Pipe dreams

Modern Formula 1 exhaust systems are about so much more than simply expelling gases, but to achieve the complex geometries required for them to work at their very best the F1 teams need to use a fair bit of compromise and a great deal of red-hot technology

- GEMMA HATTON

The primary function of any exhaust system is to release the exhaust gases from the engine out into the atmosphere. However, in modern Formula 1 they also have a whole host of other functions, including optimising engine, aerodynamic and turbocharger performance.

The journey of the exhaust gases begins once the fuel and air mixture has combusted during the power stroke of the combustion cycle. After this the piston moves back up the cylinder completing the exhaust stroke, where the exhaust valve opens and the burnt gases are expelled from an area of high pressure in the cylinder to low pressure in the exhaust pipe. At the same time, the inlet valve is also open, allowing fresh charge into the cylinder. This point in the cycle is called ‘valve overlap’.

As the exhaust gases move through the exhaust pipes they create pressure waves and when these pressure waves reach a change in geometry a negative pressure wave is created. The timing of these negative pressure waves can actually help to draw the exhaust gases out of the cylinder more effectively. In turn, this lowers the pressure in the cylinder, which then helps to draw more fresh charge through the inlet valve; helping to increase volumetric efficiency.

Hi-tech plumbing

Once the gases leave the combustion chamber, they travel into a set of primaries, or headers, which are usually of equal length, to ensure that no cylinder is overworking. There is one primary for each cylinder which is connected via a specialised flange to suit the specific geometry of the cylinder head. The three primaries coming from each bank of the engine then join together in a three-to-one primary collector. After which, two secondary pipes then go into the turbo. Depending on the engine manufacturer, the primaries, collector, and secondaries can either be all one-piece and integrated into the turbocharger, or separate pieces.