Editing Engine displacement (section)

==Governmental regulations==
{{main|Road tax}}
In several countries fees and taxes levied on road vehicles by transport authorities are scaled in proportion to engine displacement. In countries where this is practised, vehicle manufacturers often seek to increase power output through higher-revving engines or [[Turbocharger|turbocharging]], instead of increasing the displacement.

Examples of countries where the road taxes are based upon engine displacement:
* In some European countries, and which predates the EU, there is one charge for engines over 1.0 litre, and another at the level of about 1.6&nbsp;litres.
* In the United Kingdom, cars registered after 1 March 2001 are taxed based on the exhaust emissions. However, cars registered before this date are taxed based on engine displacement. Cars under 1549&nbsp;cm<sup>3</sup> qualify for a lower tax rate.<ref>[http://www.direct.gov.uk/Motoring/OwningAVehicle/HowToTaxYourVehicle/HowToTaxYourVehicleArticles/fs/en?CONTENT_ID=10012524&chk=X2gG9G Direct.gov.uk] {{webarchive |url=https://web.archive.org/web/20060616173240/http://www.direct.gov.uk/Motoring/OwningAVehicle/HowToTaxYourVehicle/HowToTaxYourVehicleArticles/fs/en?CONTENT_ID=10012524&chk=X2gG9G |date=16 June 2006 }}: The Cost of Vehicle Tax for Cars, Motorcycles, Light Goods Vehicles and Trade Licences.</ref>
* In Japan, the engine displacement is one of the factors (along with overall vehicle size and power output) used to determine the vehicle size class and therefore the cost of road tax for the vehicle.
* In France and some other EU countries, [[moped]]s with a displacement of less than {{convert|50|cc|cuin|1|abbr=on}} can be driven with minimum qualifications. This led to all light motorbikes having a displacement of about 49.9&nbsp;cm<sup>3</sup>.
* In many areas of the United States, Canada (except Quebec<ref>{{Cite web|url=https://saaq.gouv.qc.ca/en/saaq/rates-fines/vehicle-registration/additional-registration-fee-large-cylinder-capacity-vehicles/|title=Additional Registration Fee for Large Cylinder Capacity Vehicles|last=SAAQ|website=SAAQ|language=en|access-date=12 March 2018}}</ref>), Australia and New Zealand, the road taxes are not based on engine displacement. However, the engine displacement is often used in low-powered scooters or mopeds to determine whether a licence is required to operate the vehicle. A common threshold is {{convert|50|cc|cuin|1|abbr=on}}.

Wankel engines are able to produce higher power levels for a given displacement. Therefore, they are generally taxed as 1.5 times{{citation needed|date=November 2019}} their stated physical displacement (1.3&nbsp;litres becomes effectively 2.0, 2.0 becomes effectively 3.0), although actual power outputs can be higher than suggested by this conversion factor. The nominal displacement of a Wankel engine is 3 times smaller than the physical displacement, but this is compensated by the fact that the shaft has 3 times the rotational speed of the rotor. The nominal displacement is the swept volume of a single chamber.