2025/2026 Hybrid Powerunit speculation

[Tommy Cookers]

afaik
Cosworth calls this (with PI) mixture preparation time
(the time the charge exists in the port and otherwise before combustion)

btw
unfortunately the handy property called octane exists only in the imagination
octane (number) tests exist ie RON and MON but they dictate rpms below 1000 (not 20000)
(Honda beat the world with c.20000 rpm 1960s motorcycles that ran best on 73 ON - yes they wrote a paper on this)

btw 2
octane number tests work for conventional fuels ie those with latent heats matching the mandated reference fuel's
because the RON and MON tests were so designed (to quantify the detonation resistance of gasolines)
(also mixture strength is potentially a factor - but RON and MON similarly avoid this)
on alcohols RON and MON tests give around 75 (this requires charge heating to cancel their very high latent heats)
claimed alcohol octanes of c.125 are actually Blending Octane Number BON
BON is a detonation predictor (limited to specified low alcohol blending with gasoline)
BON is what might result if RON or MON tests were redesigned for alcohols (which they aren't)

hybrid F1 engines don't work like traditional race engines or road engines
they want the charge to be hot
doesn't 'more compression' work (in some part) by being hotter at times ?

[Zynerji]

afaik
Cosworth calls this notion charge preparation time
(the time the charge exists in the port and otherwise before combustion)

btw
unfortunately the handy property called octane exists only in the imagination
octane (number) tests exist ie RON and MON but they dictate rpms below 1000 (not 20000)
(Honda beat the world with c.20000 rpm 1960s motorcycles that ran best on 73 ON - yes they wrote a paper on this)

btw 2
octane number tests work for conventional fuels ie those with latent heats matching the mandated reference fuel's
because the RON and MON tests were so designed (to quantify the detonation resistance of gasolines)
(also mixture strength is potentially a factor - but RON and MON similarly avoid this)
on alcohols RON and MON tests give around 75 (this requires charge heating to cancel their very high latent heats)
claimed alcohol octanes of c.125 are actually Blending Octane Number BON
BON is a detonation predictor (limited to specified low alcohol blending with gasoline)
BON is what might result if RON or MON tests were redesigned for alcohols (which they aren't)

hybrid F1 engines don't work like traditional race engines or road engines
they want the charge to be hot

Hot enough to delete the intercoolers?

[Hoffman900]

afaik
Cosworth calls this notion charge preparation time
(the time the charge exists in the port and otherwise before combustion)

btw
unfortunately the handy property called octane exists only in the imagination
octane (number) tests exist ie RON and MON but they dictate rpms below 1000 (not 20000)
(Honda beat the world with c.20000 rpm 1960s motorcycles that ran best on 73 ON - yes they wrote a paper on this)

btw 2
octane number tests work for conventional fuels ie those with latent heats matching the mandated reference fuel's
because the RON and MON tests were so designed (to quantify the detonation resistance of gasolines)
(also mixture strength is potentially a factor - but RON and MON similarly avoid this)
on alcohols RON and MON tests give around 75 (this requires charge heating to cancel their very high latent heats)
claimed alcohol octanes of c.125 are actually Blending Octane Number BON
BON is a detonation predictor (limited to specified low alcohol blending with gasoline)
BON is what might result if RON or MON tests were redesigned for alcohols (which they aren't)

hybrid F1 engines don't work like traditional race engines or road engines
they want the charge to be hot

Cosworth does call it “charge preparation time”. Always sounded a bit “trying to sound smart and British” to me, but it’s what I described.


Not sure why the lecture on gasoline rating was necessary, but okay. I know everyone likes to take any opportunity to sound smart here . The point is that the Cosworth T50 goes from 14:1 geometric compression to 15:1 geometric compression, moving from DI to port injection, on the same 99 RON gasoline, and Bruce Wood said this has all to do with charge cooling keeping knock at bay. The current issue of Race Engine Technology has a dossier on it.

We aren’t talking about current engines. They run at or near the rules limited minimum temperature. Fun fact, their manifold temperatures see less than 1% of variance of temperature over one lap (source Ferrari).

