F1 engine power unit explained: how the hybrid works

The word engine is doing very little of the work in the phrase Formula 1 engine. Roughly half the power reaching the rear wheels of a 2026 car comes from a device with no cylinders, no fuel and no exhaust, and the part that does burn something is judged not on how much power it makes but on how little of the fuel's energy it wastes.

That is the F1 engine power unit explained in one sentence, and everything else is the consequences.

The consequences are unusually large. They decide why the cars sound the way they do, why a driver is told to lift a hundred metres before a corner they could have taken flat, why a manufacturer can be stuck with a bad engine for four seasons with no legal way out, and why a company deciding whether to enter Formula 1 spent a decade looking at one specific component and walking away.

What an F1 engine power unit actually is

Start with the parts, because the regulations treat them as parts rather than as one machine, and almost every rule that follows depends on that.

A 2026 power unit is built from five elements. The internal combustion engine, a 1.6 litre 90 degree V6 with a maximum engine speed of 15,000 revolutions per minute. The turbocharger, which raises the pressure of the air entering that engine. The MGU-K, a motor generator connected to the crankshaft, which turns the car's kinetic energy into electricity when it is slowing and turns electricity back into drive when it is accelerating. The energy store, which is the battery. And the control electronics, which decides at every instant where energy should be going.

The exhaust is allocated separately, so in practice a driver's season is tracked across six lists rather than five.

Until the end of 2025 there was a sixth element in the power unit itself, the MGU-H, a motor generator mounted on the turbocharger shaft. It is worth understanding what it did and why it is gone, because its removal is the largest single change to Formula 1 engineering in more than a decade, and it is the reason several manufacturers are on the grid at all.

None of these components is a black box bolted to the others. The interesting behaviour lives in the interactions, and so do most of the rules.

• 5Elements the regulations define
• 1Motor generator units, down from two
• 6Cylinders
• 15000Maximum engine speed, rpm

Structural counts and regulated limits from the FIA Technical Regulations, not manufacturer performance figures.

Thermal efficiency is the design target, not horsepower

Ask what a Formula 1 engine is optimised for and the intuitive answer is power. The regulations make that answer wrong in a specific way.

Because the rate at which fuel may enter the engine is capped, the chemical energy available to the combustion engine each second is a fixed quantity, the same for every manufacturer on the grid. Power out is that fixed energy in multiplied by the fraction of it converted into useful work at the crankshaft. One of those two terms is set by the rulebook. The other is the entire competition.

Thermal efficiency, then, is not a green talking point in this sport. It is the performance metric.

A good road car petrol engine converts something in the region of a third of the energy in its fuel into work at the crank, and most of the rest leaves as heat in the exhaust and the coolant. Formula 1 manufacturers have stated publicly that the current generation of racing engines passed fifty per cent, which means more of the fuel's energy ends up turning the wheels than escapes as heat. No individual manufacturer's figure is published, and any specific number attributed to a particular engine should be treated as an estimate rather than a fact.

Getting there took a set of related ideas, all of them aimed at burning a very lean mixture very fast without the fuel detonating on its own.

The central one is pre-chamber ignition. Instead of a spark plug lighting the main charge directly, a small chamber holds a richer, easily ignited mixture. The spark fires there, and the burning gas is forced out through small orifices into the main combustion chamber as a set of high-energy jets. Those jets light the main charge from many points at once rather than from a single flame front creeping across the cylinder. The burn finishes far faster, which means it can be completed before the end gases have time to auto-ignite, which in turn means the engine can run leaner and at higher pressure than a conventionally sparked one.

Everything else follows that logic. High compression, because a higher expansion ratio extracts more work from the same burn. Aggressive charge motion, because a fast burn needs a turbulent chamber. Very high injection pressures, because atomising the fuel finely is what makes lean mixtures light at all. And an obsessive campaign against friction, because every watt lost to a piston ring or an oil pump is a watt that was already paid for in fuel.

The enemy throughout is knock, the uncontrolled detonation of the unburned mixture ahead of the flame. Knock is what stops an engine from simply raising boost and compression until it wins. It is also temperature dependent, which is why an engine that is comfortable on a cool evening is on the edge of trouble on a hot afternoon, and why the pit wall turns engines down in conditions that have nothing to do with reliability in the usual sense.

Why the fuel flow limit constrains power more than displacement does

The displacement figure gets all the attention, and it is the less important of the two limits.

