircraft climbs to higher altitudes the pressure of the surrounding air quickly falls off. At 5,486 m, the air is at half the pressure of sea level and the airframe experiences only half the aerodynamic drag. Consequently, since the charge rely’s on air pressure, the engine normally produces only half-power at this altitude. The development of the Merlin engines, powering the RAF Spitfires in the 1940’s, led to supercharging, to obtain greater power and performance advantages.
Turbochargers vs superchargers (which is better?)
Turbochargers were originally called turbosuperchargers. A supercharger is actually only referred to a mechanically driven forced induction unit. The difference between a turbocharger and a supercharger is that it is driven by a belt attached to the crankshaft, whereas a turbocharger is powered by a turbine driven by exhaust gases.
Can you turbocharge and supercharge a car?
A Twin-charger refers to an engine with both a supercharger and a turbocharger. Twin-charging has been demonstrated in Gruppe B rallying cars such as the Lancia Delta S4. In commercial, mass produced vehicles, Volkswagon manufactured a variation of the popular Golf model. The 1400cc engine was both supercharged and turbocharged.
Disadvantages of supercharges
Belts, chains, shafts, and gears are methods of powering a supercharger, placing a mechanical load on the engine. An example is the single-speed supercharged Rolls-Royce Merlin engine, where the supercharger uses 150 hp. The benefits are staggering as the engine will now generate an additional 400 hp. This is still a disadvantage of a supercharger as the engine must withstand the net power output plus the power to drive the supercharger.
Superchargers have a lower adiabatic efficiency, especially Roots-type superchargers. Adiabatic efficiency is a measure of a compressor’s ability to compress air without adding excess heat. The compression process always results in high temperatures, however, more efficient compressors produce less excess heat. Roots superchargers impart significantly more heat to the air than turbochargers. Turbocharged air is cooler and denser and therefore more potential power than the supercharged air.
Turbocharger’s do not place a direct mechanical load on the engine, although they place exhaust back pressure on engines, increasing pumping losses. This is more efficient because while the increased back pressure taxes the piston exhaust stroke, much of the energy driving the turbine is provided by the still-expanding exhaust gas that would otherwise be wasted as heat through the tailpipe.
Disadvantages of turbochargers
The primary disadvantage of turbocharging is what is referred to as turbo lag. This is the time between opening the throttle and onset of increased intake pressure and power.
Variable output turbochargers
In variable output systems exhaust gas pressure at idle or low engine speeds is unable to drive the turbine. When the engine reaches sufficient speed the turbine section spools up enough to produce sufficient intake pressure.
What are the main components of a turbocharger?
The turbocharger has three main components:
- The turbine, a radial inflow turbine
- The compressor, generally a centrifugal compressor
- The centre housing rotating assembly
Many turbocharger installations use additional technologies, such as wastegates, inter-cooling and blow-off valves.
Turbine unit – turbocharger
Large turbochargers take more heat and pressure to spin the turbine, creating noticeable lag. Small turbochargers spin rapidly, but are less effective at higher engine speeds. Combinations, broadening the overall effectiveness across an engines range are popular, such as twin-turbochargers or variable-geometry turbochargers.
How to choose a turbocharger?
*Note to read more please visit the original superb article, a thorough reference to a variety of configurations, applications and bespoke to your vehicle and modification targets – click here.
Garrett turbos support an engine displacement from 1.4L up to 12.0L and horsepower at the crank from 140 up to 3000. Selecting the right size turbocharger for your application is critical.
Wheel Vs Crank Horsepower
Target horsepower refers to the peak horsepower you want the car to make when it is at max engine speed, at the crank. Parasitic loss, is the difference between power at the crank vs the wheels. Drivetrain loss is determined from the time it travels through the transmission to the driveline, and through the axles to the wheels. This is affected by transmission type and automatic transmissions typically suffer greater differences. Brakes, heavy wheels and tyres also affect drivetrain loss.
As an example we are going to start with a wheel horsepower target of 600 (RWD). In order to find a turbo that can support our target power we need to calculate for the drivetrain loss so we must multiply 600 * 1.15 = 690.
- Front Wheel Drive 10% (multiply HP target by 1.1) Wheel Horsepower * 1.1 = Crank Horsepower
- Rear Wheel Drive 15% (multiply HP target by 1.15) Wheel Horsepower * 1.15 = Crank Horsepower
- All-Wheel Drive 20% (multiply HP target by 1.2) Wheel Horsepower * 1.2 = Crank Horsepower
Twin-turbo designs have separate turbochargers working in sequence or in parallel. In the later, both turbochargers are provided an equal proportion of the exhaust gases. In a sequential setup, one turbocharger runs at low speeds and the second activates at a specified engine speed. Sequential turbochargers further reduce turbo lag, but require an intricate set of pipes to properly feed both turbochargers.
