Table of contents
Fuel, gasoline, petrol, …
Where from, where to – and why?
(Almost) nothing works on a motorcycle without fuel. Where does the stuff come from, what is it doing in the engine and where is the energy?
December 15, 2008
Motorcyclists can get fuel at around 15,000 petrol stations in Germany. Nobody really likes to do this, because gasoline is expensive, looks boring, smells nasty and is getting less and less too quickly. So on the surface, fuel is pretty boring. But if you take a closer look at the expensive juice, you might discover the fascinating side of gasoline. And that begins with gasoline production. The basis of the fuel consists – roughly simplified – of dead animals. Specifically: from dead micro-organisms whose death occurred in prehistoric times. This stuff is also called petroleum. With around 85 percent carbon, 13 percent hydrogen and some sulfur and oxygen, this raw material is an ideal energy source with a high calorific value. But in order to produce around a quarter of a liter of petrol from one liter of crude oil, the refinery has to be heated vigorously: In the first step, the crude oil is distilled at 390 degrees Celsius. The crude oil is separated into gas, petrol, diesel and gas oil. By “cracking” (splitting) at 540 degrees, further gasoline is obtained from the gas oil. After extensive post-processing, basic fuel was created that does not differ between the various oil companies, and often even comes from the same refinery. The (alleged) brand difference is only taken care of directly before the tanker is filled: Every gasoline supplier gives his product an additive package that includes, among other things. ensures an increase in the octane number and is intended to prevent deposits and corrosion in the engine. On this occasion, the fuel also gets its brand-typical color. The finance minister is now paying for the around 21 million tonnes of motor gasoline that is used in Germany every year. The combination of mineral oil, eco and VAT amounts to 80 to 90 cents per liter. When the bill has been paid and the fuel is in the tank, he only has one task: to provide propulsion as effectively as possible. It does this best when 14.7 parts air are added to one part of fuel. This ratio is referred to as lambda = 1. The lambda probe installed in the exhaust is a sensor that measures the residual oxygen content in the exhaust gas and provides the engine management system (control unit, responsible for mixture formation and ignition, among other things) with relevant information. If the lambda value rises to 1.35, which corresponds to an extremely lean mixture, or if it is much too rich with lambda = 0.75, the gasoline / air mixture is no longer ignitable and the fuel escapes unused and is more toxic because unburned carbon is in the Outlet and through the exhaust. But even without incorrect lambda values, only a maximum of 33 to 38 percent of the fuel used can be converted into drive power. Since the engine is pretty hot and strong, a large part of the energy contained in the fuel is converted into waste heat and friction instead of into drive. In addition, the alternator as well as the oil and water pump take their toll, and even the tire costs another one to two percent power due to friction and slip. In the best case scenario, only about a quarter of a liter of gasoline remains for locomotion.
Waste heat and friction cost a lot of the energy in gasoline:
Valve train and actuation:
Between 1 and 4% of the energy is “lost” through the friction of the camshafts and the actuation of the spring-loaded valves.
Waste heat through exhaust and cooler:
Up to 35% of the energy disappears in the exhaust gas, around 25% via the cooler and surface radiation.
Due to mixture residues in the piston ring zones and over-greased mixture at the top land, 5 to 20% of unburned gasoline residues disappear in the exhaust.
Piston group and connecting rod bearing:
Lateral forces on the piston and the heavily loaded plain bearings on the connecting rod and crankshaft consume 4 to 14% fuel, depending on the speed and load.
Regardless of whether it is a chain or cardan shaft, the power flow to the rear wheel costs around 3% performance, depending on the condition and construction.
Each pair of gears, i.e. primary drive and gearbox, has a power loss of around 2%.
The best fuel-saving tips
Speed down. Regardless of whether you are driving through town, surfing country roads or listening to the monotonous hum of the motorway: fifth or sixth gear noticeably reduces engine speed and consumption. This is especially true on country roads at constant speed and with little braking and acceleration.
Do without high speeds. In particular, large-volume engines have the most power in the area of the best torque and well below that. The range of the maximum torque can be marked with adhesive tape on the tachometer for a better overview.
Is the air filter dirty? or stuck together with oil from the engine ventilation, the air-to-fuel ratio is no longer correct. Over-grease engines without lambda control, consumption increases.
With older machines With a mechanically operated cold start device (choke) it can happen that poorly running trains or stiff cold start pistons no longer close the additional nozzles completely, which increases consumption because too much fuel is constantly sucked in and the ignition is interrupted by sooty plugs.
Poorly lubricated, worn or too tightly tensioned drive chains reduce the efficiency due to high friction and increase consumption, especially at higher speeds.
Bad aerodynamics causes unnecessarily high consumption. If you roar over the motorway in a flutter jacket or with empty panniers / topcase, you burn an unnecessarily large amount of fuel. With a tight-fitting station wagon and a well-tied rucksack for small luggage instead of the fat top case, consumption can be reduced by up to one liter / 100 km, depending on the speed; because the top case and pannier are in the wind, especially when driving solo, because the air flow after the driver is directed back into the center of the vehicle and hits the luggage system. Only with a pillion passenger is the topcase actually in the slipstream of the passenger.
The tire pressure also has an impact on fuel consumption because it affects rolling resistance. The highest recommended pressure should therefore always be selected for motorway journeys. When driving on country roads, on the other hand, cornering grip and self-damping have priority, so take the values recommended for this from the driver’s manual.
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