Why do F1 engines break so easily?

At this year’s Belgian Grand Prix, Lewis Hamilton was handed a 55-place grid penalty for replacing power unit components that were past their best, and breaking F1’s strict limits on how many such parts can be used in a season.

Fernando Alonso was hit with a 35-place penalty for the same reason.

What is it about F1 engines that makes them so apparently fragile?

The quick answer is… they’re not really that fragile, they’re designed to do a tough job and, by-and-large, they manage pretty well.

But failures do occur, of course. Here are three reasons why…

Tons of stress. Literally

Ask an engineer to talk about the pressures an F1 engine can be put under and you may find their answers utterly unbelievable.

For example, the pistons in an F1 car travel up 39.7mm (1.56in) and then back down the same distance in a single revolution. This is the engine’s stroke.

The engines are not permitted to rev above 15,000rpm so, at their design limit, each piston will travel 15,000 x 1.56inches x 2 (they go up and down, remember) which is 46,800 inches – that’s about 44mph.

Doesn’t sound so fast, does it? But each piston accelerates upwards from rest to that speed then decelerates to zero, before repeating the process on the way back down.

OK, enough with the maths. A fellow called Jack Kane did all the hard work for us by calculating the forces acting on F1 engines back when they revved to almost 20,000rpm.

Taking into account the weight of engine parts (eg pistons, piston pin, rings, circlips) he reckoned parts of an F1 engine were being subjected to 10,600g.

That’s 10,600 times the force of gravity. Put another way, a load of more than four tonnes was being transmitted through some small engine parts more than 500 times a second.

Now, these calculations refer to engines revving higher than they do now – maximum revs were reduced as a cost and fuel-saving measure – and they rely on estimates of some part sizes and weights.

But they give a flavour of how much pressure engine parts are placed under.

Here are a few more estimates for some of the abuse meted out to an F1 engine. Note that these are from a Mercedes engineer and they relate to the much bigger engines being used in 2012, rather than today’s modest 1.6litre models, details of which tend to be kept secret.

Oh, and they refer to what can happen in just a single second to a 2012 F1 engine running at 18,000rpm.

In a single second:

• 360litres of fuel/air mixture is used

• One litre of oil is pumped through the engine

• Three litres of coolant are pumped to the engine

• Pistons experience more than 100bar of pressure. That’s 1450psi, or 50 times the pressure in your car tyres

• 350C temperature on the top surface of the piston

• 200C temperature on the bottom surface of the piston

You get the idea – if the devil was an engineer, hell would be the inside of an F1 engine.

And that’s why they sometimes break.

It’s complicated

We no longer say that F1 cars have engines (well, we do but apparently that marks us out as being ignorant). Those in the know refer to them as power units, and they are complicated.

A power unit has six separate elements. The first is the internal combustion engine (ICE), which is assisted by a turbocharger.

To these two elements are added two energy recovery systems (one kinetic, linked to the braking, the other heat-based and connected to the turbo), an energy store and some electronics to control the whole thing.

And each one of these elements is pushing the boundaries of what technology can achieve.

It is impossible to test what will happen to these various elements in all their combinations and, occasionally, an unpleasant surprise will bring the car to a halt.

Sebastian Vettel (pictured) found this out to his cost at this year’s Bahrain Grand Prix, when his engine (well, his ICE) expired on the parade lap and, for the first time in his career, Vettel failed to start a race he’d entered.

The issue was a failed exhaust valve but that turned out to be a symptom of another problem. The power unit’s electronic ‘brain’ struggled with key engine parameters at low revs and, as a result, sent instructions that over-stressed the exhaust valve… boom. Game over.

Failure is planned

F1 power units are remarkable pieces of engineering. The tolerances in the ICE are so tiny that the engine is effectively seized when it’s cold.

The starting procedure is a little more involved than jumping in the seat and turning a key. Around 20 minutes before the engine is started, oil and water of a preset warmth (eg around 80C) is circulated around the engine to bring it up to operating temperature.

But, a side-effect of this amazing attention to detail is that the power unit components are built to last just as long as they have to. That means four or five races each of 190miles (305km) or less – less than a thousand miles.

You’d be more than a little irked if your new car blew up after 1,000 miles but, in F1, it’s pointless strengthening such parts to keep them usable for a whole season because strengthening them would add weight to the car, and heavy cars are slow cars. Don’t over-engineer unnecessary strength or endurance into race cars, it just slows them down.

As the great Ferdinand Porsche said: ‘The perfect racing car crosses the finish line first and subsequently falls into its component parts.’

Remember that the next time you see an F1 car grind to a halt in the lead of the last lap – it is probably closer to perfection than any other machine on that track.