Braking with a Kers fitted F1 ( or any other car)

[Arkle]

How do they do it? braking in a normal car seems instinctive and natural. If you have, as in F1, an extra brake attached to the rear wheels which is the Kers system recharging, this surely is a variable change to the brake balance.
When the Kers is fully charged it has no effect, when it is empty it must be like a small 8o bhp engine stopping the rear wheels, when it is half charged its a 40 bhp engine stopping the rear wheels etc. How does the driver adapt to that changing brake balance during each braking phase which can start with an potentially different Kers status for each braking area? Answers on a post card to those F1 teams new to Kers.

[touring fan]

Arkle said:

If you have, as in F1, an extra brake attached to the rear wheels which is the Kers system recharging, this surely is a variable change to the brake balance.

Your whole point centres around the way in which you have said that KERS works on an F1 car....but it just doesn't work the way you describe;

http://www.formula1.com/inside_f1/understanding_th...

Edited by touring fan on Wednesday 26th January 23:29

[rt106]

I think the OP asks a prefectly valid question. It's inevitable that KERS affects the brake balance due to the inconsistent demands placed on the rear wheels by the system, and I've often wondered how that's managed. The link above doesn't begin to explain how this is done.

[davepoth]

I guess the car is allowed to automatically adjust the brake balance to make it feel natural under braking. Good question to ask though. Mike Gascoyne's on Twitter, he'd probably know...

[Scuffers]

because KERS in 2009 was rear wheels only, it did cause balance issues (if you remember, some drivers commented about it, specifically LH said it was problematic).


on road cars it's less of a problem as most are FWD cars and thus the regenerative braking is also on the front, and for a typical road car 80-90% of the braking is from the front anyway.

That said, the Prius got a slagging for this, as when the battery get's close to being full, the regenerative braking is dropped, thus more pedal effort is required to achieve the same retardation, que a bunch of muppets complaining that the brakes failed!

[chrisobrien54]

They attributed this to the reason Fizzy and Badoa (sp?) couldn't drive that Ferrari.

All of a sudden a very average looking Kimi was looking like a kind of driving God.

[The Wookie]

Scuffers said:

because KERS in 2009 was rear wheels only, it did cause balance issues (if you remember, some drivers commented about it, specifically LH said it was problematic).


on road cars it's less of a problem as most are FWD cars and thus the regenerative braking is also on the front, and for a typical road car 80-90% of the braking is from the front anyway.

That said, the Prius got a slagging for this, as when the battery get's close to being full, the regenerative braking is dropped, thus more pedal effort is required to achieve the same retardation, que a bunch of muppets complaining that the brakes failed!

I think with the Prius the main problem is that once the vehicle approaches a standstill, it becomes difficult for the motor to apply a negative torque as the power output is so low so the regen braking is shut down at about 5mph.

The OP does have a good point though, regen brake blending and stability management is one of the many challenges of developing a hybrid road car.

I assume in F1 it's optimised to get the right amount of power over the course of a lap (bearing in mind usage limitations) with minimal disruption to the driver, and what's left he has to deal with.

They might even have some sort of thermal dump to ensure the same torque is applied even when the system is fully charged.

[JonnyFive]

Surely this difference doesn't make too much of a problem, they're formula 1 drivers.. The best drivers in the world, they can adapt, can't they?

[Scuffers]

JonnyFive said:

Surely this difference doesn't make too much of a problem, they're formula 1 drivers.. The best drivers in the world, they can adapt, can't they?

Yes, they can drive round it, but ultimately, it slows them down.

Not checked the regs, but I think they were going to allow regenerateive braking from the front wheels this year?

[joewilliams]

Scuffers said:

Not checked the regs, but I think they were going to allow regenerateive braking from the front wheels this year?

Surely that would involve the weight of a motor/generator in the front hubs, and offer the opportunity for driving the front wheels via the same system?

[ravon]

I heard a few days ago from a well connected individual that the whole KERS thing in terms of the conservation of energy is a nonsense in that to overcome the variance in rear braking effect, the car's software simply dials up enough horsepower to negate the horsepower effectively lost by KERS charging, so the driver feels no difference in braking. Problem is the whole system, designed to be energy efficient, is in fact the complete opposite, another Moseley inspired masterpiece !

