# Turbo-compound engine

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Turbo-compound_engine
> Markdown URL: https://mediated.wiki/source/Turbo-compound_engine.md
> Source: https://en.wikipedia.org/wiki/Turbo-compound_engine
> Source revision: 1343607371
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Reciprocating engine combined with a blowdown turbine

The [Napier Nomad II engine](/source/Napier_Nomad). The power-recovery 3-stage turbine sits underneath and to the rear of a two-stroke diesel engine.

A **turbo-compound engine** is a [reciprocating engine](/source/Reciprocating_engine) that uses a [turbine](/source/Turbine) to recover energy from the exhaust gases and return it as mechanical power to the engine. Instead of using that energy to drive a [turbocharger](/source/Turbocharger), as in many high-power [aircraft engines](/source/Aircraft_engine), the recovered energy is mechanically transmitted to the [crankshaft](/source/Crankshaft) to increase the total power delivered by the engine. Major aircraft examples include the [Wright R-3350 Duplex-Cyclone](/source/Wright_R-3350_Duplex-Cyclone) and the [Napier Nomad](/source/Napier_Nomad).

As this recovery process does not increase [fuel consumption](/source/Fuel_consumption), it has the effect of reducing the [specific fuel consumption](/source/Specific_fuel_consumption_(shaft_engine)), the ratio of fuel use to power.[1] Turbo-compounding was used for commercial airliners and similar long-range, long-endurance roles before the introduction of [turbojet](/source/Turbojet) engines. Examples using the Duplex-Cyclone include the [Douglas DC-7](/source/Douglas_DC-7), [Lockheed L-1049 Super Constellation](/source/Lockheed_L-1049_Super_Constellation), and [Lockheed L-1649 Starliner](/source/Lockheed_L-1649_Starliner), while other designs did not see production use for commercial flight.

## Concept

Most piston engines produce a hot exhaust that still contains considerable undeveloped energy that can be recovered for useful work. In a turbo-compound engine, a [turbine](/source/Turbine) extracts part of this energy from the exhaust stream and feeds it back mechanically into the engine, increasing power output and, in some applications, reducing [specific fuel consumption](/source/Specific_fuel_consumption_(shaft_engine)). Rather than using the recovered energy only to drive a [turbocharger](/source/Turbocharger), turbo-compounding uses it to supplement the engine's own output.

In one important aircraft arrangement, turbo-compounding was achieved by using blowdown turbines to recover energy from exhaust-gas pulses and return it to the [crankshaft](/source/Crankshaft). This system was used on the [Wright R-3350 Duplex-Cyclone](/source/Wright_R-3350_Duplex-Cyclone), whose three turbines, each driven by the exhaust from six cylinders, fed recovered power back to the crankshaft through shafts, bevel gears, and fluid couplings.[2]

Other turbo-compound engines used a separate exhaust turbine to recover energy from the engine's exhaust flow and return surplus power mechanically to the [crankshaft](/source/Crankshaft). This arrangement was used on the [Napier Nomad](/source/Napier_Nomad), in which exhaust gases drove a rear-mounted three-stage axial-flow turbine connected to the compressor and, through a variable-speed fluid coupling, to the crankshaft; at low power, the crankshaft could drive the compressor, while at higher power, excess turbine output was fed back to the crankshaft.[3]

## History

[A Wright R-3350 Duplex-Cyclone](/source/Wright_R-3350_Duplex-Cyclone) Turbo-Compound [radial engine](/source/Radial_engine). A power recovery turbine with silver blades is shown in slight center left.

Early work on exhaust power-recovery turbines began in the 1940s.[4] By the 1950s, blowdown turbines had become a characteristic feature of the last generation of long-range American piston airliners, particularly those powered by turbo-compound Wright R-3350 engines.[5]

The [Rolls-Royce Crecy](/source/Rolls-Royce_Crecy) was among the early aircraft engines investigated with an exhaust power-recovery turbine. A turbine geared to the rear of the crankshaft took exhaust from the four exhaust manifolds, providing enough power to overcome the consumption of the supercharger and assist the crankshaft. This arrangement projected a 15 to 35 percent fuel-economy advantage over the [Merlin](/source/Rolls-Royce_Merlin), depending on loading and altitude.[6]

