Information about Engine Displacement

Engine displacement is defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle; it is normally stated in cubic centimetres, litres or cubic inches. In a piston engine, this is the volume that is swept as the pistons are moved from top dead centre to bottom dead centre.

Governmental regulations

In many nations levels of taxation on automobiles have been based on engine displacement, rather than on power output. Displacement is easy to identify and difficult to modify whereas power output must be tested. This has encouraged the development of other methods to increase engine power.

There are four major regulatory constraints for automobiles: the European, the British, the Japanese, and the American. The method used in some European countries, and which predates the EU, has a level of taxation for engines over one (1.0) litre and another at the level of about 100 cubic inches, which is approximated to 1.6 litres. The British system of taxation depends upon vehicle emissions for cars registered after 1 March 2001 but for cars registered before this date it depends on engine size. Cars under 1549 cc qualify for a cheaper rate of tax [1].

The Japanese is similar to the European taxation by classes of displacement, plus a vehicle weight tax. In the American system, which includes Canada, Australia and New Zealand, there is not this sort of taxation per engine displacement. In The Netherlands and Sweden, road tax is based on vehicle weight.

Displacement is also used to distinguish categories of (heavier) motorbikes with respect to license requirements. In France and some other EU countries, mopeds, usually with a two-stroke engine and less than 50 cm³ displacement can be driven with minimum qualifications (previously, they could be driven by any person over 14). This led to all light motorbikes having a displacement of about 49.9 cm³. Some people tuned the engine by increasing the cylinder bore, increasing displacement; such mopeds cannot be driven legally on public roads since they do no longer conform to the original specifications and may go faster than 45 km/h.

Wankel engines, due to the amount of power and emissions they create for their displacement, are generally taxed as 1.5 times their actual physical displacement (1.3 litres becomes 2.0, 2.0 becomes 3.0), although actual power outputs are far greater (the 1.3 litre 13B can produce power comparable to a 3.0 V6, and the 2.0 litre 20B can produce power comparable to a 4.0L V8). As such, racing regulations actually use a much higher conversion factor.

Example regulations

• Brazil: under 1000 cc, from 1000 to 1999 cc and more than 2000 cc for passenger vehicles. As of October 2006, 56.4% of the cars sold in the Brazilian market were under 1000 cc and only 1.3% were over 2000 cc.
• Bulgaria: a special tax on non-European cars over 2.8 L, later amended to over 3.0 L
• Belgium and Portugal have a proportional tax including reference to displacement
• Ireland: There is one rate for cars under and including 1000 cc, then rates increase by increments of 100 cc up to 3000 cc - 3001 cc and higher are all charged the same. Goods vehicles are taxed by weight, buses are taxed by the number of passenger seats (except school buses which are charged a small flat rate).
• Korea: under 0.8 L; 0.8-2.0 L; over 2.0 L
• Netherlands: progressive proportional tax based on vehicle weight, fuel type and region.
• Philippines (proposal from 2000): under 1.6 L; 1.6-2.0 L; 2.0-2.8 L; over 2.8 L
• Poland excise tax not compatible with EU regulations: engines up to 2000 cc have 3.1% tax, over 2 litres have about 13.6% tax
• Spain: under 1.6 L; over 1.6 L
• Taiwan: < 500 cc, 500~600, 601~1200, 1201~1800, 1801~2400, ... , 7801~8400 cc

Increase and decrease of typical engine displacement in the US

Once V8 engines became expected on large American cars in the late 1950s, and continuing to the oil crisis in the 1970s, there was an engine displacement race in the industry. Firms would put badges on the fenders of cars giving the displacement in cubic inches. This was also a sort of trademark as well. The famous Beach Boys song, "409", refers to any full-size Chevrolet which had an engine displacement (in cubic inches) of that amount, regardless of trim level. This number was not the model number of the car.

In the mid-1960s, Chrysler offered a V8 engine of 426 cubic inches (6981 cm³) on its muscle cars and pony cars. Soon Ford came out with one of similar size, which displaced 427 cubic inches (6997 cm³), and hence was named the '427'.

NASCAR had a maximum 7-litre engine limit during this time and most automakers complied by introducing stock engines with the needed displacement. 7 litres equates to approximately 429 cubic inches, so every major manufacturer had an engine of around this size.

Engine sizes eventually grew to 440 cubic inches (7210 cm³) in Chryslers, 500 (8193 cm³) in Cadillacs, 454 (8127 cm³) in Chevrolets, and 462 (7570 cm³) in Lincolns.

With the oil shocks of the 1970s, American firms started selling cars with smaller engines. The Chevrolet Vega was initially touted as having an engine of 2300 "cc" (cubic centimetres), given in metric as it equates to 140 cubic inches, which would have been considered laughable to declare in the American market. This also differs from the European convention of two significant figures, which was in the U.S. European car models usually have a number of three digits. In this instance, the numbers are considered trademarks. These two factors in the world marketplace contributed to American cars now getting labeled in the European manner. Engines like that of the Vega would now be called 2.0 (being litres).

Conversions

• 1 L ~ 61 cu in
• 1 cubic inch ~ 16 cm³

The big engines listed above are mostly 7.0 litres. The 3.5 litre engines listed on American cars today as being large are much smaller than the 350 cubic inch (5.7 L) engines that once were considered medium size.

The 3.5 litre engine is 213 cubic inches. The 1965 Mustang's smallest Ford V8 engine of 260 cubic inches is 4.5 litres.

However, modern engines are much more efficient, using such technologies as an ECU, electronic fuel injection, and variable valve timing. Also, the engines and the total weight of cars they are fitted in are lighter, so the difference in performance is not as great as might otherwise be supposed.

See also

• Active Fuel Management
• compression ratio
• engine tuning
• variable displacement

External links

• Calculate displacement