There was a time when a grand prix driver was sacked for comparing his car to a truck. Ironically, at least half of the Formula 1 grid is now powered by a truck-engine development that's revolutionising efficiency.
Since the introduction of the current engine formula in 2014, the F1 internal combustion engine has been squeezed by fuel-flow restrictions and limited to 100kg of fuel (105kg next season). This limits the maximum instantaneous fuel flow and also the pressure at which fuel can be injected. It's been a challenge for designers to create power from so little fuel.
But this truck technology, known as pre-chamber ignition, is able to create power with a fuel/air mixture inside the cylinder that's at an almost incombustible level. This is believed to be at the heart of both the Mercedes and Ferrari power units.
CONVENTIONAL COMBUSTION
Inside a normal spark ignition engine, the fuel is injected into the space inside the cylinder. When the fuel and air inside the cylinder are compressed and ignited, the mixture burns and expands to create the power stroke of the four-stroke engine.
This works well until the fuel available is limited, creating a lean fuel/air mixture. This is hard to ignite with a single spark plug, so the engine loses power.
Under the current regulations, the fuel flow is limited to 100kg/hr and fuel pressure to 500 bar. With the high boost pressure and RPM in an F1 engine, there isn't the time to get enough fuel in and mixed homogeneously to get the right fuel/air mixture for efficient combustion.
Unable to create any more power with the fuel available, this has limited the power output of F1 engines.
What's needed is a way to burn a leaner fuel/air mix, within the regulations, which also demand a single injector and spark plug.
It was thought that homogeneous charge compression ignition (HCCI) may have been the technological breakthrough. This is a combustion method where high cylinder pressures are used to create a petrol-fuelled spark-ignited equivalent of a diesel compression ignition.
With HCCI, the fuel/air mix is highly compressed. The combustion then occurs partly from the spark plug and partly from the mixture self-igniting like a diesel from the high pressures.
While this is valid technology, it's hard to tune and F1 is believed to have found another easier to achieve technology. This brings us to pre-chamber ignition.
PRE-CHAMBER IGNITION
Pre-chamber ignition occurs on large-capacity diesel engines. Efficiently filling such large cylinders with fuel and air for combustion is difficult, so the problem is split in two.
A small chamber in the cylinder head is created, which contains the fuel injector and the spark plug. This is linked through tiny connections to the cylinder below.
This is known as the pre-chamber and is key to this concept.
During the induction stroke, hot fuel passes from the injector in the pre-chamber into the cylinder. The cylinder is filled with a lean fuel/air mix that forms a weak vapour rather than a rich mixture.
The pre-chamber is then filled with a richer fuel/air mixture just before the compression stroke and ignition.
Combustion then occurs inside the pre-chamber with the spark plug. This mix ignites easily due to its rich nature, the flame from this combustion then passes into the cylinder and the multiple jets of flame ignite the weaker mixture within.
As a result, the weak mixture is efficiently burned, almost as though there are multiple spark plugs inside the cylinder. More importantly, the weak main cylinder mix burns faster, creating more power.
This design allows the engineers to run very lean mixtures and still create power within the tight restrictions of the rules.
There remains a single injector and ignition is started with a single spark plug, so all the combustion technical regulations are met.
ADOPTION IN F1
Considering this is a well-known technology, the cloak of secrecy in F1 is unnecessary. F1 has reduced fuel consumption by well over 30 per cent since 2013, yet the achievement is not boasted about enough and the technological story is not told.
While engineers on the power-unit side are all convinced this technology is in use in F1, no team has openly admitted its introduction to its internal combustion engine.
Ferrari is known to have partnered with Mahle to adopt the 'Jet' technology, which is the German company's brand of pre-chamber ignition. It's believed Ferrari's jump in engine performance this year is largely down to this.
Mercedes is not commenting on its combustion technology, but says no Mahler parts are used in the engine.
But Mercedes has experience of large commercial engines, so its knowledge could easily come from within the group. At last September's Italian Grand Prix, Mercedes made a well-publicised step in combustion technology on its V6 engine and it's believed by other F1 engine designers that pre-chamber ignition was the step in question.
This leaves Renault and Honda, which are unlikely to be running this form of combustion. But both manufacturers are expected to bring major upgrades to their internal combustion engines during the season.
With Renault running its new power unit in this week's Barcelona test, it's likely it will benefit from pre-chamber combustion, leaving Honda to also adopt the solution with its Canada-spec power unit.
