2025/2026 Hybrid Powerunit speculation

[mzso]

a front generator and a differential and 2 shafts for driving the generator

any such interconnection of the front wheels has been banned for many years

I think the question implicitly asks: what if it was allowed? (The regs were proposed with front generation at first.)

Indeed, that’s my question, purely hypothetical. What if they had a front generator?

I know a front generator would add some extra weight, but look at how lightweight F1 brakes are compared with a normal street car. I believe they could make a very small, lightweight, compact front generator (using axial-flux technology).

Someone even suggested full-regen braking, thinking it wouldn't require much cooling because it's only used intermittently. It might be interesting as a technological challenge. Also the (probable) massive increase in brake distances should contribute to more overtakes and better on-track action.

[Tommy Cookers]

Someone even suggested full-regen braking, thinking it wouldn't require much cooling because it's only used intermittently. It might be interesting as a technological challenge. Also the (probable) massive increase in brake distances should contribute to more overtakes and better on-track action.

that would require about 1500 kW rear braking capacity and about 3000 kW front braking capacity
ie about 12 times the 2026 capacity and about 30 times the present capacity

since the banning of Renault's mass damper it's illegal to have concentrated masses of stuff dotted around the car
apart from unavoidable items such as the wheels - these must be tethered to the car

re so-called 'axial-flux technology' - this only means electrical machines that are disc-shaped not drum-shaped
we already have disc-shaped things called brakes so perhaps we should devise brakes that also generate electricity

[DenBommer]

Someone even suggested full-regen braking, thinking it wouldn't require much cooling because it's only used intermittently. It might be interesting as a technological challenge. Also the (probable) massive increase in brake distances should contribute to more overtakes and better on-track action.

that would require about 1500 kW rear braking capacity and about 3000 kW front braking capacity
ie about twelve times the present capacity

since the banning of Renault's mass damper it's illegal to have concentrated masses of stuff dotted around the car
apart from unavoidable items such as the wheels - these must be tethered to the car

re so-called 'axial-flux technology' - this only means electrical machines that are disc-shaped not drum-shaped
we already have disc-shaped things called brakes so perhaps we should devise brakes that also generate electricity

You’ve then got triboelectric technology, but that’s not very efficient.

[gruntguru]

Someone even suggested full-regen braking, thinking it wouldn't require much cooling because it's only used intermittently. It might be interesting as a technological challenge. Also the (probable) massive increase in brake distances should contribute to more overtakes and better on-track action.

If you really want to make the racing unsafe, you could simply specify cable-operated drum brakes. Much cheaper.

[wuzak]

Someone even suggested full-regen braking, thinking it wouldn't require much cooling because it's only used intermittently. It might be interesting as a technological challenge. Also the (probable) massive increase in brake distances should contribute to more overtakes and better on-track action.

If you really want to make the racing unsafe, you could simply specify cable-operated drum brakes. Much cheaper.

And more money could be save by only having the brakes on the rear wheels.

As was the norm about 120 years ago.

[wuzak]

Front brake regeneration wasn't a F1/FIA choice. It was blocked by most of the current teams with the thinking it would give Audi too much of an advantage. Mercedes led that charge of blocking front brake regeneration.

I believe that to be a myth.

Front regen would require more weight and a more extensive redesign of the chassis.

And why would it give Audi an advantage? Because they ran a car 10 years ago with a similar setup?

And is running front regen that difficult compared to rear only?

[wuzak]

This must the most stupidiest engine rules ever on hybrid era. Only braking energy allowed to charge up the battery - not even ICE can't charge it on it's own to make it thrill and interesting development. This is several steps back to what we have even now.

They can use the ICE to charge the battery.

Up to 250kW under full throttle, less at part throttle.

Yes, I know. They’re now going to burn 20–30 kg of fuel to charge the battery. But then you’re burning expensive synthetic fuel. If you can get that extra kW from braking, it’s kind of “free,” and you can save fuel.

My thought is that front regen will only give substantial gains if it increases to total power recovery.

The example Symonds had was for three 130kW generators - two on the front, one on the rear.

That gives an 11% increase in recovery, but probably slightly more due to slightly longer time at maximum energy recovery during braking.

But it either means all wheel drive or less power for deployment.

Having deployment at lower power compared to recovery means they won't run out of energy as quickly.

Using front regen at the same, or similar power, will still leave the cars at an energy shortfall, requiring fuel to burned to generate electricity.

I am sceptical about the 20-30kg of extra fuel burning. It will probably be about half that - particularly now they will reduce recovery at tracks where braking recovery potential is low - such as Spa and Silverstone.

[wuzak]

Driver maximum power demand is when the driver is at full throttle.

The rule explicitly states that the MGUK output can be reduced to 0 (must be reduced above 290km/h) and then go into energy recover, up to 250kW. But only when the driver has maximum demand (full throttle).

