2025/2026 Hybrid Powerunit speculation

[mzso]

my (first 2) suggestions above - can someone explain what would stop them working ?

Stu mentioned the accelerator pedal and injector regs. I've looked, but I'm not seeing them as limiting the ICE to MGU interaction. Perhaps he can help point out the specifics?

5.14 & 5.15 (2026) define the relationship between the pedal map and the +ve torque to the rear wheels. However, they are framed in terms of net PU output. So, for the accelerator pedal at 0%, it's possible to run the ICE at +350kW and the MGU at -350kW for a net zero PU output.

The benefit is as you say, the turbine is already producing boost when the driver goes on the throttle, so all that problem with lag goes away.... plus you're harvesting energy for the later acceleration phase. All, in all, it seems very attractive to aim for running the ICE at full power for 100% of the lap, and modulating PU output using the MGU (at least in qualifying).

Braking is a point of contention, and there's a design choice of when to bring the ICE "on power". It's perfectly possible to do it early in the braking phase when the revs have dropped sufficiently for the output from ICE to balance the harvest from the MGU.

I already hear the crying about how strange the cars sound with the engines always screaming at least on 350kW.

I wonder if anyone could actually calculate how much power can be generated in total. Obviously only break and part-throttle phases are in play, which might count for very little in Monza or Spa and such. But I guess the extra 350kW would be always available in monaco/hungary, on tracks where you least need it. The battery would be completely full after every turn...

[djos]

MZSO, 160 litres of volume is JUST for a 500kW fuel cell stack, that ignores the ancillary components like the Hydrogen circulating pump, battery (which would need to be larger than a road car due to more time spent accelerating hard) and fuel tanks. It also ignores that race cars use a heck of a lot more fuel than road cars.

The Mirai has about 120 litre fuel tank capacity (5kg of storage) and gets around 500 kms of range. How long would that last in a race car?

But keep ignoring the facts mate, FC tech is not the future of race cars, or passenger cars for that matter.

[wuzak]

Remembering that the race fuel will be something like 70% of the energy that is used now.

Did the 100kg allowance stay the same I don't remember reading that information.

I don't think it has been confirmed, but it is logical that a limit will be used.

The limit is likely to be in MJ, and probably around 3000MJ, the maximum fuel flow is 3000MJ/h, which would follow on from the (original) 100kg/h and 100kg max fuel.

3000MJ ~ 67kg.

[vorticism]

The fuel tank will presumably not scale proportionally to the downsizing of the fuel flow rate in order to accommodate not only reduced thermal efficiency but also to permit this operating regime which Tommy brought up a few pages ago which seems to be gaining traction now.

They recover 1-2mj from braking with current setup. I doubt it will be 6mj with 350kw recovery, more like 3mj

afaik
the present setup stops regenerative braking just before there's insufficient tyre grip for the 120 kW regen torque
after some downshifts (which maintain voltage but increase regen demand torque at tyre)

but there's a fair bit of regen energy available after there's insufficient grip for regen at the new normal 350 kW rate
as demanded 'back' torque (current generated) can be lowered as necessary when tyre grip reduces with DF
though downshifts will tend to increase torque demand at tyre
(& in any gear as rpm varies demanded 'back' torque is variable (already doing it ?) ie to maintain generation at 350 kW)

[mzso]

Remembering that the race fuel will be something like 70% of the energy that is used now.

Did the 100kg allowance stay the same I don't remember reading that information.

I don't think it has been confirmed, but it is logical that a limit will be used.

The limit is likely to be in MJ, and probably around 3000MJ, the maximum fuel flow is 3000MJ/h, which would follow on from the (original) 100kg/h and 100kg max fuel.

3000MJ ~ 67kg.

How do they expect 1000HP then, without putting in the energy into the system? The whole system will be less efficient to begin with...
Perhaps for 2 seconds per lap we'll get that power...

[djos]

MZSO, 160 litres of volume is JUST for a 500kW fuel cell stack, that ignores the ancillary components like the Hydrogen circulating pump, battery (which would need to be larger than a road car due to more time spent accelerating hard) and fuel tanks. It also ignores that race cars use a heck of a lot more fuel than road cars.

The Mirai has about 120 litre fuel tank capacity (5kg of storage) and gets around 500 kms of range. How long would that last in a race car?

But keep ignoring the facts mate, FC tech is not the future of race cars, or passenger cars for that matter.

Wow, getting down voted for posting facts on a technical forum!

For reference, it took over a decade of development and billions of dollars to take hydrogen fuel cell power from 1.4kW per litre to 3.1kW.

Don’t take my word for it, the data is available:

https://www.toyota-europe.com/download/ ... 564265.pdf

[CaribouBread]

How do they expect 1000HP then, without putting in the energy into the system? The whole system will be less efficient to begin with...
Perhaps for 2 seconds per lap we'll get that power...

The 1000 hp figure seems to be the expected peak output, but they won't be able to sustain that for more than a lap at a time (my guess), and when the K runs out of juice they'll be trundling around with 650hp till they recoup enough. Lowest average power output throughout the race distance in quite some time and the highest weight, will be a riot to watch

[bradipao]

First post here.

How do they expect 1000HP then, without putting in the energy into the system? The whole system will be less efficient to begin with...

Lack of energy was my first doubt when I read the spec. Is it possible that PU2026 rules are incomplete "on purpose", to avoid too much development in advance?

[Tommy Cookers]

... The whole system will be less efficient to begin with...

