2026 Hybrid Powerunits

[gruntguru]

I have explained more than once the new for 2026 rules allowing energy recovery when cornering, It seems these recovery when cornering are new, meaning this mode was not there before. Anyhow, once again: New regulations allow for MGU-K to recover energy during cornering, which is a change from previous years, this mode will happen by special maps, which triggers MGU-K into harvesting, even when driver lifts off throttle or is slightly using the brake pedal, these maps will increase engine revs (rpm) during this harvesting mode.

Engine revs cannot be controlled by maps. The driver selects a gear then engine revs will match the road speed for that particular gear.

Yes, engine revs are controlled indirectly by engine maps in formula 1, which are data tables within the ECU that manages how engine produce power in response to driver input.

You can squirm all you like but your original statement (in red) suggests that the ECU can somehow influence the rpm in a corner. WRONG!
- the car will corner at the road speed determined by the driver (on the limit hopefully)
- the car will be in the gear selected by the driver
- the rpm will be absolutely determined by the above two factors - both determined by the driver only.
- If the ECU was permitted to change the power to the wheels and influence the rpm the car would corner at the wrong speed - disastrous!
- This is not permitted by the regulations anyway. The torque to the wheels must be proportional to the driver demand.

[saviour stivala]

Engine revs cannot be controlled by maps. The driver selects a gear then engine revs will match the road speed for that particular gear.

Yes, engine revs are controlled indirectly by engine maps in formula 1, which are data tables within the ECU that manages how engine produce power in response to driver input.

You can squirm all you like but your original statement (in red) suggests that the ECU can somehow influence the rpm in a corner. WRONG!
- the car will corner at the road speed determined by the driver (on the limit hopefully)
- the car will be in the gear selected by the driver
- the rpm will be absolutely determined by the above two factors - both determined by the driver only.
- If the ECU was permitted to change the power to the wheels and influence the rpm the car would corner at the wrong speed - disastrous!
- This is not permitted by the regulations anyway. The torque to the wheels must be proportional to the driver demand.

The 2026 formula 1 regulations will introduce special engine maps that uses the MGU-K to ''harvest'' energy during corners by increasing engine revs even when the driver is off throttle. This new system will raise the engine revs in medium-to-high-speed cornes to provide load on the MGU-K, which will then slow the engine shaft to recharge the battery. Traditionally, the MGU-K harvest energy by slowing the engine shaft when driver lifts off the accelerator, the new 2026 rules allow for the opposite, the engine will be intentionally reved up to provide load for the MGU-K which then slows the engine to generate charge. This process is enabled by specific engine maps that will raise the engine revs when driver is off throttle in certain corners.

[mzso]

I guess I badly misremember then. So that's even more incentive to regen while turning, all the time.
Which I expect is a motivation towards ultra high rpm MGUs, so they can be reasonably efficient with low ICE rpm as well. (I do remember right that there can be a gear ratio between the ICE and the MGU, right?)

Maximum MGUK speed is limited.

C5.18.5 The relative rotational speed between any two parts of the MGU-K may not exceed 60,000rpm.

That's still a lot. Not sure how broad the high efficiency are of the MGU can be mad in generator mode though. But I expect it would be rather high if the RPM won't drop too low.

Why would the rpms increase when the driver lifts off/brushes the brakes and the MGUK is recovering energy?
What is the source of this "new for 2026 rules allowing energy recovery when cornering"?

How would that even be possible? The car would just speed up...

True. The driver will need to select a gear that creates appropriate rpm through the corner to meet his harvesting requirements. e.g. if maximum harvesting is required, they will have to corner in a gear that sets the rpm above 10,500.

With the motor being allowed to be geared to 60k rpm, I don't think it needs to be that extreme. But I guess they will tune the gearbox and motor to stay in a high-ish RPM range in most turns.

[mzso]

Not yet, as far as I am aware.

There most probably won't be one, considering there already is no limit since 2022. (Btw, the 15k rev limit was also removed for 2022)

Hadn't noticed that.

I'm guessing that is because neither limit was being used.

I don't remember the limit being removed from the regs. Though maybe he means, that it's never reached in practice.

[wuzak]

I guess I badly misremember then. So that's even more incentive to regen while turning, all the time.
Which I expect is a motivation towards ultra high rpm MGUs, so they can be reasonably efficient with low ICE rpm as well. (I do remember right that there can be a gear ratio between the ICE and the MGU, right?)

Maximum MGUK speed is limited.

C5.18.5 The relative rotational speed between any two parts of the MGU-K may not exceed 60,000rpm.

That's still a lot. Not sure how broad the high efficiency are of the MGU can be mad in generator mode though. But I expect it would be rather high if the RPM won't drop too low.

How would that even be possible? The car would just speed up...

True. The driver will need to select a gear that creates appropriate rpm through the corner to meet his harvesting requirements. e.g. if maximum harvesting is required, they will have to corner in a gear that sets the rpm above 10,500.

With the motor being allowed to be geared to 60k rpm, I don't think it needs to be that extreme. But I guess they will tune the gearbox and motor to stay in a high-ish RPM range in most turns.

The ICE speed would have to be at or above 10,500rpm to maximise harvesting.

Though that does depend on the driver power demand.

The rule quoted by Grunt above limits fuel flow at part throttle based on driver demand.

[mzso]

Maximum MGUK speed is limited.

C5.18.5 The relative rotational speed between any two parts of the MGU-K may not exceed 60,000rpm.

That's still a lot. Not sure how broad the high efficiency are of the MGU can be mad in generator mode though. But I expect it would be rather high if the RPM won't drop too low.

