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MGU-K Energy recovery


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#1 Wuzak

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Posted 07 February 2014 - 00:34

The 2014 regulations allow for the MGU-K to recover up to 2MJ of energy per lap to give to the ES, and an unlimited amount can be transferred to the MGU-H or other accessories. The rules also allow for the use of 4MJ of energy from the ES to the MGU-K. The rules also allow for 4MJ of storage capacity.

But how practical is all of that?

Using Brembo Braking data from last season, provided by member wrcva, I have made some basic calculations.

Braking power is more than sufficient to provide the 2MJ per lap. However, the limitations that recovery occurs only on the rear wheels and the aloowable recovery power of 120kW severely limit this.

From the data I assumed 60% front, 40% rear braking bias. I am not sure how that relates to reality. Based on the average braking power I calculated the rear braking power. For braking power greater than 120kW the energy recovered was 120kW multiplied by the braking time, otherwise it was the braking power multiplied by the braking time. The latter case is essentially the MGU-K providing all of the rear braking effort.

The recovered energy, in kJ, is:


 
Circuit        Energy
SINGAPORE      2460
ABUDHABI       1846
AUSTIN         1567
BAHRAIN        1504
MONACO         1517
MALAYSIA       1463
KOREA          1349
HUNGARY        1284
SPA            1292
CHINA          1216
NURBURGRING    1171
CANADA         1159
CATALUNYA      1138
BRAZIL         1064
INDIA          1064
SUZUKA         1061
AUSTRALIA      992
MONZA          938
SILVERSTONE    730
Clearly, only at Singapore is the braking energy recovery allowance exceeded. For all others the total is less. 
 
Assuming that the MGU-H does not contribute to filling the ES, the amount of time the MGU-K can be run, per lap, on the recovered energy is:
Circuit        Time
SINGAPORE      16.67
ABUDHABI       15.38
AUSTIN         13.06
BAHRAIN        12.53
MONACO         12.64
MALAYSIA       12.19
KOREA          11.24
HUNGARY        10.7
SPA            10.77
CHINA          10.13
NURBURGRING     9.76
CANADA          9.66
CATALUNYA       9.48
BRAZIL          8.87
INDIA           8.87
SUZUKA          8.84
AUSTRALIA       8.27
MONZA           7.82
SILVERSTONE     6.08
But at least some of that time will be as the MGU-H is also supplying the MGU-K. Based on the Cosworth data posted in the 2014 Power Unit Thread, the MGU-H gives the MGU-K around 110hp above 10,500rpm. That means the ES has to supply 50hp/37kW.

Circuit        Time
SINGAPORE      53.62
ABUDHABI       49.48
AUSTIN         42.01
BAHRAIN        40.31
MONACO         40.68
MALAYSIA       39.22
KOREA          36.17
HUNGARY        34.42
SPA            34.64
CHINA          32.59
NURBURGRING    31.4
CANADA         31.08
CATALUNYA      30.5
BRAZIL         28.54
INDIA          28.54
SUZUKA         28.44
AUSTRALIA      26.61
MONZA          25.16
SILVERSTONE    19.56
In many of these circuits time at full power will be less than that, and the ES will contribute a higher amount of power to the mix.
 
The theory of saving your energy to be able to mount a passing attempt will require 3 or more laps for most circuits to gain the 4MJ maximum.
 
Silverstone would be the most likely track to use such a strategy. Less is lost by not applying the power on the track on which it was recovered, and more is gained when using the extra power. It would, however, take 5.5 laps to gain the full 4MJ energy. It may be that the driver would not actually use the energy to pass on track, but to conserve his tyres and use the extra power/speed to try to leap frog his opponent in the pit stop phase.
 
The other side of this is the ES storage capacity. I am not sure that a full 4MJ capacity is possible within the 20-25kg weight band. 
 
A little disappointed that there is a minimum weight for the ES. I would think that some teams would figure on not actually having much storage, using the energy shortly after it is recovered (the maximum single corner recovery is ~370kJ in Abu Dhabi) and saving 5-10kg that could be the difference between being overweight or right on the weight.

EDIT: Corrected the calculated numbers. Some of the values were from a previous calculation where I had disregarded the power of the rear brakes is it was below 120kW.

Edited by Wuzak, 07 February 2014 - 03:26.


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#2 Wuzak

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Posted 07 February 2014 - 03:32

It has been pointed out to me that the rear braking percentage would be closer to 35% than 40%. This has a minor effect on the energy recovered, as most braking zones allow for the full 120kW 

 

The recovered energy with 35% rear braking are:

Circuit        Time  Change
SINGAPORE      2455    5
ABUDHABI       1843    3
AUSTIN         1559    8
BAHRAIN        1504    0
MONACO         1507   10
MALAYSIA       1449   14
KOREA          1347    2
HUNGARY        1284    0
SPA            1288    4
CHINA          1216    0
NURBURGRING    1171    0
CANADA         1159    0
CATALUNYA      1138    0
BRAZIL         1064    0
INDIA          1064    0
SUZUKA         1056    5
AUSTRALIA       992    0
MONZA           937    1
SILVERSTONE     730    0


#3 oetzi

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Posted 07 February 2014 - 03:55

A couple of thoughts - does the extra weight of this year's cars significantly increase the braking energy available to charge the ES? And did they maybe mandate the minimum weight so that as the batteries degrade after being put through numerous charge cycles over the course of 5 races, they're still large enough to retain a decent amount (nice scientific term there) of charge?



#4 Wuzak

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Posted 07 February 2014 - 04:04

The weight and extra speed (from lowr drag) of these cars will add to braking energy. However, the loss of downforce will require longer periods of lower braking power. Longer braking periods may help the amount of energy recovered, as even though the peak power will be lower, the MGU-K's braking contribution will be maintained for most braking zones.