... when the K runs out of juice they'll be trundling around with 650hp till they recoup enough. Lowest average power output throughout the race distance in quite some time and the highest weight, will be a riot to watch :? :lol:

'the whole system' could be presented as equally efficient (to the present one) because of ....
the greater KE recovery and the greater fraction of propulsive energy use at the most lap-speed beneficial times
(and carbonwise as more efficient)

isn't this the aim - that the race speed will be unchanged despite the smaller mean propulsive power available ?
with those serial downshifts followed by serial upshifts there will still be the usual sense of urgency

[CaribouBread]

'the whole system' could be presented as equally efficient (to the present one) because of ....
the greater KE recovery and the greater fraction of propulsive energy use at the most lap-speed beneficial times
(and carbonwise as more efficient)

isn't this the aim - that the race speed will be unchanged despite the smaller mean propulsive power available ?
with those serial downshifts followed by serial upshifts there will still be the usual sense of urgency

I agree with most of what you've said, I only have 2 concerns with this really;

1. I fear there might not be sufficient recovery (variety of tracks and such) to consistently deploy throughout the race distance. I know current PUs don't deploy full-tilt all the time either - but we can still see a very big performance delta between max deployment vs low/no deployment (especially in wheel2wheel scenarios).

2.With the electrical side contributing so much to the overall performance package, it will require a lot more battery management from the driver + mismanagement or insufficient recovery would mean that you get overtaken with a 350hp delta (which in my mind's eye looks very ridiculous).

Having said all that, this is just an preliminary opinion based on what I think the new PUs might turn out to be like. Even if it turns out the way i think it will, we'll probably get used to it pretty quick. Its just a paradigm shift like the 2014 PUs were, just a bit extreme. One obvious benefit I assume will happen is lengthening of braking distances which should likely improve overtaking chances. I'm sure most of my concerns will turn out to be unfounded

[mzso]

MZSO, 160 litres of volume is JUST for a 500kW fuel cell stack, that ignores the ancillary components like the Hydrogen circulating pump, battery (which would need to be larger than a road car due to more time spent accelerating hard) and fuel tanks. It also ignores that race cars use a heck of a lot more fuel than road cars.

The Mirai has about 120 litre fuel tank capacity (5kg of storage) and gets around 500 kms of range. How long would that last in a race car?

But keep ignoring the facts mate, FC tech is not the future of race cars, or passenger cars for that matter.

Wow, getting down voted for posting facts on a technical forum!

For reference, it took over a decade of development and billions of dollars to take hydrogen fuel cell power from 1.4kW per litre to 3.1kW.

Don’t take my word for it, the data is available:

https://www.toyota-europe.com/download/ ... 564265.pdf

Maybe you got downvoted for parroting your own thing, while wholly ignoring what I said. Apparently not even reading the replies.
Also, still not about hydrogen.

[mzso]

How do they expect 1000HP then, without putting in the energy into the system? The whole system will be less efficient to begin with...
Perhaps for 2 seconds per lap we'll get that power...

The 1000 hp figure seems to be the expected peak output, but they won't be able to sustain that for more than a lap at a time (my guess), and when the K runs out of juice they'll be trundling around with 650hp till they recoup enough. Lowest average power output throughout the race distance in quite some time and the highest weight, will be a riot to watch

I fail to see how they could sustain 1000 hp for a whole lap.

[mzso]

isn't this the aim - that the race speed will be unchanged despite the smaller mean propulsive power available ?

How? Much less energy means much less power.

One obvious benefit I assume will happen is lengthening of braking distances which should likely improve overtaking chances.

Why would that happen? The tires limit the brake distances, those won't change

[vorticism]

How do they expect 1000HP then, without putting in the energy into the system? The whole system will be less efficient to begin with...
Perhaps for 2 seconds per lap we'll get that power...

The 1000 hp figure seems to be the expected peak output, but they won't be able to sustain that for more than a lap at a time (my guess), and when the K runs out of juice they'll be trundling around with 650hp till they recoup enough. Lowest average power output throughout the race distance in quite some time and the highest weight, will be a riot to watch

I fail to see how they could sustain 1000 hp for a whole lap.

Do they currently? We have an idea of peak ICE power output, we know the fuel flow rate, and know that they can't carry more than 105 kg of fuel. We don't know how often they are using peak engine power as it does not correlate to RPM, nor do we know if they ever fuel light nor have an exact idea of how much fuel is used per lap or per session. If they are consistently running below peak output for engine longevity reasons, then perhaps the new fuel flow rate reflects that. 525 hp may supply a greater fraction of the current ICE motive force than we know.

[djos]

MZSO, 160 litres of volume is JUST for a 500kW fuel cell stack, that ignores the ancillary components like the Hydrogen circulating pump, battery (which would need to be larger than a road car due to more time spent accelerating hard) and fuel tanks. It also ignores that race cars use a heck of a lot more fuel than road cars.

The Mirai has about 120 litre fuel tank capacity (5kg of storage) and gets around 500 kms of range. How long would that last in a race car?

But keep ignoring the facts mate, FC tech is not the future of race cars, or passenger cars for that matter.

Wow, getting down voted for posting facts on a technical forum!

For reference, it took over a decade of development and billions of dollars to take hydrogen fuel cell power from 1.4kW per litre to 3.1kW.

Don’t take my word for it, the data is available:

https://www.toyota-europe.com/download/ ... 564265.pdf

Maybe you got downvoted for parroting your own thing, while wholly ignoring what I said. Apparently not even reading the replies.
Also, still not about hydrogen.

The fuel is irrelevant, all fuel cell types have major limitations that preclude them from being used in high end motor racing applications.

https://www.gencellenergy.com/news/comp ... hnologies/