[WEC] BoP. Brilliant or Pants.

[tomcug]

https://www.youtube.com/watch?v=OuaYbm5PJ54
Estre last year at night. A bit over 250 in the Porsche curves too but obviously a small power cut won't make a difference there

[Adam43]

Originally Posted by veeten

Also, those were night laps, where the Cadillac is at it's best. N/A engines really shine at that time, where the temps are at their coolest.

Now, think about that and remember that the Aston Martin will be sporting an N/A V-12 engine next year.

The rules dictate the output of the engine and it is measured (with the combined electric motor). So the change in conditions shouldn’t change the output.

The rules are like this to allow a variation of engines and drivetrains.

[TF110]

There must be fancy engine mapping or something with these manufacturers to be able to meet the changes in the bop. Less power, more power... now the power gain. I would like to know how they can do these adjustments seemingly from race to race.

[Adam43]

And it is the combined power with the electric motor. Clever it is.

Although I suspect the really clever bit is in the measurement and the feedback loop. Once you nail that the change is easy.

Then you get to the bit where you can be really clever and get an advantage from it.
How do you deploy the power. Electric motor or combustion. For the ones with front wheel drive as an option that gives you some advantage, but even rear wheel hybrid has meant this is an area of focus. Acura have spent a lot of time here. And it is very relevant road car tech and an area to train engineers.

[Alan52]

I just want to thank you Adam43 for your brilliant BoP analysis.By far the best I’ve seen anywhere including the “professional” media.

[Truckosaurus]

Originally Posted by TF110

...I would like to know how they can do these adjustments seemingly from race to race.

To a layman like me it seem 'magic' they can just whip out the laptop and knock a few BHP off the power output.

Are they able to divert excess power into charging the batteries? (or is that against the regulations/laws of physics?)

[Adam43]

Originally Posted by Alan52

I just want to thank you Adam43 for your brilliant BoP analysis.By far the best I’ve seen anywhere including the “professional” media.

That is very kind. Thank you. I first did it, and still do, to try and understand what is going on. To see if I can infer the reasons behind it. It’s nice to get feedback on it and also it’s a reason to keep on top of it with the forum.

[Adam43]

Originally Posted by Truckosaurus

To a layman like me it seem 'magic' they can just whip out the laptop and knock a few BHP off the power output.

Every race gives them more data. I’d argue if they didn’t make changes regularly they would be missing out.

Further we are still in early days. And with so many new cars joining this year they were always going to start conservative for these and then adjust as they got more info on these cars. As time goes on the adjustments won’t disappear. They will just get smaller. With the exception of the odd correction that is needed, jokers, or new cars.

Are they able to divert excess power into charging the batteries? (or is that against the regulations/laws of physics?)

I believe the battery is only charged by the braking regen. There is a diagram in the rules. This is pretty close to doing that anyway. Engine puts power into the drivetrain, battery gets it from there.

[tomcug]

Originally Posted by Truckosaurus

Are they able to divert excess power into charging the batteries? (or is that against the regulations/laws of physics?)

No idea about LMH but LMDh can have up to 50 kW of regen from ICE (or other similar value, it was mentioned in one of Marshall Pruett's videos). However that feature isn't any more beneficial with the power gain adjustment than without it because that potential power loss isn't some extra energy you can harvest on the hybrid and use it to extend stint's length as power cut means your maximum energy per stint is also lowered. Nice concept tho

[Adam43]

Yeah. Power is total of both.

The advantage is that you carry less fuel. Which, if nothing else, helps consistency with set up.

Also it is something you can tune to help handling. More so on FWD hybrid (albeit limited to >190km/k), but also on RWD hybrid (LMDh).

[Articus]

Originally Posted by Sodemo

One thing to note, the lightest car is still carrying 6kg more than the base weight. Why don’t they just lower all the weights by 6kg? Doesn’t look very efficient or eco friendly if all the cars are carrying 6kg more than necessary?

They need margin in the system in case a BOP adjustment during the race weekend is required.