#5 F1ultimate

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Posted 07 February 2014 - 11:43

Great thoughts and analysis. Given that the cars will be braking by wire, the brake balance and pressure won't necessarily stay static at 60% but will change dynamically to ensure that the driver has sufficient energy budget for be fast as possible. The ERS weigh quite a bit and if they aren't maximized then they are dead weight, so I can imagine energy recovery being heavily prioritized by the engine management.

 

However I doubt that drivers can perform consistently with a dynamically changing brake balance. We'll sure hear more about this from drivers as they clock more laps during testing. 



#6 oetzi

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Posted 07 February 2014 - 12:00

Cheers Wuzak, interesting to hear (as usual).

 

A couple more thoughts:

 

Does this mean that coasting and braking (relatively) gently and early to conserve fuel will now give benefits from the electrical power systems, and maybe lead to a slow, slow, quick, quick, slow kind of rhythm to the racing? Actually, re the coasting, can they turn off the MGU-K so they can coast more 'coastily' without invoking its braking effect? Not sure when they might want to, but there might be a situation where that could be beneficial (maybe if comfortable leading a race with a fully charged ES - then it might well make sense).

 

And re what F1ultimate mentioned, will there maybe be more rear brake bias at lower speeds than in previous years, with the risk of lockup v maximum braking effort shifting the balance rearwards as the car slows? 



#7 Wuzak

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Posted 07 February 2014 - 12:10

Great thoughts and analysis. Given that the cars will be braking by wire, the brake balance and pressure won't necessarily stay static at 60% but will change dynamically to ensure that the driver has sufficient energy budget for be fast as possible. The ERS weigh quite a bit and if they aren't maximized then they are dead weight, so I can imagine energy recovery being heavily prioritized by the engine management.

 

However I doubt that drivers can perform consistently with a dynamically changing brake balance. We'll sure hear more about this from drivers as they clock more laps during testing. 

 

The idea of the rear brake by wire is to change the braking effort of the actual brakes depending on the power that the MGU-K is taking and the amount of braking that is required from the rear axle - based on braking pressure and driver set braking balance. 

 

In theory, and if the system is working well, the driver should not notice the difference between the MGU-K and the brakes providing the retardation.



#8 Wuzak

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Posted 07 February 2014 - 12:23

Cheers Wuzak, interesting to hear (as usual).

 

A couple more thoughts:

 

Does this mean that coasting and braking (relatively) gently and early to conserve fuel will now give benefits from the electrical power systems, and maybe lead to a slow, slow, quick, quick, slow kind of rhythm to the racing? Actually, re the coasting, can they turn off the MGU-K so they can coast more 'coastily' without invoking its braking effect? Not sure when they might want to, but there might be a situation where that could be beneficial (maybe if comfortable leading a race with a fully charged ES - then it might well make sense).

 

And re what F1ultimate mentioned, will there maybe be more rear brake bias at lower speeds than in previous years, with the risk of lockup v maximum braking effort shifting the balance rearwards as the car slows? 

 

Braking too gently may not allow the MGU-K to get the maximum power. Lengthening the braking period, so long as you can keep the 120kW going into the MGU-K will help the energy captured, but that comes at a cost to performance (lap time).

 

The rhythm of the racing, as you put it, would probably depend on where you are in the field and what the drivers around you are doing. 

 

I don't see that capturing energy over several laps is going to do much to help in an effort to pass a slower car, because when you're on the straight he is likely to have the full 120kW/160hp extra in the passing zones. As I said earlier, this technique is best served for overtaking another driver during the pit stop cycle.

 

The MGU-K can be disconnected from the engine with a clutch. This has been the case for KERS as well, as they didn't need to recoover energy at all the corners so it would be disconnected for those where it wasn't required, and also when the KERS is not supplying power to the engine (ie most of the lap). Keeping the MGU-K connected when it isn't either generating or sending the power increases the inertia of the power unit, slowing response, as well as adding drag through friction.

 

It may be that the cars use more rearward brake bias this year, and to help that the weight balance may also be further back. To counter that, the loss of rear downfoce due to the removal of the beam wing may have more of an effect.



#9 oetzi

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Posted 07 February 2014 - 12:27

Cheers  :)



#10 Neophiliac

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Posted 07 February 2014 - 12:30

Very interesting, wuzak. What's the original data set (do you have a link?). How is braking power defined in that dataset?



#11 F1ultimate

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Posted 07 February 2014 - 12:31

It's fascinating how much there is to consider when designing and configuring these power units. I cannot wait to get my hands on F1 2014 and experience a new way of driving.



#12 Ali_G

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Posted 07 February 2014 - 12:45

I'm a little confused here.

 

Is the MGU-K still like KERS in that it is operated via a button on the steering wheel.  I thought it was going to be blended with throttle or is this just MGU-H ?



#13 F1ultimate

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Posted 07 February 2014 - 12:52

I'm a little confused here.

 

Is the MGU-K still like KERS in that it is operated via a button on the steering wheel.  I thought it was going to be blended with throttle or is this just MGU-H ?

 

The MGU-K is managed by the engine. However, driver will likely be able to engage a "full-power" mode for passing. But more the most part, the MGU-K will not be controlled by the driver. As for the MGU-H, it's only purpose is to recharge the energy store and spool the turbo during breaking. Unlike the the MGU-K, it doesn't directly power the drive shaft.



