2025/2026 Hybrid Powerunit speculation

[Holm86]

(The engines will have a significant positive pressure differential (MAP>EAP) under the new rules.)

why ?

He probably means the turbine side of the turbo will be smaller than currently, to aid the responsiveness of the Turbo, now the MGU-H isn't there anymore. This will increase exhaust back pressure. I'm wondering how much of that they can negate with the waste gate.

Could it perhaps even be beneficial to run the engine at higher RPM? As the airflow through the engine should be constant above 10.500 rpm, it means every rpm above that, you need less boost, so perhaps running at higher RPM with the waste gate fully open would give better performance due to less exhaust back pressure??

[gruntguru]

(The engines will have a significant positive pressure differential (MAP>EAP) under the new rules.)

why ?

Reduced backpressure = better ICE efficiency and power. There is no longer any advantage in maximising turbine output. They will size the turbine to generate enough power to drive the compressor with the lowest possible backpressure. This also means targeting minimum wastegate flow.

[wuzak]

He probably means the turbine side of the turbo will be smaller than currently, to aid the responsiveness of the Turbo, now the MGU-H isn't there anymore. This will increase exhaust back pressure. I'm wondering how much of that they can negate with the waste gate.

They may well be smaller than now, but they won't be small.

Some dimensions for the turbo are controlled, such as one of the dimensions for the turbine and compressor wheel diameters.

[noname]

(The engines will have a significant positive pressure differential (MAP>EAP) under the new rules.)

why ?

He probably means the turbine side of the turbo will be smaller than currently, to aid the responsiveness of the Turbo, now the MGU-H isn't there anymore. This will increase exhaust back pressure. I'm wondering how much of that they can negate with the waste gate.

Could it perhaps even be beneficial to run the engine at higher RPM? As the airflow through the engine should be constant above 10.500 rpm, it means every rpm above that, you need less boost, so perhaps running at higher RPM with the waste gate fully open would give better performance due to less exhaust back pressure??

Turbine is sized by the mass flow it has to deal with. Smaller turbine will have reduced flow capacity, and this may negatively impact power generated by ICE. It would just choke the engine.

It could be smaller if they would go for lower Lambda.

To improve transient response without hurting flow capacity you can i.e. use mixed flow turbine wheel. This approach was already used in some F1 turbos of the current era, could be there woule be more radical solutions.

[Big Tea]

Some while back, due to 'emission laws' the self-shifting automatics suffered due to a little device that held the 'throttle' open fractionally not allowing the revs to drop quickly. Would something similar be useful with the new engines? hold the revs up but open wastegates and cut fuel? Could RPM stay high(er) and power output be controlled by fuel feed?

Or is this famous 'turbo lag' a thing of the media? Things have advanced much from the old days of turbo

[noname]

Some while back, due to 'emission laws' the self-shifting automatics suffered due to a little device that held the 'throttle' open fractionally not allowing the revs to drop quickly. Would something similar be useful with the new engines? hold the revs up but open wastegates and cut fuel? Could RPM stay high(er) and power output be controlled by fuel feed?

Or is this famous 'turbo lag' a thing of the media? Things have advanced much from the old days of turbo

When development of todays' POs started teams were evaluating turbo lag in simulators. They found out their test drivers were able to adapt to even the most ridiculous amount of lag within few laps.

[djos]

Senna was famous for being able to keep the turbo spooled up with his unique style.

[Tommy Cookers]

(The engines will have a significant positive pressure differential (MAP>EAP) under the new rules.)

Could it perhaps even be beneficial to run the engine at higher RPM? As the airflow through the engine should be constant above 10.500 rpm, it means every rpm above that, you need less boost, so perhaps running at higher RPM with the waste gate fully open would give better performance due to less exhaust back pressure??

a given positive pressure differential does less with Miller cycle - does F1 currently have Miller cycle ?

the fuel energy rate will be c.75% of that current
boost can be much lower even sticking to 10500 rpm (15000 would be close to NA conditions)
but Miller cycle needs more boost than non-Miller - though not more compressor power ?

