2025/2026 Hybrid Powerunit speculation

[Martin Keene]

Unfortunately, the rules forbid the "hot vee" configuration.

C5.1.5 Engine exhaust gases may only exit the Cylinder Head through outlets outboard of the cylinder bore centre line and not from within the “V” centre.

That "could" still allow the arrangement by placing the exhaust valves in V side of bore centre and routing out vertically across centre line to exit head and above inlet cam location to fulfill that rules demand. The head exit point then being entirely in accord with directive.

Potentially yes. But packaging the ports in the cylinder head would be a nightmare and have appalling flow.

FWIW, I have no idea why they banned hot V, it would be a much better packaging solution for a single turbo engine and is widely used in road cars.

[Farnborough]

Unfortunately, the rules forbid the "hot vee" configuration.

C5.1.5 Engine exhaust gases may only exit the Cylinder Head through outlets outboard of the cylinder bore centre line and not from within the “V” centre.

That "could" still allow the arrangement by placing the exhaust valves in V side of bore centre and routing out vertically across centre line to exit head and above inlet cam location to fulfill that rules demand. The head exit point then being entirely in accord with directive.

Potentially yes. But packaging the ports in the cylinder head would be a nightmare and have appalling flow.

FWIW, I have no idea why they banned hot V, it would be a much better packaging solution for a single turbo engine and is widely used in road cars.

Are you sure of this?

Anyone have knowledge of this one https://www.mcnews.com.au/highly-succes ... l-aynsley/ to demonstrate the principal ..... here on intake side, but vertical port between cam and central spark plug location none the less.
They could exit the head in conformance with rules in being outside centre line of bore by then having a manifold bring it over the top of exhaust cam direct to turbo hot side.

[Tommy Cookers]

... I have no idea why they banned hot V, it would be a much better packaging solution for a single turbo engine and is widely used in road cars.

... Anyone have knowledge of this one https://www.mcnews.com.au/highly-succes ... l-aynsley/ to demonstrate the principal ..... here on intake side, but vertical port between cam and central spark plug location none the less...

isn't F1 packaging solution a compromise against ICE performance ?
(and production hot V firing intervals are different to F1's)
I still imagine F1 (as 1977 Renault F1) is different in left & right runner lengths to synchronise exhaust pulses at turbo

in 1972 I saw (the legendary Chris Vincent) URS win a big race ....
the crossplane inline 4 that Yamaha invented 40 years later

[Farnborough]

... I have no idea why they banned hot V, it would be a much better packaging solution for a single turbo engine and is widely used in road cars.

... Anyone have knowledge of this one https://www.mcnews.com.au/highly-succes ... l-aynsley/ to demonstrate the principal ..... here on intake side, but vertical port between cam and central spark plug location none the less...

isn't F1 packaging solution a compromise against ICE performance ?
(and production hot V firing intervals are different to F1's)
I still imagine F1 (as 1977 Renault F1) is different in left & right runner lengths to synchronise exhaust pulses at turbo

in 1972 I saw (the legendary Chris Vincent) URS win a big race ....
the crossplane inline 4 that Yamaha invented 40 years later

Going on the reduced power output required from ICE for next regulation, do you think ultimately packaging would possibly be raised to higher importance than power possibilities ?

I too saw Mr Vincent at UK circuits with that URS powered outfit when I was a kid. Could wander around paddock etc unimpeded to look at close quarters at them. Fabulous sound too
Recall Horst Owesle at post TT mallory meeting as well, with his URS WC outfit.
Rudi Kurth & Dane Roe too.

Apologies for thread drift.

[wuzak]

Going on the reduced power output required from ICE for next regulation, do you think ultimately packaging would possibly be raised to higher importance than power possibilities ?

I would say that ICE power is more important.

A 10hp drop because of packaging requirements is less significant in an 800hp engine than it is for a 500hp engine.

And also, every hp is important to help with ERS charging.

At part throttle it allows more energy to be recovered.

And it means that when energy is being deployed, less has to come from the ERS to get to the driver's power demand.

[Farnborough]

Going on the reduced power output required from ICE for next regulation, do you think ultimately packaging would possibly be raised to higher importance than power possibilities ?