#14 Ali_G

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Posted 07 February 2014 - 12:55

The MGU-K is managed by the engine. However, driver will likely be able to engage a "full-power" mode for passing. But more the most part, the MGU-K will not be controlled by the driver. As for the MGU-H, it's only purpose is to recharge the energy store and spool the turbo during breaking. Unlike the the MGU-K, it doesn't directly power the drive shaft.


Am I right in saying though that virtually always, the MGU-H will send its energy to the MGU-K instead of to the ES as the MGU-H will only generate power when the engine is being pushed hard ?

The ES will also send energy to the MGU-H in order to reduce turbo lag ?

Edited by Ali_G, 07 February 2014 - 12:55.


#15 wrcva

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Posted 07 February 2014 - 13:07

Very interesting, wuzak. What's the original data set (do you have a link?). How is braking power defined in that dataset?

Data set is compiled from Brembo Circuit Identity Cards.   Here is an example for Australia (PDF) but they have it for every track (link).   Data is scraped from pdfs and put in a data set format (178 rows = Brembo defined brake zones for all 2013 circuits) so we can play with it for some proxy estimates (also adding other interesting variables from other sources - work in progress).   If you like to play with it just pm me for the link.


Edited by wrcva, 07 February 2014 - 13:14.


#16 TC3000

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Posted 07 February 2014 - 13:59

Am I right in saying though that virtually always, the MGU-H will send its energy to the MGU-K instead of to the ES as the MGU-H will only generate power when the engine is being pushed hard ?

The ES will also send energy to the MGU-H in order to reduce turbo lag ?

 

Yes, I think, this is pretty much spot on.

 

For most of the time above app. 7500-8000 rpm, they will use the energy (electricity) generated by the MGU-H (generator mode) to drive the (MGU-K) (motor mode) directly, without the energy passing through the ES (battery), because this path is not limited by the rules (only the max. power limit for the MGU-K 120kW still applies)

 

The only times, when you would send any "excess" energy from the MGU-H into the ES, would be conditions, where the car couldn't make use of the extra power at the MGU-K anyway, because it may still being "grip limited" by the tyres.

Under these condition, you would store the energy into the ES, so that you can use it later on. - IMHO



#17 Wuzak

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Posted 07 February 2014 - 14:09

For most of the time above app. 7500-8000 rpm, they will use the energy (electricity) generated by the MGU-H (generator mode) to drive the (MGU-K) (motor mode) directly, without the energy passing through the ES (battery), because this path is not limited by the rules (only the max. power limit for the MGU-K 120kW still applies)


Agree completely with this.

Another factor involved is that there is a loss when storing the energy to the ES and another loss when extracting the energy from the store. Weheras going straight from the MGU-H to the MGU-K has only one conversion loss.


The only times, when you would send any "excess" energy from the MGU-H into the ES, would be conditions, where the car couldn't make use of the extra power at the MGU-K anyway, because it may still being "grip limited" by the tyres.
Under these condition, you would store the energy into the ES, so that you can use it later on. - IMHO


It may be that when grip limited the teams will use a lower hp from the motor combined with MGU-H->MGU-K power. eg, if 500hp was required, it may be able to get 450hp from the ICE plus 50hp from the MGU-H and thus save some fuel.

#18 F1ultimate

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Posted 07 February 2014 - 14:51


Another factor involved is that there is a loss when storing the energy to the ES and another loss when extracting the energy from the store. Weheras going straight from the MGU-H to the MGU-K has only one conversion loss.

 

I didn't know it was possible to bypass the ES.



#19 Maustinsj

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Posted 07 February 2014 - 15:04

Congratulations on spelling "braking" correctly   ;)



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#20 RoutariEnjinu

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Posted 07 February 2014 - 15:12

Weheras going straight from the MGU-H to the MGU-K has only one conversion loss.


I wonder how that works though as the MGUs are AC right? Would there still need to be any rectifying or controllers to drive the AC motors. Can it be a simple 1:1 connection with the different shaft speeds? I don't know much about AC motors or generators, but from what I've seen they need special driver circuits. 
 

I didn't know it was possible to bypass the ES.


It's shown in Renaults diagrams of the different phases of braking, corner exit, overtaking and accelerating. There may be some conversion and controlling needed, as mentioned above, but the energy doesn't all have to pass through the physical lithium cells. Although a proportion of it could, depending on the requests being made of the entire PU.

Edited by RoutariEnjinu, 07 February 2014 - 15:14.


#21 TC3000

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Posted 07 February 2014 - 15:20

as for the brake bias

 

you have to be careful, not to mix up two different things here. It's easy to do, because they are talked about by using the same expression "brake bias", but depending on the context, can mean two different things.

 

As an reasonable first order approximation, one could say, that a tyre can generate a lateral or longitudinal force as a function of it's vertical load. How good the "conversion factor (CoF - Friction coefficient) is, may changes slightly with increased load - load sensitivity of tyres, but this shouldn't concern us just yet.

 

Therefore, for a given tyre, the max. brake force is a function of it's vertical load - the vertical load (a force) being made up by the sum of the weight (mass*gravity) and the amount of downforce acting on it. From this it follows, that as an first order approximation, we can look at the weight distribution of the car.

According to the rules, this has to be:

 

 

4.2

Weight distribution :
For 2014 only, the weight applied on the front and rear wheels must not be less than 314kg and 369kg respectively at all times during the qualifying practice session.
If, when required for checking, a car is not already fitted with dry-weather tyres, it will be weighed on a set of dry-weather tyres selected by the FIA technical delegate.

 

for the empty car (no fuel) . This balance may changes a bit with fuel load, but let's use this as a starting point

 

This means, that the weight distribution, if I use the minimum weights as they are, is 46% front and 54% rear.