There was a time when a grand prix driver was sacked for comparing his car to a truck. Ironically, at least half of the Formula 1 grid is now powered by a truck-engine development that's revolutionising efficiency.
Since the introduction of the current engine formula in 2014, the F1 internal combustion engine has been squeezed by fuel-flow restrictions and limited to 100kg of fuel (105kg next season). This limits the maximum instantaneous fuel flow and also the pressure at which fuel can be injected. It's been a challenge for designers to create power from so little fuel.
But this truck technology, known as pre-chamber ignition, is able to create power with a fuel/air mixture inside the cylinder that's at an almost incombustible level. This is believed to be at the heart of both the Mercedes and Ferrari power units.
CONVENTIONAL COMBUSTION
Inside a normal spark ignition engine, the fuel is injected into the space inside the cylinder. When the fuel and air inside the cylinder are compressed and ignited, the mixture burns and expands to create the power stroke of the four-stroke engine.
This works well until the fuel available is limited, creating a lean fuel/air mixture. This is hard to ignite with a single spark plug, so the engine loses power.
Under the current regulations, the fuel flow is limited to 100kg/hr and fuel pressure to 500 bar. With the high boost pressure and RPM in an F1 engine, there isn't the time to get enough fuel in and mixed homogeneously to get the right fuel/air mixture for efficient combustion.
Unable to create any more power with the fuel available, this has limited the power output of F1 engines.
What's needed is a way to burn a leaner fuel/air mix, within the regulations, which also demand a single injector and spark plug.
It was thought that homogeneous charge compression ignition (HCCI) may have been the technological breakthrough. This is a combustion method where high cylinder pressures are used to create a petrol-fuelled spark-ignited equivalent of a diesel compression ignition.
With HCCI, the fuel/air mix is highly compressed. The combustion then occurs partly from the spark plug and partly from the mixture self-igniting like a diesel from the high pressures.
While this is valid technology, it's hard to tune and F1 is believed to have found another easier to achieve technology. This brings us to pre-chamber ignition.
PRE-CHAMBER IGNITION
Pre-chamber ignition occurs on large-capacity diesel engines. Efficiently filling such large cylinders with fuel and air for combustion is difficult, so the problem is split in two.
A small chamber in the cylinder head is created, which contains the fuel injector and the spark plug. This is linked through tiny connections to the cylinder below.
This is known as the pre-chamber and is key to this concept.
During the induction stroke, hot fuel passes from the injector in the pre-chamber into the cylinder. The cylinder is filled with a lean fuel/air mix that forms a weak vapour rather than a rich mixture.
The pre-chamber is then filled with a richer fuel/air mixture just before the compression stroke and ignition.
Combustion then occurs inside the pre-chamber with the spark plug. This mix ignites easily due to its rich nature, the flame from this combustion then passes into the cylinder and the multiple jets of flame ignite the weaker mixture within.
As a result, the weak mixture is efficiently burned, almost as though there are multiple spark plugs inside the cylinder. More importantly, the weak main cylinder mix burns faster, creating more power.
This design allows the engineers to run very lean mixtures and still create power within the tight restrictions of the rules.
There remains a single injector and ignition is started with a single spark plug, so all the combustion technical regulations are met.
ADOPTION IN F1
Considering this is a well-known technology, the cloak of secrecy in F1 is unnecessary. F1 has reduced fuel consumption by well over 30 per cent since 2013, yet the achievement is not boasted about enough and the technological story is not told.
While engineers on the power-unit side are all convinced this technology is in use in F1, no team has openly admitted its introduction to its internal combustion engine.
Ferrari is known to have partnered with Mahle to adopt the 'Jet' technology, which is the German company's brand of pre-chamber ignition. It's believed Ferrari's jump in engine performance this year is largely down to this.
Mercedes is not commenting on its combustion technology, but says no Mahler parts are used in the engine.
But Mercedes has experience of large commercial engines, so its knowledge could easily come from within the group. At last September's Italian Grand Prix, Mercedes made a well-publicised step in combustion technology on its V6 engine and it's believed by other F1 engine designers that pre-chamber ignition was the step in question.
This leaves Renault and Honda, which are unlikely to be running this form of combustion. But both manufacturers are expected to bring major upgrades to their internal combustion engines during the season.
With Renault running its new power unit in this week's Barcelona test, it's likely it will benefit from pre-chamber combustion, leaving Honda to also adopt the solution with its Canada-spec power unit.