F1 Technical series. Part 4 of 5 – Powertrain

The powertrain of any vehicle with an internal combustion engine consists of the engine, gearbox and differential. An F1 car also has the KERS motor/generator.

Formula 1 engines are amongst the most efficient ‘petrol’ spark ignition engines in the world. They use exactly the same operating principles of your ordinary car engine, the 4 stroke ‘Otto’ cycle. As James May put it ‘suck, squeeze, bang and blow’. The 8 pistons travel up and down inside bores known as cylinders that are pressed into the engine block. Each cylinder has to be a set size of capacity. Total capacity of the bores and combustion chamber must be equal to or less than 2400cc. The pistons are then in turn connected to the crankshaft at the bottom of the engine via con-rods (connecting rods) which is also connected to the camshafts by a series of gears. This means that there is no belt, or chain to snap under high speed and load conditions, and therefore the engine can rev higher, and also there is less mechanical drag on the engine, giving more performance. There’s also less weight to contend with. Each car has an alternator, and a water pump. The lubrication system actually has more than one oil pump. A high pressure one for distribution inside the engine, and a scavenge pump to take any unwanted engine oil from the sump back into the holding tank. This type of lubrication system is known as a ‘dry sump’ system and is actually more reliable under high cornering forces as the oil pump isn’t starved of oil when going around a corner.

Another difference to your ordinary road car is the valvetrain. F1 engines are limited to 4 valves per cylinder. The valves inside your average 2 litre engine are closed by springs. At high engine speeds these springs can actually cause catastrophic valve backlash, where they LITERALLY bounce in their seats and then hit the top of the piston. This then destroys the internals of the engine. So, instead of ordinary valve springs, the valves are actually set into pressure chambers that are filled with high pressure Nitrogen gas from a gas bottle in the sidepod. The compressed Nitrogen acts as the valve spring, which means that metal springs aren’t needed to close the valves, the engines can rev higher and therefore produce more power. This type of valve spring mechanism was first pioneered by Renault back in the mid 1980’s, and the engines would freely be revving in excess of 23,000rpm if it wasn’t for the regulations restricting engine speed to ‘just’ 18,000rpm. Each piston is subjected to acceleration forces of around 9,000 times the force of gravity at full engine speed, and going from 0-60mph in just 5 ten-thousandths of a second! An F1 engine can actually go from idle at 4000rpm to its limiter in just 0.3 seconds! F1 engines also have no flywheel! This is to improve acceleration and to keep the centre of gravity of the car as low as possible.

Direct-Injection fuelling is not allowed within current regulations, so the fuel is injected directly into the intake trumpets housed in the engine air intake snorkel that sits above the drivers head.  Here’s a good video of fuel being injected. http://www.youtube.com/watch?v=dB0J94ayu5k

There is also one ignition coil and one spark plug per cylinder. Both fuelling and ignition are controlled electronically by the EMU

In 2014 the engine regulations will change, as will the aero regulations too. The engines will have 6 cylinders arranged in a ‘V’ shape, and a maximum total capacity of 1600cc’s. There will also be a single turbocharger mounted in a central position of the cars.

The gearboxes in F1 cars must have 7 forward gears and 1 reverse gear. Each set of gears must be made out of steel, and must be of a set dimension. Each team is allowed a maximum of 30 different gear ratios for use on every track. The gear ratios must also be set on Saturday morning, after which they are not allowed to be changed until the next race. Each gearbox also has to last 5 races, and any unscheduled changes incur a 5 place grid penalty added to the qualifying position at the first weekend the gearbox is used. The gears are not selected y your normal ‘H-Gate’ gearshift mechanism, instead they’re electro-hydraulically selected. The gears are actually selected by a hydraulic barrel mechanism that uses valves actuated by electronic signals from the gearshift paddles on the back of the steering wheel to control the flow of high pressure hydraulic fluid from the hydraulic pump mounted to the engine. When the pressure is sent to a specific gear selector fork, the fork moves to lock the gear it’s attached to, to the shaft it sits on. There is no synchromesh mechanism in an F1 gearbox, but your road car has one. All F1 gears are straight-cut gears as they are stronger.

The differential is an integral part of the gearbox, and is of the electro-hydraulic, limited slip type. It is full adjustable and the torque bias between each side can be changed in 3 ways to help steer the car through the corners, so setting up the differential to have the perfect torque distribution between each rear wheel is critical for mid-corner rear end grip and traction under acceleration. The three ways a differential is adjustable by are entry, exit and mid-corner. The flow of hydraulic fluid is controlled by ‘moog’ valves, which actually use a very tiny amount of electric current to control the flow of a LOT of hydraulic fluid.

The clutch is actuated electro-hydraulically, no mechanical linkage to the paddles on the back of the steering wheel. The whole clutch weighs just 1.5kg for absolute minimal inertia, and is made up of several solid carbon plates, metal pressure plates and the outer casing that holds the plates together. There is a hydraulically actuated clutch fork that opens the clutch up to disengage the clutch for gear changes and for race starts.

The final part of the powertrain system is the KERS unit. This consists of a motor-generator built onto the back of the engine underneath the oil tank and attached directly to the crankshaft. When the brakes are applied this unit generates electricity that is stored in super-capacitors or batteries. When the car is travelling above 100km/h the generator can be used as an electric motor, using up the energy stored in the batteries or super-capacitors to give an extra 80hp boost for up to 6.6 seconds per lap. The time that the KERS is used for is controlled by the FIA standard ECU from McLaren Electronics. KERS was first introduced in 2009, but only McLaren and Ferrari were using it by the end of the season. Originally Renault and BMW-Sauber started the season with the system. There is another type of KERS system that Williams Hybrid Technologies started to develop, but because of the weight and packaging of it they decided to go for an electrical system. The system they started to develop was the flywheel type, where the flywheel stored rotational energy and was then engaged by a clutch that used the momentum of the flywheel to give the required power boost.


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