Therefore our rear tyres are more loaded then our front tyres, ergo our brake force distribution would need to track, the weight distribution ( down force may changes this slightly, but in general most people (designers) aim to have the CoP (center of pressure) close to the CoG (center of Gravity) to make for predictable handling.

Now, we all know, that during braking load shifts from the rear axle towards the front axle, which is the reason that a normal car/bike pitches nose down under braking.

 

This effect is, again as an first order approximation, governed by the following parameters. Total weight of the car, height of the CoG above the ground, wheelbase and how hard to we brake - deceleration value. As harder we brake as more load will shift towards the front, which is the reason, that drivers adjust the brake bias, when racing in the rain, because in general they brake less hard (less deceleration) and therefore keep more load on the rear axle.

Let's run a quick and dirty example with a generic F1 car. mass = 750 kg , height of CoG = 0.25m, wheelbase = 3.3 m, average deceleration = 3g

Our base car uses the 46/54% weight distribution, which means that it is carrying 345kg on the front and 405kg at the rear axle.

How is this looking when braking with 3g?

750*3*0.25/3.3 = 170 kg ( I will show it in mass units kg, to make it easier to follow, you can do the conversions to N if you like)

This means me have a load transfer of 170 kg @ 3g, our rear is getting 170 kg "lighter" while our front is getting "heavier".

 

front: 345kg + 170kg = 515kg  515/750 = 68.7 %

rear:  405kg - 170kg = 235kg   235/750 = 31.3 %

 

Under these new conditions, our front axle is now carrying 69% of the load, therefore it would need to provide 69% of the braking moment too.

If you run different numbers, you get different load distributions, until in the extreme case, the load at the rear axle would be zero. You can see this on Moto GP bikes, who lift the rear wheel slightly under heavy braking, because there CoG is so high.

 

If we assume, that this is the hardest braking, we would need to set our "brake bias or brake balance" to 69% front, otherwise, we would lock-up the rear, at this point.

If you cannot alter the brake balance/bias during braking, you have to preset it, to the highest deceleration values, and this is what most drivers do.

This provides the "optimum balance" at a certain deceleration value, but also means, that you "underutilized" the rear axles braking capacity at any time, you brake less hard (less deceleration). You can shift the preset bias from corner to corner, and this is what most of the drivers do, but you can't normally alter it during braking.

 

If we look at a typical brake pressure trace, it looks something like this:

 

1_12.jpg

 

It increases very rapidly, with good vales being <0.3 sec to max, and then the driver tappers of the brakes, to account for the reduction in downforce with speed.

The deceleration graph looks similar, so you see, that for the most time, after you have reached the peak value, you will brake with less then max. deceleration, which means, that with an preset/fixed bias, you don't use all of your rear axle braking capacity. 

 

As I said in the other thread, the "ideal" brake force distribution/brake bias during a braking event looks like a parable.

During the braking event, you would need, ideally to shift more and more brake bias towards the rear. 

 

eja0032a.gif

image14_w.jpg

You see, that the the numbers shown, where the diagonal lines intersect the parable, are going from 1 (100%) to 0 (0%), which in this cases shows the "offset" from the static brake force distribution, based on weight distribution. And you see as well, that for every point along the x-axis (showing front brake pressure, but could show deceleration as well), there is a different "optimum" value, for this offset.

 

I don't know, how they (FIA) plan to police this, but the new rules open up possible avenues to implement, what on an road car you would call (EBD - Electronic Brake(force) Distribution).

This is not ABS, but beneficial nonetheless (if they get it too work correctly).

Having said this, I'm sure that most teams already run a form of automatic brake force distribution anyway, you would leave "too much time on the table" if you didn't.

Just that the implementation would be a bit more "crude", and that they would approximate the parable with 2 or 3 straight lines.

This can be done, fully "mechanically" but being able to use a electronically controlled valve, would make the job easier.

It's not rocket science, most of the "better" ABS/ESC systems in road cars, will have this function implemented these days - no big deal.



#22 TC3000

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Posted 07 February 2014 - 15:30

I think, you will need a form of "frequency match/control" because in all likelihood the MGU-H and the MGU-K are not operating at the same rotational velocities (rpm), but the frequency content in the current/voltage generated by the MGU-H (or any other form of AC- generator) will be primarily a function of it's rotational speed. - IMHO

The velocity of an AC motor is normally controlled via the frequency, while it's torque is a function of the voltage supplied - see VFD ( Variable Frequency Drive) Inverters



#23 wrcva

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Posted 08 February 2014 - 12:58

image14_w.jpg

 

 

Thanks for the illustration.  Within the context of this graph the following statement from Kamu is interesting; 

 

"Even with a brake bias system we don't use much the rear brakes, so there is not much temperature at the rear. This is why we need to work a lot and spend a lot of time on it as well." (link)

 

Aside from the general reduction in downforce we know about for 2014 he is specifically referring to the brake bias not responding in a way he was used to... 

 

Whenever I hear about "<something> by wire" I always remember this (not in a bad way but) in a way that *hit happens at the bleeding edge of systems development when you are trying to debug and get hard/soft systems & humans (eventually) interacting correctly.   Doing that without being able to do adequate real life testing time must be even more fun.


Edited by wrcva, 08 February 2014 - 16:55.


#24 Tenmantaylor

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Posted 08 February 2014 - 13:36

Awesome posts :up:

Even when an optimum brake balance is calculated in such a way its not guarenteed to be the best single setting for a lap. It might not be the best setting for any single braking zone. Bumps, camber, downforce fluctuations, tyre wear, fuel load, incline/decline at each corner will throw those figures out. Add driver error and probably most critically, the balance and feel they want whilst getting the car slowed and turned in whilst coming off the brakes (the most important factor in finding time in a corner) and Im sure drivers will often end up with values +\- 5% of the optimum on a regular basis. To get the best laptime they need confidence in the car's feel.