[NL_Fer]

Some while back, due to 'emission laws' the self-shifting automatics suffered due to a little device that held the 'throttle' open fractionally not allowing the revs to drop quickly. Would something similar be useful with the new engines? hold the revs up but open wastegates and cut fuel? Could RPM stay high(er) and power output be controlled by fuel feed?

Or is this famous 'turbo lag' a thing of the media? Things have advanced much from the old days of turbo

I doubt the even close the throttle on upshift, just retard timing for a few ignitions will give a few ms of reduced torque output, but keep the exhaust flowing. The reduced torque is enough to shift up.

[gruntguru]

Some while back, due to 'emission laws' the self-shifting automatics suffered due to a little device that held the 'throttle' open fractionally not allowing the revs to drop quickly. Would something similar be useful with the new engines? hold the revs up but open wastegates and cut fuel? Could RPM stay high(er) and power output be controlled by fuel feed?

Or is this famous 'turbo lag' a thing of the media? Things have advanced much from the old days of turbo

I doubt the even close the throttle on upshift, just retard timing for a few ignitions will give a few ms of reduced torque output, but keep the exhaust flowing. The reduced torque is enough to shift up.

That would waste fuel.

[NL_Fer]

Some while back, due to 'emission laws' the self-shifting automatics suffered due to a little device that held the 'throttle' open fractionally not allowing the revs to drop quickly. Would something similar be useful with the new engines? hold the revs up but open wastegates and cut fuel? Could RPM stay high(er) and power output be controlled by fuel feed?

Or is this famous 'turbo lag' a thing of the media? Things have advanced much from the old days of turbo

I doubt the even close the throttle on upshift, just retard timing for a few ignitions will give a few ms of reduced torque output, but keep the exhaust flowing. The reduced torque is enough to shift up.

That would waste fuel.

Than why not skip a few injections or run on 3-4 cilinders for a few rotations? Everything is better than closing the throttle I think.

[Zynerji]

I doubt the even close the throttle on upshift, just retard timing for a few ignitions will give a few ms of reduced torque output, but keep the exhaust flowing. The reduced torque is enough to shift up.

That would waste fuel.

Than why not skip a few injections or run on 3-4 cilinders for a few rotations? Everything is better than closing the throttle I think.

Isn't that breaking traction control rules?

[Big Tea]

That would waste fuel.

Than why not skip a few injections or run on 3-4 cilinders for a few rotations? Everything is better than closing the throttle I think.

Isn't that breaking traction control rules?

Would that not depend on how it was 'triggered'? If it was on the shift not on (lack of) demand would it not be ok?

[NL_Fer]

That would waste fuel.

Than why not skip a few injections or run on 3-4 cilinders for a few rotations? Everything is better than closing the throttle I think.

Isn't that breaking traction control rules?

5.6 Power unit torque demand
5.6.1 The only means by which the driver may control acceleration torque to the driven wheels is
via a single foot (accelerator) pedal mounted inside the survival cell.

Don’t think that cutting a few injections on shift will break this rule. Also cutting or retarding ignition has been the default action on upshift since the begin of semi-automatic gearboxes.

[Tommy Cookers]

Isn't that breaking traction control rules?🤔

5.6 Power unit torque demand
5.6.1 The only means by which the driver may control acceleration torque to the driven wheels is
via a single foot (accelerator) pedal mounted inside the survival cell.

Don’t think that cutting a few injections on shift will break this rule. Also cutting or retarding ignition has been the default action on upshift since the begin of semi-automatic gearboxes.

the elephant in the room is that 350 kW electric motor/generator also driving and braking the crankshaft .....
its contribution will be far bigger than at present, including some behaviours rather like TC and ABS ....
maybe dynamic 'Senna-stutter' effects (pole slips/skips) beyond the scope of the present type of steady-state map rules