2025/2026 Hybrid Powerunit speculation

[Tommy Cookers]

C5.4.5 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

Engine refers to full PU or ICE alone? Because I see no sense in the ICE producing minus 50kW.
I understand that the fuel at complete PU power = 0W (ICE vs MGUK for net zero) would be 869MJ/h, which amounts to 241,8kW of gross available power.
If the PU efficiency is nearing 50% (which we cannot know, at least right now), putting the ICE vs. MGUK with clutch disengaged and none torque request from the driver, it would be possible to harvest at 120kW. Not negligible!
Even then, the wording says "at partial load". What's the definition of load? Torque request ≠ load? Load on the ICE? Load in the full PU?
If the driver don't push on the throttle, could be accounted as another scenario not under " partial load", I suppose.

-50 kW or below is the ICE power (accelerator-off) for rpms above idle - ie so-called 'engine braking'
engine power means ICEngine power not Power Unit power

clutch-disengaged or clutch-engaged the energy sum is the same

[BassVirolla]

C5.4.5 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

Engine refers to full PU or ICE alone? Because I see no sense in the ICE producing minus 50kW.
I understand that the fuel at complete PU power = 0W (ICE vs MGUK for net zero) would be 869MJ/h, which amounts to 241,8kW of gross available power.
If the PU efficiency is nearing 50% (which we cannot know, at least right now), putting the ICE vs. MGUK with clutch disengaged and none torque request from the driver, it would be possible to harvest at 120kW. Not negligible!
Even then, the wording says "at partial load". What's the definition of load? Torque request ≠ load? Load on the ICE? Load in the full PU?
If the driver don't push on the throttle, could be accounted as another scenario not under " partial load", I suppose.

-50 kW or below is the ICE power (accelerator-off) for rpms above idle - ie so-called 'engine braking'
engine power means ICEngine power not Power Unit power

clutch-disengaged or clutch-engaged the energy sum is the same

Ok, I get it. This section of the rules is for overrun of the engine. I think this shuts the possibility to burn too much fuel for antilag effects.

Still not adressing the scenario I think about...

Nevertheless, I don't know (and I don't think) if the rules take "torque request" (as throttle position) as equal to "load".

That's the question, if it would be possible to load the engine only And exclusively against the MGUK while the driver requests no torque, but still not braking.

[diffuser]

No, I think in lift & coast with clutch disengaged and ICE running for MGUK recovery.

Of course, matching ICE power with MGUK generating, net output torque would be zero while the driver has the throttle pedal lifted.

The amount of fuel flow is further restricted when the driver is off throttle. The lower the torque demand is, teh lower the fuel flow is allowed.

In lifting and coasting, the MGUK can potentially recover 350kW.

On full throttle, the maximum MGUK recovery is 100kW.

Also, disconnecting the drive from the PU using the clutch in lift and coast sort of defeats the purpose of the ERS.

Clutch operation by the ECU is limited to gearshifts, and the time is limited to prevent them using it for TC, or other.

It could be operated manually, but coordinating that with the engne controls would be difficult - the driver can't just prss on the throttle, as that gives a certain torque demand which has to be sent to the rear wheels.

In my mind it was a sort of "zero torque net output" recovery mode, possibly configurated with the clutch manually pressed while moving (not pushing the throttle pedal, but automatically accelerating the ICE vs. MGUK load until a net zero torque in the full PU).

Only sense it would possibly have would be a L&C with less speed losing that if you put 350kw of rear braking.

The 100kW limit under full torque demand would not apply while lifting.

What's the fuel limit while off throttle?

Think this all started with me wondering (or atleast part of this did) if we could recover under throttle. That has been answered with a yes 100 KW.
You're limited to how much you can recover per lap 8.5 Mj . So if you can recover 100KW under full torque, that's something!.... at 100 kW, it would take approximately 85 seconds to reach 8.5 MJ. That's more time that most track laps.