Two-stage variable twin-turbos are connected in series so that boost pressure from one turbocharger is enhanced by the second larger one. The distribution of exhaust gas is continuously variable, so the transition from using the small turbocharger to the large one can be done incrementally. These are used in Diesel engines such as the Opel bi-turbo Diesel, whereby the smaller turbocharger works at low speed, providing high torque at 1,500–1,700 rpm. Both turbochargers operate together in mid range, with the smaller one pre-compressing the air, which the larger one further compresses. At higher speed (2,500 to 3,000 RPM) the larger turbocharger takes over.
The twin-scroll turbocharger
Twin-scroll turbochargers have two exhaust gas inlets and two nozzles, a smaller sharper angled one for quick response and a larger less angled one for peak performance. In twin-scroll designs, the exhaust manifold physically separates the channels for cylinders that can interfere with each other, so that the pulsating exhaust gasses flow through separate spirals (scrolls). This leads to the pairing of cylinders. This promotes scavenging techniques, leading to improved turbine efficiency.
A variable-geometry turbocharger
Blow off valves and anti-surge valves – turbocharging
At the point when the throttle is closed and the engine is stressed, revolving at its peak rpm, the compressed air flows to the throttle valve without an exit. This rush raises the pressure of air leading to the compressor stalling and this air decompresses back across the impeller. The reverse flow across the turbocharger makes the turbine shaft speed reduce more quickly than it would naturally. To prevent this from happening, a release valve is fitted between the turbocharger and inlet, which vents off the excess air pressure.
The primary aim is to maintain the spool of the turbocharger. The air is usually recycled back into the turbocharger inlet (diverter or bypass valves), but can also be vented to the atmosphere. Valves that recycle the air also shorten the time needed to re-spool the turbocharger after sudden engine deceleration, since load on the turbocharger when the valve is active is much lower than if the air charge vents to atmosphere.
Turbocharging – going green
In the 2010’s, forced induction and a shift towards smaller capacity engines has been dictated by the ever growing shift to zero carbon. The automotive industry is undergoing another tidal shift in reducing emissions through its products and also process and manufacturing initiatives, to achieve net zero.
The inevitable turn to electrification in the late 2010’s has exponentially increased the focus of automotive manufactures to look at full electric vehicles, heightening the existing technology of car batteries. Additionally, light-weighting of vehicles plays a role in reducing emissions. Variations of composite, wood, novel carbon composites and lighter alloys are being considered for components and the chassis, structural elements of future vehicles.
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How does a turbocharger work? A turbo, is a turbine-driven, forced induction technology that increases an engine's efficiency by forcing additional compressed air into...
- Nice, Karim (4 December 2000). “How Turbochargers Work”. Auto.howstuffworks.com. Retrieved 1 June 2012.
-  Archived 26 March 2011 at the Wayback Machine
- “History of the Supercharger”. Retrieved 30 June 2011.
- “The turbocharger turns 100 years old this week”. www.newatlas.com. 18 November 2005. Retrieved 20 September 2019.
- Porsche Turbo: The Full History. Peter Vann. MotorBooks International, 11 July 2004
- Miller, Jay K. (2008). Turbo: Real World High-Performance Turbocharger Systems. CarTech Inc. p. 9. ISBN 9781932494297. Retrieved 20 September 2019.
- DE 204630 “Verbrennungskraftmaschinenanlage”
- “Alfred Büchi the inventor of the turbocharger – page 1”. www.ae-plus.com. Archived from the original on 5 April 2015.
- “Turbocharger History”. www.cummins.ru. Retrieved 20 September 2019.
- “Hill Climb”. Air & Space Magazine. Retrieved 2 August 2010.
- “Alfred Büchi the inventor of the turbocharger – page 2”. www.ae-plus.com. Archived from the original on 29 September 2017.
- Compressor Performance: Aerodynamics for the User. M. Theodore Gresh. Newnes, 29 March 2001
- Diesel and gas turbine progress, Volume 26. Diesel Engines, 1960
- “World War II – General Electric Turbosupercharges”. aviationshoppe.com.
- “History”. www.bwauto.com. Retrieved 20 September 2019.
- “HowStuffWorks “What is the difference between a turbocharger and a supercharger on a car\’s engine?““. Auto.howstuffworks.com. 1 April 2000. Retrieved 1 June 2012.
- “supercharging”. Elsberg-tuning.dk. Retrieved 1 June 2012.
- Chris Longhurst. “The Fuel and Engine Bible: page 5 of 6”. Car Bibles. Retrieved 1 June 2012.
- “How to twincharge an engine”. Torquecars.com. Retrieved 1 June 2012.
- “Four Stroke Engine Basics”. Compgoparts.com. Retrieved 1 June 2012.
- Brain, Marshall (5 April 2000). “HowStuffWorks “Internal Combustion““. Howstuffworks.com. Retrieved 1 June 2012.
- “Volumetric Efficiency (and the REAL factor: mass airflow)”. Epi-eng.com. 18 November 2011. Retrieved 1 June 2012.
- “Variable-Geometry Turbochargers”. Large.stanford.edu. 24 October 2010. Retrieved 1 June2012.
