2025/2026 Hybrid Powerunit speculation

[Just_a_fan]

I guess a nice thing about a hot vee is that you have your heat sources at the top of the engine. No need to worry about heat soak from hot exhaust / turbo sat below the engine as in a normal layout. Just provide a route for hot air to exit the engine bay above the engine. Nice and easy. With turbos and exhausts tucked under and around the engine, all of that heat is soaking in to the engine and ancillaries e.g. alternator.

I guess you're moving a bit of mass upwards which isn't ideal, but in a road car at least it won't make a noticeable difference.

[wuzak]

Here’s a few numbers on energy recovery from braking.

Brembo used to produce what they called Brake Circuit Identity Cards. I have 3 from 2014. They have braking duration and average power for each corner. From these we can get the overall energy dissipated per lap and the average braking power for the lap.

Silverstone 10MJ 1200kW
Canada 14.5MJ 1400kW
Austria 15.6MJ 1500kW

The theoretical upper bound of energy recovery is Kpower/Average power x Lap Energy

For K = 120KW
Silverstone 1MJ
Canada 1.2MJ
Austria 1.2MJ

If the K is increased the recovery goes up but not proportionately because the speed below which this power would lock the rear brakes goes up.

A 450kW MGU acting on the rear wheels has a theoretical energy recovery 3.75x higher but would lock the rear axle at 200 KPH, maybe higher and so the energy recovery would be much less.

Of course one could change the car rules to suit with a rearward bias to mass and downforce.

To have that amount of recovery they would, no doubt, have front MGU(s) and a rear mounted MGU.

I think that if 450kW was the MGU power, a system of 3 150kW could be used - 2 on the front axle and one on the rear.

That would help balance the braking front to rear. The ICE could be smaller, maybe a V4 of ~1.0L. This would help save some weight.

[Jolle]

Here’s a few numbers on energy recovery from braking.

Brembo used to produce what they called Brake Circuit Identity Cards. I have 3 from 2014. They have braking duration and average power for each corner. From these we can get the overall energy dissipated per lap and the average braking power for the lap.

Silverstone 10MJ 1200kW
Canada 14.5MJ 1400kW
Austria 15.6MJ 1500kW

The theoretical upper bound of energy recovery is Kpower/Average power x Lap Energy

For K = 120KW
Silverstone 1MJ
Canada 1.2MJ
Austria 1.2MJ

If the K is increased the recovery goes up but not proportionately because the speed below which this power would lock the rear brakes goes up.

A 450kW MGU acting on the rear wheels has a theoretical energy recovery 3.75x higher but would lock the rear axle at 200 KPH, maybe higher and so the energy recovery would be much less.

Of course one could change the car rules to suit with a rearward bias to mass and downforce.

To have that amount of recovery they would, no doubt, have front MGU(s) and a rear mounted MGU.

I think that if 450kW was the MGU power, a system of 3 150kW could be used - 2 on the front axle and one on the rear.

That would help balance the braking front to rear. The ICE could be smaller, maybe a V4 of ~1.0L. This would help save some weight.

With a turbo and fuel flow restrictions, the size of the ICE doesn't really matter. Making it smaller, only makes it more expensive and less reliable because of the smaller area to cool the cylinders.

[J.A.W.]

...The ICE could be smaller, maybe a V4 of ~1.0L. This would help save some weight.

With a turbo and fuel flow restrictions, the size of the ICE doesn't really matter. Making it smaller, only makes it more expensive and less reliable because of the smaller area to cool the cylinders.

How'd you figure that Jolle?

Care to provide a rationale as to why a 2/3rds slice of the current ICE - would suffer any reliability/$
issues with a proportionately calculated coolant/heat-rejection system - at a ^ time/% power output?

[Tommy Cookers]

With a turbo and fuel flow restrictions, the size of the ICE doesn't really matter. Making it smaller, only makes it more expensive and less reliable because of the smaller area to cool the cylinders.

I disagree ....

the smaller engine can be more efficient (assuming the compression ratio can be maintained) because ....
with less displacement (combustion chamber area really) less heat energy needs to be dumped via the coolant
and friction is somewhat less eg at partial power

[Jolle]

...The ICE could be smaller, maybe a V4 of ~1.0L. This would help save some weight.

With a turbo and fuel flow restrictions, the size of the ICE doesn't really matter. Making it smaller, only makes it more expensive and less reliable because of the smaller area to cool the cylinders.

How'd you figure that Jolle?

Care to provide a rationale as to why a 2/3rds slice of the current ICE - would suffer any reliability/$
issues with a proportionately calculated coolant/heat-rejection system - at a ^ time/% power output?

Simple reasoning. The amount of surface area of a 1.0 is less than a 1.6, so at the same power it will be harder too cool, so, it will be less reliable, durable and more expensive.

For the power output, the dominating factor is how much fuel you can burn in a certain time. With the fuel flow restrictions that is set (and the amount of air is set by the boost, not the capacity of the ICE).

If, you keep the 100kg/h and just cut the engine in half (0.8l three in line), the power wouldn't be cut in half. (The efficiency could even go up because of less moving parts and less lean burn, giving it more power). But the same amount of heat would need to be extracted through the cooling from half the block.

The better route would be to keep the 1.6l and lower the fuel flow. This would stress the ICE much less and therefore cheaper and more in line with the ability for other manufactures to enter the sport.