I would say that ICE power is more important.

A 10hp drop because of packaging requirements is less significant in an 800hp engine than it is for a 500hp engine.

And also, every hp is important to help with ERS charging.

At part throttle it allows more energy to be recovered.

And it means that when energy is being deployed, less has to come from the ERS to get to the driver's power demand.

Isn't this projecting a loss for something that's not tested ? The ICE is effectively limited anyway by regulations, which gives a different scenario than trying g to extract absolute/maximum power from it. Loss is, at this point, an assumption against perceived "conventiinal" design here.

It looks like the whole rules set will favour torque over absolute bhp anyway, with lower revs maximised in importance to fit regeneration profile and reduce frictional loss while generating E store replenishment.

To make clear, I noted Audi and Honda NOT because of any particular "hot vee" experience , but because they can, both of them, produce a completely unique PU with only one chassis to fulfill. There's absolutely zero customer liability to consider.

[saviour stivala]

Due to increased reliance on the new PU energy recovery system, an ''Expanded energy recovery''. The system allows the MGU-K to recover energy not only during braking, but also when the driver lifts off the throttle (Partial throttle) and even during cornering. ''When Andrea Algeri of Brembo said that the 2026 rear brakes might not be used at all in some corners to slow the car down''. The 2026 regulation changes will allow the MGU-K to recover energy during cornering without direct pressure on the hydraulic system via the brake pedal. Instead the system uses a fully decoupled setup with a pedal-operated sensor or actuator to signal a hydraulic pump, which simulates 'pedal feel' and integrates with the MGU-K for regenerative braking during deceleration and cornering. This means the driver still experience 'brake pedal resistance', but the actual braking force and energy recovery are handled by a combination of electric MGU-K and hydraulic system

[michl420]

As I understand this rules, everything will be make most power from fuel inside the cylinder. It is the only difference between the manufactuars.
And about the hot vee. This is also one of this strange (stupid) rules. If they really want the cars lighter they would allowed it. I would imagine it makes the exhaust much shorter (and lighter).
Another question. Is there a reason why they keep the mono turbo?

[wuzak]

Going on the reduced power output required from ICE for next regulation, do you think ultimately packaging would possibly be raised to higher importance than power possibilities ?

I would say that ICE power is more important.

A 10hp drop because of packaging requirements is less significant in an 800hp engine than it is for a 500hp engine.

And also, every hp is important to help with ERS charging.

At part throttle it allows more energy to be recovered.

And it means that when energy is being deployed, less has to come from the ERS to get to the driver's power demand.

Isn't this projecting a loss for something that's not tested ? The ICE is effectively limited anyway by regulations, which gives a different scenario than trying g to extract absolute/maximum power from it. Loss is, at this point, an assumption against perceived "conventiinal" design here.

My point is, if designing the ICE around packaging requirements loses power, then they won't follow that path.

But, you would think that rearranging the exhaust port in the way I think you propose (exhaust valve on the outside of vee, exhaust port between exhaust and intake cams) you would have to change the position of spark plug and fuel injector, potentially reducing efficiency.

It looks like the whole rules set will favour torque over absolute bhp anyway, with lower revs maximised in importance to fit regeneration profile and reduce frictional loss while generating E store replenishment.

The fuel flow regulations will dictate the power and torque curves.

The rules make the maximum torque at low rpm, but that will be much less power for the engine at peak fuel flow (10,500rpm and above).

And it is power that they need for best performance, so they will stay, as much as possible, 10-13,000rpm, much as they do today.

To make clear, I noted Audi and Honda NOT because of any particular "hot vee" experience , but because they can, both of them, produce a completely unique PU with only one chassis to fulfill. There's absolutely zero customer liability to consider.

Mercedes and Ferrari will make the PU to suit themselves.

Their customers will have to deal with what they get.

However, the mounting of the PU to the chassis and to the gearbox are standard across all manufacturers. And the position of the turbo is dictated in the rules, so no great variation there.

[wuzak]

As I understand this rules, everything will be make most power from fuel inside the cylinder. It is the only difference between the manufactuars.

