2025/2026 Hybrid Powerunit speculation

[Tommy Cookers]

.... but still has a really strong focus on combustion efficiency .....

the significant matter isn't combustion efficiency CE - it's indicated thermal efficiency ITE

combustion efficiency is simply the percentage of fuel burnt (eg 95%) without any regard to conversion of heat to work
there's no reason to think the CE of these cars is outstanding (even though there can be a bit of post-cylinder burning)

the ITE is outstanding - and yes that's largely due to the novel and nearer-to-ideal combustion rate behaviour
ITE is the ratio of work developed in cylinder (ie work at piston crown) to the heat released in-cylinder
(it is derived from the continuous measurement of in-cylinder' pressure and volume)

what science types parrot as 'thermal efficiency' is correctly known by engineers as brake thermal efficiency BTE
BTE is the ratio of work (at the crankshaft nose) to the heat (lower heating value LHV) of the fuel taken
(LHV ignores the fuel heat heat 'trapped' as latent heat in exhaust water and fuel vapours)

[gruntguru]

From Pat Symond’s presentation:
. . . .
* Lambda 1.3-1.4.
. . . .
* They are Miller Cycle engines, with IVC before BDC
. . . .
* Modeling from the FIA shows around 5.5bar boost (~80psi or so)

It is years since I ran the numbers but it would be interesting to extract the VE from those above. Certainly well below 100%.

Couldn't resist - here we go. Feel free to correct any dodgy assumptions.

Fuel flow = 100 kg/hr. (100/60 kg/min)
Airflow = fuel flow x AFR = 100/60 x 14.7 x 1.35 = 33.1 kg/min
5.5 bar boost = 6.5 P.R. lets assume intercooling is not down to ambient so density ratio (DR) is only 5.0
Air density = 1.2 x DR = 6 kg/m3
Air volume flow = air mass flow/density = 33.1/6 = 5.5 m3/min = 5,500 l/min
Air volume flow also = rpm x displacement/2 x VE
So VE = volume flow x 2 / rpm / displacement = 5,500 x 2 /10,500 / 1.6 = 0.65
VE = 65% (Killed by EIVC.)
Probably pessimistic. eg DR = 5.0 sounds high to me.

[Tommy Cookers]

I think re the FIA they meant 5.5 bar absolute ....
haven't they issued in the 2026 rules a pressure limit in absolute terms ?

PS in the 80s it's said 'boost' was limited to 4 bar then 2.5 bar - but it was actually 4 bar absolute then 2.5 bar absolute

[wuzak]

I think re the FIA they meant 5.5 bar absolute ....
haven't they issued in the 2026 rules a pressure limit in absolute terms ?

5.5.2 Engine intake air pressure must be less than 4.8 barA at all times. The pressure of the air will be measured by two FIA approved and sealed devices through which all air destined for combustion must flow. These devices must be installed in FIA approved locations situated in the engine inlet intake air system downstream of the charge air cooling system (as described in Article 5.25.2).

[CaribouBread]

Slightly OffTopic but there's some irony in the fact that Audi/Porsche were the main force in getting rid of the MGUH for these new regs, but now Porsche is making a 911 GTS with a MGUH/MGUK PU. Something something "road relevance"

[Cold Fussion]

Slightly OffTopic but there's some irony in the fact that Audi/Porsche were the main force in getting rid of the MGUH for these new regs, but now Porsche is making a 911 GTS with a MGUH/MGUK PU. Something something "road relevance"

Before any of the other manufacturers add MGU-H's to their road car engines no less.

[Holm86]

Slightly OffTopic but there's some irony in the fact that Audi/Porsche were the main force in getting rid of the MGUH for these new regs, but now Porsche is making a 911 GTS with a MGUH/MGUK PU. Something something "road relevance"

When I heard they were making a 911 Hybrid I instantly thought 'how boring' but the tech in their new T-Hybrid system is actually pretty cool.

[Vanja #66]

2026 PUs are going to reach 1100 HP according to Tombazis

https://www.racefans.net/2024/06/12/for ... s-in-2026/

[wuzak]

2026 PUs are going to reach 1100 HP according to Tombazis

https://www.racefans.net/2024/06/12/for ... s-in-2026/

A copy of my post from the 2026 chassis thread.

1,100hp = 820kW

MGUK power = 350kW

Which means ICE power = 470kW

Which is much more than the originally expected 400kW, and makes it even less 50/50 between ICE and MGUK.

Maximum fuel flow is 3,000MJ/h = 833kW

Which means that the ICE efficiency would be ~56%.

Which would be quite astounding.

If that was truly the case, they could reduce the MGUK output power to 250kW, which would give maximum power of 965hp. But it would make the energy last longer.