[Tommy Cookers]

hybrid F1 engines don't work like traditional race engines or road engines (heat at tdc is good)
they want the charge to be hot

Hot enough to delete the intercoolers?

don't know, don't care
with DI charge cooling is rather independent of fuel vapourisation cooling

[Hoffman900]

hybrid F1 engines don't work like traditional race engines or road engines (heat at tdc is good)
they want the charge to be hot

Hot enough to delete the intercoolers?

don't know, don't care
with DI charge cooling is rather independent of fuel vapourisation cooling

You’re not seeing the big picture

From a paper co-authored with Ferrari (that no one seems to read here because everyone already has the answers)

Next, we investigate the suboptimality entailed by a smaller intercooler choice in
Figure 13. In such a case, to keep the same intake manifold temperature, the compressor
outlet temperature needs to be lowered. As an example we include a constraint to decrease
the maximum outlet temperature of the compressor by 3 % compared to the unconstrained
case, i.e., θlim 6 0.97 · max θunlim . The compressor outlet temperature was modeled using cc
the assumptions presented in Section 2.3 and fitted with the methodology of Appendix C, i.e., θ (s) = M E (s), p (s). To better visualize the transient phenomena during
c θctcim
the gearshifts, thin vertical lines have been inserted at the upshift locations. The battery recharge target and fuel consumption target are the same for both scenarios. It can be noticed at first glance that the intake manifold and turbocharger speed trajectories are different and almost everywhere lower compared to the unconstrained case. This is mainly due to their dependency on the compressor outlet temperature. In addition, the engine air and fuel mass flows, as well as the gearshift strategy, differ markedly to case studies previously analyzed. Since the intake manifold pressure is (indirectly) limited, the gearshifts occur at higher engine speeds to avoid large engine air mass flow deficits after the upshift. Despite the throttle valve being completely opened after the upshifts, the fuel mass flow is limited by the available engine air mass flow and the allowed fuel-to-air ratio range. Consequently, the injected fuel displays a transient behavior induced by the intake manifold inertia. The influence of the gradual increase of both the fuel injection and the air mass flow are visible in the exhaust manifold quantities: The pressure is lower because of a lower total mass flow through the turbine, whilst the temperature is higher due to the larger fuel-to-air ratio. Finally, the lap time loss is roughly 12 ms and arises from the engine power deficits occurring after the upshifts.

[chaoticflounder]

at the base level, intercoolers are removing work (heat) that the system is putting into it via the compressor so they do represent net loss in efficiency

in road cars I know they go a long way to reducing the NOx emissions due to reducing the inlet charge temperature

also, they allow for a denser air charge so you can react more fuel to get more power, but not necessarily more efficiency

What Tommy's saying above is with Direct Injection fuel is introduced at the last possible moment and is not a factor in cooling the charge air like it is for port injection

[AR3-GP]

https://www.formel1.de/news/news/2023-0 ... i-und-audi

[AR3-GP]

Discuss:

https://www.racefans.net/2023/08/16/tea ... its-krack/

Teams will need “drastic steps” on chassis to suit 2026 power units – Krack

Aston Martin team principal Mike Krack says he shares Red Bull counterpart Christian Horner’s concerns over Formula 1’s 2026 power unit regulations.

Red Bull’s Horner has repeatedly expressed worries this year about the power unit regulations set to be introduced in 2026. Although 1.6-litre V6 engines will be retained, the power unit designs will see heavily revised as F1 plans to drop the MGU-H element and greatly increases electrical power as a proportion of overall output.
Horner suggested that the rules risk creating “Frankenstein” cars and could lead to undesirable driving situations where drivers would have to shift down on long straights to maximise power unit performance. Reigning world champion Max Verstappen has also said the current regulations would produce “terrible” cars based on Red Bull’s early simulator analysis.

In an exclusive conversation with RaceFans, Krack was asked whether the 2026 regulations were a concern to him and his response was: “Yes, it is.”

“It is for all of us,” he continued. “I think the engine manufacturers – or the PU manufacturers that we have to call them – together with the FIA, they made this set of regulations believing that the chassis can follow. And then we have seen that we have to take some drastic steps on the chassis regulations to make it work. But it is technically possible.

“That is why I always say let’s work together in the interests of the whole thing to make it work. I’m quite confident that we can find a set of regs that will make it work and that everybody will be happy with.”

Aston Martin will move on from a long-term partnership with Mercedes predating the 1.6L V6 era when the 2026 power unit formula comes into effect as they switch supplier to Honda. Krack says that his team are already involved in heavy discussions with the Japanese manufacturer about the new power units.

“There is a dialogue on all fronts,” he said. “Be it from sporting – how many passes do you need – be it what structure you need in the paddock, do we sit together, do we do separate, these kind of things because they also have long, long lead times.

“But then it’s also about how is the packaging of the engine in a ’26 chassis from what we know so far. So these are these preliminary talks. You discuss basically from sporting, finance, technical, the whole areas, we all have defined partners or business partners. And the collaboration has started there with discussions regularly. We try to see each other here and there.”

