2025/2026 Hybrid Powerunit speculation

[gruntguru]

Plus whole volume vs area ratio is inherently definitely much worse than conventional ice. Hence worse thermal efficiency.

Agree but there are also pluses for TE as I mentioned. On balance the TE could be similar - and then there are some serious power/weight advantages.

[PlatinumZealot]

nevertheless the F1 ICE has inertia and the MGU-K inertia adds more inertia
a much larger eg 300 kW MGU-K will add a further inertia

But the MGU is not dead weight. It can add or take away energy at will.

(and the PU will be slower to accelerate/decelerate itself)
the ICE's ability to accelerate/decelerate itself is always better than an MGU-K's ability to accelerate/decelerate itself

How do you figure this? This can't be right. ICE's can't even decelerate itself. And MGU can decelerate by the same amount of power as it can accelerate. Even besides this (for acceleration) it can go to full power a lot quicker than an ICE, as well as being able to provide max torque in a much wider range.

the MGU IS 'dead weight' ... insofar as ....

it can't add or take away (mechanical) energy except within accelerations limited by its own inertia ... ie ....
its torque can change in c.2 msec - (the 'electrical time constant') if that torque change doesn't go into rpm change
but otherwise there will be no torque (eg output) unless rate-of-change demanded is much slower eg 20 msec
this torque-going-into-rpm-change response time can be called the 'electro-mechanical time constant'

the (NA anyway) F1 ICE has a torque-change-going-into-rpm-change 'response time' of less than 10 msec
(shown in Honda's paper on in-shift modulation of clutch transmitted torque - and Renault's 'Marseillaise' sound demo)
far better than the response time of the MGU-K

yes I have designed electro-mechanical servo systems

We will have to talk after this. I haven't done anything with motor inertia since university a long time ago, but as a mechanical person I am trying to get my electrical skills up with some robotic kits... so.. expect some PM's from me if I run into trouble. I won't be a pest.

[gruntguru]

But the MGU is not dead weight. It can add or take away energy at will.

How do you figure this? This can't be right. ICE's can't even decelerate itself. And MGU can decelerate by the same amount of power as it can accelerate. Even besides this (for acceleration) it can go to full power a lot quicker than an ICE, as well as being able to provide max torque in a much wider range.

the MGU IS 'dead weight' ... insofar as ....

it can't add or take away (mechanical) energy except within accelerations limited by its own inertia ... ie ....
its torque can change in c.2 msec - (the 'electrical time constant') if that torque change doesn't go into rpm change
but otherwise there will be no torque (eg output) unless rate-of-change demanded is much slower eg 20 msec
this torque-going-into-rpm-change response time can be called the 'electro-mechanical time constant'

the (NA anyway) F1 ICE has a torque-change-going-into-rpm-change 'response time' of less than 10 msec
(shown in Honda's paper on in-shift modulation of clutch transmitted torque - and Renault's 'Marseillaise' sound demo)
far better than the response time of the MGU-K

yes I have designed electro-mechanical servo systems

We will have to talk after this. I haven't done anything with motor inertia since university a long time ago, but as a mechanical person I am trying to get my electrical skills up with some robotic kits... so.. expect some PM's from me if I run into trouble. I won't be a pest.

If you look at the MGUK in isolation and apply maximum torque, it will accelerate at a rate determined by its own inertia and maximum torque. If you attach it to a PU which is accelerating at the same rate or greater, the MGUK will not be able to contribute any torque to the PU - all the MGUK torque will be expended in accelerating its own inertia. It follows that, even at lower accelerations, the full torque of the MGUK will not be available to the PU - some of it will be expended overcoming the MGUK's own inertia.

[Tommy Cookers]

... If you look at the MGUK in isolation and apply maximum torque, it will accelerate at a rate determined by its own inertia and maximum torque. If you attach it to a PU which is accelerating at the same rate or greater, the MGUK will not be able to contribute any torque to the PU - all the MGUK torque will be expended in accelerating its own inertia. It follows that, even at lower accelerations, the full torque of the MGUK will not be available to the PU - some of it will be expended overcoming the MGUK's own inertia.

at present in this relationship the c.500 kW ICE is the dog and the c.120 kW MGU-K is the tail

an MGU-K of c.350 kW will have much more inertia and its limiting response will be slower
the ICE (which may be smaller than presently) won't be the dog - because the MG won't like to be the tail
(and eg sometimes we use eg 8th gear only to allow M-K action but this won't stretch to allow 350 kW M-K action)

ie we might need in effect to couple the ICE and the MG via some mechanically continuous variability as in hybrid cars
this of course is more mechanically efficient than the type of CVT mechanism used on ICE-only cars

[gruntguru]

A reasonable guesstimate would be that inertia will increase in rough proportion to the power. (eg this is the case if you simply used 2 of the existing MGUK. The power would double as would the inertia.)

So the inertia handicap will not increase with increasing MGUK power.

[Tommy Cookers]

(a larger MG would be somewhat slower in response - so with its greater inertia be a bigger burden to the system) ...
unless .....

hybrids having 2 electrical machines and 1 ICE ....
this combination (seamlessly, efficiently and cleverly mixed via the transmission) has outstanding possibilities
even maybe a 'super-flywheel' in the mix ?

but yes 'they' might just strap a second MG onto the ICE crankshaft - and keep the ICE and the gear-shifty stuff
the original plan (year-on-year reductions of permitted fuel quantity) having been abandoned ?