Turbo-compounding was used on several [airplane](/source/Airplane) engines after [World War II](/source/World_War_II), including the [Napier Nomad](/source/Napier_Nomad)[7][8] and the [Wright R-3350](/source/Wright_R-3350_Duplex-Cyclone).[9][10] Wright sources stated that the complete exhaust system of the turbo-compound [Wright R-3350 Duplex-Cyclone](/source/Wright_R-3350_Duplex-Cyclone) was equivalent to a well-designed jet-stack installation in the way it influenced engine operation. Near the end of the exhaust stroke, exhaust pressure dropped below atmospheric, rather than creating harmful [Back pressure](/source/Back_pressure), thereby aiding scavenging, while the turbo-compound system recovered about 240 hp (180 kW) at cruise settings and about 550 hp (410 kW) at takeoff power over a similar non-turbocompounded R-3350. Turbo-compound versions of the [Napier Deltic](/source/Napier_Deltic), [Rolls-Royce Crecy](/source/Rolls-Royce_Crecy), and [Allison V-1710](/source/Allison_V-1710) were constructed, but none were developed beyond the prototype stage. A turbo-compound [Rolls-Royce Griffon](/source/Rolls-Royce_Griffon) was likewise proposed, though it remained an unbuilt paper project. Turbo-compound aero engines were later supplanted by [turboprop](/source/Turboprop) and [turbojet](/source/Turbojet) engines.

Some modern heavy-truck diesel manufacturers have incorporated turbo-compounding into their designs. Examples include the [Volvo](/source/Volvo) [D13TC](/source/Volvo_D13) engine, the [Detroit Diesel](/source/Detroit_Diesel) DD15, and Scania's 11-liter DTC1101 turbocompound diesel, as used in the [R113.400](/source/Scania_3-series).[11][12]

Starting with the 2014 season, Formula One adopted 1.6-liter turbocharged V6 hybrid power units.[13] These incorporated a motor generator unit–heat (MGU-H), defined by the FIA as an electrical machine linked to the exhaust turbine of the pressure-charging system, and a motor generator unit–kinetic (MGU-K) linked to the drivetrain as part of the energy recovery system.[14] The MGU-H recovered energy from the exhaust-driven turbocharger as electrical energy, which could be stored in the energy store, used to power the MGU-K, or used to control turbocharger speed and reduce turbo lag.[15][16]

## List of types

Diagram showing a true turbo-compound at the bottom, and a gas turbine loosely coupled to a piston engine at the top

- [Detroit Diesel](/source/Detroit_Diesel) - [DD15](/source/Daimler_Trucks_North_America#2000s)[17]

- [Napier](/source/Napier_%26_Son) - [Napier Nomad](/source/Napier_Nomad)

- [Wright Aeronautical](/source/Wright_Aeronautical) - [Wright R-3350](/source/Wright_R-3350): The turbo-compound version was the only turbo-compound [aero-engine](/source/Aircraft_engine) to see mass production and widespread usage.

- Dobrynin - [Dobrynin VD-4K](/source/Dobrynin_VD-4K)

- Zvezda - [Zvezda M503](/source/Zvezda_M503): Soviet-built 42-cylinder diesel naval engine used in the [Osa-class missile boat](/source/Osa-class_missile_boat).[18] - [M504](/source/Zvezda_M503): Soviet-built 56-cylinder diesel naval engine.[18] - [M507](/source/Zvezda_M503): Soviet-built 112-cylinder diesel naval engine formed by coupling two [M504](/source/Zvezda_M503) engines through a common gearbox.[18]

- Ferrari - [Ferrari 059/3](/source/Ferrari_F14_T): 1.6-Liter turbocharged V6 Formula One hybrid power unit with MGU-H exhaust-energy recovery, used in the Ferrari F14 T.[19][20]

- [Renault](/source/Renault) - [Renault Energy F1-2014](/source/Renault_V6_hybrid_Formula_One_power_unit): 1.6-liter turbocharged V6 Formula One hybrid power unit with MGU-H exhaust-energy recovery.[19][21]

- Mercedes-Benz - [Mercedes-Benz PU106A Hybrid](/source/Mercedes_V6_hybrid_Formula_One_power_unit): 1.6-Liter turbocharged V6 Formula One hybrid power unit with MGU-H exhaust-energy recovery.[19][22]

- Honda - [Honda RA615H](/source/McLaren_MP4-30): 1.6-Liter turbocharged V6 Formula One hybrid power unit with MGU-H exhaust-energy recovery, used in the McLaren Honda MP4-30.[19][23]

- [Volvo](/source/Volvo) - [D13TC](/source/Volvo_D13)

## See also

- [Motorjet](/source/Motorjet)

- [Turbosteamer](/source/Turbosteamer)

- [Cogeneration](/source/Cogeneration)

- [Turbocharger](/source/Turbocharger)

- [Gas turbine](/source/Gas_turbine)

- [Electric turbo-compound](/source/Electric_turbo-compound)

## References

1. **[^](#cite_ref-popmech0256_1-0)** Stimson, Thomas E. Jr (February 1956). ["The Race of the Airliners"](https://books.google.com/books?id=u-EDAAAAMBAJ&pg=PA113). *Popular Mechanics*. Vol. 105, no. 2. pp. 113–118. [ISSN](/source/ISSN_(identifier)) [0032-4558](https://search.worldcat.org/issn/0032-4558). Retrieved 19 February 2016.

