2025/2026 Hybrid Powerunit speculation

[mzso]

I wonder if efficiency could be pushed past 60%, and with what technology.

No, we are thinking of the same thing!
Until they started designing for the 2014 engine regs there was no heed paid to the efficiency (TE) of F1 engines, therefore to build an efficient rotary would be a challenge for the builders!!

What needs to be borne in mind with any upcoming engine regs is that if they want it to be road-relevant they need to push the regs in a direction that leads to the ICE being a part of an electrical generator unit.

No-one's been talking about (much less using) rotary engines though. Even if Liquidpiston and the sort seem intriguing.

[saviour stivala]

‘’Until they started designing for the 2014 engine regs there was ‘no head’ paid to the efficiency (TE) OF F1 engine’’. Me thinks/believe that statement is the biggest contradiction amounting to blasphemy when it comes to F1 engine design or any engine design for that matter. The total energy contained in fuel used and the amount of energy extracted out of its use ‘energy used to perform’ was always/is always at the very top of the design priorities.

[gruntguru]

Under current rules there is 100 kg of fuel and we can assume the heating value is about 45 MJ/kg so there is a maximum of about 4500 MJ of energy available. If we assume a conversion efficiency of 50% and a race duration of 2 hours, the average engine output is 312 kW.

That's not too bad. Though the races are more typically 1.5 hours long.

Thanks. That would make it 416 kW.

[henry]

Under current rules there is 100 kg of fuel and we can assume the heating value is about 45 MJ/kg so there is a maximum of about 4500 MJ of energy available. If we assume a conversion efficiency of 50% and a race duration of 2 hours, the average engine output is 312 kW.

That's not too bad. Though the races are more typically 1.5 hours long.

Thanks. That would make it 416 kW.

I think some account needs to be made for the zero output parts of a lap, braking and coasting in corners. Maybe 15%. This raises the average power to about 490kW.

This reflects how much of a typical lap is conducted at WOT, 600kW+

[NL_Fer]

No, we are thinking of the same thing!
Until they started designing for the 2014 engine regs there was no heed paid to the efficiency (TE) of F1 engines, therefore to build an efficient rotary would be a challenge for the builders!!

What needs to be borne in mind with any upcoming engine regs is that if they want it to be road-relevant they need to push the regs in a direction that leads to the ICE being a part of an electrical generator unit.

No , a series hybrid (ice-generator-electric motor) is only 70% efficient.

That is why all latest generation hybrid have the ICE mechanically linked to the wheels.

[mzso]

I think some account needs to be made for the zero output parts of a lap, braking and coasting in corners. Maybe 15%. This raises the average power to about 490kW.

This reflects how much of a typical lap is conducted at WOT, 600kW+

There's no need for zero output, when talking about series hybrids. A modest buffer would suffice.

No, we are thinking of the same thing!
Until they started designing for the 2014 engine regs there was no heed paid to the efficiency (TE) of F1 engines, therefore to build an efficient rotary would be a challenge for the builders!!

What needs to be borne in mind with any upcoming engine regs is that if they want it to be road-relevant they need to push the regs in a direction that leads to the ICE being a part of an electrical generator unit.

No , a series hybrid (ice-generator-electric motor) is only 70% efficient.

That is why all latest generation hybrid have the ICE mechanically linked to the wheels.

That doesn't seem realistic. The ICE itself can't get to 70%, which can only get worse with the conversions after.

There are barely any hybrids of notability. They're like that because it's easier to just slap on an electric motor. Not because it's more efficient, because it isn't.

[henry]

I think some account needs to be made for the zero output parts of a lap, braking and coasting in corners. Maybe 15%. This raises the average power to about 490kW.

This reflects how much of a typical lap is conducted at WOT, 600kW+

There's no need for zero output, when talking about series hybrids. A modest buffer would suffice.

You are right. @gruntguru’s estimate stands.

Your buffer would need to provide at least the difference between the mean output and peak for the longest straight on the calendar. Say 200kW for 30 seconds, 6MJ. The physical battery pack would need to be bigger to allow for operation in a high efficiency zone. About 10MJ would do, which is not too far from today’s batteries. It may need to be larger depending on how much opportunity there is to charge in the preceding part of the circuit.

[Stu]

‘’Until they started designing for the 2014 engine regs there was ‘no head’ paid to the efficiency (TE) OF F1 engine’’. Me thinks/believe that statement is the biggest contradiction amounting to blasphemy when it comes to F1 engine design or any engine design for that matter. The total energy contained in fuel used and the amount of energy extracted out of its use ‘energy used to perform’ was always/is always at the very top of the design priorities.

When revs were the goal thermal efficiency was appalling... the big gains were in frictional loss reduction and getting them to breathe sufficiently to increase engine speeds.
Now that Thermal Efficiency is the goal the engines perform significantly differently, almost diesel-like in their operation.

