Rear brake/tire temp and regen

[autodoctor911]

What is limiting the amount of braking force applied to the rear wheels via mgu-k application of regenerative braking??? Have anyone been using shunts to bleed off extra current that the battery can't absorb? Also, what about just throwing a bunch of excess current to the mguh under braking? Once the rear tires and brakes are up to temperature, you could reduce the chance of overheating by using more mguk braking, which is liquid cooled and away from the tires

If you can't get rid of all the rear braking energy to the battery, would it not be possible to just feed it to the turbo, and or some big resistors (air or liquid cooled)

[michl420]

What is limiting the amount of braking force applied to the rear wheels via mgu-k application of regenerative braking??? Have anyone been using shunts to bleed off extra current that the battery can't absorb? Also, what about just throwing a bunch of excess current to the mguh under braking? Once the rear tires and brakes are up to temperature, you could reduce the chance of overheating by using more mguk braking, which is liquid cooled and away from the tires

If you can't get rid of all the rear braking energy to the battery, would it not be possible to just feed it to the turbo, and or some big resistors (air or liquid cooled)

The max power input and output of the mguk is 120 kw and is monitored with a torque sensor. So there should be no chance to absorb more mechanic energy. Technical regulations are availabe on the FIA website.

[Tommy Cookers]

The max power input and output of the mguk is 120 kw and is monitored with a torque sensor. So there should be no chance to absorb more mechanic energy....

rubbish !
unless the rules have changed

the K machine's motoring power is limited only as 126.3 kW electrical power in the DC line
to (the rules allowing an assumed 95% efficiency) make 120.0 kW mechanical power legally deliverable to the crankshaft

there is no limit to the mechanical power absorbed when generating provided the DC line power doesn't go over 120 kW
so yes IF the K could dump enough mechanical power as heat it could absorb mechanical power at a much higher rate
also a limited amount of electrical energy can be absorbed by the limited capacitive storage allowed onboard the CE

the K machine is torque-capped below c.5700 rpm so the notional 120 kW envelope disappears by that rpm

[michl420]

The max power input and output of the mguk is 120 kw and is monitored with a torque sensor. So there should be no chance to absorb more mechanic energy....

rubbish !
unless the rules have changed

the K machine's motoring power is limited only as 126.3 kW electrical power in the DC line
to (the rules allowing an assumed 95% efficiency) make 120.0 kW mechanical power legally deliverable to the crankshaft

there is no limit to the mechanical power absorbed when generating provided the DC line power doesn't go over 120 kW
so yes IF the K could dump enough mechanical power as heat it could absorb mechanical power at a much higher rate
also a limited amount of electrical energy can be absorbed by the limited capacitive storage allowed onboard the CE

the K mach.ine is torque-capped below c.5700 rpm so the notional 120 kW envelope disappears by that rpm

5.3.3
"The power of the MGU-K may not exceed 120 kW. The maximum torque of the MGU-K may
not exceed 200Nm. The torque will be referenced to the crankshaft speed and the fixed
efficiency correction defined in Article 5.3.2 will be used to monitor the maximum MGU-K
power and torque"

I think this rule limted the power of the mguk for generation AND regeneration.

If someone would dump some energy in the mguk in form of heat, the energy must also go first through the mguk shaft and thus over the torque sensor.

So as I understand it, whatever you do after the torque sensor (on the mguk shaft), doesen´t mater, because you can`t bring the force throught the shaft.

Exept you think that the torque limit is not releated to this 120 kw limit, but I think it is.

About the rpm limit I don`t know.

[Greg Locock]

-150 kW is less than 120 kW

[Tommy Cookers]

5.3.3
"The power of the MGU-K may not exceed 120 kW. The maximum torque of the MGU-K may
not exceed 200Nm. The torque will be referenced to the crankshaft speed and the fixed
efficiency correction defined in Article 5.3.2 will be used to monitor the maximum MGU-K
power and torque"
I think this rule limted the power of the mguk for generation AND regeneration.
If someone would dump some energy in the mguk in form of heat, the energy must also go first through the mguk shaft and thus over the torque sensor.
So as I understand it, whatever you do after the torque sensor (on the mguk shaft), doesen´t mater, because you can`t bring the force throught the shaft.
Exept you think that the torque limit is not releated to this 120 kw limit, but I think it is.
About the rpm limit I don`t know.

unless I'm wrong ....
there is no torque sensor on the MGU-K shaft
(PU torque sensing is downstream of the crankshaft/MGU-K merge)

200 Nm torque above 5730 rpm is more than 120 kW
200 Nm torque below 5730 rpm is less than 120 kW
109 Nm torque at 10500 rpm is 120 kW

'the power of the MGU-K is 120 kW'
if it's 120 kW output power generating or motoring the input power will be more than 120 kW
if eg generating is limited to 114 kW so that mechanical power input kept to 120 kW .....
'the power of the MGU-K' isn't 120 kW

[vorticism]

2025 regs list two torque sensors. One between the ICE and transmission, another between the MGUK and ICE.

[Tommy Cookers]

2025 regs list two torque sensors. One between the ICE and transmission, another between the MGUK and ICE.

well I thank you for that information
and apolagise to michl