2025/2026 Hybrid Powerunit speculation

[lio007]

I've recently read an Italian report about Ferrari's material experiments for the new PU.
It stated that they tried a cylinder head made of steel, but couldn't make it work and reverted back to aluminum.
Why is it hard to make to it work and what are the benefits if a PU manufacturer succeed with steel?

current F1 engines have steel pistons as aluminium alloy has insufficient fatigue strength at the temperatures involved
(as they more than SI ever has before release the combustion heat in-cylinder before expansion)

and the engines have structural cut-outs in the head for the separate (CuBe) valve seat rings
steel heads would have no cut-outs - that might make more room for bigger valves/ports ...
or enable some other feature in eg the jet injector system

Thanks! Ok, so for me it doesn't sound to be that big of an advantage using steel.

[diffuser]

I've recently read an Italian report about Ferrari's material experiments for the new PU.
It stated that they tried a cylinder head made of steel, but couldn't make it work and reverted back to aluminum.
Why is it hard to make to it work and what are the benefits if a PU manufacturer succeed with steel?

current F1 engines have steel pistons as aluminium alloy has insufficient fatigue strength at the temperatures involved
(as they more than SI ever has before release the combustion heat in-cylinder before expansion)

and the engines have structural cut-outs in the head for the separate (CuBe) valve seat rings
steel heads would have no cut-outs - that might make more room for bigger valves/ports ...
or enable some other feature in eg the jet injector system

I guess the "can't make steel heads work" is that they can't get the weight down enough?

[wuzak]

I've recently read an Italian report about Ferrari's material experiments for the new PU.
It stated that they tried a cylinder head made of steel, but couldn't make it work and reverted back to aluminum.
Why is it hard to make to it work and what are the benefits if a PU manufacturer succeed with steel?

current F1 engines have steel pistons as aluminium alloy has insufficient fatigue strength at the temperatures involved
(as they more than SI ever has before release the combustion heat in-cylinder before expansion)

and the engines have structural cut-outs in the head for the separate (CuBe) valve seat rings
steel heads would have no cut-outs - that might make more room for bigger valves/ports ...
or enable some other feature in eg the jet injector system

I guess the "can't make steel heads work" is that they can't get the weight down enough?

Or the CoG is too high?

IIRC, Ferrari used a cast steel block in the last of their F1 V12s.

I am not sure how much steel heads would weigh extra, but if t is more than 1-2kg then it suggests the ICE minimum weight could be reduced.

[saviour stivala]

Ferrari haven't used a cast-steel block in their last of the V-12 engine, and never used a cast-steel block. But Ferrari did indeed use a thin-wall lightweight nodular cast-iron V-12 cylinder block in combination with aluminum heads for the F-140 engine family.

[Tommy Cookers]

... IIRC, Ferrari used a cast steel block in the last of their F1 V12s.

I remember a steel gearbox or transmission casing (for an F1 Ferrari c.20 years ago)

with boosted engines we might choose steel to allow cylinder liners integral with heads (losing gasket & deck & studs)
liner strength/stiffness might allow a thinner liner (if steel)

didn't BMW try this 'monobloc' with their V10 ? (in alloy not steel of course)

[diffuser]

current F1 engines have steel pistons as aluminium alloy has insufficient fatigue strength at the temperatures involved
(as they more than SI ever has before release the combustion heat in-cylinder before expansion)

and the engines have structural cut-outs in the head for the separate (CuBe) valve seat rings
steel heads would have no cut-outs - that might make more room for bigger valves/ports ...
or enable some other feature in eg the jet injector system

I guess the "can't make steel heads work" is that they can't get the weight down enough?

Or the CoG is too high?

IIRC, Ferrari used a cast steel block in the last of their F1 V12s.

I am not sure how much steel heads would weigh extra, but if t is more than 1-2kg then it suggests the ICE minimum weight could be reduced.

Think that steel heads are close to 100% heavier. Generally speaking, 8kg for aluminum vs 16kg for steel.

[saviour stivala]

... IIRC, Ferrari used a cast steel block in the last of their F1 V12s.

I remember a steel gearbox or transmission casing (for an F1 Ferrari c.20 years ago)

with boosted engines we might choose steel to allow cylinder liners integral with heads (losing gasket & deck & studs)
liner strength/stiffness might allow a thinner liner (if steel)

didn't BMW try this 'monobloc' with their V10 ? (in alloy not steel of course)

In 1994 John Barnard (technical director of Ferrari) desined a transverse gearbox for the 412T1, the case of which was made up as fabricated steel box, with the sides machined out of 25mm plate, CNC milled down to 1.2mm wall thickness and ribs. That gear case weighed only a little less than the magnesium one it replaced which was a disappointment, so the switch was made to a titanium one which yelded an imediate 40 persent weight reduction. For 1995 this fabricated titanium gear case was bolted to a CFRP bell housing/oiltank. This gearbox was a three bearing arrangment.

