2025/2026 Hybrid Powerunit speculation

[gruntguru]

Nobody mentioned maximum power to the wheels. Thermal efficiency is calculated by dividing power out by power in (fuel flow) with no change in stored energy within the system.

[gruntguru]

Wasn't the reported 50% efficiency of the current engines achieved when the compressor side was run as a supercharger with MGU-H and the turbine side running with the wastegates open?

I've always thought the above 50% figures were the ICE + MGU-H recovery.

Sorry, I have no knowledge of that claim or its validity.

[mzso]

I would think that the peak efficiency was achieved with the MGUH and MGUK working in a turbo-compound mode.

That is, the recovered energy from the MGUH directly drives the MGUK and no energy is transferred to or from the battery.

When the MGUH is driving the turbo it is taking energy from the battery. Therefore using more energy than can be extracted from the fuel.

That is a good mode, but that is not the maximum power to the wheels.

Assuming 1000hp in total in qualifying
160 hp comes from MGUK
840 hp comes from ICE with battery powering the MGUH to drive the compressor and turbines running with waste gates open
840 hp is 620 kw which is 50% of available energy from 100 kg of fuel

Okay, but the discussion was about efficiency.

[wuzak]

I would think that the peak efficiency was achieved with the MGUH and MGUK working in a turbo-compound mode.

That is, the recovered energy from the MGUH directly drives the MGUK and no energy is transferred to or from the battery.

When the MGUH is driving the turbo it is taking energy from the battery. Therefore using more energy than can be extracted from the fuel.

That is a good mode, but that is not the maximum power to the wheels.

Assuming 1000hp in total in qualifying
160 hp comes from MGUK
840 hp comes from ICE with battery powering the MGUH to drive the compressor and turbines running with waste gates open
840 hp is 620 kw which is 50% of available energy from 100 kg of fuel

Fuel power is 1,250kW at 100kg/h, assuming 45MJ/kg fuel.

840hp is 626kW. Which gives 50.1% thermal efficiency.

If we say the ICE gives 600kW (804hp) and that the MGUH can recover 40kW and send it to the MGUK then the total ICE output is 640kW, which is an efficiency of 51.2%.

If the MGUH recovers 60kW, the efficiency jumps to 52.8%.

The total power of the PU is less because the MGUK output is limited. In both turbo compounding modes the total power available is the ICE power (600kW) plus the maximum MGUK output (120kW), which is 720kW.

1,000hp is ~750kW.

[saviour stivala]

Running with wastegates closed is considered to be the most efficient solution for normal racing conditions. however, in qualifying conditions and during a race were defending and or overtaking are encountered, running the engine with wastegate open the power of the ICE is vastly boosted.

[wuzak]

Without the MGUH spooling the turbo in maximum power mode, it would appear that the 2026 PUs should have the same performance in the race as they do qualifying.

[saviour stivala]

Without the MGUH spooling the turbo in maximum power mode, it would appear that the 2026 PUs should have the same performance in the race as they do qualifying.

Obvious when the rules have eliminated the 'ICE free-load-mode'.

[wuzak]

Without the MGUH spooling the turbo in maximum power mode, it would appear that the 2026 PUs should have the same performance in the race as they do qualifying.

Obvious when the rules have eliminated the 'ICE free-load-mode'.

They will be able to use more energy on qualifying laps as they don't have to balance usage with recovery.

[saviour stivala]

Without the MGUH spooling the turbo in maximum power mode, it would appear that the 2026 PUs should have the same performance in the race as they do qualifying.

Obvious when the rules have eliminated the 'ICE free-load-mode'.

They will be able to use more energy on qualifying laps as they don't have to balance usage with recovery.

Battery power, yes they will, the same as they do now, in qualifying mode over a lap battery power and fuel burn is no problem.

[wuzak]

Under the latest version of the regulations posted by the FIA there will be 8 forward gears.

I had expected them to reduce the number of gears, perhaps to 6.

Fewer gears would save some weight, but would also means that the engines would have to run to higher rpm in order to stay in the peak power range.

[Tommy Cookers]

Under the latest version of the regulations posted by the FIA there will be 8 forward gears.
I had expected them to reduce the number of gears, perhaps to 6.
Fewer gears would save some weight, but would also means that the engines would have to run to higher rpm in order to stay in the peak power range.

8 speeds is even more helpful to the electric side than 6 speeds would be

[michl420]

Without the mgu-h, will they go away from the split turbo? Is it even allowed to change this?

[Holm86]

Without the mgu-h, will they go away from the split turbo? Is it even allowed to change this?

If i remember correctly the split turbo had been banned for 2026, FIA hates innovation

[Vappy]

Without the mgu-h, will they go away from the split turbo? Is it even allowed to change this?

If i remember correctly the split turbo had been banned for 2026, FIA hates innovation

Wait.. what? It's banned?? Is that an effort to cut cost due to stabilising a very high RPM part across the distance of the V vs hot/cold being right next to one another?

[Holm86]

Without the mgu-h, will they go away from the split turbo? Is it even allowed to change this?

If i remember correctly the split turbo had been banned for 2026, FIA hates innovation

Wait.. what? It's banned?? Is that an effort to cut cost due to stabilising a very high RPM part across the distance of the V vs hot/cold being right next to one another?

This is the regulation that basically bans split turbochargers:

Referring to Drawing 4 of Appendix C3, the turbocharger compressor and turbine must satisfy the
following dimensional constraints. Only compressor and turbine wheels approved by the FIA
Technical Department will be allowed:

a. The compressor exducer blade outer diameter (A) must lie between 100mm and 110mm. For
the avoidance of doubt, no part of the compressor wheel (including blades, hub and any
blade/hub fillet radius) can have a diameter more than the upper limit and the maximum
diameter of the compressor wheel (including blades, hub and any blade/hub fillet radius)
cannot have a diameter smaller than the lower limit.
b. The compressor axial distance from the outside diameter of the inducer blade edge to rear
plane of exducer, at its outer diameter (B) must lie between 30mm and 35mm
c.
The turbine inducer blade outer diameter (C) must lie between 90mm and 100mm. For the
avoidance of doubt, no part of the turbine wheel (including blades, hub and any blade/hub fillet
radius) can have a diameter more than the upper limit and the maximum diameter of the
turbine wheel (including blades, hub and any blade/hub fillet radius) cannot have a diameter
smaller than the lower limit.
d. The turbine axial distance from the outside diameter of the exducer blade edge to forward
plane of inducer, at its outer diameter (D) must lie between 35mm and 40mm
e.
The maximum distance between the rear of the compressor exducer and the front of the
turbine inducer (E) will be 175mm

https://www.fia.com/sites/default/files ... -12-11.pdf