- “How Turbo Chargers Work”. Conceptengine.tripod.com. Retrieved 1 June 2012.
- Knuteson, Randy (July 1999). “Boosting Your Knowledge of Turbocharging” (PDF). Aircraft Maintenance Technology. Archived from the original (PDF) on 17 June 2012. Retrieved 18 April 2012.
- “Effects of Variable Geometry Turbochargers in Increasing Efficiency and Reducing Lag – Thermal Systems”. Me1065.wikidot.com. 6 December 2007. doi:10.1243/0954407991526766. S2CID 110226579. Retrieved 1 June 2012.
- Parkhurst, Terry. “Turbochargers: an interview with Garrett’s Martin Verschoor”. Allpar. Retrieved 12 December 2006.
- Mechanical engineering: Volume 106, Issues 7-12; p.51
- Popular Science. Detroit’s big switch to Turbo Power. Apr 1984.
- Veltman, Thomas (24 October 2010). “Variable-Geometry Turbochargers”. Coursework for Physics 240. Retrieved 17 April 2012.
- Tan, Paul (16 August 2006). “How does Variable Turbine Geometry work?”. PaulTan.com. Retrieved 17 April 2012.
- A National Maritime Academy Presentation. Variable Turbine Geometry.
- Turbo FAQ. Garrett by Honeywell. Retrieved 17 April 2012.
- “Insignia BiTurbo Diesel: A New Chapter For Opel Flagship” (Press release). Media.gm.com. 14 February 2012. Retrieved 28 September 2012.
- Pratte, David. “Twin Scroll Turbo System Design”. Modified Magazine. Retrieved 28 September 2012.
- Nice, Karim. “How Turbochargers Work”. Auto.howstuffworks.com. Retrieved 2 August 2010.
- Hartman, Jeff (2007). Turbocharging Performance Handbook. MotorBooks International. p. 95. ISBN 978-1-61059-231-4.
- Jircitano, Alan J. “Gas Laws”. chemistry.bd.psu.edu. Retrieved 6 December 2017.
- “FMIC vs TMIC | Which One Is Right For You?”. Modern Automotive Performance. Retrieved 6 December 2017.
- Gearhart, Mark (22 July 2011). “Get Schooled: Water Methanol Injection 101”. Dragzine.
- “How Turbocharged Piston Engines Work”. TurboKart.com. Retrieved 17 April 2012.
- “GT Turbo Basics”. Retrieved 17 April 2012.
- Richard Whitehead (25 May 2010). “Road Test: 2011 Mercedes-Benz CL63 AMG”. Thenational.ae. Retrieved 1 June 2012.
- “Turbocharging Turns 100”. Honeywell. 2005. Archived from the original on 19 June 2013. Retrieved 28 September 2012.
- “The history of turbocharging”. En.turbolader.net. 27 October 1959. Retrieved 1 June 2012.
- “Articles”. The Turbo Forums.
- Smith, Robert (January–February 2013). “1978 Kawasaki Z1R-TC: Turbo Power”. Motorcycle Classics. 8 (3). Retrieved 7 February 2013.
- “BorgWarner turbo history”. Turbodriven.com. Retrieved 2 August 2010.
- White, Graham (1995). Allied Aircraft Piston Engines of World War II. Airlife Publishing. p. 192. ISBN 1-85310-734-4.
It is a little appreciated fact that the General Electric turbosupercharger was key to the Army Air Corps/Army Air Forces long-range high-altitude strategic bombing strategy for World War II. All [US] four-engine bombers were fitted with them.
- Kitamura, Makiko (24 July 2008). “IHI Aims to Double Turbocharger Sales by 2013 on Europe Demand”. Bloomberg. Retrieved 1 June 2012.
- CLEPA CEO Lars Holmqvist is retiring (18 November 2002). “Turbochargers – European growth driven by spread to small cars”. Just-auto.com. Retrieved 1 June 2012.
- Walsh, Dustin (20 November 2011). “Lights, cameras, interaction”. Crain’s Detroit Business. Retrieved 23 November 2011.
- Kahl, Martin (3 November 2010). “Interview: David Paja, VP, Global Marketing and Craig Balis, VP, Engineering Honeywell Turbo” (PDF). Automotive World. Retrieved 11 November2011.
- Macaluso, Grace (28 November 2011). “Turbo engines fuel industry’s ‘quiet revolution‘“. The Gazette. Retrieved 28 November 2011.
- “Honeywell sees hot turbo growth ahead”. Automotive News. Retrieved 19 May 2017.
- “U.S. Coalition for Advanced diesel Cars Calls for Technology Neutral Public Policies and Regulations”. MotorVehicleRegs.com. 9 December 2011. Retrieved 25 January 2012.
- “Turbo title: Honeywell or BorgWarner?”. Automotive News. 24 March 2011. Archived from the original on 26 March 2011. Retrieved 19 November 2011.
- Why trucks catch fire. Australian Road Transport Suppliers Association (ARTSA). November 2006. Retrieved 2020-07-22.