1. **[^](#cite_ref-2)** ["DC-7 Review Booklet"](https://deltamuseum.org/docs/site/aircraft-pages/delta-aircraft/1954-delta-dc-7-review-booklet.pdf?sfvrsn=2733e0e9_1) (PDF). Delta Flight Museum. 1954. Retrieved 14 March 2026.

1. **[^](#cite_ref-3)** ["Napier Nomad Compound Aircraft Engine"](https://oldmachinepress.com/2019/08/05/napier-nomad-compound-aircraft-engine/). *Old Machine Press*. Retrieved 14 March 2026.

1. **[^](#cite_ref-4)** ["Turbo Compounds"](https://www.enginehistory.org/Piston/Wright/Kuhns/CurtissWrightTC18/TurboCompounds.shtml). *Aircraft Engine Historical Society*. Retrieved 15 March 2026.

1. **[^](#cite_ref-5)** ["Waste Heat Utilization in High Output Aircraft Piston Engines"](https://www.enginehistory.org/members/articles/WasteHeat/WasteHeat.shtml). *Aircraft Engine Historical Society*. 27 November 2019. Retrieved 15 March 2026.

1. **[^](#cite_ref-nzrrbc_6-0)** ["Rolls-Royce and the Sleeve Valve"](https://web.archive.org/web/20101206092033/http://kda132.com/Praeclarum/NZ07-3.pdf) (PDF). *New Zealand Rolls-Royce & Bentley Club Inc* (7–3): 15. 2007. Archived from [the original](http://www.kda132.com/Praeclarum/NZ07-3.pdf) (PDF) on 6 December 2010.

1. **[^](#cite_ref-Flight,_30_April_1954,_Napier_Nomad_7-0)** [Gunston, Bill](/source/Bill_Gunston) (30 April 1954). ["Napier Nomad: An engine of outstanding efficiency"](https://web.archive.org/web/20160305034809/https://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201215.html). *[Flight](/source/Flight_(magazine))*: 543–551. Archived from [the original](http://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201215.html) (PDF) on 5 March 2016. Retrieved 19 February 2010.

1. **[^](#cite_ref-Flight,_30_April_1954,_Napier_diesels_8-0)** E. E. Chatterton (22 April 1954). ["Napier Diesels: An RAeS Lecture"](http://www.flightglobal.com/pdfarchive/view/1954/1954%20-%201223.html) (PDF). *[Flight](/source/Flight_(magazine))*: 552. Retrieved 19 February 2010.

1. **[^](#cite_ref-Flight,_2003,_Ten_ideas_that_failed_9-0)** ["Ten Ideas That Failed: 2 Turbo-compound Piston Engine"](http://www.flightglobal.com/articles/2003/12/16/175396/ten-ideas-that-failed.html) (PDF). *[Flight](/source/Flight_(magazine))*. 16 December 2003. Retrieved 19 February 2010.

1. **[^](#cite_ref-Flight,_1997,_Super_survivor_10-0)** ["Super Survivor"](http://www.flightglobal.com/articles/1997/06/18/4788/super-survivor.html) (PDF). *[Flight](/source/Flight_(magazine))*. 18 June 1997. Retrieved 19 February 2010. in its hey-day, the Connie was often called the world's best tri-motor

1. **[^](#cite_ref-11)** ["ROADTEST: Scania R113.400"](https://archive.commercialmotor.com/article/17th-october-1991/32/roadtest). *Commercial Motor*. 17 October 1991. Retrieved 14 March 2026.

1. **[^](#cite_ref-12)** ["Scania looks to the future"](https://archive.commercialmotor.com/article/6th-june-1991/13/sonia-looks-to-the-future). *Commercial Motor*. 6 June 1991. Retrieved 14 March 2026.

1. **[^](#cite_ref-13)** ["A racing revolution? Understanding 2014's technical regulations"](https://www.formula1.com/en/latest/article/a-racing-revolution-understanding-2014s-technical-regulations.1bTbN3OAEksY00PVE62KvC). *Formula1.com*. 23 January 2014. Retrieved 14 March 2026.

