4 Ways Formula 1 Engines are more efficient than your road car
Just a Big Air Pump…
OK, we are way past the golden era of gas guzzling V8s and V10s, producing over 20,000RPMs, but the modern engine still deserves praise. They are without a doubt the most efficent engine ever.
That 1.6L V6 is the most power dense engine on the planet, at over 400hp… PER LITRE!
The engines are the unsung heroes of today.
In 2017, Mercedes F1 hit the magic ‘50%’ for the thermal efficiency for its engine. This means, 50% of the chemical energy stored in the fuel produces useful work to the flywheel i.e. power.
So how have they achieved this monumental feat?
An easy answer would be the electrical integration of the hybrid system, which doesn’t require combustion. But, there's a lot more tricks in play, and long term gains are a combination of multivariate optimisations in:
- Reducing friction
- Minimising pumping losses
- Using up wasted heat energy
- Suppressing engine ‘knock’
“Technical development is a team effort, it is about setting a target, presenting a vision of where you want to go and including everybody in that journey.”
- Andy Cowell, Managing Director at Mercedes High Performance Powertrains (2014–2020)
Teams are obviously very secretive with what goes on with their engine, but here are some notable innovations:
1. Integrated Hybrid Recovery System via Electrical Motor Generator Units (MGU-H and MGU-K)
This IS the biggest factor.
They’re ‘motor-generators’, meaning they both expend and recover eneergy, one recovers from the wheels (MGU-K), the other galvanising surplus heat energy from the exhaust gases (MGU-H).
The MGU-K is connected and geared to the crankshaft:
- When it wants to deploy, it will act like a 160hp ‘boost/starter motor’, and spin the crankshaft.
- In its regenative phase, it acts like an alternator and resists the rotational speed of the crankshaft, slowing the car down. This resistance, via electromagnetism, creates a ‘charge’, which is collected and stored in the battery.
The MGU-H is a more unique design, where it is connected to the turbocharger:
- In a conventional turbo, the turbines job is to spin the compressor, to force ‘boost’ into the engine. At times, when the compressor is spinning at its optimum rate, there is unwanted boost/heat energy which bypasses the turbo and ‘blown-off’ at the wastegate. This is wasted heat energy.
- In MGU-H controlled turbo system, the turbo has 2 functions, to spin the compressor and charge the MGU-K. More boost equals a greater rotational speed of the MGU-K, charging the battery more. Excess exhaust can now be fed through the turbine and controlled via the MGU-H and create a resistance (charge). Subsequently, teams can adopt larger turbochargers for greater boost compliance, increasing power, without the penalty of turbo lag, as the MGU-H can instantanously spin the turbine.
The MGU-H and the MGU-K allows for direct speed and control of 2 of the most crucial parts of the engine, the turbo, and the crankshaft.
2. Pre-chamber Ignition — small spark, great effect
One of the biggest challenges that goes unnoticed is deciding the correct amount of air and fuel, to generate enough power, whilst being fuel efficient. The recent prominence of carbon emission control is felt by both market and micro-competition regulatory demands. This has desire has accordingly led to explorations in alternative injection solutions to improve fuel efficiency, one of these being coined as ‘pre-chamber ignition’.
In a traditional engine, fuel along with incoming air is injected into the main combustion chamber, ignited by a spark plug, creating power. At high loads, issues with traditional systems can be realised in engine ‘knock’ — combustion within the chamber is uncontrolled and not homogenous across the surface of the piston.
The technology in question is also known as ‘turbulent-jet ignition’ (TJI) or ‘mahle jet ignition’. F1 uses a passive pre-chamber ignition, which is a ‘lean-burn solution’. Pre-chamber ignition allows engines to use less fuel, with high compression ratios, creating more ‘effective’ power.
