2025/2026 Hybrid Powerunit speculation

[Hoffman900]

Utilizing only a portion of a cylinder's displacement would be incomplete filling in terms of displacement utilized, via valve timing, and regardless of boost pressure or the absence of it (Atkinson). That's where the advantageous asymmetry arises from--the expansion ratio being greater than the compression ratio.

The advantage is the over expansion allowing for a cooler charge at time of ignition, allowing for greater knock control, thus allowing for more cylinder pressure for a given fuel (which the rules limit).

This allows for more boost. Since the engines are fuel limited (flow and chemistry - per rules), they’re on the edge of knock the entire time.

In a fuel limited format, you work really hard to prevent knock. It’s quicker to run a constant boost / varying lamba than it is a varying boost / constant lamba. There is a really good dossier on the Audi DTM engine in Race Engine Technology from some years ago that explains this better.

[Rikhart]

Great video by Yellistener, I just can't wrap my head around how weird and artificial this will feel.

[vorticism]

Utilizing only a portion of a cylinder's displacement would be incomplete filling in terms of displacement utilized, via valve timing, and regardless of boost pressure or the absence of it (Atkinson). That's where the advantageous asymmetry arises from--the expansion ratio being greater than the compression ratio.

The advantage is the over expansion allowing for a cooler charge at time of ignition, allowing for greater knock control, thus allowing for more cylinder pressure for a given fuel (which the rules limit).

This allows for more boost. Since the engines are fuel limited (flow and chemistry - per rules), they’re on the edge of knock the entire time.

In a fuel limited format, you work really hard to prevent knock. It’s quicker to run a constant boost / varying lamba than it is a varying boost / constant lamba. There is a really good dossier on the Audi DTM engine in Race Engine Technology from some years ago that explains this better.

Not what I was getting at. I made a general statement about what defines the Miller cycle. Check the preceding posts.

[peewon]

Great video by Yellistener, I just can't wrap my head around how weird and artificial this will feel.

Absolutely bizarre that this formula was allowed to continue unchanged despite early warnings from multiple teams.

[FittingMechanics]

I'm not convinced it will look like that. Looking at speeds in Bahrain you don't see this slowdown at the end of straights. It may be more noticeable at less energy rich tracks.

[Rikhart]

I'm not convinced it will look like that. Looking at speeds in Bahrain you don't see this slowdown at the end of straights. It may be more noticeable at less energy rich tracks.

Apparently this track is not representative because it's great to harvest energy, see this post:

viewtopic.php?p=1323148#p1323148

[AR3-GP]

Would teams use the MGU-K to suppress the crankshaft torque for milliseconds during the gear change? Could that extract any meaningful amount of energy over a lap? Probably not worth much.

[Tommy Cookers]

on every upshift the K dumps a good fraction of the PU's rotational KE to the ERS (and fuel-burn in 200 msec window)

though it uses some electricity to help the PU rpm match the needs for down-shifting, then resumes regen

[BorisTheBlade]

Would teams use the MGU-K to suppress the crankshaft torque for milliseconds during the gear change? Could that extract any meaningful amount of energy over a lap? Probably not worth much.

I honestly have no clue, how much accumulated time is spent during shifts - is it in the range of 1-2s per lap? With a technical best-case that could be worth roughly 700 KWs or 8% of the max budget per lap - not nothing in F1.
If (big if) one Team had such an advantage, it could be significant for race pace on an energy starved track.
But as Bahrain is not such a track and as I have faith in at least some of the others to not have failed miserably with "ordinary" recovery, they might just be on different programmes.
Otherwise, Melbourne could be a blood bath come raceday.

[johnnycesup]

F1 cars have seamless shift gearboxes, and pretty fast ones at that IIRC. I don't think trying to harvest in upshifts is worth the trouble to be honest.

[Tommy Cookers]

F1 cars have seamless shift gearboxes, and pretty fast ones at that IIRC. I don't think trying to harvest in upshifts is worth the trouble to be honest.

it's free electricity
it's a doddle

the 'seamlessness' of an up-shift done any other way is an illusion
(energy flow rate is cut pre-shift & dumped in the transmission string - worse, PU inertia is far greater than in older cars)

[mzso]

But as Bahrain is not such a track and as I have faith in at least some of the others to not have failed miserably with "ordinary" recovery, they might just be on different programmes.
Otherwise, Melbourne could be a blood bath come raceday.

Others compared to who?

[AR3-GP]

I have no idea if there's any connection to Red Bull. I was just curious if it's something that a team would do. IIf you were going to cut the fuel, then you should harvest for a split second instead. I also wonder how well the FIA sensors detect short burst of current and/or torque spikes. There could be recoverable energy hidden in the "noise".

[chipengineer]

I have no idea if there's any connection to Red Bull. I was just curious if it's something that a team would do. IIf you were going to cut the fuel, then you should harvest for a split second instead. I also wonder how well the FIA sensors detect short burst of current and/or torque spikes. There could be recoverable energy hidden in the "noise".

Maybe gearbox weight could be reduced if shifts were not so fast. Then this harvesting could recover any energy lost to slower shifts.

[gearboxtrouble]

I have no idea if there's any connection to Red Bull. I was just curious if it's something that a team would do. IIf you were going to cut the fuel, then you should harvest for a split second instead. I also wonder how well the FIA sensors detect short burst of current and/or torque spikes. There could be recoverable energy hidden in the "noise".

To take that one step further there might be a harvesting benefit it trying to maximize the rotational inertia in the ICE. This might allow some of that to be harvested after throttle cutoff and the disadvantage of a "lazy" higher rotational mass engine that takes longer to rev could be offset by torque fill from the MGUK.