And the more power the ICE makes, the better the ERS can operate.

And about the hot vee. This is also one of this strange (stupid) rules. If they really want the cars lighter they would allowed it. I would imagine it makes the exhaust much shorter (and lighter).

I'm not sure it would make the exhausts lighter.

They may still have to be the same length for the exhaust tuning anyway.

Plus it complicates intake air to the turbo.

Another question. Is there a reason why they keep the mono turbo?

We had some discussion about this in the thread about the current PUs.

It seems that there would be higher efficiency of the turbo.

The size of the turbo may be an attempt to induce some lag, but the large ERS will mitigate that, and they will spend most of the time at engine speeds where lag is not an issue.

[saviour stivala]

For the driver to still experience 'brake pedal resistance', while the actual braking force and energy recovery are being handled by a combination of electric MGU-K and hydraulic system, (A fully decoupled setup), the driver's foot would have to be pressing the brake pedal, if the driver is not pressing the brake pedal, he will not be able to experience 'brake pedal resistance'.

[Farnborough]

There seems to be a prevailing presumption, and therefore projection, that a different design absolutely will not match the existing architecture in "power" as you're labelling it. There's no proof of that forwarded.

Collectively , you appear to be making statements of power as only BHP in ultimate achievement, when it doesn't give enough resolution to examine the topic.

Isn't BHP just a computation of torque (the real power) with rpm as part of the calculation as a gain factor ? My understanding is that BHP gives a work rate "computation" which can have advantage IF running at that elevated position at correct gearing. It simply "punches" more power strokes into each kilometer if run like that.
If the peak torque is aimed at a lower rpm point (and geared accordingly) the ICE covers the same distance with less power pulses, less heat (potentially produced) and les fuel demand. Likely more suitable for a generator type installation. It doesn't demand higher rpm/bhp facility to be effective.

This coming formula seems to have a projected BHP at significantly less than current ICE unit output.

Avoiding elevated rpm should bring efficiency and heat benefit, plus lowered fuel demands to produce that. It doesn't need to chase higher rpm and BHP notional figures to be effective. They are substantially moving toward running a electricity generating set.

To simply dispell it by offering the status quo (current design) fails to examine any design of different layout. That's just stating tbe same thing over and over .... without sensible enquiry about something different.

[Tommy Cookers]

... Likely more suitable for a generator type installation. It doesn't demand higher rpm/bhp facility to be effective....

we have a generator - it's called the MGU-K
it's slaved to the ICE crankshaft
to recover KE effectively it needs to be doing 10500 crankshaft rpm or more

[wuzak]

This coming formula seems to have a projected BHP at significantly less than current ICE unit output.

Fuel flow is going from 100kg/hr (roughly 4,500MJ/h) to 3,000MJ/h. That is, the 2026 fuel flow is approximately 1/3 lower, and power will be reduced by a similar amount.

The number usually quoted is 400kW (536hp).

There seems to be a prevailing presumption, and therefore projection, that a different design absolutely will not match the existing architecture in "power" as you're labelling it. There's no proof of that forwarded.

No proof, just strong suspicion.

There is no proof that alternative valve arrangements will provide packaging benefits either, given that the "hot vee" is forbidden.

Isn't BHP just a computation of torque (the real power) with rpm as part of the calculation as a gain factor ?

Yes, power is prortional to rotational velocity and torque.

My understanding is that BHP gives a work rate "computation" which can have advantage IF running at that elevated position at correct gearing. It simply "punches" more power strokes into each kilometer if run like that.
If the peak torque is aimed at a lower rpm point (and geared accordingly) the ICE covers the same distance with less power pulses, less heat (potentially produced) and les fuel demand.

The peak torque will be at a much lower rpm than peak power. This is, partly, a function of the fuel flow restrictions, with fuel flow ramping up as rpm increases, until its peak at 10,500rpm, after which it is constant.

The torque vs power is an argument that has been going on for years.

At lower rpm, higher torque and lower power, with higher gearing the speeds that can be achieved are lower.

Likely more suitable for a generator type installation. It doesn't demand higher rpm/bhp facility to be effective.

The 2026 rules are not for a "generator type installation".

