Twin - turbo - wikipedia Twin - turbo This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( November 2016 ) Twin - turbo or biturbo refers to a turbocharged engine in which two turbochargers compress the intake charge. The most common layout features two identical turbochargers in parallel ; other twin - turbo layouts include sequential and staged turbocharging, the latter of which is used in diesel auto racing applications. Contents 1 Parallel twin - turbo 2 Sequential turbocharging 3 Staged turbocharging 4 Advantages in diesel emissions 5 See also 6 References Parallel twin - turbo 3.5 Ford EcoBoost engine ( Twin Turbo ) Paralleled twin - turbo refers to the turbocharger configuration in which two identical turbochargers function simultaneously, splitting the turbocharging duties equally. Each turbocharger is driven by half of the engine 's spent exhaust energy. In most applications, the compressed air from both turbos is combined in a common intake manifold and sent to the individual cylinders. Usually, each turbocharger is mounted to its own individual exhaust / turbo manifold, but on inline - type engines both turbochargers can be mounted to a single turbo manifold. Parallel twin turbos applied to V - shaped engines are usually mounted with one turbo assigned to each cylinder bank, providing packaging symmetry and simplifying plumbing over a single turbo setup. When used on inline engines, parallel twin turbos are commonly applied with two smaller turbos, which can provide similar performance with less turbo lag than a single larger turbo. Some examples of parallel twin - turbo inline engines are Nissan 's RB26DETT, BMW 's N54 and Volvo 's B6284T and B6294T. Some examples of V formation engines with parallel twin - turbos include Mitsubishi 's 6A12TT, 6A13TT and 6G72TT ; Nissan 's VG30DETT and VR38DETT ; and Audi 's 1997 - 2002 S4 ( B5 ), 1997 - 2005 A6, and 2003 - 2017 RS6. While a parallel twin - turbo set - up theoretically has less turbo lag than a single turbocharger set up, this is not always the case due to many factors. Marginally reduced combined inertial resistance, simplified exhaust plumbing, and the simultaneous spooling of both turbos means that there can still be a noticeable bit of lag, especially in high - flow turbo / high boost applications. Some ways to counter this are to use a light pressure set up with smaller turbos, where the turbos are designed to output less boost but spool earlier. While this setup sacrifices some top end power, it still has less lag than a similar engine with a single turbo set up making the same power. Another system would be the use of variable geometry turbochargers. This system changes the angle of the guide vanes depending on the exhaust pressure, giving the system excellent power throughout the rev range. Once used mainly in turbocharged diesel engines, Chrysler was the first to use it in mass - production gasoline - powered vehicles with the Shelby CSX, debuted in 1989. It is possible to use parallel operation with more than two turbochargers. Two such examples are the Bugatti EB110 and Bugatti Veyron, both of which run four turbochargers in parallel. The EB110 runs 4 turbos on a 3.5 litre V12 engine, producing 542 hp ( 404 kW ) at 8000 rpm, while the Veyron uses an 8.0 litre 16 cylinder engine to generate 1,001 PS ( 736 kW ; 987 hp ). The Bugatti Veyron Super Sport uses the quad - turbo 8.0 W16 engine that produces 1216 PS ( 894 kW ; 1,200 hp ). Sequential turbocharging BMW 3 Series Diesel turbo setup ( Sequential turbo ) Sequential turbos refer to a set - up in which the engine uses one turbocharger for lower engine speeds, and a second or both turbochargers at higher engine speeds. Typically, larger high - flow turbochargers are not as efficient at low RPM, resulting in lower intake manifold pressures under these conditions. On the other hand, smaller turbos spool up quickly at low RPM but can not supply enough air at higher engine speed. During low to mid engine speeds, when available spent exhaust energy is minimal, only one relatively small turbocharger ( called the primary turbocharger ) is active. During this period, all of the engine 's exhaust energy is directed to the primary turbocharger only, providing the small turbo 's benefits of a lower boost threshold, minimal turbo lag, and increased power output at low engine speeds. As RPM increases, the secondary turbocharger is partially activated in order to pre-spool prior to its full utilization. Once a preset engine speed or boost pressure is attained, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely. ( The primary turbocharger is deactivated at this point in some applications. ) In this way a full twin - turbocharger setup provides the benefits associated with a large turbo, including maximum power output, without the disadvantage of increased turbo lag. Sequential turbocharger systems provide a way to decrease turbo lag without compromising ultimate boost output and engine power. Perhaps the most noteworthy application of this system is the fourth - generation Toyota Supra ( 1993 - 1998 ), which is generally regarded as having the most reliable sequential turbo system yet fitted to a production automobile, with a reported failure rate of less than 1 % as of 2011. Other examples of cars with a sequential twin - turbo setup include the 1986 - 1988 Porsche 959, the 1990 - 1995 Eunos Cosmo JC, 1992 - 2002 Mazda RX - 7 FD3S Turbo ( 13B - REW engine ), the 1994 - 2005 JDM Subaru Legacy GT, GT - B & B4 RSK ( EJ20TT engine ), and the Peugeot 407 2.2 HDi. GM has filed a patent for a sequential twin - turbo system that uses a new bypass valve design said to optimize exhaust flow to the turbines of both turbochargers. According to the 2016 patent description, the exhaust manifold features two outlets with one