Explained: F1’s complex power unit upgrade system

Thomas Maher 10 Jan 2026 1:00 PM

An artist's render of how the F1 2026 car could look.

F1 power unit manufacturers’ development has been opened up again after a four-year engine freeze, but what are the constraints on upgrades?

With F1’s hybrid power units restricted from performance-related development between 2022 and ’25, the next-generation 1.6-litre V6 hybrids, using sustainable fuels, hit the track this year. But how, and when, will the manufacturers be permitted to upgrade these power units during this regulations cycle?

How long is the new power unit regulations cycle?

F1 2026 will use the same basic architecture as the previous generation, utilising a 1.6-litre V6 hybrid with electrical ancillaries.

But this is a complete overhaul in design and thinking, with the sport switching to sustainable fuels and increased electrification that sees a near-50/50 split between electrical power output and that of the internal combustion engine.

While there have been plenty of concerns aired about the unusual nature of the new regulations development, given that the power unit rules were defined before the chassis, any possibility of a switch in engine formula was shut down in late 2025.

Discussions about a possible change to a simplified V8 or V10 formula, utilising sustainable fuels, were held, but, with no agreement across the board, and significant financial investment from the power unit manufacturers into the new formula, the rules cycle for the engines will run from 2026 until the end of 2030.

All five of the 2026 power unit manufacturers must submit homologation dossiers for their new designs to the FIA by the 1st of March, with this dossier including details on their internal combustion engines (ICE), control electronics (CE), exhaust, turbocharger (TC), energy store (ES), and MGU-K, as well as all minor parts associated with all PU elements. The new power units no longer have MGU-Hs.

This homologation dossier must also apply to the units it supplies to any and all customer teams, with the only permitted differences being fuel suppliers, engine oil specification, and minor tweaks for the purposes of bespoke installations within different chassis, such as wiring looms, exhaust positioning, and turbo positioning (within 20mm of original), and positioning of wastegate and pop-off valves.

The FIA will approve compliant designs within 14 days of submission of the dossier, and by the 1st of April, the power unit manufacturers are required to present a full reference power unit for sealing.

How are power unit manufacturers permitted to update their designs?

The FIA’s regulations governing Power Unit (PU) development for the 2026–2030 cycle impose strict limits on when and how manufacturers may introduce changes.

Once a power unit has been homologated, only specific upgrades and modifications are allowed, and all are subject to detailed approval processes. These rules are designed to balance cost control, sporting fairness, and reliability across the championship.

Any subsequent upgrades are only permitted if they fall within the scope of Article 3 of the technical regulations.

However, separate from this, the FIA has introduced a concept known as ADUO (Additional Development and Upgrade Opportunities) as a safety net for lagging power unit manufacturers, in order to give them a greater chance of closing any performance deficits. These upgrades still fall under the newly introduced power unit manufacturers’ budget cap.

How ADUO works is explained further down, but for now, let’s focus on the normal permitted upgrade and development paths.

The FIA has split up all the components of the power unit and electrical recovery systems and assigned permissions to each component as to if, and when, these components can be updated as part of the regular cycle, or under ADUO allowances.

This is a long and forensic list. For example, the very first item is defined as the “Main ICE assembly comprising crankcase, cylinder heads (except combustion chamber and ports and injector port machining), crankshaft, camshaft (excluding camshaft lobe profiles), cam drive, cam covers, front and rear covers, valves, finger followers, Internal gear drives, any part which provides a structural connection between the Survival Cell and the gearbox case through the ICE mounting studs.”

This area of the engine is permitted to be worked on in 2026, but not through ’27, ’28, ’29, or ’30, but is permitted for manufacturers assigned ADUO opportunities.

While the main ICE assembly is blocked from regular development after 2026, aside from ADUO, all power unit manufacturers will be permitted to work on developing the third item on the list, the flywheel.

The list is too long and detailed to be easily written out, so I suggest, if you’re interested, having a read of Appendix 4 of the new Technical Regulations.

A key factor to note is that any upgrades developed are only permitted to be introduced for the first Grand Prix of the season in which they are permitted. This means that, using the examples above, the main ICE assembly is effectively locked in from the homologation date, 1st of March, with only ADUO-permitted teams able to make further changes through the rest of the five-year cycle.

For the flywheel, each power unit manufacturer can develop as it likes, but it can only introduce its upgraded component at the first Grand Prix of the next permitted season. As the flywheel is permitted for all five years, a PU manufacturer can develop a new one each year, if it so pleases, but a flywheel developed during 2026 can only be introduced at the season opener for ’27, regardless of when the new flywheel was actually ready to go.

As another example, item five on the list pertains to the “ICE intake air system components, including Trumpets, Throttle system, and Plenum.”

These components can be worked on for 2026, ’27, and ’29, but not for 2028 and ’30. This means a new part developed during 2026 could be fitted for the first race in ’27, but one developed during 2027 could not be fitted until the first race of ’29. Again, ADUO opens up these opportunities further for any lagging power unit manufacturers.

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How will ADUO work?

Essentially, think of ADUO as a more complex, power unit-specific version of the Aerodynamic Testing Regulations that we’ve become accustomed to in recent years.

Manufacturers that meet certain criteria outlined in Article 4 of the Appendix are eligible for the additional opportunities outlined under the ADUO rules.

These allow for extra specification upgrades in both the qualifying year (Year N) and the following year (Year N+1).

Most of the power unit components have been left eligible for ADUO, aside from certain items such as the fuel pump and injectors, knock sensors, and a wide range of temperature, electrical, and regulatory sensors.

Throughout the next five years, the FIA will closely monitor the performance levels of the internal combustion engines part of all the power units supplied by each manufacturer.

For each engine, an “ICE Performance Index” will be calculated, utilising data and supplementary information from the manufacturers and their customer teams.

This index will be used to benchmark the PUs against each other during each assessment period and used to determine which, if any, manufacturers need the additional upgrade opportunities.

If granted, the relevant manufacturer can implement upgrades to the prescribed components, as outlined in Appendix 4, extend the usage of their power unit test benches, as well as make a downward adjustment in their cost cap reporting.

PU manufacturers will be granted opportunities on the following criteria:

PU Manufacturers whose ICE Performance Index is at least two per cent but less than four per cent below the best-performing ICE will be eligible for:
1 additional homologation upgrade in season N
1 additional homologation upgrade in season N+1
PU Manufacturers whose ICE Performance Index is at least four per cent below the best-performing ICE will be eligible for:
2 additional homologation upgrades in season N
2 additional homologation upgrades in season N+1

ADUO homologation upgrades are not cumulative within a season and will only be granted following the first occasion that the PU Manufacturer is assessed by the FIA as eligible for ADUO.

Each season will be split into four equal-length periods, with the 24-race calendar of 2026 split into four sections of six races. Manufacturers granted ADUO opportunities can introduce the updates at the first race of the following period. For instance, any manufacturer given an upgrade opportunity after the first six races of 2026 may only introduce a new component, as defined under the criteria of Appendix 4, at the 13th round of the championship. If this opportunity is granted after the 12th round of the championship, it can only be introduced at the 19th round.

Any unused homologation upgrades not used during season N are forfeited.

Any changes made to the power units by the manufacturer, whether under ADUO or standard development permissions, must submit an updated version of its homologation dossier at least 14 days before the first race weekend in which it is used.

Some very minor prescribed updates are also permitted, on the grounds of “the sole purposes of reliability, safety, cost saving, or supply issues, subject to approval”.

Other modifications may be (but are not limited to) due to different branding, a change of supplier, a change of part number, etc., and may have no or very limited effect on reliability or functionality.