[Hoffman900]

I’ve seen the same engine make 150hp difference depending on the dyno.

Never believe advertised numbers, especially from OEM racing programs.

[Sevach]

2026 PUs are going to reach 1100 HP according to Tombazis

https://www.racefans.net/2024/06/12/for ... s-in-2026/

If that was truly the case, they could reduce the MGUK output power to 250kW, which would give maximum power of 965hp. But it would make the energy last longer.

Sounds totally reasonable and no one would be hurt by it.

When I heard they were making a 911 Hybrid I instantly thought 'how boring' but the tech in their new T-Hybrid system is actually pretty cool.

Most interesting Hybrid integration yet, small battery, not a lot of weight... T-Hybrid.
Instead F1 had to go for 50/50(which isn't really 50/50).

And next they are talking if we are using renewable fuels do we really need hybrids? No F... clue what direction they need to be going.

[Vanja #66]

But what you're saying there makes zero sense, why on earth would you have a 44MJ battery if in could never go under 40MJ in that case.

The battery will probably have a minimum charge of perhaps 0.5MJ which means the maximum charge capacity probably won't be over 5MJ as the maximum state can only ever go 4MJ over the minimum, you need a bit og leeway

And as I said, the current regulations say exactly the same as those of 2026 when it comes to the delta charge of the battery, so why would it need to be bigger

Because ES needs to last a long time. Today they should live through 12 race weekends, meaning at least 7500-8000km of hard and constant use. By making an oversized battery you reduce the current (Amps) and thus the charge/discharge rate (aka C-rate) which needs to be kept low for long battery life.

[Holm86]

But what you're saying there makes zero sense, why on earth would you have a 44MJ battery if in could never go under 40MJ in that case.

The battery will probably have a minimum charge of perhaps 0.5MJ which means the maximum charge capacity probably won't be over 5MJ as the maximum state can only ever go 4MJ over the minimum, you need a bit og leeway

And as I said, the current regulations say exactly the same as those of 2026 when it comes to the delta charge of the battery, so why would it need to be bigger

Because ES needs to last a long time. Today they should live through 12 race weekends, meaning at least 7500-8000km of hard and constant use. By making an oversized battery you reduce the current (Amps) and thus the charge/discharge rate (aka C-rate) which needs to be kept low for long battery life.

How does battery size influence amps?
And C rate will just increase as battery size does, all other aspects kept the same.
I know there need to be some overhead, as a battery charges faster at the lower end of its capacity.
If you want to lower amps, you need to raise the voltage.
Only thing I can't think off is if internal resistance of the battery lowers as capacity increases, but it shouldn't be so much that I can't be overcome with higher voltage

[Vanja #66]

How does battery size influence amps?
And C rate will just increase as battery size does, all other aspects kept the same.
I know there need to be some overhead, as a battery charges faster at the lower end of its capacity.
If you want to lower amps, you need to raise the voltage.
Only thing I can't think off is if internal resistance of the battery lowers as capacity increases, but it shouldn't be so much that I can't be overcome with higher voltage

I've mentioned battery size and Amps as a general relation, 2026 PU will be limited to 1000V, so the peak current won't be lower than 350A. C rate depends on battery capacity (Ah), which is the parameter teams can play with. 4MJ is only 1111Wh of capacity, which can be achieved with 4-5kg of LiPo batteries. ES has to be at least 35kg (with casing and everything) so batteries can be oversized for bigger capacity and lower C rate.

I guess we can assume batteries will have around 6kWh (25-30kg of LiPo cells in this case) capacity to keep it round and simple, so at 1000V max capacity (for a LiHV cell) that's 4.3V per cell, ie 232 theoretical cells and that's working voltage of 858V - meaning 7Ah of batteries. At 408A (350kW at 858V), you have a C rate of 58C which is quite ok, there are cells that can go over 100C. So if you reduce capacity to 3kWh you are at 115C and if you drop to 2kWh you are already at 175C which is usually too high.

If you limit your LiPo cells to their nominal voltage of 3.7V and settle for 270 theoretical cells to reach maximal=nominal 1000V, you are "down" to 6Ah capacity, but your current is now also "down" to 350A and this keeps C rate at 58C of course. Lower current means less heat and higher number of cells means closer Voltage between min and max SOC for each cell and in this case cells will practically stay around 3.7V the whole time since you are only using 1.1Ah of 6Ah of capacity. This will also extend their working life a lot, compared to having them go from 4.2V to 3.2V and back 2-3 times a lap.

[gruntguru]

I’ve seen the same engine make 150hp difference depending on the dyno.

Never believe advertised numbers, especially from OEM racing programs.

I have never doubted a power claim from an F1 team. (and they use accurate dynos)