Capacity tells you how much air an engine can swallow per revolution. On a naturally aspirated engine that is close to a power limit, which is why capacity limits were the traditional way to control racing engines. On a turbocharged engine it is not, because the turbocharger can raise the density of the incoming air more or less at will. A 1.6 litre engine with enough boost can flow the air of a much larger one.

So the rulebook limits the fuel instead.

Until the end of 2025 the ceiling was expressed as mass, at 100 kilograms of fuel per hour, with the permitted rate scaled downwards below a defined engine speed so that revving harder for its own sake stopped paying. From 2026 the ceiling is expressed as energy, at 3,000 megajoules per hour, which corresponds to roughly 70 kilograms an hour for the sustainable fuel specification the regulations now require.

That change of unit is not cosmetic. Sustainable fuels made from carbon capture, municipal waste and non-food biomass do not all carry the same energy per kilogram, and a mass-based limit would have quietly handed an advantage to whichever supplier produced the most energy-dense blend. An energy-based limit removes the incentive to chase calorific value and leaves the competition where the rule-makers wanted it, in efficiency.

Here is what the limit means, worked through on the published numbers.

Three thousand megajoules per hour is 3,000 divided by 3,600 seconds, which is 0.833 megajoules per second, or 833 kilowatts of chemical energy arriving at the engine. That is the entire budget. An engine converting half of it produces around 417 kilowatts at the crank. An engine converting forty-five per cent produces around 375. The difference between those two engines, five percentage points of efficiency, is about forty kilowatts, and forty kilowatts is the gap between a car that wins races and one that does not.

This is why nobody in a modern Formula 1 engine department talks about horsepower. They talk about the fraction.

The limit is policed at the point of measurement, and for 2026 the policing changed. Previously the governing body ran its own fuel flow meter and teams ran theirs, and the discrepancy between the two produced one of the more memorable technical disputes of the era. From 2026 a single standardised meter supplies identical data to the FIA and the team, which removes the argument about whose instrument was right by removing the second instrument. It is a small rule with a long history behind it, and the wider question of how fuel and energy are metered and rationed across a race distance deserves working through separately.

There is a second fuel constraint that matters as much on a Sunday. The regulations set a maximum quantity of fuel for the race, cut for 2026 to around 70 kilograms. A car that starts with less fuel than it needs to run flat out must save some, and fuel saving is not a marginal activity. It changes braking points, throttle traces and overtaking opportunities, and it is one of the reasons a race can look slower than qualifying by a margin that has nothing to do with tyres.

The split turbocharger, and why the compressor sits at the other end of the engine

A turbocharger is two wheels on one shaft. Exhaust gas spins the turbine, the turbine spins the compressor, the compressor forces more air into the engine than atmospheric pressure would deliver on its own. More air allows more fuel, and until the flow limit binds, more fuel means more power.

The Formula 1 refinement is to separate the two wheels and put them at opposite ends of the engine.

In a conventional installation the turbine and compressor sit next to each other in a single housing, because that is the shortest shaft and the simplest packaging. It also puts the compressor directly beside a component glowing at exhaust temperature. Air that has just been compressed is already hot, because compressing a gas heats it, and heating it further with radiated and conducted energy from the turbine makes it less dense, which is the opposite of what a compressor is for. The intercooler then has to work harder to undo the damage, and an intercooler is drag, weight and packaging volume.

The split layout puts the compressor at the front of the vee, the turbine at the back, and a shaft running between them through the centre of the engine. The compressor now sits in cool air a long way from the turbine. The charge air path to the cylinders gets shorter, which improves throttle response, because less air has to be moved before a change at the compressor is felt in the combustion chamber. The intercooler shrinks. The masses are distributed more evenly along the car. And with the two wheels no longer sharing a housing, each can be sized for its own job rather than for a compromise between them, which allows a larger, more efficient turbine than a compact installation would tolerate.

The cost is a long, thin, extremely fast-spinning shaft passing through the hot centre of an engine, with bearings that have to survive there. When the concept first appeared, plenty of people in the paddock thought it would not last a season. It did, and within a few years everyone had a version of it.

Turbo lag is the other half of the story, and it is where 2026 changes the picture. A turbocharger only makes boost when there is enough exhaust energy to spin it, so coming off a slow corner there is a delay between the driver asking for power and the engine producing it. For twelve seasons Formula 1 simply deleted that problem by putting a motor on the turbo shaft, spinning the compressor electrically before the exhaust could do it. Without the MGU-H, lag comes back as an engineering problem to be solved rather than a nuisance to be electrically erased, and the solutions are the ones the rest of motorsport uses: smaller turbine housings, careful valve timing, control strategies that keep the turbo spinning when the throttle is closed, and MGU-K torque filling the hole while the boost builds. Anyone who drove a turbocharged road car in the 1980s knows how large that hole can be. Anyone watching a 2026 car exit a hairpin is watching a team's answer to it.

