When Honda introduced in 2013 they’d return to Method 1 as an influence unit provider to McLaren, many with fond recollections of Ayrton Senna and Alain Prost’s dominant title wins of the eighties and nineties hoped for a return to these glory days.
Nevertheless, the fact proved very completely different. Honda struggled each with reliability and efficiency from the phrase go. Their lengthy path to competitiveness was uncovered in an in-depth characteristic printed by Japanese journal Motor Fan Illustrated.
The engine Honda launched in 2015, RA615H, was designed to fulfill what McLaren’s then-boss Ron Dennis termed a “dimension zero” idea. It was not Honda that selected this design course. McLaren’s sturdy need for Honda to maintain the facility unit as small and as compact as attainable was the driving issue.
Nevertheless the Honda staff didn’t create a compact design on the expense of efficiency. In hindsight, the staff had set specs for the V6 combustion engine improvement with out a clear concept of the turbo pressures required or the best air-fuel combination. The Honda Energy Unit staff assumed they’d be capable of determine it out in the end.
That assumption didn’t survive its first contact with actuality. When the 2015 season rolled round, it was painfully apparent that they have been severely missing efficiency. A lot in order that at one race Fernando Alonso famously commented over the staff radio to his engineer “It appears like GP2. Embarrassing. Very embarrassing.” His selection of occasion was no coincidence both: The Japanese Grand Prix on the Honda-owned Suzuka circuit.
Engineers at Honda have been already at work making an attempt to enhance efficiency for the 2016 season. The RA616H had a revised plenum and the turbo housed contained in the V-bank of the engine was elevated in dimension to maintain up with the growing energy demand of the inner combustion engine (ICE).
Whereas the revised plenum elevated the general peak of the engine by a number of centimetres, it allowed for a extra optimised consumption system which facilitated smoother airflow into the combustion chamber by decreasing the variety of bends within the branches of the consumption system. The variable consumption system housed contained in the plenum was additionally redesigned earlier than that 12 months’s British Grand Prix to additional optimise airflow into the engine.
“On the time, we have been making an attempt varied completely different know-how upgrades, so it’s exhausting to say that the revisions within the consumption system have been the one impact, however I do recall an enchancment of about 7kW in energy after the modifications with McLaren’s assist,” recollects Tetsushi Kakuta, government chief engineer of F1 energy unit improvement at Honda Racing Growth Sakura.
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In a world the place 5kW could make an enormous distinction within the general competitiveness of energy items, this was clearly an enormous step ahead. Nevertheless, the modifications within the consumption system additionally introduced some main setbacks.
As a result of the general peak of the engine had elevated, the engine’s centre of gravity additionally moved up by about 8mm. Within the pursuit of improved reliability and efficiency, the facility unit additionally turned round 4.2 kg heavier.
For the following season, McLaren’s designers pushed Honda to give attention to decreasing the centre of gravity and assist to ‘shrink wrap’ the highest of the engine cowl for higher aerodynamics. Taking this suggestions to coronary heart, the Honda staff went again to the drafting board to create an all-new design for the 2017 season.
The ensuing RA617H was the primary of Honda’s engines to implement the ‘split-turbo’ design which Mercedes adopted from the outset of the laws with its standard-setting energy unit. The compressor sits within the entrance of the engine and the turbine on the rear, with the MGU-H motor housed within the V-bank.
Switching to this design meant Honda’s turbo may now be sized with out being restricted by the area between the cylinder banks. It additionally helped decrease the centre of gravity by bringing down the place of the shaft connecting the compressor and turbine. With this variation, the RA617H was capable of drop the CG peak by over 25mm in comparison with the earlier 12 months.
Nevertheless, probably the most important technological enchancment over the RA616H was the introduction of the pre-combustion chamber. It is a separate chamber contained in the cylinder head linked to the primary cylinder space that surrounds the tip of the spark plug.
On this chamber, a richer air-fuel combination is ignited and powerful jets of sizzling gasses escape from tiny holes within the partitions of the pre-combustion chamber. These sturdy jets of sizzling gasses shortly ignite the remainder of the air-fuel combination within the cylinder. This pre-chamber ignition know-how enabled Honda to make massive features in efficiency that will not have been attainable with typical spark strategies.
Whereas the introduction of the pre-combustion chamber supplied nice potential for efficiency enchancment, improvement time was required to completely get a deal with on pre-chamber ignition. The primary iteration of the design appeared like a cap with perforations screwed onto the tip of the spark plug.