[ravon]

I heard a few days ago from a well connected individual that the whole KERS thing in terms of the conservation of energy is a nonsense in that to overcome the variance in rear braking effect, the car's software simply dials up enough horsepower to negate the horsepower effectively lost by KERS charging, so the driver feels no difference in braking. Problem is the whole system, designed to be energy efficient, is in fact the complete opposite, another Moseley inspired masterpiece !

[davepoth]

ravon said:

I heard a few days ago from a well connected individual that the whole KERS thing in terms of the conservation of energy is a nonsense in that to overcome the variance in rear braking effect, the car's software simply dials up enough horsepower to negate the horsepower effectively lost by KERS charging, so the driver feels no difference in braking. Problem is the whole system, designed to be energy efficient, is in fact the complete opposite, another Moseley inspired masterpiece !

That sounds wrong. The engine couldn't be used in that manner; if you wanted to make it feel the same you'd need to either reduce the engine braking effect by negating the manifold vacuum and compression, or alter the brake balance forwards.

[mrmr96]

The Wookie said:

They might even have some sort of thermal dump to ensure the same torque is applied even when the system is fully charged.

That's the best way of dealing with it. I think it should be applied to regen road cars too, so that in the Prius you'd get the same retardation for the same pedal effort regardless of the battery's charged status. (I do understand the 5mph thing which isn't related to this.)

[PhillipM]

davepoth said:

That sounds wrong. The engine couldn't be used in that manner; if you wanted to make it feel the same you'd need to either reduce the engine braking effect by negating the manifold vacuum and compression, or alter the brake balance forwards.

Why couldn't it? The engine is a brake itself when the throttle is shut, open the throttle slightly and it would easily compensate for the kers system, in fact, you could employ some 3d mapping to it so that it alters the amount depending upon the speed to compensate for the changes in downforce, unless that comes under the brake bias rulings.

[Scuffers]

PhillipM said:

davepoth said:

That sounds wrong. The engine couldn't be used in that manner; if you wanted to make it feel the same you'd need to either reduce the engine braking effect by negating the manifold vacuum and compression, or alter the brake balance forwards.

Why couldn't it? The engine is a brake itself when the throttle is shut, open the throttle slightly and it would easily compensate for the kers system, in fact, you could employ some 3d mapping to it so that it alters the amount depending upon the speed to compensate for the changes in downforce, unless that comes under the brake bias rulings.

which is exactly what they used to do to 'manage' rear braking (also known as ABS)

[Zad]

Road cars don't have the sort of restrictions that F1 cars do. The F1 regs will prevent them modulating the motor/generator because it would effectively give them ABS on the rear wheels. Clearly on a road car that isn't a problem. It is a relatively trivial electronic / software problem to modulate the hydraulic pressure and motor shunt in order to generate a consistent retardation for any given pedal pressure. Quite why the Prius doesn't choose to do that, I don't know. I suspect the next generation of road cars will be using supercapacitors to take the high transient energies associated with braking from speed.

[The Wookie]

JonnyFive said:

Surely this difference doesn't make too much of a problem, they're formula 1 drivers.. The best drivers in the world, they can adapt, can't they?

Sorry if I'm stating the obvious, but the job of an F1 driver is to drive the car as fast as possible without binning it, which requires an element of predictability. If the system is unpredictable, then the driver will only push the car as far as his lowest expectation of what it will do at any given point, rather than how far it will actually go at any given point.

[The Wookie]

PhillipM said:

Why couldn't it? The engine is a brake itself when the throttle is shut, open the throttle slightly and it would easily compensate for the kers system, in fact, you could employ some 3d mapping to it so that it alters the amount depending upon the speed to compensate for the changes in downforce, unless that comes under the brake bias rulings.

I think that pretty much answers the question. Pretty easy to balance it out, as long as it doesn't fall foul of the regs

[Scuffers]

The Wookie said:

PhillipM said:

Why couldn't it? The engine is a brake itself when the throttle is shut, open the throttle slightly and it would easily compensate for the kers system, in fact, you could employ some 3d mapping to it so that it alters the amount depending upon the speed to compensate for the changes in downforce, unless that comes under the brake bias rulings.

I think that pretty much answers the question. Pretty easy to balance it out, as long as it doesn't fall foul of the regs

which it does (fall foul of the regs)

issue here is that technically, there is nothing stopping you use the engine to charge the Kers when the driver is 'off' the throttle (in other words, use the over-run time instead of using regenerative braking), but this is banned in the reggs too.