2025/2026 Hybrid Powerunit speculation

[saviour stivala]

''An indicated thermal efficiency of almost 28% is obtainable with gasoline engines having a moderate compression ratio''. Is this quote from Henry Ford time?.

about 100 posters here have trotted out M-B's proclamation that NA F1 (ie till 2013) was 28 or 29% efficient
so about 33% ITE

NA FI TILL 2013? Silly me, and I thought we were talking about the forthcoming 2026 new generation formula one power unit, or at least the ICE combustion efficiency part of it.

[saviour stivala]

Anyhow, up to the end of the NA indirect injected formula one engine and up till when max engine RPM was free for all, concentration in obtaining maximum power was spend trying to keep the engine in one piece at the highest maximum power speed possible, that was the total concentration spend in obtaining maximum power. With the advent of the direct injected turbo power unit, with its restricted mandated fuel flow, developments efforts were concentrated fully on combustion efficiency. now since last year's new power unit amendments and the resultant development freeze, for the rest of the power unit life span, combustion efficiency development was recognized as about the only major item to concentrate development on. The new combustion developments trends were to obtain ever faster combustion time, because the faster the combustion, the reduced time available for heat loss - will result in more power to the pistons and less into cooling and exhaust. The more power produced, the more the efficiency is.

[gruntguru]

. . . developments efforts were concentrated fully on combustion efficiency. . . .

Not "Combustion efficiency" - "Thermal efficiency".
There is a difference, read Tommy's posts - he is correct.

[Venturiation]

Redbull powertrains won’t be considered as new https://www.gazzetta.it/Formula-1/09-02 ... _amp.shtml

[Juzh]

A company that never produced an endothermic engine is somehow not considered a new entrant, meanwhile audi with hundred years experience is. baffling decision.

[godlameroso]

The new power units will have even less thermal efficiency than the current ones. They're capping compression ratio at 16:1, where it is currently 18:1, boost is also capped at 3.8 bar/55 psi. These turbo regulations seem a bit strange to me, they're basically allowing a turbo that can flow enough for 1500 HP, but these engines aren't going to see anywhere near that. A Garrett GTX4709 with an 80mm housing, is roughly what the regulations are specifying for a turbo. Surely the F1 version will cost 20x what an off the shelf one will cost. It's like the regulations are forcing you to make a turbo that's slightly too big for the engine displacement, like they're trying to bring back turbo lag.

[Tommy Cookers]

The new power units will have even less thermal efficiency than the current ones.
They're capping compression ratio at 16:1, where it is currently 18:1, boost is also capped at 3.8 bar/55 psi.

capping may only mean using what they have already been using

Mercedes said the biggest TE improvement came from the turbine recovery
this has now been eliminated - so BTE will be c.45%

[saviour stivala]

FIA F1 2026 power unit technical regulations. 5.5.2 Engine inlet air pressure must be less than 4.8 bar.

[henry]

The new power units will have even less thermal efficiency than the current ones.
They're capping compression ratio at 16:1, where it is currently 18:1, boost is also capped at 3.8 bar/55 psi.

capping may only mean using what they have already been using

Mercedes said the biggest TE improvement came from the turbine recovery
this has now been eliminated - so BTE will be c.45%

So if BTE in self sustain is around 51% that puts MGU-H power at about 75kW. I’ve seen various figures between 50 and 52%.

For a track with 50secs WOT that’s 3.75 MJ that’s available now and won’t be in 2026. They probably get some recovery at part throttle as well so total shortfall will be higher. The higher braking recovery in 2026 will be much less than this.

I would expect this to be particularly relevant to race pace since qualifying pace is more dependant on stored energy. So I think the difference between qualy and race pace is likely to be larger than we have now.

[godlameroso]

FIA F1 2026 power unit technical regulations. 5.5.2 Engine inlet air pressure must be less than 4.8 bar.

4.8A, I read that to mean absolute.

[saviour stivala]

69.61 psi.

[BassVirolla]

FIA F1 2026 power unit technical regulations. 5.5.2 Engine inlet air pressure must be less than 4.8 bar.

4.8A, I read that to mean absolute.

Unless specified in a appendix, I would do with manometric and a good lawyer.

[johnny comelately]

The new power units will have even less thermal efficiency than the current ones. They're capping compression ratio at 16:1, where it is currently 18:1, boost is also capped at 3.8 bar/55 psi. These turbo regulations seem a bit strange to me, they're basically allowing a turbo that can flow enough for 1500 HP, but these engines aren't going to see anywhere near that. A Garrett GTX4709 with an 80mm housing, is roughly what the regulations are specifying for a turbo. Surely the F1 version will cost 20x what an off the shelf one will cost. It's like the regulations are forcing you to make a turbo that's slightly too big for the engine displacement, like they're trying to bring back turbo lag.

If this is the case and being in a competitive environment it puts the ball in court of fuel design. As I have mentioned elsewhere the fuel construct regulations are not as restrictive as thought by the public.

[wuzak]

It's like the regulations are forcing you to make a turbo that's slightly too big for the engine displacement, like they're trying to bring back turbo lag.

I think they have have admitted that, saying that it would make it more difficult for the drivers and more spectacular for the spectators.

I am unconvinced.

My thought is that the MGUK will spend very little time at +350kW, this largely being at the exit of corners where turbo lag might exist. So the driveability will be not much worse than currently, if at all.

As soon as the turbo is on boost the MGUK will ramp down its output, and will probably fall to -100kW 1/2-3/4 of the length of the straights. The drivers will then lift off early to maximise the full 350kW recovery as they head into the braking zone.

9MJ recovered takes ~25s @ 350kW, and not many tracks have 25s of braking, let alone hard braking where the rear axle could recover 350kW.

[wuzak]

FIA F1 2026 power unit technical regulations. 5.5.2 Engine inlet air pressure must be less than 4.8 bar.

4.8A, I read that to mean absolute.

It is.

You did specify 3.8 bar boost in your earlier post, which would be 4.8 bar absolute.