#25 TC3000

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Posted 08 February 2014 - 17:23

Thanks for the illustration.  Within the context of this graph the following statement from Kamu is interesting; 

 

"Even with a brake bias system we don't use much the rear brakes, so there is not much temperature at the rear. This is why we need to work a lot and spend a lot of time on it as well." (link)

 

Aside from the general reduction in downforce we know about for 2014 he is specifically referring to the brake bias not responding in a way he was used to... 

 

Whenever I hear <something> by wire I always remember this (not in a bad way but) in a way that *hit happens at the bleeding edge of systems development when you are trying to debug and get hard/soft systems & humans (eventually) interacting correctly.   Doing that without being able to do adequate real life testing time must be even more fun.

 

I think, what Kamu means in this context is, that they seem to struggle with bringing the rear tyres up into their working temperature range.

Maybe Pirelli went "very" conservative to avoid any issues and bad publicity. A driver bitching about the tyres being "difficult to drive, too hard ...whatever" is one thing, and you can just tell them to STFU, and deal with it, that's what you get paid for.

But tyres throwing their thread/belt or disintegrating in any other way structurally is a different, much bigger (PR) problem.

 

One, could ask, whats the issue?  - Just put the power down, and when the tyres spin, they will heat up --> that's true, but not what you want, because you just melt the outer layer of the thread away (wear) and still have not more grip.

Is a bit of an chicken and egg problem. To make a slick racing tyre work (any), you need a minimum amount of energy to go through the tyre.

If you drive it too gently you don't put enough energy through the tyre, and the structure (construction) doesn't warm up enough --> the tyre "doesn't switch on".

 

But in order to do so, the driver needs confidence in the car & tyre, to "lean" on it. But it's difficult to have confidence, when you don't "feel the grip", when the car is moving around, and is trying to break away from you.

It's a vicious circle, you need to break through it, if you reach the critical energy threshold, and the tyre "switches on" life becomes easy, you need to force yourself & the car/tyre through this region of "pain", and believe/have confidence that it will be o.k. "on the other side".

 

Downforce helps a lot, to get the tyre to work properly, not just "cooking/melting away" the surface layer with wheel spin, and radiated heat from the brakes can help too.

Some will remeber all the constructions, the teams put on the car, to adjust brake cooling "on the fly" during a pitstop.

Therefore, I think, that this is Kamu's point, now, with much of the retardation on the rear axle coming from the MGU-K and arriving at the wheel, as a torque via the driveshafts , there is "less work" done by the brake -->, ergo less heat generated inside the wheel.

 

That's not a bad thing, as you need less cooling, good for aero - unless you have issues with bringing your tyres up to temp, then it makes a already difficult situation worse, because you lose one tool which could have helped you the mitigate the problem.

 

Another challenge for the engineers (and the driver, because he need to "fix" the situation, when the engineers got it wrong), is that the CoF of C/C brakes change quite dramatically with temperature (a little bit like tyres).

So while calculating the pressure is one thing, the control engineer also needs to consider, that the brakes convert a given pressure at a different rate into torque, when they are hot/cold --> the conversion rate is a function of the brake temperature.

The temperature will change, so when switching between the two "brake torque generators (brakes and MGU-K)" the engineer needs to account for the fact, that the brakes in the meantime may have cooled down a lot, therefore would require a different pressure then before.

 

Interesting times ahead, I thing both sites engineers & drivers have their work cut out early on.

With more experience and data to fall back onto, it will get easier, people learn, gain experience and with the experience comes normally a level of confidence.

But for the first third of the season, it will be a lot "playing by ear" & "seat of the pants" engineering, this will be interesting to watch.

As the old saying goes " At the end of the day, everybody just cooks with water, but some will make the water boil faster then others"


Edited by TC3000, 08 February 2014 - 18:08.


#26 chipmcdonald

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Posted 08 February 2014 - 17:39

Last year if you used fuel to get in front, you could save fuel by going slower and hoping you stay in front as the faster cars behind you catch up.

 

If you go slower to save fuel, you're temporarily saving fuel but increasing the distance to the car you want to pass.  You're also allowing trailing cars to get closer.  Nobody was driving slow *before* trying to pass last year.  There is no reason for the leading car not to drive to the maximum speed given fuel flow parameters, he is not going to slow down while the trailing driver slows down to save fuel.

 

No, I am not saying there will be "no passing or overtaking".   I am saying that this year trying to force an error isn't likely to happen, and taking a non-efficient line is not going to be rewarded, the hystereis in energy use is much greater.  

 

Outside the DRS zone, if a trailing driver sees what he thinks is an error happening, or about to happen in front of him, does he step on it to try to take advantage?  Last year he would,  this year - outside of the first lap, I don't think so.  Another thing is the potential unaccountable waste in the first lap-first turn train, the concertina effect may exceed energy harvesting parameters.

 

I'm just thinking outloud.  Outside of the differences from last year, trying to make this year's math fit last year is not entertaining IMO.   If someone wants to be condescending or pretentious in response, have fun.  That's what I'm trying to do... :wave:



#27 TC3000

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Posted 08 February 2014 - 18:52

Whenever I hear about "<something> by wire" I always remember this (not in a bad way but) in a way that *hit happens at the bleeding edge of systems development when you are trying to debug and get hard/soft systems & humans (eventually) interacting correctly.   Doing that without being able to do adequate real life testing time must be even more fun.