directing exhaust gases to the turbine of the high - pressure turbocharger, while the second exhaust manifold outlet directs exhaust gases to the turbine of the low - pressure turbocharger via a connecting channel. Additionally, exhaust gas exiting the high - pressure turbine is directed to the inlet of the low - pressure turbine. The new bypass system features two throttle valves located on the same spindle mounted perpendicular to each other. With the throttle valves mounted on the same plane, one valve opens to direct exhaust gas flow to one of the turbochargers while the other valves simultaneously blocks exhaust gas flow to the other turbocharger. The vehicle ECU ( electronic control unit ) sends a signal to the spindle 's actuator to rotate the throttle valves based on rpm and load. GM says the new design allows engineers to optimize exhaust gas flow to both turbines without the compromises of traditional sequential turbocharger systems. Additionally, the system could utilize a variable - geometry turbine or a fixed - geometry turbine on the high - pressure turbo. Staged turbocharging A sequential turbo can also be of use to a system where the output pressure must be greater than can be provided by a single turbo, commonly called a staged twin turbo system. In this case, multiple similarly sized turbochargers are used in sequence, but both operate constantly. The first turbo boosts pressure as much as possible ( for example to three times the intake pressure ). Subsequent turbos take the charge from the previous stage and compress it further ( for example to an additional three times intake pressure, for a total boost of nine times atmospheric pressure ). This configuration is commonly found on piston engine aircraft which usually do not need to rapidly raise and lower engine speed ( and thus where turbo lag is not a primary design consideration ), and where the intake pressure is quite low due to low atmospheric pressure at altitude, requiring a very high pressure ratio. High - performance diesel engines also sometimes use this configuration, since diesel engines do not suffer from pre-ignition issues and can use significantly higher boost pressure than Otto cycle engines. Advantages in diesel emissions While spark ignition engines have fallen out of favor of the sequential turbo design, many diesel companies now make engines with sequential turbos in order to reduce emissions. See also Boost gauge Boost controller Supercharger Intercooler Twincharger References Jump up ^ http://www.motortrend.com/news/gm-patents-sequential-turbocharger-system-unique-bypass-valve/ Automotive engine Part of the Automobile series Basic terminology Bore Compression ratio Crank Cylinder Dead centre Diesel engine Dry sump Engine balance Engine configuration Engine displacement Engine knocking Firing order Hydrolock Petrol engine Power band Redline Spark - ignition engine Stroke Stroke ratio Wet sump Main components Connecting rod Crankcase Crankpin Crankshaft Crossplane Cylinder bank Cylinder block Cylinder head ( crossflow, reverse - flow ) Flywheel Head gasket Hypereutectic piston Main bearing Piston Piston ring Starter ring gear Sump Valvetrain Cam Cam follower Camshaft Desmodromic valve Hydraulic tappet Multi-valve Overhead camshaft Overhead valve Pneumatic valve springs Poppet valve Pushrod Rocker arm Sleeve valve Tappet Timing belt Timing mark Valve float Variable valve timing Aspiration Air filter Blowoff valve Boost controller Butterfly valve Centrifugal - type supercharger Cold air intake Dump valve Electronic throttle control Forced induction Inlet manifold Intake Intercooler Manifold vacuum Naturally aspirated engine Ram - air intake Scroll - type supercharger Short ram air intake Supercharger Throttle Throttle body Turbocharger Twin - turbo Variable - geometry turbocharger Variable - length intake manifold Warm air intake Fuel system Carburetor Common rail Direct injection Fuel filter Fuel injection Fuel pump Fuel tank Gasoline direct injection Indirect injection Injection pump Lean - burn Stratified charge engine Turbo fuel stratified injection Unit injector Ignition Contact breaker Magneto Distributor Electrical ballast High tension leads Ignition coil Spark plug Wasted spark Electrics and engine management Air -- fuel ratio meter Alternator Automatic Performance Control Car battery ( lead -- acid battery ) Crankshaft position sensor Dynamo Drive by wire Electronic control unit Engine control unit Engine coolant temperature sensor Glow plug Idle air control actuator MAP sensor Mass flow sensor Oxygen sensor Starter motor Throttle position sensor Exhaust system Automobile emissions control Catalytic converter Diesel particulate filter Exhaust manifold Glasspack Muffler Engine cooling Air cooling Antifreeze ( ethylene glycol ) Core plug Electric fan Fan belt Radiator Thermostat Water cooling Viscous fan ( fan clutch ) Other components Balance shaft Block heater Combustion chamber Cylinder head porting Gasket Motor oil Oil filter Oil pump Oil sludge PCV valve Seal Synthetic oil Underdrive pulleys Portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Twin-turbo&oldid=845087181 '' Categories : Turbochargers Hidden categories : Articles needing additional references from November 2016 All articles needing additional references All articles with unsourced statements Articles with unsourced statements from July 2012 Articles with unsourced statements from December 2012 Articles with unsourced statements from June 2012 Talk Contents About Wikipedia Čeština Nederlands 日本 語 Português Slovenčina Edit links This page was last edited on 9 June 2018, at 08 : 22. 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Question: what is a twin turbo engine in cars
Answer: a turbocharged engine in which two turbochargers compress the intake charge