It would take 24 seconds of braking to reach 8.5 MJs.

Please let me know if I got that right.

[BassVirolla]

Think this all started with me wondering (or atleast part of this did) if we could recover under throttle. That has been answered with a yes 100 KW.
You're limited to how much you can recover per lap 8.5 Mj . So if you can recover 100KW under full torque, that's something!.... at 100 kW, it would take approximately 85 seconds to reach 8.5 MJ. That's more time that most track laps.

It would take 24 seconds of braking to reach 8.5 MJs.

Please let me know if I got that right.

Thanks, all info is welcome.

Nevertheless, my idea is quite "loophooled".

If the driver requests zero torque (a.k.a. lifting), there's something in the rules that forbids putting the ICE positive torque against MGUK negative torque (a.k.a. electric braking) for a net zero torque output from the whole PU?

It would make possibly L&C with less speed loss and getting some recovery, before applying full braking with zero ICE torque.

[diffuser]

Think this all started with me wondering (or atleast part of this did) if we could recover under throttle. That has been answered with a yes 100 KW.
You're limited to how much you can recover per lap 8.5 Mj . So if you can recover 100KW under full torque, that's something!.... at 100 kW, it would take approximately 85 seconds to reach 8.5 MJ. That's more time that most track laps.

It would take 24 seconds of braking to reach 8.5 MJs.

Please let me know if I got that right.

Thanks, all info is welcome.

Nevertheless, my idea is quite "loophooled".

If the driver requests zero torque (a.k.a. lifting), there's something in the rules that forbids putting the ICE positive torque against MGUK negative torque (a.k.a. electric braking) for a net zero torque output from the whole PU?

It would make possibly L&C with less speed loss and getting some recovery, before applying full braking with zero ICE torque.

Think I understand you. When the drivers lifts can you spin the MGU-K minimally.

The thing is, if you're lifting, why wouldn't you brake? Even if you could do what you suggest. You could recharge much more by just braking.

[wuzak]

The amount of fuel flow is further restricted when the driver is off throttle. The lower the torque demand is, teh lower the fuel flow is allowed.

In lifting and coasting, the MGUK can potentially recover 350kW.

On full throttle, the maximum MGUK recovery is 100kW.

Also, disconnecting the drive from the PU using the clutch in lift and coast sort of defeats the purpose of the ERS.

Clutch operation by the ECU is limited to gearshifts, and the time is limited to prevent them using it for TC, or other.

It could be operated manually, but coordinating that with the engne controls would be difficult - the driver can't just prss on the throttle, as that gives a certain torque demand which has to be sent to the rear wheels.

In my mind it was a sort of "zero torque net output" recovery mode, possibly configurated with the clutch manually pressed while moving (not pushing the throttle pedal, but automatically accelerating the ICE vs. MGUK load until a net zero torque in the full PU).

Only sense it would possibly have would be a L&C with less speed losing that if you put 350kw of rear braking.

The 100kW limit under full torque demand would not apply while lifting.

What's the fuel limit while off throttle?

Think this all started with me wondering (or atleast part of this did) if we could recover under throttle. That has been answered with a yes 100 KW.
You're limited to how much you can recover per lap 8.5 Mj . So if you can recover 100KW under full torque, that's something!.... at 100 kW, it would take approximately 85 seconds to reach 8.5 MJ. That's more time that most track laps.

It would take 24 seconds of braking to reach 8.5 MJs.

Please let me know if I got that right.

Correct.

Maximum recovery when driver has full throttle is 100kW.
24s to recover 8.5MJ @ 350kW under braking, though braking is 15s or less at most tracks, and a lot of that isn't at maximum braking.

So the rest has to be made by the 100kW under full throttle at the end of straights, and by recovering energy in part throttle scenarios.

The irony in these rules is that many of the tracks which require the full 8.5MJ to be deployed are the ones least able to recover that energy. Think tracks like Silverstone.