1. **[^](#cite_ref-14)** ["2014 Formula One Technical Regulations"](https://argent.fia.com/web/fia-public.nsf/A0425C3A0A7D69C0C12578D3002EBECA/%24FILE/2014_F1_TECHNICAL_REGULATIONS_-_Published_on_20.07.pdf) (PDF). Fédération Internationale de l'Automobile. p. 8. Retrieved 14 March 2026.

1. **[^](#cite_ref-15)** ["2014 Formula One Technical Regulations"](https://argent.fia.com/web/fia-public.nsf/A0425C3A0A7D69C0C12578D3002EBECA/%24FILE/2014_F1_TECHNICAL_REGULATIONS_-_Published_on_20.07.pdf) (PDF). Fédération Internationale de l'Automobile. p. 8. Retrieved 14 March 2026.

1. **[^](#cite_ref-16)** ["7 things you need to know about the 2026 F1 engine regulations"](https://www.formula1.com/en/latest/article/more-efficient-less-fuel-and-carbon-net-zero-7-things-you-need-to-know-about.ZhtzvU3cPCv8QO7jtFxQR). *Formula1.com*. 16 August 2022. Retrieved 14 March 2026.

1. **[^](#cite_ref-17)** ["The Turbo Compounding Boost"](http://detroitdiesel.com/engines/dd15/economy.aspx). 2007.

1. ^ [***a***](#cite_ref-Pearce2016Zvezda_18-0) [***b***](#cite_ref-Pearce2016Zvezda_18-1) [***c***](#cite_ref-Pearce2016Zvezda_18-2) Pearce, William (5 September 2016). ["Yakovlev M-501 and Zvezda M503 and M504 Diesel Engines"](https://oldmachinepress.com/2016/09/05/yakovlev-m-501-and-zvezda-m503-and-m504-diesel-engines/). *Old Machine Press*. Retrieved 15 March 2026.

1. ^ [***a***](#cite_ref-F1PU2014_19-0) [***b***](#cite_ref-F1PU2014_19-1) [***c***](#cite_ref-F1PU2014_19-2) [***d***](#cite_ref-F1PU2014_19-3) ["2014 Season Preview - the dawn of a new Formula One era"](https://www.formula1.com/en/latest/article/2014-season-preview-the-dawn-of-a-new-formula-one-era.7wgUnlDeHx2CLBJQZM5VuX). *Formula1.com*. 6 March 2014. Retrieved 15 March 2026.

1. **[^](#cite_ref-FerrariF14T_20-0)** ["Ferrari F14 T: 2014 F1 single-seater"](https://www.ferrari.com/en-EN/formula1/f14-t). *Ferrari*. Retrieved 15 March 2026.

1. **[^](#cite_ref-21)** ["Lotus and Renault confirm partnership extension"](https://www.formula1.com/en/latest/article/lotus-and-renault-confirm-partnership-extension.4XhDbnGUPd1EOVX0cssXgZ). *Formula1.com*. 19 February 2014. Retrieved 15 March 2026.

1. **[^](#cite_ref-MercedesPU106_22-0)** ["2014-2018 Formula One Power Units"](https://media.mercedesamgf1.com/marsF1/en/instance/picture/2014-2018-Formula-One-Power-Units.xhtml?oid=177509575). *Mercedes-AMG Petronas F1 Media*. Retrieved 15 March 2026.

1. **[^](#cite_ref-HondaRA615H_23-0)** ["RA615H"](https://global.honda/en/POWEREDbyHONDA/2015_ra615h/). *Honda*. Retrieved 15 March 2026.

v t e Engine configurations for piston engines Type Atmospheric Axial Beam Cornish Rotative Bourke Cam engine Camless Compound Double-acting cylinder Flathead Free-piston Stelzer Hemi Heron head Intake over exhaust Oscillating cylinder Opposed-piston Overhead camshaft Overhead valve Pentroof Rotary Single-acting cylinder Split cycle Swing-piston Uniflow Watt Wedge Stroke cycle Two-stroke Four-stroke Five-stroke Six-stroke Two-and four-stroke Cylinder layout Inline – straight I1 I2 I3 I4 I5 I6 I7 I8 I9 I12 I14 Flat – boxer F2 F4 F6 F8 F10 F12 F16 V – vee V2 V3 V4 V5 VR5 V6 VR6 V8 V10 V12 V14 V16 V18 V20 V24 W W3 W6 W8 W12 W16 W18 W24 W30 Deltic H Radial Split-single U X

---
Adapted from the Wikipedia article [Turbo-compound engine](https://en.wikipedia.org/wiki/Turbo-compound_engine) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Turbo-compound_engine?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.