Optimising the situation the place the jet of sizzling gasses emitted from the holes perforated within the pre-combustion chamber landed was a crucial improvement level to realize efficiency. Moreover, if the floor of the pre-combustion chamber was not cooled correctly, the remaining warmth from the floor would auto-ignite the primary chamber, inflicting pre-ignition.
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Whereas the Honda staff resolved this by making the pre-combustion chamber out of a cloth with high-heat switch properties, this induced the spark plug to retain a lot of the warmth, inflicting them to soften. Honda labored with NGK to design a pre-combustion chamber that was totally built-in into the spark plug to additional assist with warmth dissipation.
The variety of holes, the outlet diameters, and the amount of the pre-combustion chamber have been additionally optimised for max flame propagation. All this enabled Honda to grasp a efficiency achieve of round 40kW over their unique design launched in 2015.
Regardless of their struggles and rocky relationship with McLaren, Honda managed to make efficiency features. However so had their rival energy unit producers.
McLaren completed the 2015 season, their first 12 months again with Honda, a lowly ninth within the championship, with solely the Manor staff behind them. They improved to sixth the next 12 months, however continual unreliability pegged them again to ninth in 2017. McLaren’s persistence had run out, and nicely earlier than the season was over it turned clear the 2 events would go separate methods.
Earlier within the season Sauber had introduced it could change into a second Honda person in 2018. However the staff was subsequently offered to new house owners and inside three months new staff principal Frederic Vasseur had cancelled the Honda deal.
Nevertheless inside two years Honda turned a two-team effort. A profitable 12 months supplying engines to Crimson Bull’s junior staff Toro Rosso (now AlphaTauri) paved the way in which for a fruitful tie-up with the senior squad.
For 2018 season with Toro Rosso, Honda turned their consideration to additional enhancing the thermal effectivity of the inner combustion engine. That is sometimes completed by growing the compression ratio or the air-to-fuel ratio. Pre-chamber ignition know-how allowed Honda to make progress on each fronts, however the energy unit improvement staff felt that this alone was not sufficient to catch the leaders. To fill this hole, Honda developed what they referred to as ‘Excessive-Velocity Combustion’.
In a standard combustion course of, the flame entrance followers out from the tip of the spark plug the place it’s ignited. Nevertheless, this course of takes time for the flame to completely ignite all of the gas within the piston. It might additionally result in incomplete combustion and since the flame propagation takes time, which means full combustion will not be achieved at top-dead centre (most compression) the place most energy might be produced.
Pre-chamber ignition hastens flame propagation by igniting a bigger flame entrance space within the piston utilizing the recent ignited gasses jettisoned out of the pre-combustion chamber. Taking this concept one step additional, Honda’s engineers got here up with its Excessive-Velocity Combustion approach.
Throughout this course of, the recent ignited gasses from the pre-combustion chamber are directed in the direction of the cylinder partitions and the warmth from this auto-ignites air-fuel combination. Thus, as a substitute of the flame entrance propagating centre-out, the flame ignites in a hoop form (like a doughnut) and propagates outside-in, in a three-dimensional style. This vastly will increase the velocity of the flame propagation, therefore the title Excessive-Velocity Combustion. This know-how was applied on the Russian GP in 2018 within the ‘spec three’ model of the RA618H.
This concept was additional developed on the RA619H which was used the next 12 months by Toro Rosso and – for the primary time – Crimson Bull.
“By utilising Excessive Velocity Combustion, we have been capable of vastly enhance each the compression ratio and the air-fuel ratio” recalled Kakuta. “By optimising the valve geometry and repositioning the injector that used to sit down on the exhaust facet, the RA619H was capable of make important features over the earlier years.”
Honda’s staff was met with a unique tradition once they switched from McLaren to the 2 Crimson Bull groups. “Crimson Bull provided to supply extra cooling if the facility output might be elevated,” Kakuta defined.
“After we have been partnered with McLaren, they claimed that their earlier engine provider (Mercedes) may run their PU hotter and requested us to lift our working temperature window. With Crimson Bull, maybe Renault’s working temperatures have been a lot decrease they usually have been pleased to work with us to optimise the working temperature window.”
Crimson Bull began with securing area and airflow for a cost air cooler. By lowering the inlet temperatures, the compression ratio of the engine might be elevated with out worrying about knocking. In 2019 Honda additionally began growing gas blends and made massive leaps on this entrance. Lastly, on the Austrian Grand Prix, Honda achieved its first victory of the V6 hybrid turbo period.
