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We are debating how efficiency should be defined, partly in order to decide exactly what the Mercedes means when it quotes efficiency targets.

Lest we forget ... There's no way they'll be giving any usable information away ... misleading gnomic statements are all part of the game.

E.g. Cosworth HB "using ceramic materials in cylinder head components".

xpensive wrote:

gruntguru wrote:No! That would include energy that has been used more than once. You cannot include regenerative braking in an efficiency calculation.
...

"Energy that has been used more than once"? An interesting concept that, as energy is indestructible, kindly elaborate?

Used to "propel the car" more than once. So some work is used to accelerate the car it is recovered during braking, stored in the ES the used to accelerate the car again" This work has nothing to do with the ICE and would never be included in an efficiency calculation by Mercedes.

Matters little IMO, it's still energy recovery improving the PU's efficiency, not the ICE's.

wuzak wrote:

Pierce89 wrote: You do realise that energy also came from the fuel don't you?

The problem is that the fuel that is used to store energy in the ES is not part of the 100kg/s on which you are basing your efficiency calculation.

It is also, partly, chassis dependent. ie some cars are faster in a straight line, allowing more braking potential, some are better, more stable, under braking and can recover energy better.

The fuel that creates energy in the ES, absolutely came out of the 100kg/h.

gruntguru wrote:

xpensive wrote:

gruntguru wrote:No! That would include energy that has been used more than once. You cannot include regenerative braking in an efficiency calculation.
...

"Energy that has been used more than once"? An interesting concept that, as energy is indestructible, kindly elaborate?

Used to "propel the car" more than once. So some work is used to accelerate the car it is recovered during braking, stored in the ES the used to accelerate the car again" This work has nothing to do with the ICE and would never be included in an efficiency calculation by Mercedes.

Why are you so sure Merc's claim is "only ICE" and not the total PU. It makes more sense to efficency rate the whole PU as it was all designed to run in an integrated fashion.

Pierce89 wrote:Why are you so sure Merc's claim is "only ICE" and not the total PU.

Because:
1. What you are suggesting does not meet any definition of an efficiency that could be used to usefully compare power units. The number obtained would depend on a vast array of irrelevant variables including aerodynamic drag, friction, rule limitations on MGUK output, track layout etc
2. Mercedes Benz actually employ engineers - people who understand thermodynamics - and would never use such a nonsensical metric. Their reputation would be trashed.
3. 40% is way too low for the metric you describe. 40% is the thermal efficiency being currently achieved by auto makers - without compounding. With compounding 40+% is what you would expect from the current F1 PU's.

It makes more sense to efficency rate the whole PU as it was all designed to run in an integrated fashion.

No it doesn't. All you are doing is adding a number dictated by the rules - 120kW - to the crankshaft output of the ICE. Doesn't make any sense at all.

Pierce89 wrote:

wuzak wrote:

Pierce89 wrote: You do realise that energy also came from the fuel don't you?

The problem is that the fuel that is used to store energy in the ES is not part of the 100kg/s on which you are basing your efficiency calculation.

It is also, partly, chassis dependent. ie some cars are faster in a straight line, allowing more braking potential, some are better, more stable, under braking and can recover energy better.

The fuel that creates energy in the ES, absolutely came out of the 100kg/h.

Not necessarily. 100kg/hr is an "instantaneous" value and an efficiency calculation is only valid if the output and the input are measured in the same instant. It is not valid to store energy that was generated some time previously then add it in to the current power measurement and claim it was generated from the current fuel flow.

If you begin to take the fourth dimension into consideration, there's simply no end to where you go.

Myself, I'm happy with with dividing Pout with Pin, but I guess I'm a dinosaur.

Pierce89 wrote:

wuzak wrote:

Pierce89 wrote: You do realise that energy also came from the fuel don't you?

The problem is that the fuel that is used to store energy in the ES is not part of the 100kg/s on which you are basing your efficiency calculation.

It is also, partly, chassis dependent. ie some cars are faster in a straight line, allowing more braking potential, some are better, more stable, under braking and can recover energy better.

The fuel that creates energy in the ES, absolutely came out of the 100kg/h.

I can't recall if the energy in the ES can be added in the pits. If it can, them its energy is not from the 100kg/hr limit.

In any case, the energy from the ES is not from the fuel flow at point of efficiency measurement. It has been stored at another time.

It is an additional input to the system. The ES is equivalent to the fuel tank - it holds energy in a different way.

I believe the fourth dimension is messing with our minds here, with all this discussion, I'm not so sure myself how to behold
and express it intellectually.

It is however clear to me that no other energy than the 27.8 g/s has entered the fray, which is Pin to me.

What is Pout?

xpensive wrote:I believe the fourth dimension is messing with our minds here, with all this discussion, I'm not so sure myself how to behold
and express it intellectually.

It is however clear to me that no other energy than the 27.8 g/s has entered the fray, which is Pin to me.

What is Pout?

Pin is the 100kg/hr fuel flow plus the power being transferred from the ES.

Pout is the drive to the rear wheels and energy transferred directly to the ES (from the MGUH or from dragging the MGUK against the engine).

wuzak wrote: I can't recall if the energy in the ES can be added in the pits. If it can, them its energy is not from the 100kg/hr limit.

In any case, the energy from the ES is not from the fuel flow at point of efficiency measurement. It has been stored at another time.

It is an additional input to the system. The ES is equivalent to the fuel tank - it holds energy in a different way.

I believe they can, I remembering the commentators mentioning charging the batteries of Rosberg's car in the pits during one the Austrian free practices.

wuzak wrote:

xpensive wrote:I believe the fourth dimension is messing with our minds here, with all this discussion, I'm not so sure myself how to behold
and express it intellectually.

It is however clear to me that no other energy than the 27.8 g/s has entered the fray, which is Pin to me.

What is Pout?

Pin is the 100kg/hr fuel flow plus the power being transferred from the ES.

Pout is the drive to the rear wheels and energy transferred directly to the ES (from the MGUH or from dragging the MGUK against the engine).

I think this is where time is playing tricks here, over a certain sequence, there is no other Pin than 27.8 g/sec, is there?

Pout must always be power delivered to the driving wheels, no?

xpensive wrote:If you begin to take the fourth dimension into consideration, there's simply no end to where you go.
Myself, I'm happy with with dividing Pout with Pin, but I guess I'm a dinosaur.

I agree - and Pout is P (crankshaft) + P (nett turbine)

Whether they include the ERS in their brandished efficiency numbers I'm really not sure. However one point that many who commented here missed is that up yes there is a 120kW boost but don't forget that using all 120kW means that you will only have something like 31 or 33 seconds or whatever it was of ERS-K per lap. If you want to find a final efficiency number including the ERS system then I suggest you take the average time a car spends on the throttle per lap and work out how much of a continuous power boost the ERS-K can provide for the whole time the car is on throttle. I'm pretty sure it will be quite a bit less than 120kW.

The Mercedes engine with its large turbocharger turbine seems to be biased towards pure reduction in back pressure at high exhaust mass flows. This means that it will have less capacity to charge the battery pack through the ERS-H system while simultaneously powering the turbocharger compressor. Because of that I wouldn't try to include power coming from the ERS-H to the battery pack into any efficiency calculations for the Mercedes engine.