[gruntguru]

(a larger MG would be somewhat slower in response - so with its greater inertia be a bigger burden to the system) ...

I still don't see how. Inertia increases by X% - but MG power to overcome that inertia also increases by X%.

[Tommy Cookers]

(a larger MG would be somewhat slower in response - so with its greater inertia be a bigger burden to the system) ...

I still don't see how. Inertia increases by X% - but MG power to overcome that inertia also increases by X%.

with size increase the inertia increases more than the power or torque does
so a bigger machine has a greater mechanical time constant (and greater electrical time constant)

iirc from some work I did many years ago
selecting so-called 'servo-motors' for application at various scales
the system for a notional 5 kW per axis would have a frequency response 'break point' at c. 3 Hz
the system for a maybe 800 W per axis would have a BP at c. 5 Hz

thermal time constants (response in temporary overheating) were/are also available from the manufacturers
this concept is presumably applicable to the ICE - eg combustion chamber internals etc

[henry]

(a larger MG would be somewhat slower in response - so with its greater inertia be a bigger burden to the system) ...

I still don't see how. Inertia increases by X% - but MG power to overcome that inertia also increases by X%.

with size increase the inertia increases more than the power or torque does
so a bigger machine has a greater electromechanical time constant (and greater electromagnetic time constant)

iirc from some work I did many years ago
selecting so-called 'servo-motors' for application at various scales
the system for a notional 5 kW per axis would have a frequency response 'break point' at c. 3 Hz
the system for a maybe 800 W per axis would have a BP at c. 5 Hz

thermal time constants (response in temporary overheating) were/are also available from the manufacturers
this approach could be applied to the ICE - eg combustion chamber internals etc

Does this assume that the size increase to gain the increases in torque and power are radial? Could a longer unit, or multiple units, give increases with no change in the relationship between power/torque and inertia?

[Tommy Cookers]

Does this assume that the size increase to gain the increases in torque and power are radial? Could a longer unit, or multiple units, give increases with no change in the relationship between power/torque and inertia?

servo-motors are anyway usually 'long and thin' for best ratio of torque to inertia
though the smallest sizes don't have the best response either

but dual MGU-Ks will likely be more responsive than 1 big one
and dual units open great possibilities via a hybrid-style transmission (though that might not need great response)

[PlatinumZealot]

(a larger MG would be somewhat slower in response - so with its greater inertia be a bigger burden to the system) ...

I still don't see how. Inertia increases by X% - but MG power to overcome that inertia also increases by X%.

with size increase the inertia increases more than the power or torque does
so a bigger machine has a greater electromechanical time constant (and greater electromagnetic time constant)

iirc from some work I did many years ago
selecting so-called 'servo-motors' for application at various scales
the system for a notional 5 kW per axis would have a frequency response 'break point' at c. 3 Hz
the system for a maybe 800 W per axis would have a BP at c. 5 Hz

thermal time constants (response in temporary overheating) were/are also available from the manufacturers
this approach could be applied to the ICE - eg combustion chamber internals etc

What sort of electrical power will be required to cancel out the inertia from the MUGK rotor when it is desired that the engine accelerates /decelerates "freely?"
And will this electrical power input be measured towards the MGUK energy limit?

[gruntguru]

I still don't see how. Inertia increases by X% - but MG power to overcome that inertia also increases by X%.

with size increase the inertia increases more than the power or torque does
so a bigger machine has a greater electromechanical time constant (and greater electromagnetic time constant)

iirc from some work I did many years ago
selecting so-called 'servo-motors' for application at various scales
the system for a notional 5 kW per axis would have a frequency response 'break point' at c. 3 Hz
the system for a maybe 800 W per axis would have a BP at c. 5 Hz

thermal time constants (response in temporary overheating) were/are also available from the manufacturers
this approach could be applied to the ICE - eg combustion chamber internals etc

Does this assume that the size increase to gain the increases in torque and power are radial? Could a longer unit, or multiple units, give increases with no change in the relationship between power/torque and inertia?

My point exactly.

[Tommy Cookers]

What sort of electrical power will be required to cancel out the inertia from the MUGK rotor when it is desired that the engine accelerates /decelerates "freely?"
And will this electrical power input be measured towards the MGUK energy limit?

no sort of electrical power will do it ... because of ....

motor action being really due to the opposition of 2 magnetic forces .....
the so-called motor field and the field produced by the current passing through the conductor (armature) ....
the magnetic field will be weakened by an abnormal conductor magnetic field if the conductor current is abnormal
(this weakening will reduce the torque:current ratio ie increase the mechanical time constant so is self-defeating)

overheating

the field weakening may be permanent

the MGU-K energy limit doesn't count energy moves to & fro between the MG and the CU's capacitive 'float'

APOLOGIES & CORRECTION - this time constant is MECHANICAL time constant (the other is ELECTRICAL)

[FW17]

I hope the final regulation involves an electric super charger and exhaust driven generator unit.

Feels like a waste of exhaust energy to use as a turbo charger.

I also feel it is time that they move the MGUk to the front, but keep that as a driver controlled deployment.

[Jolle]

I hope the final regulation involves an electric super charger and exhaust driven generator unit.

Feels like a waste of exhaust energy to use as a turbo charger.

I also feel it is time that they move the MGUk to the front, but keep that as a driver controlled deployment.

What would be the advantage to move the K to the front? There would be serious packaging difficulties with the tub, fuel tank and battery.