They are for an ICE with ERS assistance and allow the ICE to operate as a generator in some circumstances, such as part throttle and end of straights.

Higher power from the ICE allows for more generation at part throttle, and less speed loss at the end of straights when the ERS is recovering while the driver is at full throttle.

Avoiding elevated rpm should bring efficiency and heat benefit, plus lowered fuel demands to produce that. It doesn't need to chase higher rpm and BHP notional figures to be effective. They are substantially moving toward running a electricity generating set.

The are not running towards a "electricity generating set".

The ICE remains the most important producer of power.

The ERS is limited by the amount of recovery allowed. And for tracks with lower brake energy recovery, that limit will be lowered.

To simply dispell it by offering the status quo (current design) fails to examine any design of different layout. That's just stating tbe same thing over and over .... without sensible enquiry about something different.

Are you talking about the 2026 rules, or something for the future?

The 2026 regulations have fairly rigid rules around the PU's configuration.

They are already talking about N/A V8s with ERS for future rules cycles. Usually described as "simplified", but for me the complex part of teh 2026 regulations is energy managment, which would surely not go away if they keep the ERS at the same importance, or even slightly lesss impatance.

Weight savings may not be as much as people expect either.

[DenBommer]

This coming formula seems to have a projected BHP at significantly less than current ICE unit output.

Fuel flow is going from 100kg/hr (roughly 4,500MJ/h) to 3,000MJ/h. That is, the 2026 fuel flow is approximately 1/3 lower, and power will be reduced by a similar amount.

The number usually quoted is 400kW (536hp).

There seems to be a prevailing presumption, and therefore projection, that a different design absolutely will not match the existing architecture in "power" as you're labelling it. There's no proof of that forwarded.

No proof, just strong suspicion.

There is no proof that alternative valve arrangements will provide packaging benefits either, given that the "hot vee" is forbidden.

Isn't BHP just a computation of torque (the real power) with rpm as part of the calculation as a gain factor ?

Yes, power is prortional to rotational velocity and torque.

My understanding is that BHP gives a work rate "computation" which can have advantage IF running at that elevated position at correct gearing. It simply "punches" more power strokes into each kilometer if run like that.
If the peak torque is aimed at a lower rpm point (and geared accordingly) the ICE covers the same distance with less power pulses, less heat (potentially produced) and les fuel demand.

The peak torque will be at a much lower rpm than peak power. This is, partly, a function of the fuel flow restrictions, with fuel flow ramping up as rpm increases, until its peak at 10,500rpm, after which it is constant.

The torque vs power is an argument that has been going on for years.

At lower rpm, higher torque and lower power, with higher gearing the speeds that can be achieved are lower.

Likely more suitable for a generator type installation. It doesn't demand higher rpm/bhp facility to be effective.

The 2026 rules are not for a "generator type installation".

They are for an ICE with ERS assistance and allow the ICE to operate as a generator in some circumstances, such as part throttle and end of straights.

Higher power from the ICE allows for more generation at part throttle, and less speed loss at the end of straights when the ERS is recovering while the driver is at full throttle.

Avoiding elevated rpm should bring efficiency and heat benefit, plus lowered fuel demands to produce that. It doesn't need to chase higher rpm and BHP notional figures to be effective. They are substantially moving toward running a electricity generating set.

The are not running towards a "electricity generating set".

The ICE remains the most important producer of power.

The ERS is limited by the amount of recovery allowed. And for tracks with lower brake energy recovery, that limit will be lowered.

To simply dispell it by offering the status quo (current design) fails to examine any design of different layout. That's just stating tbe same thing over and over .... without sensible enquiry about something different.

Are you talking about the 2026 rules, or something for the future?

The 2026 regulations have fairly rigid rules around the PU's configuration.

They are already talking about N/A V8s with ERS for future rules cycles. Usually described as "simplified", but for me the complex part of teh 2026 regulations is energy managment, which would surely not go away if they keep the ERS at the same importance, or even slightly lesss impatance.

Weight savings may not be as much as people expect either.

Do you mean with “weight savings may not be as much as people expect either” that if they go with a NA V8 ICE, they’re not going to save that much weight?