This works as it it called, there is a smaller combustion pocket, located and segregated just above the main combustion chamber. The small pocket contains a rich air-to-fuel ratio, whilst the primary large combustion chamber contains a much leaner air-to-fuel ratio. The spark plug is retained, but now relocated to the pre-chamber. Once the spark plug ignites the rich fuel mixture in the small pocket, this is then jetted out precisely into the main chamber, igniting the leaner mixture. Usually, this lean mixture wouldn’t be enough to ignite on its own, but the high temperature jets from the pre chamber allow a controlled, clean burn.
This jetting of rich burning flames from the pre chamber to the leaner main chamber allows for a more instantaneous, and controlled power stroke, increasing cycle efficiency, whilst using less fuel.
‘While ignition normally takes place in the centre of the cylinder, with Mahle Jet Ignition it essentially takes place from the outside toward the inside. This allows significantly better combustion of the fuel mixture. The result: more power with considerably less residue.’ — Mahle
3. Miller Cycles
Another way to improve thermal efficiency, in theory, is to raise the compression ratio. i.e. squeeze the air as much as you can by cramming in more air. Turbos are good at this. But there is a caveat:
The engines STILL HAVE TO DEAL WITH KNOCK. Increasing compression ratios are accompanied with high expansion ratios — suck in more air. These come at a cost of friction and high temperatures at the top of the piston.
Additionally, after the induction stroke, the intake valve immediately shuts, effectively trapping those gases, with little reciprocating force to push the piston back up. The work to push the piston back up and compress those gases has to be done by the flywheel. This causes more friction.
To suppress engine knock in a traditional engine, you have to sacrifice both expansion AND compression, hurting fuel and thermal efficiency.
The Miller Cycle optimises the displacement and heat cycle via delayed closure of the intake valve, which separates the expansion ratio (ER) and compression ratio (CR).
The separation, allows for knocking suppression to still be achieved, with high ER:CR ratios — Thus controlling thermal efficiency.
Friction is now reduced:
- Delayed valve closure now gives more/longer time and space for those gases to expand, allowing the piston to be forced upwards easier.
- Delayed valve closure and reduced compression reduces temperatures at the surface of the piston.
Reduction in pressures can be offset with a turbocharger.
4. The Parts themselves
F1 Piston cost ≈ £50,000 ; Regular Piston cost ≈ £50.
There is a lot of energy spent in forcing pistons up and down. F1 pistons have to withstand the force of 4 elephants, and get VERY HOT. To be as efficient as possible at these loads, the aims are similar;
- a snug fit
- good durability
- low friction
To understand this, we must first look at thermal expansion coefficients: Parts are different sizes and shapes and come in different materials. A piston’s operating temperature is… VERY HOT!
They are also metal. Metals expand when hot.
Accordingly, the pistons are built with just the right amount of thermal expansion, relative to the cylinder wall, to fit snug within the cylinder wall, when both are >2000°c.
Too snug — the piston seizes and scrapes against the wall. Too wide, and you’re wasting a lot of air-fuel mixture. High cost manufacturing processes with advanced in-house software have to be employed to accommodate for the little margin for error and tight tolerances.
The precise control of these clearances is what matters the most.
In reality, the F1 pistons are oval shaped, and seize at room temperature. With exhaust flow on one side, and air flow on the other, the pistons expand circular when running. It takes around 30mins preheat the engine with lubricants and coolant.
The use of DLCC and advanced lubricants further reduce friction and increase durability.
DLCC — (diamond like carbon coating)- is a very low friction, high durability coating applied to metallic elements of the engine.
Cost reduction for these technologies are a real problem, and are unlike anything you’ll see on a road car.
Ok, but did I ask?
50% is a great number…. FOR AN ENGINE! This is still WAAYYYYY off electric car thermal efficiency, which sits closer to 80%.
The 2026 engine regulations are a mini-death sentence for the ICE. To be expected with market demands, electrification has increased from 120kW to 350kW, but the big change is the abolishment of the MGU-H, the greatest feature in aiding thermal efficiency in ICE.
We know that the the MGU-H gives direct control to the turbo, so turbo lag could come back in 2026 — probably not.
If the relation between F1 and road car development is still strong, we could expect ICEs to be gone sooner than expected
I pray to the FIA engines sound good once again.
