2025/2026 Hybrid Powerunit speculation

[henry]

What do we make of this rule?

5.14.5 The driver maximum torque demand may only be reduced at a maximum rate of 100kW in any 1s period and the power reduction will be limited to a maximum of 450kW.


How does that work with the generation strategy theories?

Seems to suggest that max regen power, ICE driving the K, should be 100kW and to get to that at the end of straight will take 3.5 seconds. I’m guessing for safety to prevent very high decelerations under software control.

Suggests most regen under part throttle and braking.

100kw / 1s is:

[(force x distance) /time] / time

It think it's a rate of application of braking force, to prevent sudden braking of the car when switching from full power to full regen (without applying brakes, i.e. lift & coast).

Edit: Sorry, Henry. I've just read now your response.

I think you’re right about minimising sudden torque, and hence speed, reduction. The situation I was contemplating is not lift and coast but software initiated regen. The driver continues to demand max torque but the system gives much less than it was previously. The max current change is 240kw, from +120 to -120.

Lift and coast needs the driver to reduce torque demand and so potentially reduce power by up to 700kw. If the 5.14.5 applies they might not be able to use lift and coast if they’re at software decided max power. Currently the max reduction for lift and coast is 700kW.

[johnny comelately]

Showing my naivety, why does this rule exist?

[BassVirolla]

Seems to suggest that max regen power, ICE driving the K, should be 100kW and to get to that at the end of straight will take 3.5 seconds. I’m guessing for safety to prevent very high decelerations under software control.

Suggests most regen under part throttle and braking.

100kw / 1s is:

[(force x distance) /time] / time

It think it's a rate of application of braking force, to prevent sudden braking of the car when switching from full power to full regen (without applying brakes, i.e. lift & coast).

Edit: Sorry, Henry. I've just read now your response.

I think you’re right about minimising sudden torque, and hence speed, reduction. The situation I was contemplating is not lift and coast but software initiated regen. The driver continues to demand max torque but the system gives much less than it was previously. The max current change is 240kw, from +120 to -120.

Lift and coast needs the driver to reduce torque demand and so potentially reduce power by up to 700kw. If the 5.14.5 applies they might not be able to use lift and coast if they’re at software decided max power. Currently the max reduction for lift and coast is 700kW.

Yes, probably you are right: Full ICE power minus full K recovery. Makes sense.

[wuzak]

Could it be for the start of a straight?

Car exits the corner and the driver demands full power, which means that, at some point, the power given is 350kW MGUK + 400kW ICE.

But with only 4MJ of storage, 350kW can only last for so long.

Is this rule to stop cars accelerating with 750kW suddenly only having 400kW?

A straight like Spa's La Source to Les Combes is ~23s. 4MJ will allow 5s of MGUK @ 350kW and 15s of MGUK @ 150kW. This rule could mean that the transition must take a minimum of 2s.

[Zynerji]

Could it be for the start of a straight?

Car exits the corner and the driver demands full power, which means that, at some point, the power given is 350kW MGUK + 400kW ICE.

But with only 4MJ of storage, 350kW can only last for so long.

Is this rule to stop cars accelerating with 750kW suddenly only having 400kW?

A straight like Spa's La Source to Les Combes is ~23s. 4MJ will allow 5s of MGUK @ 350kW and 15s of MGUK @ 150kW. This rule could mean that the transition must take a minimum of 2s.

Not terrible with small, 500kg cars.

But these limousines?

[mzso]

Could it be for the start of a straight?

Car exits the corner and the driver demands full power, which means that, at some point, the power given is 350kW MGUK + 400kW ICE.

But with only 4MJ of storage, 350kW can only last for so long.

Is this rule to stop cars accelerating with 750kW suddenly only having 400kW?

A straight like Spa's La Source to Les Combes is ~23s. 4MJ will allow 5s of MGUK @ 350kW and 15s of MGUK @ 150kW. This rule could mean that the transition must take a minimum of 2s.

This rule is wacky. So the maximum reduction can only be 450kW. Meaning there can't be any regen if the straight is started with full power with the K active.

[wuzak]

Could it be for the start of a straight?

