We know anti-lock brakes are illegal but while I was perusing the construction of an F1 car I ran across a diagram that showed an ERS Brake Pressure Reduction Valve. Since it is wired into the ECU as well as the brake lines it brings doubt into my mind as to whether it can work or be used as an anti-lock brake system. If not what is it's purpose other than to limit the line brake pressure as the name implies?
Thoughts from our experts?
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss
They have a +/-120kW K that effectively gives them 120kW of mild TC and/or mild non wheel specific rear ABS if you like? The ECU controls the BBW system, not the driver.
“ERS brake pressure reduction valve”. F1 brake-by-wire system introduced in 2014. The rule changes allow the recovery of 2mj of energy per lap through the rear brakes. To achieve this, the braking system has two hydraulic circuits, with a separate master cylinder for the front brakes, and another for the rear. The front brakes operate conventionally:- Where the driver pushes the brake pedal with a force of 160kg, applying pressure to the fluid in the master cylinder. This fluid is used to actuate the 6-pistons within the front caliper’s which clamps the brake-pads to the carbon disc:- reducing the speed of the wheels through friction. The rear brakes however, have an additional master cylinder which is electrically controlled. Therefore, during braking, fluid is moved through the rear master cylinder as normally, however the MGU-K then determines the amount of pressure applied to the rear calipers, in this way, the energy from the rear brakes is recovered, but once the 2mj limit has been reached, the rear brakes operate conventionally.
saviour stivala wrote:“ERS brake pressure reduction valve”. F1 brake-by-wire system introduced in 2014. The rule changes allow the recovery of 2mj of energy per lap through the rear brakes. To achieve this, the braking system has two hydraulic circuits, with a separate master cylinder for the front brakes, and another for the rear. The front brakes operate conventionally:- Where the driver pushes the brake pedal with a force of 160kg, applying pressure to the fluid in the master cylinder. This fluid is used to actuate the 6-pistons within the front caliper’s which clamps the brake-pads to the carbon disc:- reducing the speed of the wheels through friction. The rear brakes however, have an additional master cylinder which is electrically controlled. Therefore, during braking, fluid is moved through the rear master cylinder as normally, however the MGU-K then determines the amount of pressure applied to the rear calipers, in this way, the energy from the rear brakes is recovered, but once the 2mj limit has been reached, the rear brakes operate conventionally.
Forgive my ignorance but would this not mean the balance between front and rear brakes was not only variable but unknown to the driver until he applied the brakes?
.... the energy from the rear brakes is recovered, but once the 2mj limit has been reached, the rear brakes operate conventionally.
of course the recovery from braking is usually far less than 2 MJ per lap
so presumably the scenario described doesn't occur
It could if they’ve been driving the ICE against the MGU-K
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus
For the MGU-K to determine the amount of pressure applied to the rear calipers there must be pressure applied by the driver to the rear calipers and the MGU-K must start harvesting/be in harvesting mode. To drive the ICE against the MGU-K (something which is used/done by drivers when situations first permit and secondly are called for, done by using brake and accelerator pedals at the same time) the MGU-K must start harvesting/be in harvesting mode, which in turn is triggered by the driver applying pressure to the rear calipers and the MGU-K determining the amount of pressure applied.
And the discussion on MGUK harvesting when braking is not wished, and in particular whether the brake pedal has to be pressed or not for that to happen ends here. Under which conditions the rules allow or do not allow MGUK to harvest, has been discussed on many threads already. The two posts above are the opinion of those two members. If further discussion is wished, open a thread for it.
saviour stivala wrote:“ERS brake pressure reduction valve”. F1 brake-by-wire system introduced in 2014. The rule changes allow the recovery of 2mj of energy per lap through the rear brakes. To achieve this, the braking system has two hydraulic circuits, with a separate master cylinder for the front brakes, and another for the rear. The front brakes operate conventionally:- Where the driver pushes the brake pedal with a force of 160kg, applying pressure to the fluid in the master cylinder. This fluid is used to actuate the 6-pistons within the front caliper’s which clamps the brake-pads to the carbon disc:- reducing the speed of the wheels through friction. The rear brakes however, have an additional master cylinder which is electrically controlled. Therefore, during braking, fluid is moved through the rear master cylinder as normally, however the MGU-K then determines the amount of pressure applied to the rear calipers, in this way, the energy from the rear brakes is recovered, but once the 2mj limit has been reached, the rear brakes operate conventionally.
Forgive my ignorance but would this not mean the balance between front and rear brakes was not only variable but unknown to the driver until he applied the brakes?
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The brake balance at the beginning of the stop is set by the driver. The brake balance moves rearward during the course of the stop. I believe the rate at which it moves rearward is also controlled by the driver using the Brake Migration setting. The division of braking effort between the rear friction brakes and MGU-K is calculated through the stop by the Brake By Wire software.
So the brake balance, brake migration and absolute braking level (through pedal effort) are all under control of the driver.
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus
I am just asking for expert input on the use and purpose of the ERS Brake Pressure Reduction Valve.
The diagram I saw that valve was on the main brake line. Not the front or rear and wired into the ECU.
Since it is pretty much out in the open and not hidden I can only assume it's legal so my question remains,,, What is it's purpose?
IF when a driver stabs the brakes too hard does it automatically lessen the line pressure? I would think that amounts to an anti-lock device and as such would be illegal. Since it is apparently on all or almost all cars I can't/don't believe that's it. So my question. Since so many members seem to have inside information I thought someone might have an answer.
If a mod wants to delete this thread that's fine. I was in the dark before and can remain in the dark if the question is going to stir up conspiracy theory's.
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss
