Forced induction in motorcycles

Forced induction in motorcycles is the application of forced induction (turbochargers or superchargers) to a motorcycle engine. Special automotive engineering and human factors considerations exist for the application of forced induction with motorcycles, compared to other forms of motorized transportation.

Forced induction in production motorcycles

Prior to the late 2010s, forced induction was only used on a handful of production motorcycles, all from Japanese Big Four manufacturers in the early 1980s.[1][2][3]

Honda CX650 Turbo had 674 CC, 100 BHP and Moto Guzzi-style V-twin engine. It is contestably the best forced induction production bikes of 1980s from Japanese manufacturers. 1983-model of Honda CX650 Turbos had solved lag problems, which earlier models like CX500 Turbo encountered. To rectify turbo lags, capacity and compression ratio was raised from 7.2:1 to 7.8:1.[4]

Additionally, in 1978 Kawasaki offered the Z1R-TC, a semi-production model built by Turbo Cycle Corporation and sold through Kawasaki dealers. This is generally considered to be the first Japanese turbocharged motorcycle.[5]

The Honda, Kawasaki and Suzuki bikes were all listed on a State Farm insurance "blacklist" published by American Motorcyclist in 1989.[6]

21st century

A scooter with a supercharger, the Peugeot JetForce Compressor, was available in late 2003.

Kawasaki confirmed it would be re-entering the market with the supercharged Kawasaki Ninja H2, announced in October, 2014.[7][8][9] This was followed by the H2 SX SE sports tourer,[10] and for 2020 Kawasaki announced a new naked model, designated Z H2.[11][12]

Engineering and usability challenges

Designers have been able to address packaging issues and fit turbochargers even in fully faired motorcycles.[13][14]

Turbo lag was noted as a problem with all four Japanese turbos of the 1980s by several critics.[15][16][17][18] Motorcycle engineering expert and journalist Kevin Cameron has said that turbo lag is a critical problem with turbocharger applications on motorcycles: "[U]nless you are a pure drag racer, most of your riding will be off-boost. The lower your compression ratio, the less snap your bike will have...don't expect your turbo bike to be much use in sportbike-type canyon racing."[19] Using a variable-geometry turbocharger can mitigate turbo lag,[20][1] but has not yet been used in series production (the first mass market application was to late 1980s automobiles; see Variable-geometry turbocharger#History and examples of use).

Writer Mick Walker has listed turbo lag along with other challenges like a higher center of gravity and heat transfer to rider due to turbocharger and associated exhaust plumbing.[13] Bennett noted excessive weight and complexity in addition to weak bottom-end performance.[21]

The German magazine Motorrad said in 2014, that a turbocharger would probably never be practical on mass market motorcycles due to cost of high-tech materials able to withstand the high temperatures of a variable geometry turbocharger, plus weight and space considerations, though they left the door open for a good supercharged solution.[22]

Emissions

Emissions considerations, driven in particular by carbon dioxide limits in the European emission standards, are leading motorcycle manufacturers in the 2010s to reconsider applications of forced induction.[23][24]

In racing

In road racing, superchargers were not uncommon in the 1930s, and machines originally built for road racing also set many land speed records (see the list below for examples). Motorcycle racing in Europe went through a hiatus during the 1940s as World War II and its aftermath, and racing only restarted in 1946.[25] That same year, forced induction was banned from road racing by the Fédération Internationale de Motocyclisme (FIM),[25][26][27][28] effectively relegating it to specialized forms of racing and speed record runs, discussed further below. Rules from the FIM and other sanctioning bodies cover aspects of motorcycle design as diverse as motorcycle fairing coverage, gasoline direct injection, and the use of dual-clutch transmissions, and may influence street bike design by setting public expectations.[29]

Drag racing

Specialized motorcycles used in drag racing, called dragbikes, are an application for forced induction, including nitrous oxide and multistage turbochargers.[30] The first dragbike to run the quarter-mile in under 7 seconds was using a Roots-type supercharger.[19][31]

Motorcycle clubs

At least one motorcycle club, Turbo Motorcycle International Owners Association, has been formed to support turbo motorcycle enthusiasts.[32]

Notable prototypes and record setters
BMW WR 750 from 1930s, note supercharger under rider's saddle

Notes
  1. Motorrad 2014.
  2. Walker 2006,  "other manufacturers built prototypes and small batches of turbocharged machines, only the Japanese giants attempted to exploit the turbo for series-production bikes".
  3. Bennett 1999, p. 57a "Neither system [superchargers nor turbochargers] has found acceptance in the mass-produced motorcycle market, although a significant effort to build turbos was made by the Japanese motorcycle makers in the early 1980s. Factory turbos were shipped by Honda (the 82-horsepower CX500T V-twin), Yamaha (the 85-horsepower XJ650T transverse-four), Suzuki (the 85-horsepower XN85, using a GS650 transverse-four) and Kawasaki (the 110-horsepower ZX750 transverse-four)."
  4. Siegal 2009.
  5. Smith 2013.
  6. American Motorcyclist 1989.
  7. Newland 2014.
  8. Stock 2014.
  9. Cameron 2014b.
  10. Kunitsugu 2018.
  11. Motorcycle News 2019.
  12. Bike Sport News 2019.
  13. Walker 2006.
  14. Cycle World 1981.
  15. American Motorcyclist 1998 said low compression ratio made for sluggish around-town riding
  16. Cycle World 1981,  Problems faced by Honda included charge stagnation with twins, no off-the-shelf turbo sized properly for a bike, and packaging inside fairing. Unsolved problems included throttle lag, throttle-close lag leading to a rider sensation like a stuck throttle..
  17. Bennett 1999, p. 57b,  "At the top end, they were fantastic speed machines, but only once you got into fifth and opened the throttle. Too many compromises were made ... retarded ignition timing; extra weight due to the turbo and beefed-up crank, rods, bearings, etc.; exotic carburetion; extra cooling devices and turbo lag all hurt the bottom-end performance... mechanically... the turbos were extremely complex. Riders did not buy them.".
  18. Siegal 2009 quotes an expert's dry summary of these bikes' "difficult power characteristics"
  19. Cameron 2008.
  20. Rook 2007.
  21. Bennett 1999, p. 57b.
  22. Motorrad 2014, "Kompressor oder Turbo?" "Perhaps the use of a so-called VTG charger with variable turbine geometry, which improves the responsiveness of the charger at low gas flow might be accomplished. A possible but expensive option, since the VTG charger now widely used in Diesel vehicles must deal with significantly higher exhaust gas temperatures in the gasoline engine (about 1100° instead of the usual 850° for Diesel) by resorting to special heat-resistant, but also particularly expensive alloys... A lot of expensive, heavy and space-consuming techniques are necessary. The bottom line: probably too much." [Translated from original German]
  23. Tibu 2014 "With the displacement of bikes being one of the key factors in the CO2 emissions, finding ways to raise or maintain the power output of the engines while lowering the cc figures seems like one solution Honda and possibly more manufacturers will have to consider very seriously in the upcoming years."
  24. Gentili 2014.
  25. Hough & Setright 1966, p. 153.
  26. Walker 2006b, p. 33.
  27. Wilson 2002, p. 50.
  28. Falloon 2011, pp. 10–11.
  29. Cameron 2014a.
  30. Lee 2010.
  31. Cycle World 1979.
  32. Holmstrom & Everett 2004.
  33. d'Orléans 2014.
  34. New Zealand Herald 2014.
  35. Hindustan Times 2014.
  36. Crowe 2006.
  37. Slotnik 2013.
  38. Quinn 2004.
  39. Robinson 2007, p. 126.
  40. Inman 2014.
  41. Visordown 2014.
  42. Mann 2014.
  43. Cathcart 2009.
  44. Clink 2012.
  45. Patil 2018.

References

Books

  • Bennett, Jim (1999), "Mechanics and mechanisms", The Complete Motorcycle Book: A Consumer's Guide (Second ed.), ISBN 0-8160-3854-6
  • Holmstrom, Darwin; Everett, Charles (2004), "The Motorcycling Community", Complete Idiot's Guide to Motorcycles (Third ed.), ISBN 1-59257-303-7
  • Rook, Bill (2007), "Supercharger and turbocharger", How to Build a Harley-Davidson Torque Monster, MotorBooks International, p. 51, ISBN 9781610609692
  • Robinson, Rocky (2007), Flat Out: The Race for the Motorcycle Land Speed Record, Motorbooks, ISBN 9781610609296
  • Cameron, Kevin (2008), "Turbocharging, supercharging, and nitrous oxide", Sportbike Performance Handbook (eBook) (2nd ed.), Motorbooks, p. 103, ISBN 9781616730710
  • Walker, Mick (2006), "Turbocharging", Motorcycle: Evolution, Design, Passion, JHU Press, p. 166, ISBN 9780801885303
  • Lee, Keith (2010), Drag Bike Racing in Britain From the Mid '60s to the Mid '80s, Veloce, p. 90, ISBN 9781845843144
  • Walker, Mick (2006b), The Manx Norton, Redline Books, ISBN 9780954435790
  • Wilson, Hugo (2002), Hot Bikes, DK ADULT, ISBN 978-0789483966
  • Falloon, Ian (2011), The Book of the Classic MV Agusta Fours, Veloce Publishing, ISBN 9781845842031
  • Hough, Richard Alexander; Setright, L.J.K. (1966), A history of the world's motorcycles, New York: Harper & Row, LCCN 66018583

Periodicals

Further reading
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