What each motor generator unit recovers, and what the second one was for

The MGU-K is easy to describe and hard to make well. It is a motor generator geared to the crankshaft. When the driver brakes, it resists the crankshaft, converting the car's kinetic energy into electricity and slowing the car in the process. When the driver accelerates, it runs the other way, drawing from the battery and adding torque.

From 2026 it delivers up to 350 kilowatts, an increase from 120. Its minimum permitted mass rose with it, from around seven kilograms to sixteen, precisely because the regulations expected manufacturers to spend enormous sums chasing power density and wanted a floor under how far that could go.

The braking consequence is the part most people miss. If the MGU-K is absorbing energy at the rear axle, the amount of retardation it provides varies with how much charge the battery will accept and how much energy the software wants to harvest. That is a rear brake torque that changes from lap to lap and corner to corner, which no driver could modulate through a pedal. So the rear brakes are controlled by wire: the driver's pedal is a request, and an electronic system decides how much of the requested retardation comes from friction and how much from the generator, blending the two so the pedal feel stays constant. Brake-by-wire in Formula 1 is not a convenience. It is the only way a car with heavy regeneration can be driven at all.

The MGU-H was a different animal, and it is worth explaining properly now that it is gone.

It was a motor generator on the turbocharger shaft. As a generator it captured exhaust energy that the turbine was producing beyond what the compressor needed, energy that would otherwise have been dumped through the wastegate. As a motor it drove the compressor directly, which is how lag was eliminated. It could also act as a bridge, sending energy it had just recovered straight to the MGU-K without passing through the battery, which mattered because the per-lap limits on recovery and deployment were written around the energy store rather than around that pathway.

It was, on paper, a beautiful device. It was also brutally difficult. A generator on a shaft turning at six figures of rpm, in exhaust heat, controlled to millisecond precision, and integrated with a combustion strategy that depended on it. Manufacturers who arrived late to the formula lost years to it. Companies evaluating an entry looked at it, calculated what it would cost to become competitive, and declined.

Removing it for 2026 was a decision about the size of the grid rather than about engineering elegance. The sport traded a clever energy recovery route and easy turbo response for a power unit that a competent engineering company can build without a decade of accumulated learning. Whether that was the right trade is a matter of taste. That it worked is not: the 2026 grid carries manufacturers who were not there before, and the deleted component is the reason.

50%50%

• Internal combustion engine50
• Electrical, through the MGU-K50

The regulations are written around a target of roughly half the total output coming from each side of the power unit, replacing the approximate 80 to 20 split of the previous rules. This is the design intent stated by the championship, not a measured figure for any car.

Show the numbers

Where a 2026 car's power is meant to come from

Item	Value
Internal combustion engine	50
Electrical, through the MGU-K	50

The energy store, and the rules about when a power unit may use it

The battery in a Formula 1 car is not big. It is not meant to be. Its job is to absorb a large amount of energy very quickly under braking and release it very quickly under acceleration, several dozen times a lap, for two hours, without its temperature running away.

The regulations control it in three ways at once. There is a permitted mass window with a floor as well as a ceiling, which stops both an unusable brick and an arms race in exotic cell chemistry. There is a location requirement, with the store housed inside the survival cell for 2026, because a battery is the most energetic thing on the car after the fuel and the safest place for it is inside the strongest structure. And there are limits on how much energy may move in and out of it per lap.

Those flow limits are where the racing lives.

Under the previous rules the MGU-K could recover two megajoules per lap and the energy store could send four megajoules per lap to the MGU-K. The asymmetry existed because the MGU-H could top the store up without counting against the MGU-K's recovery allowance. From 2026, with the MGU-H gone, recovery through the MGU-K rises to around nine megajoules per lap, and deployment is permitted in multiple separate bursts rather than the single allocation the old rules effectively imposed.

Multiply out and the numbers become legible. At 350 kilowatts, a four megajoule burst lasts about eleven and a half seconds. That is the arithmetic behind the whole 2026 driving style: a driver has a small number of eleven-second full-power windows per lap and has to decide where to spend them, while also finding places to put nine megajoules back in.

