Its progress this year, that has put it in a super close title fight with Mercedes, has been helped significantly by the work of engine partner Honda, which itself is leading the F1 title standings for the first time since 1991.
What is most impressive about Honda's form this year is how quickly its fortunes in F1 have turned around. From the incredibly tough days with McLaren, its engine is now on a par with Mercedes – an impressive feat.
Honda has been quite open about the kind of changes it introduced with its current power unit, and here we take a look at some of the details, and why they have been especially important.
At the heart of the new power unit lies a redesigned ICE, with numerous changes made that not only help to improve combustion efficiency but also reduce the overall size of the unit.
Paramount to this is a new cylinder coating that was developed by Honda's motorcycle division and has rightfully been dubbed 'Kumamoto plating', owing to the factory where it was developed.
Whilst cylinder sleeve plating is far from a new idea, that doesn't mean you can't still make advances in the field, especially when you're applying ideas and technology from the generally higher revving field of motorcycles to another project.
This new cylinder coating helps to reduce temperatures and friction, and this allowed the F1 division to rethink the design parameters of the engine block, as they were now able to run the engine harder, for longer.
Honda RA620H vs RA621H cylinder spacing
This had a dramatic knock-on effect, with the design team able to reduce the overall size of the ICE. This not only led to a lower position for the crankshaft to improve CoG, it also coincided with a more compact layout that resulted in the design team adjusting the bore pitch.
This essentially allowed Honda to move the cylinders closer to one another, without the fear that cylinder integrity might be compromised. This has resulted in a shorter and narrower cylinder head.
As we can see in the illustration (above), moving the cylinders closer together means that the overall size of the cylinder head can be reduced too.
The design team also took this as an opportunity to address the ICE's bank offset, as the RA620H which sported a forward left bank (above, left), has been exchanged for a right-handed arrangement for the RA621H (above, right).
This has allowed for some of the other power unit elements and ancillaries to be repackaged whilst also altering the overall balance too.
As a consequence of these dimensional changes to the cylinder head, the cylinder head cover has also gone through a dramatic overhaul too. This is evident when the RA620H's cylinder head cover is compared with a prototype for the RA621H in an image released by Honda earlier this year.
The only similarity between the two covers is the mounting frame for the power unit, the positions of which are governed by the regulations.
Taking a look at the cylinder head cover from one end (below), we can see that not only is the shape different between the two specifications, owing to how they mount to the head, but the spacing between the cams has been reduced massively too, altering the valve offset as a result.
Honda Powerunit CAM distance comparison
Altering the angle of the valves obviously alters the angle of the flow into the cylinder too, which has likely been met by further changes to the design of the valves and inlet and outlet ports.
But, perhaps more importantly, all of these alterations have led to a higher compression ratio. This has likely resulted in a change to the design of the piston crown too.
The changes to increase the compression ratio and combustion efficiency do have a downside though, as the amount of exhaust energy being created is reduced, resulting in less electrical energy being recovered by the MGU-H, which obviously leaves a shortfall in terms of deployment.
To counter this, Honda has also redesigned aspects of its turbocharger, with another division within the company at hand to lend support, once more.
Having helped the F1 division when it switched to the larger, outboard mounted compressor and turbine in 2017, HondaJet was perfectly placed to help revise the shape of the turbocharger's impellers and offset the lower flow volume.
We've covered the how but now we need to ask the why…
So why did Honda feel compelled to overhaul its power unit design, especially as it had already approached a similar level of performance to Mercedes in 2020?
The answer lies in how Honda's previous power units had put more of an onus on the recovery and deployment of electrical energy, forsaking some combustion efficiency as a consequence.
Technical directives issued by the FIA before and during the 2020 season scuppered these strategies and eroded any performance gains that might have been possible with a future development programme focused upon them.
As such Honda, which had already planned to introduce a new power unit for 2021 before electing to delay the plan, decided to reverse its actions and bring the new design forward once more.
This will give it an even greater understanding of the new power unit design ahead of the introduction of E10 fuels in 2022, which it is continuing to work on with Red Bull despite its imminent withdrawal from F1.
One of the big upshots of shrinking the power unit and lowering its centre of gravity is the performance that has been gained on the chassis side, something that's of even greater importance given the homologation freeze in place this season.
This has undoubtedly helped both AlphaTauri and Red Bull make headway when compared with last season, and has resulted in a much tighter rear end on both cars.
The aero departments have therefore been able to take advantage of the tighter power unit packaging and what appears to be a lower cooling requirement.
Max Verstappen, Red Bull Racing RB16B
Photo by: Charles Coates / Motorsport Images
Obviously you can draw comparisons with Honda's return to the sport in 2015 here, with McLaren's claims of a 'size-zero' rear end now finally realised.
And, whilst many suspected that the Japanese manufacturer might wind down its development push having closed the gap to Mercedes last year, the exact opposite has been true. It has worked diligently to accelerate past Ferrari and Renault en route to its ultimate goal.
Honda's push forwards hasn't been without hardship though and the power unit has gone through numerous transformations along the way…
The RA615H featured a split turbocharger arrangement akin to the one pioneered by Mercedes just a year earlier but, in order to keep the power unit's silhouette as small as possible, the compressor and turbine were also housed within the confines of the engines Vee.
Meanwhile, a low-line inlet plenum and log-style manifold are just two of the other standout features that were designed to keep the power unit as small as possible in order to aid McLaren in its quest for a smaller, more aerodynamically efficient rear end to their car.
The RA616H was a development of its forebear, as the Japanese manufacturer was restricted in what it could change about the architecture whilst also trying to consider the aims of partner McLaren.