It was the Japanese producer’s first F1 win since 2006. However whereas that proved a one-off for its short-lived producer staff, there was extra to come back for its hybrid engine undertaking.
For 2020 their objective was to “maximise the potential” of the facility unit design based mostly on the RA619H. One of many main disadvantages of utilising Excessive-Velocity Combustion was the decline in efficiency over the lifetime of the engine. As a result of combustion strain was elevated as a result of Excessive-Velocity Combustion course of, the strain utilized onto the cylinder partitions by the piston ring additionally elevated and induced the cylinder partitions to deteriorate faster. In consequence, floor put on accelerated and the seal between the piston ring and the cylinder wall leaked, resulting in strain loss and energy output loss.
To fight this, Honda Racing Growth (HRD) Sakura collaborated with Honda’s Kumamoto Manufacturing centre to develop a particular plating course of to coat the within of the cylinder partitions, dubbed “Kuma-Mekki” (“Kuma” from “Kumamoto” and “Mekki” which means ‘plating’). This plating was a breakthrough for Honda because it allowed the facility items to take care of their efficiency till the top of life. This enhance in reliability additionally allowed the staff to run the engines in increased modes for longer durations over the race weekends. This was exactly what “maximising the potential” was all about.
Upon deepening their understanding of the Excessive-Velocity Combustion course of and optimising compression ratio and air-fuel combination to maximise energy output and reliability, it turned clear to the facility unit improvement staff that the ICE design Honda had been utilizing since 2017 had reached its limits and a complete new idea was required to additional enhance efficiency.
Initially, the HRD Sakura staff deliberate to introduce this new design in keeping with the Method 1 regulation change in 2022 (initially deliberate for 2021 however pushed again a 12 months as a result of Covid-19 pandemic). Nevertheless in 2020 the Honda board made an surprising determination to drag out of Method 1 fully on the finish of the next season, prompting the staff to carry this design ahead.
The RA621H was a full bottom-up redesign for the ICE. One of many objectives of this redesign was to combine higher into the Crimson Bull chassis and assist contribute in the direction of higher packaging for aerodynamic efficiency. On the RA621H, the valve angle was lowered to optimise for a better compression ratio, and the size of the valves was additionally lowered to assist with packaging.
The staff additionally introduced the exhaust-side camshaft additional inboard by decreasing the scale of the gear practice. General, this introduced the outer-facing exhaust valves over 30mm additional inboard and allowed for tighter packaging on Crimson Bull’s finish. To additional contribute to a smaller engine cowl, Honda additionally eliminated a rib that was on the exhaust facet initially supposed to extend the rigidity of the cylinder head cowl.
Nevertheless growing the energy of the cylinder head and block was additionally obligatory because the pressures they have been subjected to had elevated through the years of improvement of the ICE. In 2018 and 2019, the aluminium alloy used for the cylinder heads was modified to a stronger alloy. The cylinder block additionally adopted swimsuit in 2021 when the design of the block was utterly modified for the RA621H. The brand new, stronger materials additionally allowed Honda to chop down a few of the materials thicknesses, permitting for a lighter however stronger bundle.
Having powered Crimson Bull to a few wins in 2019, three additional victories adopted within the shortened 2020 season, one in every of which got here courtesy of AlphaTauri. This fell in need of the specified progress on either side. Honda publicly claimed its withdrawal from F1 was for different causes, however the restricted success it loved as much as that time absolutely had a bearing on its fourth withdrawal from the game.
However from the beginning of 2021 it was clear the Crimson Bull-Honda bundle was able to preventing Mercedes for the championship. This was the hardest opposition the Silver Arrows had confronted because the V6 hybrid turbos have been launched. The battle went to the ultimate spherical, and whereas Mercedes prevailed within the constructors championship, the drivers trophy went the way in which of Crimson Bull’s Max Verstappen, albeit in contentious circumstances.
It might not have occurred with out an unimaginable effort from Honda which, from their decrease level in 2015, propelled them previous Ferrari and Renault to the identical degree as Mercedes. Over seven seasons, Honda elevated their general energy output by some 100kW (round 134 bhp) – a monumental feat.
Honda is certainly the “most improved” energy unit producer on this turbo-hybrid period. Its engines are actually Crimson Bull branded, and whereas they’ve had some issues firstly of the brand new season, they’ve already taken their first victory of the 12 months in Jeddah, and will but propel Crimson Bull to even better successes than they loved final 12 months.
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