It is quiet, surprisingly quiet. A long, white corridor leads to a rather small, rectangular room with a glass front. ‘Clean Area’ say the signs on every one of the many glass doors on the approach to the room. There is a box on the wall containing lots of fresh gloves. Thick tubes extend into the far corners of the room – we are in the holy of holies, in one of the Mercedes-Benz engine dynos at Brixworth, the birthplace of the Mercedes-Benz V6 Hybrid Power Unit. The result: The most powerful F1 engine ever built by Mercedes – and yet it is also the most efficient.
The Mercedes-Benz Power Unit has already proven in the previous two seasons that efficiency does not mean having to compromise on performance. On the contrary, the 1.6-litre V6 turbo internal combustion engine alone produces roughly 98% of the power of the 2.4-litre V8 engines which were used in Formula One until 2013 – even though its capacity has shrunk by a third. The crucial difference is the Hybrid Energy Recovery system. While KERS was in use until 2013, the letter ‘K’ was dropped from 2014 because the Hybrid system no longer relies on kinetic components alone.
KERS produced around 81hp in 2013. ERS now delivers twice the performance. Based on the Power Unit’s total output, this means that today’s engines are around ten percent more powerful than their immediate predecessors. But that’s only half the story. While KERS was only on tap for 6.7 seconds per lap during the V8 era, the MGU-H and MGU-K combine to deliver maximum power over an entire lap in the best case scenario. The increase in performance over a race distance is thus considerably more than ten percent.
What is thermal efficiency?
Basically, there is only one source of energy – the petrol. It all starts with the engine. It needs to produce as much power at the crankshaft as possible by burning the injected fuel. The fuel-air mixture ignites in the combustion chambers and moves the pistons. Consequently, chemically bound energy is turned into kinetic energy. The aim is to release as much kinetic energy as possible from a predetermined amount of chemical energy. Fuel flow is limited to a maximum of 100 kilogrammes per hour. Between eleven and twelve kilowatt hours of chemical energy are bound up in one kilogramme of gasoline. If 100 percent of the chemical energy could be transmitted to the crankshaft, the power delivered by the internal combustion engine would be more than 1,500 hp.
The energy that is not converted into kinetic energy through combustion then exists as thermal energy or as hot exhaust gases to be more specific. In a turbo-charged engine, the exhaust gases are not extracted without doing any work but are reused. The cooler the exhaust gases coming from the engine, the more efficient the combustion process has been. The turbocharger has to make further use of the remaining thermal energy. The turbine vanes are driven by the flow of exhaust gases, driving in turn the compressor and the MGU-H. An overall efficiency of around 50 percent can be achieved by the Power Unit’s internal combustion engine due to its high thermal efficiency. Half of the chemical energy introduced into the system is finally converted into torque at the crankshaft. The efficiency of conventional combustion engines is less than 40 percent.
Historic highs of engine power in Formula One
A comparison with the V10 engines which were in use until 2005 produces more incredible statistics. In their second year of running, the current Power Units already have more power than the high-revving naturally aspirated engines at the end of their development cycle – figures that were never equalled in the V8 era.
But these figures are even more impressive when you take into account that the V10 units fuel flow rate of 194 kg of fuel per hour at maximum power, whereas the modern Power Units do so on just 100 kg per hour. Aside from the very short-life turbo engines of the 1980s, this means we are currently enjoying historic highs of engine power in Formula One.
“We now need about half the amount of fuel to produce the same power – that’s a phenomenal improvement in efficiency. From this data, we can see that the Power Units are not only incredibly efficient but are also amazingly powerful,” says Managing Director of Mercedes-AMG High Performance Powertrains, Andy Cowell. “This small 1.6 litre unit packs an awful lot of power at the crankshaft.”
The benefits of the Power Unit
The Power Unit has several key advantages over the extremely powerful turbo engines of the 1980s. Apart from being much more thermally efficient, they are also long-lasting. While engines run in qualifying back then were only good for one session, a driver today has to complete a full season with only four Power Units – an average life per unit of around 3,400 km.
In addition, there’s the wide power band over which this enormous power is available. Back in the day, peak power was very high but only over a narrow rev range. Older drivers used to talk about ‘turbo lag’. Sometimes, it was two seconds before the power was there. Thanks to the MGU-H, by means of which the compressor can be spinning as the driver makes a torque demand with his right foot, driveability is so good nowadays that it’s even better than it was with the normally aspirated engines.
“The work that we have put into the combustion process, electric turbochargers and extremely small but highly tuned engines has a direct bearing on series production,” says Cowell. “Cars with electric turbochargers are not yet available at dealerships, but work on them is already in full swing. I have no doubt that this technology will also be used on the road.”
So, once again, Formula One is at the pinnacle of technology. And, as in the past, many innovations from Formula One are being adopted into production cars. “Four-valve engines and BDA cylinder heads are standard everywhere nowadays, because they increase efficiency,” says Cowell.
And development work still has a long way to go before it reaches its peak, too… (Source: Mercedes)