 

Yes, s... happens, and more often then not, the reason is twofold

- often you have insufficient data &/or informations, so at one point assumptions & best guesses are being made, this brings inherent risk, as whenever you "guess", you can do so wrongly.

- the second issue, is that you can only prepare/account for situations that you have "foreseen" during development. It's more a problem of imagination/fantasy then a "pure" technical

  problem. After something has happened, often it doesn't take too long to implement a "fix" for it, it was just a question that no one thought about such a situation while designing the system.

  There is are whole books written on it, when it comes to aviation accidents. I think one title is/was "Computer related Accidents" or something like this.

 

BTW, some aircrafts use 100% true "brake by wire" "E-brakes" (non hydraulic operation) these days, but it think it's still not permitted for the use in consumer cars, at least in some countries.

Funnily enough, I noted a minute change in terminology used in the FIA tech. Regs. For many years, it read, that the brake pressure within one circuit, has to be equal on the left to right calipers, to prevent "brake steer" ala McLaren. and systems which stop the inner unloaded front wheel from locking up, these systems where used in some Touring car race series. This paragraph is written into many tech. regs for race series around the world, these days.

In the 2014 regs, they replaced the "equal brake pressure" term with "equal force at the brake pads" --> so, "the writing is/was on the wall", some teams probably considered a form of "E-brakes". While 100% E-brakes are still not permitted for cars in most countries, you find E-brakes in the from of the parking brake in some newer cars. If the technology matures, we likely will see them as main operational brakes, similar to the aircraft ones, at one point in the future. Maybe still 5 year down the road.



#28 dau

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Posted 08 February 2014 - 19:29

[...]

Whenever I hear about "<something> by wire" I always remember this (not in a bad way but) in a way that *hit happens at the bleeding edge of systems development when you are trying to debug and get hard/soft systems & humans (eventually) interacting correctly.   Doing that without being able to do adequate real life testing time must be even more fun.

To be fair, that accident didn't really have much to do with the fly-by-wire system, but everything with irresponsible flying and macho attitude. I know this often gets blamed on Airbus and the FBW, because the alpha protection prevented them from pulling up, but it did so because they were already too close to stall speed. It was the crew that failed to maintain altitude, failed to maintain airspeed and failed to realize their situation until it was too late. 


Edited by dau, 08 February 2014 - 19:29.


#29 chipmcdonald

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Posted 09 February 2014 - 01:18

Chip, what you're writing is just as big a load of horse shit as it was the first 300 times you wrote it, I don't see the need for you to keep posting it over and over and over and over and over and over and over and over again.

 

 

 Lap times are going to be the same, torque at a lower rpm is the same thing as horsepower, and that someone is going to drive slower than the car they're following before they pass them.  Ok, I got it now.  2014 is just like last year, it's no different than 1982, restricted fuel and turbos.  Yep.  Ok.   :well:

 

/ Classy place.



#30 Wuzak

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Posted 09 February 2014 - 03:31

Last year if you used fuel to get in front, you could save fuel by going slower and hoping you stay in front as the faster cars behind you catch up.

 

If you go slower to save fuel, you're temporarily saving fuel but increasing the distance to the car you want to pass.  You're also allowing trailing cars to get closer.  Nobody was driving slow *before* trying to pass last year.  There is no reason for the leading car not to drive to the maximum speed given fuel flow parameters, he is not going to slow down while the trailing driver slows down to save fuel.

 

No, I am not saying there will be "no passing or overtaking".   I am saying that this year trying to force an error isn't likely to happen, and taking a non-efficient line is not going to be rewarded, the hystereis in energy use is much greater.  

 

Outside the DRS zone, if a trailing driver sees what he thinks is an error happening, or about to happen in front of him, does he step on it to try to take advantage?  Last year he would,  this year - outside of the first lap, I don't think so.  Another thing is the potential unaccountable waste in the first lap-first turn train, the concertina effect may exceed energy harvesting parameters.

 

I'm just thinking outloud.  Outside of the differences from last year, trying to make this year's math fit last year is not entertaining IMO.   If someone wants to be condescending or pretentious in response, have fun.  That's what I'm trying to do... :wave:

 

Let's say that there are two cars racing together. The one leading is going as hard as he can, while the one behind is keeping up easily, and could go faster if he could only get past. It is highly likely that the trailing car is using less fuel, because he is using less of his car's capabilities. Falling back and catching up may actually cost more fuel.

 

As this thread is about the use of the MGU-K and ES I will put it in those terms. The trailing car doesn't need as much power for acceleration as the one he is following because, presumably, he can maintain momentum better through corners (providing he is not too close) and will not need to use the MGU-K for acceleration. Thus he can store the energy for later use. Or he can replace the power of the ICE with that of the MGU-K, thus saving fuel.

 

If he elects to not use the MGU-K and instead stores the energy, he will fill up his ES in 2 laps at a track like Singapore. He could then choose to use that in a passing attempt, or save it up for an in-lap, out-lap or for when the driver ahead pits.

 

At Silverstone it will take 5 or 6 laps to fill the ES, so the ES/MGU-K will be less effective there.

 

In the first lap, there will, undoubtedly, be some energy used from the start. It is also unlikely that the first corner will have energy recovery more than for a normal lap. More than likely it will be less. The teams will have to account for how much energy they will use from the ES and how much they will recover in the first few corners to determine the amount of energy to store before the start. If they get it wrong, the brake-by-wire system will simply use more actual rear brakes and less MGU-K braking.



#31 toofast

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Posted 09 February 2014 - 04:15

 

At Silverstone it will take 5 or 6 laps to fill the ES, so the ES/MGU-K will be less effective there.