At least, that is my understanding.

[saviour stivala]

‘’Until they started designing for the 2014 engine regs there was ‘no head’ paid to the efficiency (TE) OF F1 engine’’. Me thinks/believe that statement is the biggest contradiction amounting to blasphemy when it comes to F1 engine design or any engine design for that matter. The total energy contained in fuel used and the amount of energy extracted out of its use ‘energy used to perform’ was always/is always at the very top of the design priorities.

When revs were the goal thermal efficiency was appalling... the big gains were in frictional loss reduction and getting them to breathe sufficiently to increase engine speeds.
Now that Thermal Efficiency is the goal the engines perform significantly differently, almost diesel-like in their operation.

At least, that is my understanding.

Still. That statement is total contradiction and amount to engine design blasphemy.

[Tommy Cookers]

When revs were the goal thermal efficiency was appalling... the big gains were in frictional loss reduction and getting them to breathe sufficiently to increase engine speeds.
Now that Thermal Efficiency is the goal the engines perform significantly differently, almost diesel-like in their operation.

perhaps people should use the term thermodynamic efficiency ....

thermal efficiency usually means ....
(indicated) thermal efficiency - the ratio of heat liberated in-cylinder to work on-piston ... but confusingly there's ...
... (brake) thermal efficiency - the ratio of heat liberated in-cylinder to work ex-crankshaft

the NA F1 thermal efficiency was conveniently presented by Mercedes as 29% - but as 32 % by Ferrari
'push-to-pass' running ie 'very' rich mixture helped rpm - but other running mandated lower rpm so allowed less richness
durability rules didn't help efficiency eg unnecessarily short stroke increased the combustion chamber heat loss

old engines eg Coventry-Climax or Cosworth would beat this if they had modern anti-friction & anti-heat coatings
and DI of course - DI (Mercedes-Benz) won races in 1954/5 and (Ferrari)1964 but was later banned (until 2014)
the 1950s F1 Ferrari 2.5 litre twin cylinder engine didn't race - and such a cylinder count was later banned
and diesels weren't banned - until 2014

F1 fuel capacity was first formally limited (to 250 litres) in 1978 and eg in 1989 to 195 litres

[NL_Fer]

That doesn't seem realistic. The ICE itself can't get to 70%, which can only get worse with the conversions after.

There are barely any hybrids of notability. They're like that because it's easier to just slap on an electric motor. Not because it's more efficient, because it isn't.

70% crank to wheels, when is passes through an electric generator-charger-battery-motor setup. Compared to over 96% for a mechanical link/gearbox.

[Tommy Cookers]

... 70% crank to wheels, when is passes through an electric generator-charger-battery-motor setup. Compared to over 96% for a mechanical link/gearbox.

much of the ICE-generated energy would go directly into motor action - not through the battery

[gruntguru]

... 70% crank to wheels, when is passes through an electric generator-charger-battery-motor setup. Compared to over 96% for a mechanical link/gearbox.

much of the ICE-generated energy would go directly into motor action - not through the battery

Yes. In which case the transmission efficiency would be well over 90%.

[Stu]

No, we are thinking of the same thing!
Until they started designing for the 2014 engine regs there was no heed paid to the efficiency (TE) of F1 engines, therefore to build an efficient rotary would be a challenge for the builders!!

What needs to be borne in mind with any upcoming engine regs is that if they want it to be road-relevant they need to push the regs in a direction that leads to the ICE being a part of an electrical generator unit.

No , a series hybrid (ice-generator-electric motor) is only 70% efficient.

That is why all latest generation hybrid have the ICE mechanically linked to the wheels.

‘I think’ that they are built that way as most manufacturers seem to building towards ‘plug-in’ hybrids, so the most cost-effective method is to use the electric drive as a bolt-on to the ICE.
About the only company that I can think of that has been using the ICE as a generator is BMW with the i8 & i3, both of which are now discontinued (due to cost) - i3 is now electric only AFAIK.
While the proportion of hybrids on the roads is quite low, the idea of a plug-in charge system is not a bad idea (reasonably cheap to fill the battery), but when 75% plus of all vehicles are electric or hybrid the electrical grid does not have the infrastructure to cope (I’m talking UK). It will also NOT be a cheap fill-up. We know what electrical charges are planned to be in 2030-35 as the owners/builders at the new Hinckley Point power station have been guaranteed a £/kWh for generation (I’m going to check, but I seem to recall £0.90/kWh) that is substantially higher than current charges -500% increase.

[henry]

Monza would be an edge case for series hybrid.

Currently run at about 80% full throttle averaging around 600kW. The ICE in a series hybrid would need to be making 480kW for the whole lap to produce this. Plus a bit more for part throttle work. Doesn’t seem to give give much opportunity for downsizing the ICE.