Recovery is the harder half. There are not enough heavy braking events on most circuits to harvest nine megajoules through the brakes alone, so drivers harvest in ways that cost lap time on purpose. Lifting early and coasting into a corner converts speed into charge instead of into heat in the discs. Harvesting at partial throttle on a straight, sometimes described as clipping, deliberately holds the car below its potential speed in order to bank energy for the next lap. A 2026 lap is therefore not a continuous attempt to go as fast as possible. It is a sequence of decisions about when to be slower on purpose.

The deployment side is capped by speed as well as by energy. A leading car's electrical deployment begins to taper at 290 kilometres per hour and reaches zero at 355. The reason is partly straightforward physics, in that adding 350 kilowatts on top of a combustion engine at the end of a long straight would produce top speeds the circuits were not designed for, and partly a racing decision: with everyone's deployment tapering in the same place, the end of a straight becomes a level playing field rather than a contest of who has the most charge left.

Which sets up the replacement for the movable rear wing.

• Leading car
• Car using manual override

Constructed illustration. The three speeds are the published ones, with a leading car's deployment tapering from 290 km/h to zero at 355 km/h and an overriding car permitted to hold full deployment to 337 km/h. The straight lines between those points are drawn for legibility only; the actual profile is defined in the Technical Regulations. Deployment is shown as an index in which 100 is the full 350 kilowatts.

Show the numbers

Worked example: how deployment tapers with speed

Item	Leading car	Car using manual override
260 km/h	100	100
290 km/h	100	100
310 km/h	69	100
337 km/h	28	100
355 km/h	0	0

The overtaking aid is now electrical, and the rear wing no longer moves

The movable rear wing was removed for 2026. That is worth stating plainly, because it had been part of the sport for so long that a great deal of writing about Formula 1 still assumes it exists, and race commentary has had to relearn a vocabulary.

Its replacement is manual override. A driver within one second of the car ahead at a detection point may activate it, and doing so allows them to hold full electrical deployment to 337 kilometres per hour rather than watching it taper away from 290, along with an additional allowance of around half a megajoule. The following car does not get a bigger engine. It gets to keep using the one it has for longer, in exactly the speed band where the car ahead is losing its own deployment.

The design intent is the same as the old system and the mechanism is the opposite. The rear wing flap that opened on designated straights worked by removing drag from the chasing car, which made the pass easier but also made it artificial in a way many people disliked, because the following driver's advantage came from a device rather than from anything they did. Manual override works by giving the chasing driver more energy to spend, which means it can be wasted. Use it early and there is nothing left at the end of the straight. Save it and the moment may pass. Whether that turns out to be more interesting than a flap is the open question of the new rules, and it will not be settled in one season.

There is a second-order effect on strategy. A driver who has been managing energy for five laps to build a charge advantage now has a reason to spend it in a particular place, which means the timing of an attack is a decision about the battery as well as about the tyres. Anyone reading a race through the lens of when a driver commits a set of tyres to an attack now has a second resource to track alongside it.

Reliability allocations are a performance rule wearing a safety costume

A driver does not get an unlimited supply of power units, and the way the rationing is written shapes how engines are designed.

Each element has its own allowance for the season, so a driver can be short of internal combustion engines while comfortable on energy stores. In 2026 the allowance is four internal combustion engines, four turbochargers and four exhaust systems, and three each of the MGU-K, the energy store and the control electronics. Each of those figures includes one additional unit granted for the first year of the new rules, and each drops by one for 2027.

• 2026 allowance
• 2027 allowance

Internal combustion engine43

Turbocharger43

Exhaust43

MGU-K32

Energy store32

Control electronics32

Per-driver allowances from the FIA Sporting Regulations. The 2026 figures include one extra unit of each element, granted because the regulations were new; the allowance for 2027 is one lower across the board.

Show the numbers

Power unit elements a driver may use in a season

Item	2026 allowance	2027 allowance
Internal combustion engine	4	3
Turbocharger	4	3
Exhaust	4	3
MGU-K	3	2
Energy store	3	2
Control electronics	3	2

Exceed the allowance on any one element and the first breach brings a ten place grid penalty. Each subsequent breach brings five. Accumulate more than fifteen places of penalty and the driver starts from the back of the grid regardless, which is the detail that shapes the strategy, because once a driver is going to the back anyway there is no marginal cost to taking every other new component at the same time. A team that needs one new engine will frequently take a new turbocharger, a new energy store and a new set of control electronics in the same weekend, at a circuit where overtaking is comparatively easy, and then run the rest of the season on fresh hardware. Penalties in Formula 1 are not accidents. They are scheduled, and the arithmetic behind when a team chooses to take them is a small planning exercise in itself.