 

 

How long you reckon it will take if the MGU-H used solely to recharge ES without feeding MGU-K? I imagine it must be difficult to run more than two flying laps in Q3. Even 2 run is tight as you can't charge the ES in the pitlane.



#32 Wuzak

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Posted 09 February 2014 - 06:35

How long you reckon it will take if the MGU-H used solely to recharge ES without feeding MGU-K? I imagine it must be difficult to run more than two flying laps in Q3. Even 2 run is tight as you can't charge the ES in the pitlane.

 

About 50s at full engine power.



#33 mariner

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Posted 09 February 2014 - 11:12

Great thread, really interesting and it shows just what challenge the new rules will give the engineers.

 

I can see some opportunities for the best engineers to get a bgt advantage over the opposition early on with clever optimisation.

 

As a not very relevant but well tested comparison is regen. braking on electric trains

 

http://www.railwayga...redentials.html

 

The power savings dont usually exceed 15% despite having a theorectically umlimited "energy storage" capacity in the form of other trains drawing continously  on the regen.


Edited by mariner, 09 February 2014 - 11:34.


#34 BillBald

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Posted 09 February 2014 - 15:35

Let's say that there are two cars racing together. The one leading is going as hard as he can, while the one behind is keeping up easily, and could go faster if he could only get past. It is highly likely that the trailing car is using less fuel, because he is using less of his car's capabilities. Falling back and catching up may actually cost more fuel.

 

As this thread is about the use of the MGU-K and ES I will put it in those terms. The trailing car doesn't need as much power for acceleration as the one he is following because, presumably, he can maintain momentum better through corners (providing he is not too close) and will not need to use the MGU-K for acceleration. Thus he can store the energy for later use. Or he can replace the power of the ICE with that of the MGU-K, thus saving fuel.

 

If he elects to not use the MGU-K and instead stores the energy, he will fill up his ES in 2 laps at a track like Singapore. He could then choose to use that in a passing attempt, or save it up for an in-lap, out-lap or for when the driver ahead pits.

 

 

I think the following car can approach overtaking in different ways.

 

He could choose to close the gap to within 1 second to get the benefit of DRS. He could then allow the car in front to gain ground on initial acceleration, knowing that the DRS would allow him to close the gap again. So the car in front is using maximum ERS, the car behind is saving all of his. It shouldn't take very long at all before an overtake is possible.

 

The downside would be loss of downforce, but with less downforce that would be less of a factor. If the tyres are more durable this year, we shouldn't see the degradation which close running caused in previous years.

 

One interesting question is: how much info will the viewers have on a driver's fuel/ERS status? Ideally we'd like to know where each driver stands, but from the team and driver's point of view, this is info which they would not want to share.



#35 Ali_G

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Posted 09 February 2014 - 16:08

About 50s at full engine power.


You allowed to charge the ES via the MGU-H in the pits by just running the engine when in neutral ?

Edited by Ali_G, 09 February 2014 - 16:09.


#36 l2k2

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Posted 09 February 2014 - 19:27

You allowed to charge the ES via the MGU-H in the pits by just running the engine when in neutral ?

 

My gut-feeling says: Why would you not? It is normal engine operation after all.

 

However, why on earth would you do that? If you could do it, it would; first, waste fuel (which would rather be used for having more power later); second, overheat your engine (a stationary car does not have adequate air flow in the radiators).

 

Fortunately one can not do it (in any practical scale): because there is no load in neutral, little power is needed for hitting 15k limiter (and thus, there is no power to be harvested from the exhaust gases by the MGU-H).



#37 turssi

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Posted 09 February 2014 - 20:31

Can you drop the rear brakes altogether? Just recover up to the allowed limit and after that just use MGU-K to brake but not to recover. No redundant slowing down systems in my mind equals less weight to carry around.

#38 Wuzak

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Posted 09 February 2014 - 21:18

Can you drop the rear brakes altogether? Just recover up to the allowed limit and after that just use MGU-K to brake but not to recover. No redundant slowing down systems in my mind equals less weight to carry around.

 

No, the MGU-K is not powerful enough.



#39 TC3000

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Posted 09 February 2014 - 21:21

Can you drop the rear brakes altogether? Just recover up to the allowed limit and after that just use MGU-K to brake but not to recover. No redundant slowing down systems in my mind equals less weight to carry around.

 

there are some "issues" with your idea/proposal

 

- the rules stills mandate/stipulate the existence of what you call "a redundant slowing down system" (the brakes)

- if your are no charging the ES (battery) you would need to provide a "load" to dump the energy recovered into, a resistor or something like this, which would have it's own

  weight and would require cooling as well, so there is maybe not such a high gain

- you would limit your maximum rear braking performance to a max. of 120 kW, which would be quite a disadvantage overall - IMHO

 

but according to some reports, the rear brakes have become smaller this year because overall, the will do less work then before, not sure how correct, these reports are


Edited by TC3000, 09 February 2014 - 21:24.


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#40 Wuzak

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Posted 09 February 2014 - 21:22

You allowed to charge the ES via the MGU-H in the pits by just running the engine when in neutral ?

 

The engine would have to run at significant rpm and fuelusage to be able to actually recover energy.

 

According to the Cosworth estimations, the MGU-H does not start recovering power until ~8000rpm. And that's at full throttle. 



#41 balmybaldwin

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Posted 09 February 2014 - 21:32

Can you use the mgu k to drive the mgu h?

If youve recovered as much as you are allowed from the mgu k, but are still braking, can you use the excess power from the mgu k to spool up the turbo? would you want to?

I hope we get some good info on the power blends on screen when braking and accellerating

#42 Wuzak

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Posted 09 February 2014 - 22:22

Can you use the mgu k to drive the mgu h?