Car exits the corner and the driver demands full power, which means that, at some point, the power given is 350kW MGUK + 400kW ICE.

But with only 4MJ of storage, 350kW can only last for so long.

Is this rule to stop cars accelerating with 750kW suddenly only having 400kW?

A straight like Spa's La Source to Les Combes is ~23s. 4MJ will allow 5s of MGUK @ 350kW and 15s of MGUK @ 150kW. This rule could mean that the transition must take a minimum of 2s.

This rule is wacky. So the maximum reduction can only be 450kW. Meaning there can't be any regen if the straight is started with full power with the K active.

Does it mean that the maximum regen when the driver has his foot on the throttle is 100kW?

Start the straight with 400kW ICE and 350kW MGUK, 750kW total, which can be reduced by a maximum of 450kW, which gives a minimum power of 300kW, meaning only 100kW of generation is allowed.

That, of course, changes when the driver brakes, as there is no longer any torque demand.

[wuzak]

Let's assume 15s of braking heavy enough to recover @ 350kW.

That gives 5.25MJ, leaving 3.75MJ that is allowed to be recovered.

3.75MJ @ 100kW = 37.5s. That's about 40-50% of most laps in F1 where they would be flat chat down the straights with 300kw/400hp!

[Big Tea]

Guys, every way I read regen when the driver has throttle on seems to suggest reducing the power delivered to the tyres, -to whit, traction control. Is this correct or am I missing out on something besides the 'you can not use traction control' rule?

[Tommy Cookers]

doesn't the FIA say that ? .....

1 traction control is only traction control if the wheel rpm is measured
2 accelerator position/PU torque map rate-limits (accelerator-fixed) PU torque eg reduction with crank rpm increase

[Big Tea]

doesn't the FIA say that ? .....

1 traction control is only traction control if the wheel rpm is measured
2 accelerator position/PU torque map rate-limits (accelerator-fixed) PU torque reduction with crankshaft rpm

But how do they measure demand? does it include switching generation in and out?

Processor sees that the max power can not be used at wheels, so does it increase the load on the generator accordingly?

It is still 'required' or requested by the peddle

[Tommy Cookers]

doesn't the FIA say that ? .....
1 traction control is only traction control if the wheel rpm is measured
2 accelerator position/PU torque map rate-limits (accelerator-fixed) PU torque reduction with crankshaft rpm

Processor sees that the max power can not be used at wheels, so does it increase the load on the generator accordingly?

demand is accelerator position
PU output is PU output - for all combinations of ICE torque and MGU-K torque
F1 already uses different combinations of ICE torque and MGU-K torque at different times - so nothing to see here

in reality the K runs synchronously so likely .....
will at times algebraically-reduce its torque quicker than the FIA map seems to allow
yes a generating torque can at times increase quicker than the FIA map seems to allow
the processor or whatever will ignore this (because this isn't a closed-loop system)

presumably the new 350 kW F1 MGU(K) will behave rather like the 350 kW FE MGU(K)

[wuzak]

Guys, every way I read regen when the driver has throttle on seems to suggest reducing the power delivered to the tyres, -to whit, traction control. Is this correct or am I missing out on something besides the 'you can not use traction control' rule?

Would the maximum 100kW reduction in 1s be too slow for effective traction control?

It would be interesting to see if it is interpreted as a linear reduction (ie 0.25s = 25kW reduction, 0.50s = 50kW, 0.75s = 75kW) or if they are able to do things creatively - drop 99kW as fast as the motor will allow and take the remainder of the second to drop the last kW.

[wuzak]

Indycar is also going hybrid in 2026.

Engine is going from 2.2L V6 to 2.4L V6, and from about 600-650hp to 800hp + 100hp MGUK, with development it is expected to reach 1,000hp combined.

F1 is going from ~850hp + 160hp to ~530hp + 470hp.

Indycar is going to be the more powerful package overall, with the peak power of F1 being more, but the availability of that is questionable.

[Zynerji]

Is that rules about decel a rolling second?

Don't they "pulse" the K at like 40Hz, where it always has a bit of regen by doing m,m,m,m,m,m,m,r,m,m,m,m,m,m,m,m,r type cycling?