[Jolle]

With a turbo and fuel flow restrictions, the size of the ICE doesn't really matter. Making it smaller, only makes it more expensive and less reliable because of the smaller area to cool the cylinders.

I disagree ....

the smaller engine can be more efficient (assuming the compression ratio can be maintained) because ....
with less displacement (combustion chamber area really) less heat energy needs to be dumped via the coolant
and friction (contact area really) is somewhat less

Yes and no... Yes, it would be more efficient but that only goes so far when you inject twice the amount of fuel (and heat) per second in there (for a 0.8l engine). The smaller lining doesn't become 50% more efficient while the energy injected in the cylinders will increase by that factor.
The whole fuel flow is messing with the normal way of thought.

[Tommy Cookers]

... If, you keep the 100kg/h and just cut the engine in half (0.8l three in line), the power wouldn't be cut in half. (The efficiency could even go up because of less moving parts and less lean burn, giving it more power). But the same amount of heat would need to be extracted through the cooling from half the block. ...

I think ...
only half the amount of heat would need to be extracted by the coolant from the new 'half-block' engine .. cause ...
the potential excess temperature of the hot surface is unchanged (if the fuel rate and the air rate are maintained)
and the heat to be extracted is the product of gas temperature and total area of the hot surface
(cooling hot surface to prevent related damage and related detonation - the cylinder gas isn't cooled throughout)

RETRO ANALOGY
a dam design strength is according to 'water 'depth' only .... ie ...
regardless of whether the water is a 10m deep canal 10m wide - or a 10m deep lake 100000m wide
ie the new engine cooling doesn't know or care whether the cylinders have more gas in them than the original engine
the new gas temperature is the same as the original gas temperature


yes maintaining the fuel rate and the air rate would require doubling the induction pressure .....
which would require a 2 stage compressor (this was an official suggestion) to maintain the required cycle efficiency

going less lean isn't possible - as it will only reduce efficiency

[FW17]

But can they make a turbo engine weigh less than what it does now?

[Just_a_fan]

Simple reasoning. The amount of surface area of a 1.0 is less than a 1.6, so at the same power it will be harder too cool, so, it will be less reliable, durable and more expensive.

Surface area to volume ratio increases as size reduces, however, if you just reduce the number of cylinders, each cylinder has the same surface area for heat transfer in each configuration. Whilst an engine with the same power from a smaller number of cylinders would put out more heat per cylinder, the radiator size can remain the same so the total heat that is removed from the engine to atmosphere is the same. So cooling shouldn't be an issue.

[Jolle]

Simple reasoning. The amount of surface area of a 1.0 is less than a 1.6, so at the same power it will be harder too cool, so, it will be less reliable, durable and more expensive.

Surface area to volume ratio increases as size reduces, however, if you just reduce the number of cylinders, each cylinder has the same surface area for heat transfer in each configuration. Whilst an engine with the same power from a smaller number of cylinders would put out more heat per cylinder, the radiator size can remain the same so the total heat that is removed from the engine to atmosphere is the same. So cooling shouldn't be an issue.

Dissipating the same amount of (heat) energy over half the surface area is a challenge and would make everything a lot hotter inside the engine.

[Just_a_fan]

Simple reasoning. The amount of surface area of a 1.0 is less than a 1.6, so at the same power it will be harder too cool, so, it will be less reliable, durable and more expensive.

Surface area to volume ratio increases as size reduces, however, if you just reduce the number of cylinders, each cylinder has the same surface area for heat transfer in each configuration. Whilst an engine with the same power from a smaller number of cylinders would put out more heat per cylinder, the radiator size can remain the same so the total heat that is removed from the engine to atmosphere is the same. So cooling shouldn't be an issue.

Dissipating the same amount of (heat) energy over half the surface area is a challenge and would make everything a lot hotter inside the engine.

I don't think it would be such an issue. With a good enough water pump to ensure the coolant is circulating correctly, there's no reason why it should be a problem. It'll be important to ensure the temptation to halve the size of the radiators isn't taken. The radiators will need to be as big as now.

[Jolle]

Surface area to volume ratio increases as size reduces, however, if you just reduce the number of cylinders, each cylinder has the same surface area for heat transfer in each configuration. Whilst an engine with the same power from a smaller number of cylinders would put out more heat per cylinder, the radiator size can remain the same so the total heat that is removed from the engine to atmosphere is the same. So cooling shouldn't be an issue.

Dissipating the same amount of (heat) energy over half the surface area is a challenge and would make everything a lot hotter inside the engine.

I don't think it would be such an issue. With a good enough water pump to ensure the coolant is circulating correctly, there's no reason why it should be a problem. It'll be important to ensure the temptation to halve the size of the radiators isn't taken. The radiators will need to be as big as now.

Could be. Anyway… my original point was that with a fuel flow formula, engine capacity doesn’t have the impact some people think it has. Going to a v4 1.0 for instance doesn’t effect output so much. Lowering the fuel flow does (and could be done cheaply with the current engines as base, you just need a smaller compressor for less boost).

[NL_Fer]

Current cars are to long and to heavy. Front recovery and bigger MGK will add more weight, so a lighter ICE would be welcome.

[mzso]

Current cars are to long and to heavy. Front recovery and bigger MGK will add more weight, so a lighter ICE would be welcome.

Adding "cars must not be longer than 4.5m" to the regulations would accomplish length reduction much more simply, and with a lot more certainty.
Teams wouldn't decrease the length of cars, they would just make the them slimmer with a smaller ICE.