True. The driver will need to select a gear that creates appropriate rpm through the corner to meet his harvesting requirements. e.g. if maximum harvesting is required, they will have to corner in a gear that sets the rpm above 10,500.

With the motor being allowed to be geared to 60k rpm, I don't think it needs to be that extreme. But I guess they will tune the gearbox and motor to stay in a high-ish RPM range in most turns.

The ICE speed would have to be at or above 10,500rpm to maximise harvesting.

Though that does depend on the driver power demand.

The rule quoted by Grunt above limits fuel flow at part throttle based on driver demand.

Why?

[wuzak]

That's still a lot. Not sure how broad the high efficiency are of the MGU can be mad in generator mode though. But I expect it would be rather high if the RPM won't drop too low.


With the motor being allowed to be geared to 60k rpm, I don't think it needs to be that extreme. But I guess they will tune the gearbox and motor to stay in a high-ish RPM range in most turns.

The ICE speed would have to be at or above 10,500rpm to maximise harvesting.

Though that does depend on the driver power demand.

The rule quoted by Grunt above limits fuel flow at part throttle based on driver demand.

Why?

Fuel flow.

As I said, it depends on driver demand.

At driver demand of 218kW the maximum fuel flow can be achieved with C5.2.5. But that can also only be achieved from 10,500rpm and above.

If the rpm is lower, the fuel flow is restricted by C5.2.4.

If the engine is at 9,500rpm it will have approximately 36kW less power than if it is at 10,500rpm (based on 48% TE).

So, at 10,500rpm, the ICE delivers 400kW, the MGUK harvests 182kW to match the driver demand of 218kW.
At 9,500rpm, the ICE delivers 364kW, the MGUK harvests 146kW to match the driver demand of 218kW.

A reduction of approximatley 20% of harvesting power for a reduction of fuel flow of 9%.

If they used 9,500rpm for harvesting at that part throttle demand they would need more fuel for a race distance.

[karana]

There most probably won't be one, considering there already is no limit since 2022. (Btw, the 15k rev limit was also removed for 2022)

Hadn't noticed that.

I'm guessing that is because neither limit was being used.

I don't remember the limit being removed from the regs. Though maybe he means, that it's never reached in practice.

By saying the limits were removed I mean that the rules limiting fuel load and revs don't exist anymore since 2022.

[vorticism]

Just noticed that another thing changing '25-'26 is spark count. Currently five "per engine cycle" per cylinder are permitted. In '26 only one is permitted. Was/is "cycle" meant as a full engine cycle (720* crank rotation) or as a stroke (180* crank rotation)?

[saviour stivala]

Just noticed that another thing changing '25-'26 is spark count. Currently five "per engine cycle" per cylinder are permitted. In '26 only one is permitted. Was/is "cycle" meant as a full engine cycle (720* crank rotation) or as a stroke (180* crank rotation)?

720 degrees of crankshaft rotation is considered as a complete cycle for a four-stroke cycle each cylinder (intake, compression, power and exhaust). The new for 2026 change from five sparks to one per cycle means that a single spark will now initiate each power stroke.

[gruntguru]

720*

[mzso]

Just noticed that another thing changing '25-'26 is spark count. Currently five "per engine cycle" per cylinder are permitted. In '26 only one is permitted. Was/is "cycle" meant as a full engine cycle (720* crank rotation) or as a stroke (180* crank rotation)?

What does this even mean? Why even regulate it?
What would five sparks compared to one would achieve?

[Tommy Cookers]

Just noticed that another thing changing '25-'26 is spark count. Currently five "per engine cycle" per cylinder are permitted. In '26 only one is permitted....

... What would five sparks compared to one would achieve?

(given that there's 5 permitted fueling events)
extra gas could be made late in the stroke - increasing MGU-H made electricity rather than ICE power
maybe other effects
Honda had a name for the increased electricity

[karana]

Just noticed that another thing changing '25-'26 is spark count. Currently five "per engine cycle" per cylinder are permitted. In '26 only one is permitted....

... What would five sparks compared to one would achieve?

(given that there's 5 permitted fueling events)
extra gas could be made late in the stroke - increasing MGU-H made electricity rather than ICE power
maybe other effects
Honda had a name for the increased electricity

Based on this, are we sure 'engine power' in

C5.2.5 At partial load, the fuel energy flow must not exceed the limit curve defined below:
EF (MJ/h) = 380 when the engine power is equal to or below −50kW
EF (MJ/h) = 9.78 x engine power (kW) + 869 when the engine power is above −50kW

really refers to the PU power?

[vorticism]

Just noticed that another thing changing '25-'26 is spark count. Currently five "per engine cycle" per cylinder are permitted. In '26 only one is permitted....

... What would five sparks compared to one would achieve?

(given that there's 5 permitted fueling events)
extra gas could be made late in the stroke - increasing MGU-H made electricity rather than ICE power
maybe other effects
Honda had a name for the increased electricity

I thought this was the case, too, but I don't find any references to fuel injection limits in the '25 nor '26 regs. Seems like only the overall fuel pressure and flow rate are defined. As it relates, some of you probably already know, but peak permitted fuel pressure is currently 500 bar and will reduce to 350 bar in '26.

If one spark per cycle truly means one spark per 4-stroke cycle, then both the fueling and ignition should be typical. 'Cycle' is sometimes used in place of 'stroke,' perhaps erroneously as 'cycle' implies something cyclical i.e. returning to a starting point. I thought it was more common tongue, colloquial parlance, but even wikipedia has it in the first sentence of their associated article. So if you can argue it before the FIA, would you not then have optionally 1 spark per stroke & unregulated fuel injection (puff, squirt, mist...) timing & duration?