Here is why this is a performance rule rather than a durability rule. If a manufacturer could use a fresh engine every weekend, it would build the most aggressive engine it could and accept that the engine would be worn out afterwards. The allowance removes that option. Every setting a team runs is a withdrawal from a fixed account of component life, so an engine mode that is worth two tenths a lap costs mileage that has to come from somewhere.

That is what people are describing, imprecisely, when they talk about turning an engine up. The hardware does not change. What changes is the combination of boost, mixture, ignition timing and deployment strategy the team is willing to run given how much life it has left and how many races remain. The regulations also constrain how much that combination may change between qualifying and the race, which closed off an era in which cars ran a brief and violent setting for one lap on Saturday that they could not have sustained on Sunday.

1. 1Fuel enters at a rationed rateThe regulations cap the energy reaching the engine at 3,000 megajoules per hour, measured by a standardised flow meter. Every manufacturer receives the same energy budget per second, so the competition is entirely about what fraction of it becomes work.
2. 2Air is compressedThe turbocharger's compressor, sitting at the front of the vee, raises the density of the incoming air. Compression heats it, so an intercooler removes that heat before the air reaches the cylinders, because denser air allows the rationed fuel to burn completely.
3. 3Combustion, as fast and as lean as the fuel will allowPre-chamber ignition lights the charge from many points at once. The burn finishes quickly enough to avoid knock, which is what permits the high pressures and lean mixtures that push thermal efficiency past the level any road engine reaches.
4. 4Work at the crankshaftExpansion pushes the pistons and turns the crank. This is the combustion half of the power split, and under the 2026 rules it is meant to be roughly half of the total.
5. 5Exhaust gas drives the turbineThe remaining pressure and heat in the exhaust spin the turbine at the back of the engine, which drives the compressor through a shaft running the length of the vee. Surplus energy is dumped through the wastegate, and since 2026 there is no longer a generator there to catch it.
6. 6Braking becomes electricityThe MGU-K resists the crankshaft under deceleration, generating up to a regulated maximum and sending it to the energy store. Brake-by-wire blends this varying rear retardation with the friction brakes so the driver's pedal feels the same every time.
7. 7The energy store holds the chargeThe battery sits inside the survival cell, absorbing and releasing energy within per-lap limits set by the regulations. It is small, worked extremely hard, and cooled continuously.
8. 8Deployment, in bursts, tapering with speedThe control electronics releases up to 350 kilowatts back through the MGU-K. Full deployment is available to 290 km/h and tapers to nothing at 355, unless the driver is within a second of the car ahead and uses manual override.
9. 9The driver decides what to give upNine megajoules a lap has to be harvested from somewhere, so the lap includes deliberate lifts, coasting and part-throttle running. A fast lap in this formula is a sequence of choices about where to be slower.

Each stage depends on the one before it. The loop through the energy store is what makes the arrangement a hybrid rather than a turbocharged engine with a motor attached.

Why F1 power unit development was frozen, and what a freeze costs

For four seasons, from 2022 to the end of 2025, it was illegal to make a Formula 1 engine faster.

The freeze worked through homologation. Each manufacturer lodged the specification of its power unit with the FIA by a stated deadline, after which that specification could not be changed except for reliability, safety or cost reasons, and each of those exceptions required the governing body's approval rather than the manufacturer's own judgement. The combustion engine, turbocharger, exhaust and the fuel and oil specifications were locked first, with a later deadline for the control electronics, energy store and MGU-K.

The reasoning was practical. The 2026 rules required every manufacturer to design an entirely new power unit, and running two full development programmes at once would have cost more than any of them wanted to spend. Freezing the old one released the engineers to work on the new one. It also removed the risk that a manufacturer would spend a fortune on the final year of an architecture about to be thrown away.

There was a second motive that was less discussed and mattered a great deal. One team was taking over the intellectual property of a departing manufacturer and building its own engine operation from scratch, and it could not do that while competing against continuous development from established rivals. The freeze was the condition on which that transition happened.

The cost of a freeze is that it locks in whatever gaps exist on the day it starts. A manufacturer that arrived at the deadline with a deficit had four seasons in which the only legal remedy was to be better at everything else. That is a harsh sanction for a bad year, and it is one reason the reliability exemption was policed with such suspicion, because a change that improves reliability very often improves performance as well and the line between the two is a matter of argument rather than measurement.