If youve recovered as much as you are allowed from the mgu k, but are still braking, can you use the excess power from the mgu k to spool up the turbo? would you want to?

I hope we get some good info on the power blends on screen when braking and accellerating

 

Yes you can. And the amount of transfer is unlimited.

 

The question is, would you want to?

 

The turbo can and will be spooled by the MGU-H to give better response. This is on the accelerating phase, and not likely to be desireable during braking.



#43 Ali_G

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Posted 09 February 2014 - 23:00

My thoughts are about charging the ES in the pits before a qualifying run.

Now that I think of it, this could be done quite easily via the MGU-K while having the rear wheels off the ground. All it would take would be an alternative engine management map I guess.

#44 toofast

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Posted 09 February 2014 - 23:12

My thoughts are about charging the ES in the pits before a qualifying run.

Now that I think of it, this could be done quite easily via the MGU-K while having the rear wheels off the ground. All it would take would be an alternative engine management map I guess.

 

The rule states you can't increase the amount of stored energy in ES in the pitlane. Whether you directly charge the battery or running MGU-K in the pitlane, you are in fact increasing the charge which is specifically prohibited.


Edited by toofast, 09 February 2014 - 23:13.


#45 Wuzak

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Posted 09 February 2014 - 23:13

My thoughts are about charging the ES in the pits before a qualifying run.

Now that I think of it, this could be done quite easily via the MGU-K while having the rear wheels off the ground. All it would take would be an alternative engine management map I guess.

 

Put the gearbox in neutral and run the pragram. At 120kW it would take 16.7s (2MJ) and 33.3s (4MJ) to charge.

 

Or you could get that on the out-lap.


Edited by Wuzak, 09 February 2014 - 23:24.


#46 toofast

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Posted 09 February 2014 - 23:27

Putthe gearbox in neutral and run the pragram. At 120kW it would take 16.7s (2MJ) and 33.3s (4MJ) to charge.

 

Or you could get that on the out-lap.

 

Not in the pit of course.

 

Out-lap would probably be enough but I think they need to push it a little bit more compare to last year.

 

One more important factor in qualifying this year, it is unlikely for drivers to do 2 consecutive max power lap, so you will need a recharge lap in between two max power lap.



#47 grunge

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Posted 10 February 2014 - 13:03

A few points
1.about kamui's comments...well he specifically referred to loss in rear aero downforce..last time he drove,there was significant rear exhaust blowing going on and the rear grip was way more than what he'll be experiencing now..loss of rear downforce will lead to sliding of the rear...the driver doesnt have enough confidence in getting back on the throttle on corner exit..less stress on the tires and theyll take longer to heat up as a result.

2.@Billbald...agreed on most points,though whether following cars will actually be easier this year,only time will tell..the overall downforce levels have decreased and the rear wash will be less,how that will work out in actual racing,no one knows.

3.@wuzak....kudos on an excellent analysis..although as someone pointed put brake bias is altered many times during a single lap,and then many times during different phases of the race..very difficult/impossible to use a fixed value in calculations

#48 Ali_G

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Posted 10 February 2014 - 13:05

Put the gearbox in neutral and run the pragram. At 120kW it would take 16.7s (2MJ) and 33.3s (4MJ) to charge.
 
Or you could get that on the out-lap.


Are you allowed to charge the ES via MGU-K while not under braking ? Aka, drawing energy off of the engine instead of under braking ? If this is the case, charging the ES fully for laps in qual won't be an issue at all ?

#49 TC3000

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Posted 10 February 2014 - 13:08

Put the gearbox in neutral and run the pragram. At 120kW it would take 16.7s (2MJ) and 33.3s (4MJ) to charge.

 

Or you could get that on the out-lap.

 

I think I'm with I2K2 in this one, you not only need the rpm, you need the "load" on the engine as well.

To be able to harvest the extra app. 110 hp (82 kW) from the MGU-H you not only need 11k rpm, you need your engine to make 600 hp at 11k rpm.

In neutral, with no load, you will have 11 rpm but your engine doesn't produce the power.

How much throttle do you need, to rev your roadcar (or bike) to the limiter (in neural)?

 

What you could do, but I don't think, that's the way they will do it, is to jack the car up, and drive it against the brakes, the same think you do, in a "normal" turbo car, if you want to built up the boost pressure. Rally cars at the start of an stage for example, used to do this - hard on your clutch as well, if the car is at standstill. (like a airplane, applying trust but still having the brakes on, before takeoff)

 

Which brings us to another question, and this was already bandied around last year, what do the rules say about "left foot braking", meaning in this context, what if you have an overlay between throttle and brake input? Are you allowed to harvest from the MGU-K under this condition?

If so, you could use this technique to charge the ES at the maximum possible rate.

It will cost a load of fuel, but in Qualifying this shouldn't matter.

The question is, do the rules allow this?


Edited by TC3000, 10 February 2014 - 13:59.


#50 wrcva

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Posted 10 February 2014 - 13:34

3.@wuzak....kudos on an excellent analysis..although as someone pointed put brake bias is altered many times during a single lap,and then many times during different phases of the race..very difficult/impossible to use a fixed value in calculations

 

since Wuzak's model is a rough proxy estimation, a point or interval estimate (+/- a few) won't make much of a difference, imo, as to how the underlying idea may result in practice (see TC's I curve graph above).   My bottom line take from the estimate is that the fuel constraint may not be as important issue as the ongoing perceived drama about it.   There are zillions of other variables that may produce totally unexpected outcomes but models are just that: educated guesses in the face of lack of better data/variables...  Some of TC's posts in the engine thread are also supporting similar outcomes.  

Thanks to both for sharing their knowledge in a language mortals can understand!