However, in order to make gains, a switch to a conventional multi-branch exhaust manifold was made. The inlet plenum was also enlarged and the overall design of most aspects of the power unit increased in size slightly in order that it had more margin built in to deliver durability - a major issue during the first season.
2017 saw Honda make its first major change in layout as it attempted to resolve some of the major drawbacks of its initial design.
Honda retained the split turbo approach but rather than be housed entirely within the Vee, it moved to a design more closely aligned with Mercedes', whereby the turbine and compressor are mounted on either end of the engine.
This 'pancake' style arrangement, as it is known, gave Honda more headroom in terms of the turbo design but also created some more engineering headaches as the connecting shaft and MGU-H had to be redesigned to account for the greater distance between the turbine and compressor.
The combustion chamber design was also altered in this redesign and, once again, you can see the inlet plenum and exhaust system were adjusted in correlation. Even with these substantial changes the 2017 power unit was actually down on total output when compared to its predecessor, which became the straw that broke the camel's back in its relationship with McLaren.
Nonetheless, even given the reduction in output, this transition was necessary, as the previous design had reached a dead end. But Honda's switch to Toro Rosso proved to be a turning point in its F1 fortunes.
Scuderia Toro Rosso STR13 rear
The RA618H continued to build on the foundations of the power unit redesign of the previous season, with plenty of changes under the hood and the usual redesign of the inlet plenum and exhaust.
Meanwhile, Honda and Toro Rosso worked on the installation aspect too, as the former made concessions in terms of changing the location of the boost pipework, whilst Toro Rosso installed a 'saddle' cooler above the power unit in a similar fashion to how McLaren had done so in the years prior.
The RA619H was to be the first Honda power unit to be installed within more than one team and, whilst the relationship with Toro Rosso had been a good one, having Red Bull onboard would bring with it a greater weight of expectation.
The RA619H and the RA620H that followed saw Honda able to capture double the data and use that to make steady progress in terms of output and durability before making the major changes we've already outlined for 2021.
Ilott in "very good position" should F1 opportunity arise
Sainz: How I'm pushing myself to adapt to Ferrari F1 car
Why McLaren has abandoned its original sidepod concept
French GP: Latest technical images from Paul Ricard
Exposed: The F1 flexi floor tricks that teams were playing
Red Bull: Lobbying for 2023 F1 floor changes about helping "certain team"
Verstappen: Red Bull still chasing "more dominant" Ferrari in F1 2022
How Perez ended the curse of Red Bull’s second F1 seat
Why McLaren has abandoned its original sidepod concept
McLaren is the latest team to abandon its launch sidepod solution as the Formula 1 grid appears to be converging on similar designs.
Sainz: It will be trickier to climb through F1 French GP field than expected
Carlos Sainz admits that it could be harder for him to come through the field in Sunday’s Formula 1 French Grand Prix than his Ferrari team had anticipated.
F1 French Grand Prix qualifying – Start time, how to watch, channel
Circuit Paul Ricard hosts the 12th round of the 2022 Formula 1 season this weekend on July 22-24. Here's how and when you can watch qualifying for the French Grand Prix.
Ferrari, Red Bull and Mercedes F1 upgrades explained
Formula 1's top teams Ferrari, Red Bull and Mercedes have all brought detailed upgrades to the French Grand Prix.
The familiar Paul Ricard weakness that should worry Ferrari
The Red Bull and Ferrari battle for supremacy takes to Formula 1's next battleground at the Paul Ricard circuit. Although the Scuderia ended Friday's running ahead of the French Grand Prix with an advantage in the timesheets, it has a clear weakness - displayed last year - that Red Bull has a chance to exploit...
How Perez ended the curse of Red Bull’s second F1 seat
Being Max Verstappen’s teammate has been the undoing of several drivers, but Sergio Perez has finally made the job his own. Here’s how the Mexican has succeeded where Pierre Gasly and Alex Albon before him stumbled
Why F1 drivers can't have their cake and eat it over track limits
One of the biggest gripes over track limits in Formula 1 has been consistency, and thus new race director Niels Wittich has chosen to enforce track limits at every corner - with the white line the outer permissible extremity. The drivers aren't exactly happy with that in practice, but it does afford the uniformity that they desired...
Why a title-less 2022 F1 season won't stop Hamilton's legacy from growing
OPINION: Lewis Hamilton appears unlikely to extend his tally of seven Formula 1 world championships in 2022, as Mercedes tries to recover the ground it has lost with its new car. Regardless, his legacy only looks set to be further cemented thanks to his tireless work off-track to help boost a rising star and also make motorsport a better place.
How F1's new rules really rate halfway through their first season
OPINION: Formula 1 is now exactly halfway through its first season running the new cars championship owner Liberty Media set about introducing after its 2017 purchase. So, how exactly are those major rule changes really working now the evidence has mounted up?
How Red Bull's gateway F1 car overcame a baked-in disadvantage
The RB5 was the first Red Bull to win a GP but, as Stuart Codling explains, the early success of the car in 2009 was somewhat against the run of form.
The Saturday morning tricks that expose Alonso's true mindset
They were unnoticed by many, and eventually rendered futile due to a car problem that prevented him from starting the sprint race. But Fernando Alonso's tactics in second practice at the Austrian Grand Prix revealed that the Alpine driver is as sharp as he ever has been and wasting no opportunity to gain an advantage, which will play to his favour when his recent run of poor luck turns
The elements of Leclerc’s Austria win that bode well for his F1 future
OPINION: By winning at the Red Bull Ring last weekend, Charles Leclerc ended a 19-year victory drought for Ferrari in Austria. But it was the manner of his triumph over Max Verstappen that Formula 1 fans should savour now and recall later. Here’s why.