Formula 1 did not repeat the arrangement for 2026. Instead it wrote a development framework into the regulations that specifies which components may be worked on in which season, with the main combustion engine assembly locked early in the cycle and other parts remaining open for longer, and with upgrades permitted only at the start of a season rather than whenever a team chooses. Alongside it sits a catch-up mechanism: an index of combustion engine performance is assessed through the year, and a manufacturer found to be a few per cent behind the best on the grid earns additional upgrade opportunities, extra time on its test benches, and an adjustment to how the spending it does on that catch-up counts against its ceiling. A manufacturer further behind earns more of all three.

That is an unusual piece of rule-making, and it is worth being clear about what it is. It is a deliberate suppression of the reward for winning the engine race, on the grounds that a grid in which one power unit is dominant for a rule cycle is worse for the championship than a grid in which nobody is. Formula 1 has accepted that trade before. The separate spending ceiling that applies to power unit manufacturers rests on the same reasoning as the one that applies to the teams, and the mechanics of what a cost ceiling does and does not cover are set out in the FIA's Financial Regulations rather than left to the manufacturers to disclose.

What 2026 actually changed, and what it cost to change it

Pulling the threads together, the 2026 power unit differs from its predecessor in six ways that matter.

The MGU-H is gone, which lowered the barrier to entry and brought manufacturers to the grid, at the price of turbo response and a recovery pathway.

Electrical power rose from 120 kilowatts to 350, and the target split moved from roughly eighty per cent combustion to something near even. A modern power unit is no longer a combustion engine with electrical assistance. It is two power sources of comparable size sharing a crankshaft.

Per-lap recovery rose from two megajoules to around nine, which is the change that reshapes how a lap is driven. Harvesting is now a substantial part of the job rather than a by-product of braking.

The fuel flow ceiling fell and changed units, from 100 kilograms per hour to 3,000 megajoules per hour, and the race allowance fell to around 70 kilograms. Less fuel, less energy, more efficiency required to stand still.

The fuel itself became fully sustainable, produced from carbon capture, municipal waste or non-food biomass rather than from crude oil. This is the change with the largest reach outside the sport, because a drop-in fuel that works in a highly stressed racing engine is a fuel that works in a great many other engines, and unlike the MGU-H it has an obvious application beyond a race track.

And the overtaking aid became electrical, with the movable rear wing removed and manual override put in its place, alongside bodywork that changes configuration between low-drag and high-downforce states. That last change interacts with the power unit in a way the old rules never did, because the amount of drag a car is carrying at the end of a straight now determines how quickly it uses its deployment, which makes the aerodynamic configuration a car runs an energy decision as well as a downforce one.

The honest summary of the trade is that Formula 1 gave up some engineering exoticism, some turbo response and some of the pure lap time that unfettered development would have found, and bought a larger grid of manufacturers, a fuel with a future, and a set of racing rules where the overtaking aid is a resource the driver has to manage rather than a button that works. Whether that is a good bargain is the argument the sport will be having for the rest of the decade, and it is a version of the argument that runs through everything else written about motorsport on this site: the rules are never only technical, because every technical rule is a decision about what kind of racing you want to watch.

Four things to check on any power unit story

When a report claims a manufacturer has found power, or a driver complains about deployment, or a team takes a penalty that looks self-defeating, four checks will tell you what is actually being described.

Check whether the claim is about efficiency or about energy. Fuel flow is fixed and equal for everyone, so any genuine combustion gain is a gain in the fraction converted. A story about more power without a story about efficiency, friction or combustion speed is a story about deployment strategy wearing the wrong label.

Check the allocation table, not the engine. Element counts are published through the season. A driver who has already used their internal combustion engines but has energy stores in hand is in a different position from one who is short on both, and it changes what their team can do for the rest of the year.

Check where in the lap the deficit appears. A car losing time at the end of long straights is running out of deployment or carrying too much drag to sustain it. A car losing time on the exit of slow corners is fighting turbo response or traction. They are different problems with different fixes, and the speed trace separates them.

Check when the upgrade was allowed. Under the current framework, combustion engine changes are permitted at defined points in the cycle rather than whenever a manufacturer likes, and additional opportunities are earned by being measurably behind. A power unit that improves mid-season is either fixing reliability, has earned a catch-up allowance, or is doing something with energy management that required no new hardware at all.