engines
There is plenty of technical language used to describe the engines which power the racing prototypes on which the riders participate in the MotoGP World Championship, but most of it is fairly easy to understand if taken piece by piece and explained simply, even if the machinery itself is technologically advanced and complex in structure.
DEFINITIONS
2-stroke and 4-stroke – 2-stroke engines were predominant in the World Championship until the switch to the 990cc 4-stroke class in 2002, reflecting production trends, as 2-stroke bikes became increasingly popular from the 1960s through to the 1990s.
If 2-stroke engines proved more powerful than 4-strokes with similar engine capacities and similar rev counts, 4-strokes engines are more energy efficient and greener. This is because 4-strokes have a dedicated lubrication system, while 2-stroke engines burn a mixture of oil and gas.
As most manufacturers shifted their production towards bigger 4-stroke powered machines, the move to a 4-stroke prototype formula only seemed natural.
The key difference between the two types of engine lies in the combustion process: the four ‘strokes’ refer to the
intake, compression, combustion and exhaust movements which occur during two crankshaft rotations per working cycle.
The 2-stroke internal combustion engine differs from the 4-stroke engine in that it completes the same four processes in only two strokes of the piston.
Single cylinder, two cylinder, four cylinder and six cylinder engines – While technical rules restrict the 125cc World Championship to single cylinder engines and give the options of single or two cylinder engines for the 250cc manufacturers, MotoGP bikes can have from one cylinder to six cylinders or more.
According to the FIM rulebook, the number of cylinders from one to six, or more, dictate what the minimum accepted weight of the bike will be, as ballast may be added to achieve it. Due to unit cylinder performance and power-to-weight ratio, all the MotoGP manufacturers now use four cylinder engines.
However, those engines come in different forms, as some factories, such as Ducati, Honda and Suzuki currently opt for V4 architecture, while Yamaha and Kawasaki have developed ‘inline four’ engines.
With V4’s the HYPERLINK "http://en.wikipedia.org/wiki/Cylinder_%28engine%29" \o "Cylinder (engine)" cylinders and HYPERLINK "http://en.wikipedia.org/wiki/Piston" \o "Piston" pistons are aligned separately to each other, so that they take on a ‘V-shape’ from an angle looking along the HYPERLINK "http://en.wikipedia.org/wiki/Crankshaft" \o "Crankshaft" crankshaft axis. This configuration decreases the total height, length and weight of the engine, in comparison with HYPERLINK "http://en.wikipedia.org/wiki/Straight_engine" \o "Straight engine" inline equivalents.
The choice of engine architecture has as much to do with design philosophy and the manufacturer’s heritage as with weight transfer and goals in terms of bike ‘rideability’.
Meanwhile, the terms
125cc, 250cc, 800cc (MotoGP) used to describe the three current categories in the World Championship simply refer to the ‘engine displacement’ or ‘cubic capacity’ of the respective machinery.
DEVELOPMENT THROUGH THE AGES
The biggest change in the premier class over the years has been the switch from 4-stroke, to 2-stroke engines, and back to 4-stroke in 2002, reflecting the need for technical progression and innovation in the sport - in keeping with the development of production bikes.
In the early days of the World Championship the premier class was dominated by 4-stroke machinery from mostly European manufacturers. The early 4-stroke engines were cumbersome, heavy, required a lot of maintenance and were never the most reliable of units.
Through the 1960s Japanese manufacturers such as Suzuki and Yamaha started to make their presence felt in the smaller cylinder classes with 2-stroke machinery. The lighter 2-stroke presented more possibilities for tuning and was seen as the future of the sport.
Although the 1970s and even 1980s saw a period of technical change that permitted even private ‘built in the garage’ motorcycles to go Grand Prix racing it was the might of the Japanese engineering and initiative that would soon provide the most competitive racing tools.
THE EMERGENCE OF 2-STROKE
As the Japanese slowly forged ahead with 2-stroke technology, the 4-strokes would fade out in a matter of seasons as the 500cc four cylinder 2-stroke became available on a production scale from Japan.
With the 2-strokes becoming more reliable and more powerful the engines actually threw more emphasis onto the rest of the motorcycle and evolution began at a rapid rate through the 1980s. Tyres, suspension, aerodynamics and even chassis design all saw a wealth of development.
In the early 1990s speeds had reached a peak in MotoGP. The 500cc bikes were harder and faster to ride than ever as an all-Japanese premier class sought to push the performances of the machines to the limit and new heights. By 1992 a breakthrough emerged when Honda started to experiment with a revised firing order on their all-conquering NS500.
BIG BANG & THE SCREAMER
Dubbed ‘Big Bang’ the revised crankshaft mechanism placed an emphasis more on acceleration than outright top speed and Mick Doohan went on to dominate the class on the new bike. Honda also produced a V-twin version of their four cylinder motorcycle which helped privateers remain competitive against the factory bikes and for the first time technical emphasis leaned more towards corner speed than outright horse-power; a trait that remains present to a certain degree in MotoGP today.
By the late 1990s Doohan had reverted back to the ‘harsher’ engine order in his quest for more speed. Nicknamed the ‘Screamer’, this and the ‘Big Bang’ version of the NS500 won World Championships from 1994 to 1999.
In 2000 Suzuki enjoyed a last hoorah on the RGV 500 2-stroke; a motorcycle which developed from predecessors that had originally dominated the class back in the late 1970s and early 80s.
4-STROKE 990cc
With 2-stroke technology reaching a plateau improved 4-stroke engines marked the way forward. The MotoGP landscape changed in 2002 and the last six seasons have again seen a massive acceleration in the technical possibilities with variable cylinder structures and quantities, telemetry, data collection and manually adjustable engine mapping switches now standard.
MotoGP is now a highly evolved and scientific competition with traction control and electronics playing an important role in the delivery of the power and adjusting the balance of the motorcycle to make the best use of the engine’s performance.
The MotoGP category saw the engine size reduced from 990cc to 800cc in 2007, with an aim to reduce speed. So far the speeds have remained the same but the size and dynamics of the new motors have placed more focus on the corner speed of the machinery, as opposed to the brute power of the 990s.
SMALLER CLASSES
The 125 and 250cc classes have remained hosts to 2-stroke engines, being the original homes of the 2-stoke. Firms such as Derbi, Kreidler and Bultaco were 50cc, 80cc and 125cc competitors with 2-strokes in the 1960s and 2-strokes littered the 350cc division.
Outside the premier class 2-strokes permitted the most cost-effective means of racing and being competitive. The 2-stroke prospered with carburetion, tuning and set-up becoming a specialised skill that saw a host of names in the Grand Prix paddock making their names through the late 1970s, 80s and into the 90s.
In modern times the accepted wisdom is that the limits of 2-stroke technology have been largely reached. Honda’s announcement that they will cease development on their quarter-litre bikes perhaps provides proof that there is no further ground for significant progress.