Despite Honda infamously struggling during the early years of the hybrid turbo V6 era after they rejoined F1 as a power unit supplier in 2015, Krack says he is “very confident” that Honda will deliver a strong power unit in 2026.

“I’m very confident because from what I see Honda is fantastic, they are real racers,” Krack said. “They push everything and you see, they are giving the world championship engine.

“It is more about being humble, like how can we cope and how can we maintain a high level with them. But there is no prejudice at all, from what I have seen so far I’m very impressed.”

[AR3-GP]

Krack thinks that the changes to the chassis will be drastic, but attainable. I'm guessing he's referring to a considerable drag reduction by some means so that they don't clip 500 meters away from the brake zone.

[FW17]

Will this be lowest ICE power since the cosworth DFV?

[wuzak]

Will this be lowest ICE power since the cosworth DFV?

Yes.

[Dr. Acula]

at the base level, intercoolers are removing work (heat) that the system is putting into it via the compressor so they do represent net loss in efficiency

in road cars I know they go a long way to reducing the NOx emissions due to reducing the inlet charge temperature

also, they allow for a denser air charge so you can react more fuel to get more power, but not necessarily more efficiency

What Tommy's saying above is with Direct Injection fuel is introduced at the last possible moment and is not a factor in cooling the charge air like it is for port injection

Well, it really isn't that simple.
Let us start and just look at the system before the air enters the cylinder. Yes technically an intercooler removes energy from the system, but the question is how much oxygen you need. By removing heat, you get more oxygen per volume at the same pressure. Or with other words, an intercooler allows you to run with lower boost pressure to get the same amount of oxygen into the cylinder. More boostpressure means more work for the turbo which means even more heat and so on. So overall, an intercooler makes the charge cycle more efficient. The whole point of any charge system is to get more oxygen into the cylinder. You don't need more pressure, that's just an unavoidable side effect.

It really doesn't matter if you have port- or direct injection. The evaporative cooling effect happens all the same. Direct injection can't beat physics and liquids don't burn.

But overall, it really is a question of how high the thermal limits are set. If you don't remove the heat of the compressed air before it reaches the cylinder, the heat will simply end up somewhere else. Which means higher cylinder wall, piston crown, exhaust valve and so on temperature. If all these components can easely deal with that, sure run without an intercooler. But in most cases, you will run into thermal problems somewhere.

[Zynerji]

Banks did a video on one of his turbo-diesels and the breakdown of where the 1000hp came from was interesting, as he showed the intercooler adding over 250hp and the turbo just over 300hp.

It blew my mind how much an intercooler adds to the power of a system. Especially compared to a turbocharger!

[FW17]

Will this be lowest ICE power since the cosworth DFV?

Yes.

So overall is this going to be somewhere near to the 919 Evo or less powerful?

[Tommy Cookers]

Let us start and just look at the system before the air enters the cylinder. Yes technically an intercooler removes energy from the system, but the question is how much oxygen you need. By removing heat, you get more oxygen per volume at the same pressure. Or with other words, an intercooler allows you to run with lower boost pressure to get the same amount of oxygen into the cylinder. More boostpressure means more work for the turbo which means even more heat and so on. So overall, an intercooler makes the charge cycle more efficient. The whole point of any charge system is to get more oxygen into the cylinder. You don't need more pressure, that's just an unavoidable side effect.
It really doesn't matter if you have port- or direct injection. The evaporative cooling effect happens all the same. Direct injection can't beat physics and liquids don't burn.
But overall, it really is a question of how high the thermal limits are set. If you don't remove the heat of the compressed air before it reaches the cylinder, the heat will simply end up somewhere else. Which means higher cylinder wall, piston crown, exhaust valve and so on temperature. If all these components can easely deal with that, sure run without an intercooler. But in most cases, you will run into thermal problems somewhere.

the above has little to do with F1 engines since 2014 - the question today isn't 'how much oxygen you need'
these engines having unprecedented capabilities ie .....
actively managed and optimised combustion heat release 'by-the-microsecond' (eg 5 injections during power stroke)
extremely low AFR ie much surplus air for heat dilution ....
more-complete-expansion along Miller cycle lines ....
SACI ....
(and for 2026 much greater ratio of fuel latent heat to combustion heat and lower MAP than currently)

in-cylinder compression work is anyway very much higher than supercharger work
and we no longer need to minimise that work in pursuit of MGU-H recovery