But it's still possible to recover at partial power demand isn't it? And off throttle?

Yes and yes.

Driver demands X, ICE delivers Y and the MGUK recovers X - Y to give the desired output.

Off throttle = lift and coasting, which will happen.

[wuzak]

The rule itself doesn't slow the cars, it actually prevents them from harvesting at 350kW and hence from slowing the cars too much. Harvesting at full and partial throttle is anyway something that can be done already with the current PUs.

With an assumed ICE power of 400kW, harvesting at 250kW will still mean a net power of 150KW. What's supposed to be dangerous about it?

Power is proportional to drag and the cube of power.

If a car can go 300km/h using 400kW, and then power is cut to 150kW, speed will reduce to ~216km/h.

The worry was that the drop would be sudden when the battery ran out of energy, but that is mitigated by the ramp rates now.

[diffuser]

Front brake regeneration wasn't a F1/FIA choice. It was blocked by most of the current teams with the thinking it would give Audi too much of an advantage. Mercedes led that charge of blocking front brake regeneration.

I believe that to be a myth.

Front regen would require more weight and a more extensive redesign of the chassis.

And why would it give Audi an advantage? Because they ran a car 10 years ago with a similar setup?

And is running front regen that difficult compared to rear only?

Yeah, I read that Merc said that too...in 2022. I guess I could have lead with that. In any case, it wasn't the FIA/F1 that didn't want it.


You'd probably go with 4 wheel drive, if you're gonna have front wheel regeneration. No point in having a a motor to regenerate but not feed it power to power the car.

They could have made the rear motor smaller to compensate.

[DenBommer]

Front brake regeneration wasn't a F1/FIA choice. It was blocked by most of the current teams with the thinking it would give Audi too much of an advantage. Mercedes led that charge of blocking front brake regeneration.

I believe that to be a myth.

Front regen would require more weight and a more extensive redesign of the chassis.

And why would it give Audi an advantage? Because they ran a car 10 years ago with a similar setup?

And is running front regen that difficult compared to rear only?

Yeah, I read that Merc said that too...in 2022. I guess I could have lead with that. In any case, it wasn't the FIA/F1 that didn't want it.


You'd probably go with 4 wheel drive, if you're gonna have front wheel regeneration. No point in having a a motor to regenerate but not feed it power to power the car.

They could have made the rear motor smaller to compensate.

They could then use the front motor as a push-to-pass system, or just for exiting corners and then disconnect it for more efficiency (like the principle of the Mercedes AMG GT XX).

Or, like in WEC, the front motor could be activated only within a speed limit (for example, 150 km/h).

[gruntguru]

Power is proportional to drag and the cube of power.

Typo. I know you meant velocity.

[wuzak]

Power is proportional to drag and the cube of power.

Typo. I know you meant velocity.

Yes, thanks for that correction.

[wuzak]

The standard ramp rate is 100kW/s, which means the cars will go from 300km/h to 216km/h in 2.5s.

That equates to a deceleration rate of about 0.95G.

But, if the drivers stay in the same gear, the rpm will be reduced.

If it is 12,000rpm @ 300km/h (equates to a top speed of 375km/h @ 15,000rpm), the engine speed will be reduced to 8,653rpm.

At that engine speed, by the fuel flow rules and esimated 48% TE (gives 400kW at maximum fuel flow), the ICE will produce only 334kW, which would mean 84kW left to propel the car.

Speed would be down to 178km/h, the deceleration would be around 1.38G.

The energy recovered during this would be approximately 250kW * 2.5s / 2 = 312.5kJ.


Of course, slowing the car this much would mean that the braking time is short and the time that the maximum braking recovery can occur will be very short.

So it would be balancing using the ICE to drive the generator and using brakes.

[mzso]

If you really want to make the racing unsafe, you could simply specify cable-operated drum brakes. Much cheaper.

Braking earlier and from less speed in most cases, would be safer. Why do you want to put this strawman everywhere?

that would require about 1500 kW rear braking capacity and about 3000 kW front braking capacity
ie about 12 times the 2026 capacity and about 30 times the present capacity

If you want to exactly match F1 levels. I don't see braking at 150m or 200m instead of 100 from top speed necessarily a bad thing.
On the other hand. I don't think anyone honestly knows how far F1 style technology could take these. Special insulation could allow them to heat up a lot more than normal generators/motors, and the high speed airflow could cool them down.

since the banning of Renault's mass damper it's illegal to have concentrated masses of stuff dotted around the car
apart from unavoidable items such as the wheels - these must be tethered to the car

Okay. Why do you bring it up?

re so-called 'axial-flux technology' - this only means electrical machines that are disc-shaped not drum-shaped
we already have disc-shaped things called brakes so perhaps we should devise brakes that also generate electricity

Well, that would be the axial-flux (M)GU, a brake that produces electricity via braking. They can design axial flux motors with a much better power density, that's why it's trending.