A Formula One engine operates on the same basic principle as any old petroleum-fired motor. It’s an internal combustion engine, with a cylinder block, cylinders, pistons and valves. The pistons inside the cylinders move up and down, driven by an explosive combustion of fuel and air allowed in by the inlet valves. The spent gases are allowed to escape via the exhaust valves. The pistons connect to a crankshaft which in turn drives camshafts – and those are the things that open and close those valves. Nothing new there. The radical thing about a Formula One engine is its light weight and humungous horsepower. Reconciling almost 900 horsepower with something that weighs less than 90kg may seem impossible, but a Formula One engine does so.
The engine uses very exotic metals – and some non-metallic materials too –to keep its weight and heat expansion down. A Formula One engine relies on speed to get much of its power, with the best of the current engines running to almost 19,000 revs per minute (rpm), about double the speed of the highestrevving road cars. How is that possible? Well, the engines have to be rebuilt after around 500 miles – kind of expensive. Any engine can be squeezed for more revs and power if it only has to last such a short distance. Current regulations limit the engine size to 3000cc (cubic centimetres), and turbo, or supercharging, is prohibited. The engine must have 10 cylinders. Four pneumatically-operated valves – two inlet and two exhaust – feed each cylinder (although up to five are allowed, no-one has found an advantage from this).
The pneumatic operation gives greater accuracy at high speeds than conventional valve springs. The cylinders are arranged in two banks of five, the banks splayed at an angle to each other to form a vee, hence the term of “V10” in describing the layout of the engines.
Why 10 cylinders and not less or not more? The pros and cons are as follows:
- Engine speeds: The greater the number of cylinders an engine has, the more power it can theoretically produce. For a given engine capacity, each cylinder will be smaller the more of them there are; for example, each cylinder in an eight-cylinder, 3-litre engine would be of 375cc whereas a cylinder in a 10-cylinder 3-litre would be only 300cc. The smaller pistons inside these smaller cylinders can be moved up and down the cylinders faster. The faster they move, the more power they produce.
- Valve area: Having more cylinders means greater inlet and exhaust valve area, which in turn means that more fuel and air can be pumped through the engine. That translates to more power.
- Heat expansion: With more cylinders, less energy is lost to heat expansion because smaller cylinders and pistons can disperse their heat easier. Again, this means more power. On the other hand, higher speeds from more pistons mean more heat is generated. Complex, isn’t it?
- Frictional losses: These refer to the energy you lose through the friction of one surface against another (in this case, a piston within a cylinder). The more cylinders, the more frictional losses.
- Weight: The more cylinders, the more weight because not only does the engine have to be physically longer to fit in all those cylinders, but each cylinder brings its associated pistons, valves, connecting rods, and so on.
- Fuel economy: Spreading the engine’s explosions between 10 cylinders rather than 8 is less fuel-efficient, so with more cylinders comes the need to carry more fuel, making the car yet heavier.
Many years of experience established that 10 cylinders was the optimum trade-off between these opposing pulls. As materials technology advanced, however, a real possibility existed that the optimum trade-off might have moved onto 12 cylinders or more (as many as 16 have been used in Formula One in the past). To close down an area of future expense, the governing body nailed the limit as 10 back in 1999.
The angle between the vee of cylinders is an area of key concern – and not just to the engine designer, but for the chassis designers too. The wider the angle is, the lower the car’s centre of gravity becomes, to the advantage of its grip and handling. But if the angle is too wide, the engine starts to block up the airflow around the back of the car, which leads to less efficient aerodynamics. Certain vee angles introduce bad vibrations that limit engine speeds and, therefore, power. At the moment, 90 degrees is the favourite trade-off between these conflicting pulls, though there are some shallower and one wider than that.
You might assume that power is everything and that an engine’s fuel consumption can go and be damned. But you’d be only partly right. Power and light weight are primary goals. But, within those requirements, the better an engine designer can make the fuel mileage, the less fuel in the tanks at the start of a race. Less fuel makes the car lighter – and therefore faster – and also keeps the fuel tank size down, to the benefit of the car’s aerodynamics.
The angle between the vee of cylinders is an area of key concern – and not just to the engine designer, but for the chassis designers too. The wider the angle is, the lower the car’s centre of gravity becomes, to the advantage of its grip and handling. But if the angle is too wide, the engine starts to block up the airflow around the back of the car, which leads to less efficient aerodynamics. Certain vee angles introduce bad vibrations that limit engine speeds and, therefore, power. At the moment, 90 degrees is the favourite trade-off between these conflicting pulls, though there are some shallower and one wider than that.
You might assume that power is everything and that an engine’s fuel consumption can go and be damned. But you’d be only partly right. Power and light weight are primary goals. But, within those requirements, the better an engine designer can make the fuel mileage, the less fuel in the tanks at the start of a race. Less fuel makes the car lighter – and therefore faster – and also keeps the fuel tank size down, to the benefit of the car’s aerodynamics.
No comments:
Post a Comment