Indian Autos blog

Saturday, September 22, 2007

Secret Formula

The sound sends a shrill through our spines on race weekends. The engine that power a F1 car is quite different when compared to a normal car's engine. But how different are they? Lets find out.

Close to 5000 parts have to be put together to build a F1 engine. So a week and 750hp later, the work is declared complete. Weighing less than 100 kg, a F1 engine has 8 cylinders in a 90 degree V-angle and displace 2.4 litres. They have two inlet and two exhaust valves per cylinder which are reciprocating poppet type. At full throttle the engines rev upto 20,000 rpm and consume around 60 litres of petrol for 100km of distance covered. These engines are made from forged aluminium alloy, because of the weight advantages and higher heat dissapation capability it has in comparison to steel. Dry sump lubrication system is used which helps in achieving a lower centre of gravity and avoidance of oil sloshing during hard cornering. The oil gets recirculated and thus fresh oil arrives to lubricate the engine components 3 to 4 times every minute. The engine is mounted in between the monocoque and the gearbox thus making the car a mid-engined one.

A smooth and consistent delivery of power is crucial for enabling the driver to place the car continually on the edge of traction and avoid sliding or spinning out. This translates to a flat torque curve, ie a constant production of torque across the useful rev range, and therefore a linear power curve. To ensure the responsiveness of the engine (easy to accelerate/decelerate), the inertia of the rotational components such as the pistons and crankshaft should be less. Utilizing light weight materials might be one solution but only to an extent as they can hamper low-end torque. Revving at massive speeds again can only be upto a certain limit beyond which there is drastic increase in engine friction and the accelerative force on the pistons at maximum operating condition is nearly equal to 9000 times gravitational force.

A F1 engine has a lifetime that spans to about 400km before it is overhauled. Thus, the stress it goes through during its lifetime is by no means easy as it has to withstand heat, g-forces and maximum rpm without failing. Periodic factory tests are unable to fully simulate the g-forces, airflow/cooling characteristics, and track surface vibrations encountered in racing. Thus track testing is still invaluable as a source of information when looking at reliability. Engineers use telemetry data to study the various engine components . In addition, the Bi-Telemetry technology is also used to maximise reliability by allowing the team to control some aspects like the engine's rev range or switching to the spare oil reservoir from a remote location during a race.

Just above the driver's head is an air inlet that supplies air to the engine. It is commonly thought that the purpose of this airbox is to force air into the engine like a supercharger, but the airbox does the opposite. Between the airbox and the engine there is a carbon-fibre duct that gradually widens out as it approaches the engine. This it provides a constant pressure and speed of air intake regardless of outside weather conditions, at all parts of the track including tight corners. This results in the increase of volumetric effeciency. The role of Computational Fluid Dynamics is eminent as it used to simulate and predict gas flow through these passages.

Essentially, proper cooling is a vital aspect of the internal combustion engine. Even an advanced modern F1 engine is relatively inefficient when it comes to converting the power available from the fuel/air mixture into power at the rear wheels. The engines produce about 1750kW of heat that must be expelled to the atmosphere through the radiators and the exhaust, which can reach temperatures of over 1000 degrees Celsius. The radiators, are located in the sidepods, to the right and left of the engine contain around three litres of coolant which aid in maintaining the engine at optimum working temperatures. Airflow is controlled by different configurations of radiator outlet to cope with all manner of conditions. The configuration used at a particular circuit is defined according to the ambient temperatures, circuit factors such as how much full throttle is used, and the temperature limits that an engine can run at. A Formula One engine is 20% more efficient at turning fuel into power than even the most economical small car.

A Formula 1 car's exhaust serves a purpose just like any other road car’s – it takes hot gases away from the engine and expels them safely at the back of the car. The intricate welding and precision design of the exhaust looks closer to a work of automotive art. In order for the bodywork to be as aerodynamically-efficient as possible at the rear of the car, the exhaust system is designed to fit as tightly around the engine as possible. Therefore, a successful exhaust design serves two purposes – maximising engine performance and minimising aerodynamic compromises. Hence the pipes of the exhaust system are individually tuned in length, diameter and curvature as to minimise blockage and ensure that the gases to/from the cylinders do not interfere with each other.



FIA rules and Specification for the year 2007:

Only 4-stroke engines with reciprocating pistons are permitted.
Engine capacity must not exceed 2400 cc.
Supercharging is forbidden.
All engines must have 8 cylinders arranged in a 90ยบ “V” configuration and the normal section of each cylinder must be circular.
Engines must have two inlet and two exhaust valves per cylinder.
Only reciprocating poppet valves are permitted.
The sealing interface between the moving valve component and the stationary engine component must be circular.

Dimensions, weight and centre of gravity:

Cylinder bore diameter may not exceed 98mm.
Cylinder spacing must be fixed at 106.5mm (+/- 0.2mm).
The crankshaft centreline must not be less than 58mm above the reference plane.
The overall weight of the engine must be a minimum of 95kg.
The centre of gravity of the engine may not lie less than 165mm above the reference plane.
The longitudinal and lateral position of the centre of gravity of the engine must fall within a region that is the geometric centre of the engine, +/- 50mm. The geometric centre of the engine in a lateral sense will be considered to lie on the centre of the crankshaft and at the mid point between the centres of the forward and rear most cylinder bores longitudinally.
Variable geometry systems are not permitted

Materials:

Magnesium based alloys, Metal Matrix Composites (MMC’s) and Intermetallic materials may not be used anywhere in an engine
Coatings are free provided and must not exceed 0.8mm.
Pistons must be manufactured from an aluminium alloy which is either Al-Si ; Al-Cu ; Al-Mg or Al-Zn based.
Piston pins, crankshafts and camshafts must be manufactured from an iron based alloy and must be machined from a single piece of material.
A supplementary device temporarily connected to the car may be used to start the engine both on the grid and in the pits.

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