[BassVirolla]

current F1 engines have steel pistons as aluminium alloy has insufficient fatigue strength at the temperatures involved
(as they more than SI ever has before release the combustion heat in-cylinder before expansion)

and the engines have structural cut-outs in the head for the separate (CuBe) valve seat rings
steel heads would have no cut-outs - that might make more room for bigger valves/ports ...
or enable some other feature in eg the jet injector system

I guess the "can't make steel heads work" is that they can't get the weight down enough?

Or the CoG is too high?

IIRC, Ferrari used a cast steel block in the last of their F1 V12s.

I am not sure how much steel heads would weigh extra, but if t is more than 1-2kg then it suggests the ICE minimum weight could be reduced.

Or simply what mostly rode manufacturers away from them: Cooling concerns.

Yes, steel heads can withstand much strongee combustion and lead to lesser heat losses, but the lower heat transfer is the same for good combustion efficiency and for bad cooling.

[saviour stivala]

... IIRC, Ferrari used a cast steel block in the last of their F1 V12s.

I remember a steel gearbox or transmission casing (for an F1 Ferrari c.20 years ago)

with boosted engines we might choose steel to allow cylinder liners integral with heads (losing gasket & deck & studs)
liner strength/stiffness might allow a thinner liner (if steel)

didn't BMW try this 'monobloc' with their V10 ? (in alloy not steel of course)

Yes, The formula 1 BMW P85 cylinder head and piston bore (cylinders) was cast as a single casting, this casting used long tie-rods to connect it with the crankcase which was machined from the solid. This formula 1 BMW P85 was never raced. John Judd avioded such long tie-rods in his design of the Yamaha formula 1 V-10 by having the clinder liners screwd into the cylinder heads.

[Mattchu]

You need to clarify if when you use the term "braking", do you account for engine braking or has the brake pedal got to be pressed for it to be considered "braking"?

The energy recovery is performed by the motor generator unit - kinetic (MGU-K) when the driver brakes by applying the brake pedal, not by lifting foot off the throttle. Lifting foot off the throttle engages the engine's natural engine breaking, which is separate effect from the ERS-based energy recovery, though both reduce the car speed.

Ive read many articles on this and nowhere have I seen that regeneration is only allowed/achieved when the brake pedal has been pressed. Can you show me anywhere where it says transfer of energy to the battery is only allowed/occurs when the brake pedal in engaged?

This is a quote from Brembo engineer Max Algeri:

Charging strategies could result in some corners where braking is done only through the electric motor. Disc brakes might remain unused for extended periods, cooling down and creating new challenges for designers. The Brembo engineer explains: “Carbon needs a certain temperature to work optimally. That’s why modifications will be required to allow it to perform like a road brake, ready to operate immediately after 50 kilometers on a highway. This will be a key challenge next year.”

Yes or No: Does the brake pedal have to be pressed (in your opinion) for energy to be sent to the battery? Do you have any proof of this?

[Tommy Cookers]

The energy recovery is performed by the motor generator unit - kinetic (MGU-K) when the driver brakes by applying the brake pedal, not by lifting foot off the throttle. Lifting foot off the throttle engages the engine's natural engine breaking, which is separate effect from the ERS-based energy recovery, though both reduce the car speed.

the driver can only lift his foot off the accelerator pedal - this doesn't have a fixed relationship to the throttle

the ICE doesn't have the traditional engine braking - it has only engine braking due to friction
because there is no throttling of the air being sucked through
using such throttling would greatly reduce the amount of regeneration available to the ERS

the F1 ICE can/will do what our road cars did 40 years ago - be fuel-off accelerator-off throttle-open

[diffuser]

This is a quote from Brembo engineer Max Algeri:

Charging strategies could result in some corners where braking is done only through the electric motor. Disc brakes might remain unused for extended periods, cooling down and creating new challenges for designers. The Brembo engineer explains: “Carbon needs a certain temperature to work optimally. That’s why modifications will be required to allow it to perform like a road brake, ready to operate immediately after 50 kilometers on a highway. This will be a key challenge next year.”

Yes or No: Does the brake pedal have to be pressed (in your opinion) for energy to be sent to the battery? Do you have any proof of this?

IMO, that statement doesn't specify if the driver's foot is on the brake or not in that corner. It doesn't answer the question "does the driver have brake bias 100% to the rear and only be braking hard enough to Engauge the MGU-K and not the actual pads or is there some kind of automated system engaging the ICE braking based on the amount of throttle the driver has applied".