[Vappy]

With that in mind and taking silverstones as an example, @wuzak what scenario is likely to play out as a result?

[BassVirolla]

Think this all started with me wondering (or atleast part of this did) if we could recover under throttle. That has been answered with a yes 100 KW.
You're limited to how much you can recover per lap 8.5 Mj . So if you can recover 100KW under full torque, that's something!.... at 100 kW, it would take approximately 85 seconds to reach 8.5 MJ. That's more time that most track laps.

It would take 24 seconds of braking to reach 8.5 MJs.

Please let me know if I got that right.

Thanks, all info is welcome.

Nevertheless, my idea is quite "loophooled".

If the driver requests zero torque (a.k.a. lifting), there's something in the rules that forbids putting the ICE positive torque against MGUK negative torque (a.k.a. electric braking) for a net zero torque output from the whole PU?

It would make possibly L&C with less speed loss and getting some recovery, before applying full braking with zero ICE torque.

Think I understand you. When the drivers lifts can you spin the MGU-K minimally.

The thing is, if you're lifting, why wouldn't you brake? Even if you could do what you suggest. You could recharge much more by just braking.

I don't know.

Possibly while defending, to carry a bit more speed until the braking point than if you do a full electric brake regen while lift & coast. The simulations would say if this makes some sense, not me.

[Tommy Cookers]

.. If the driver requests zero torque (a.k.a. lifting), there's something in the rules that forbids putting the ICE positive torque against MGUK negative torque (a.k.a. electric braking) for a net zero torque output from the whole PU?

yes there's something in the rules ....
monotonicity .....
for any rpm above idle PU torque output must always increase with increase in accelerator displacement
(so the PU behaves like a conventional engine not a freak show)

[BassVirolla]

.. If the driver requests zero torque (a.k.a. lifting), there's something in the rules that forbids putting the ICE positive torque against MGUK negative torque (a.k.a. electric braking) for a net zero torque output from the whole PU?

yes there's something in the rules ....
monotonicity .....
for any rpm above idle PU torque output must always increase with increase in accelerator displacement
(so the PU behaves like a conventional engine not a freak show)

Still, ICE actuating versus MGUK recovery, can amount to zero torque output of whole PU.

But if the same wording applies to PU and ICE that would be an effective clampdown on what I'm guessing.

[diffuser]

There is no rule that prevents a driver from applying the throttle and the brakes at the same time?

[BassVirolla]

There is no rule that prevents a driver from applying the throttle and the brakes at the same time?

I'm not versed in reading FIA documents.

But this makes me wonder if would be possible to burn the maximum allowed fuel under no throttle (equivalent to 120kw gross chemical power) for "idling" the engine, and regulate the idling speed putting the MGUK opposing this fuel burning in the ICE.

In this way, you could override the PU with no significative braking nor positive torque but up to 120kW of theoretical maximum recovery.

[FW17]

There is no rule that prevents a driver from applying the throttle and the brakes at the same time?

What's the point? MGUH will already be harvesting when the brake pedal is applied

[diffuser]

There is no rule that prevents a driver from applying the throttle and the brakes at the same time?

What's the point? MGUH will already be harvesting when the brake pedal is applied

no MGU-H in 2026. Only way to harvest is with MGU-K.

[diffuser]

.. If the driver requests zero torque (a.k.a. lifting), there's something in the rules that forbids putting the ICE positive torque against MGUK negative torque (a.k.a. electric braking) for a net zero torque output from the whole PU?

yes there's something in the rules ....
monotonicity .....
for any rpm above idle PU torque output must always increase with increase in accelerator displacement
(so the PU behaves like a conventional engine not a freak show)

Still, ICE actuating versus MGUK recovery, can amount to zero torque output of whole PU.

But if the same wording applies to PU and ICE that would be an effective clampdown on what I'm guessing.

I think the whole monotonicity thing means you can't do that.