As most F1 fans know by now, the engine regulations have been altered for 2014 onwards. The main changes can be summarized as follows: Cubic capacity drops from 2.4 lt to 1.6 lt and, at the same time, the number of cylinder goes down from 8 to 6, always in “V” configuration, revs are limited to 15,000 RPM, direct fuel injection is limited to 500 bar, single turbo charger is allowed and, finally, the fuel flow will be controlled (i.e. limited). For those interested in reading more, you can find the changes here. We will have the pleasure of watching turbo engines again after 26 years, for it was back in 1988 when the McLarens of Ayrton Senna and Alain Prost dominated the season, using a 1.5 lt V6 Honda turbocharged engine.
Many people believe that F1 engines are no longer the great differentiator in performance that they used to be, and that’s true. However, the level of competition is such at the moment, that one can never rest and there is always scope for development and investment. Recently imposed regulations such as the DRS have brought engine performance back under the spotlight. Renault, according to their F1 director Mr. Francois Caubet, have developed an engine so efficient that it allows Red Bull to start a race with 15 – 18 liters of fuel less than their opposition, even though it is slightly down on power in comparison to Mercedes (by about 15 BHP). Teams like Mercedes and Ferrari will be spending millions of dollars developing their engine plants, so I believe it’s worth examining the new engine regulations a little bit further.
Let’s start with the most intriguing aspect, which is of course the fuel flow rate limitation. The upper limit is set at 100 kg/h, and below 10,500 RPM the fuel mass flow must not exceed the amount of Q (kg/h) = (0.009 x RPM) + 5. This means, that the fuel flow tops up @ 10,500 RPM and has the linear graph shown below. Of course, the curve below represents the maximum allowed fuel flow in all circumstances and does not represent the actual flow graph, which will be considerably different.
The question is, how do we get more power in the 10,500 – 15,000 RPM range when our fuel flow is limited? Many people traditionally associate increase in power with increase in fuel supply, which is of course wrong. You can have an increase in power by using different (leaner) air/fuel ratios (and/or different ignition advance settings), and all modern engines are managed that way through air/fuel ratio maps which are embedded in the cars’ computer (and, quite often, tweaked afterwards…). Typically, a road car achieves 100% (or even slightly more) of fuel injector duty cycle at about 80% of its RPM range, and then has 20% more RPM to give (and, often, more power) by changing the air/fuel ratio and increasing the advance (i.e. increasing the degrees before TDC that the ignition takes place). So, you may end up getting 1,000 more RPM and at the same time the fuel injectors workload has dropped to 80% (these are ballpark figures).
The logical question is, how do we get more power by increasing the air/fuel ratio? The reason is stoichiometry. A stoichiometric mixture is considered an air/fuel mixture that has just enough air to burn the entire fuel quantity. For typical gasoline that we put in our cars, this ranges anywhere between 12.5 to 13.3. In F1 fuels, this may be slightly lower (due to the additives that have the effect of lowering the stoichiometric ratio). In reality, however, cars never run stoichiometric mixtures. There are three main reasons for that: (a) a stoichiometric mixture burns very hot and can impart severe thermal stresses to the engine components, (b) the temperature is further increased because we no longer have the cooling effect of the fuel spray on the combustion chamber and, (c) due to the high temperatures, early detonation of the mixture is possible, causing the famous “knocking” effect under load. All cars therefore (even F1 single seaters) use rich mixtures (i.e. air mass / fuel mass less than the stoichiometric one).
The new fuel flow rate limitation nevertheless means that F1 engineers will be forced to explore the upper limits of the air/fuel ratio. The increased ratios combined with increased advance will cause severe thermal stresses to the engines and will dramatically increase the cooling needs of the power plant. Also, since the cars will be turbo-charged, the charge air (i.e. the compressed air supplied by the turbo compressor wheel to the combustion chamber) must also be cooled down. Overall, thermal management of the engines will be crucial in 2014, and I expect most early reliability problems to come from that, as the aerodynamicists will be pushing for leaner sidepods and smaller coolers and air intakes. The engines themselves may be smaller, but this is more than countered by the addition of the turbo and the complexity of the exhaust piping arrangement (see further down in this post).
The problem of cooling is further exacerbated by one addition to the 2014 rules (5.8.2) which states that “over 80% of the maximum permitted fuel flow rate (author note: i.e. over approximately 8400 RPM), at least 75% of the fuel flow must be injected directly into the cylinders”. This means you have a very small time window to get all the fuel delivered directly via the fuel injectors (which are also limited to 500 bar), since you can only direct 25% of the fuel via the air intakes, which would help to keep the valves clean and to achieve more homogeneous mixtures inside the combustion chamber.
Also, the exhaust gases (having worked the turbine wheel) will have lost a lot of their kinetic and thermal energy, so there will be less scope for using them for aerodynamic purposes. Since only one, single-stage turbo is allowed, we will now get a single exhaust outlet from the turbo, although I don’t see anything in the rules preventing the teams from splitting the exhaust manifold in two after the turbo.
How does the 100 kg/hr compare to today’s F1 cars and consumption figures? Typically, contemporary F1 cars consume 75 lt / 100 km (4 mpg). 75 liters are about 68 kg. A typical race distance is around 310km and is done (again, typically) in about 1 hour and 30 minutes. This means that, currently, F1 cars consume on average 140.5 kg/hr of fuel. Please remember that the 100 kg/hr is the maximum amount allowed, we therefore expect the average number to be even less. Assuming (and that’s a big assumption) that the average figure will be around 80 kg/hr, this means that the new generation engines will be about 43% more economical than the current power plants. A 2011 car had to start the race with about 180 kg of fuel – in 2014 they will be starting with 120 kg. This means considerably smaller fuel tanks; and there’s a reason right there for the aerodynamicists to feel a bit better after all.
An interesting addition to the rules is 5.19, which states: “Engine exhaust gases may only exit the cylinder head through outlets outboard of the cylinder bore center line and not from within the “V” centre”. The way I understand this is that exhaust piping must travel outboard the engine and cannot be located in the middle, between the two cylinder banks, as shown in the figure below (the green area is where it’s not allowed to installed the exhaust outlets). This would have been an obvious solution for the engineers, i.e. to join the exhaust outlets from the two cylinder banks in one common manifold running between the V. Now, they will have to keep the exhaust outlets from the cylinder heads pretty much as they are at the moment and resort to more elaborate and complicated exhaust piping arrangements in order to feed the turbo charger.
So, what should we expect from the 2014 engines? I am really not willing to get into the debate of how they will “sound”. They will sound terrific, just like they always have. For those who are interested in the technology, it will be fascinating to observe the new engines and the various solutions that the engineers will come up with.