[Articus]

@Adam43, do you have an opinion on the lack of a reference driver weight in the regulations? Does this not corrupt and/or manipulate the BOP process or do you think the FIA accounts for this somehow?

The drivers in the hypercar class vary in weight anywhere from 60 to 75 kg. The Porsche motorsport website list Julian Andlauer at 60kg. They list Michael Christensen at 75 kg. This is a 15kg difference in driver weight. This is larger than the size of an average BOP adjustment.

Since the BOP weight does not include the driver, this means that larger drivers make their cars slower than the lighter drivers. When we are comparing cars like the Toyota, Ferrari, Alpine, Porsche, how can BOP be designed without this consideration? Also, why are the larger drivers being punished?

[Articus]

Originally Posted by Adam43

250 not 210km/h

Toyota
They also received a relative drop in power >250km/h (yes, a + adjustment, but they lost power overall). They've been a little up and down through the year, but generally lower than most.
It seems to be working the opposite way to Lamborghini as they seem to want to cut acceleration (they have AWD unlike Lambo). They returned some of that for top speed, but didn't quite offset that from a top speed. Perhaps the ACO didn't want to give more than the +0.9% as that is the max anyone got. Another theory.

I also cannot understand the strange figures in the power gain table. 0.9% feels like a pulled out of the arse number. How can so many cars figure precisely a 0.9% gain to balance them. On the surface, it is a random gain because the base power level for each car differs. I am suspicious about the meaning of it.

[Adam43]

Originally Posted by Articus

They need margin in the system in case a BOP adjustment during the race weekend is required.

That’s an interesting theory.

Whether during the Le Mans or just between events it could mean your just changing one or two cars instead of them all. I suppose it doesn’t really matter, but I like the theory.

[Adam43]

Originally Posted by Articus

I also cannot understand the strange figures in the power gain table. 0.9% feels like a pulled out of the arse number. How can so many cars figure precisely a 0.9% gain to balance them. On the surface, it is a random gain because the base power level for each car differs. I am suspicious about the meaning of it.

I think you have to consider with the other change from Spa. I could imagine they didn’t want to go higher than a certain amount with the new parameter and this is what they chose as a cap. Then you have to consider with the base power change.

Still we’ve had they can’t be that precise that they have every car different in BoP and also why are some the same.

It is also the first time they’ve used this. They’ve probably kept the adjustment relatively small and simple for the first iteration. Which is fair approach.

[TF110]

Imo, this is a trial for the test day and they're using data they have so far, but I expect changes and some complaints/praise on it.

[Articus]

Originally Posted by Adam43

250 not 210km/h

Lamborghini
It gets a reduction in >250km/h power despite being the slowest top speed.
I think there are potentially two things here. Firstly the data from Spa is rubbish. There is only one car and it didn't have that many competitive laps.
If you look at the overall event though it still doesn't look good. If you look at Imola it was much nearer the top. Qatar near the bottom. So inconclusive here - you could argue anything.
I wonder if there is a subtlety here. Overall all it got the biggest bump in power from Spa to Le Mans (<250km/h). Maybe the ACO wanted to give it a little more acceleration, but that needed offsetting at high speed. Well, it's a theory.

Toyota
They also received a relative drop in power >250km/h (yes, a + adjustment, but they lost power overall). They've been a little up and down through the year, but generally lower than most.
It seems to be working the opposite way to Lamborghini as they seem to want to cut acceleration (they have AWD unlike Lambo). They returned some of that for top speed, but didn't quite offset that from a top speed. Perhaps the ACO didn't want to give more than the +0.9% as that is the max anyone got. Another theory.

As always, if you spot anything; a typo, an error in the calculation, let me know.

The chart shows the relationship between Spa Max Speed and the total adjustment to >250km/h power between Spa and Le Mans:

It wouldn't make sense to me that the ACO would use the top speeds in Spa directly to make the power gain table at Le Mans so that may be an explanation for why Lamborghini and Toyota do not correlate.

I think there is an explanation. Each team makes a choice of how much downforce and cooling to run each weekend within their setup window. The regulations permit a single adjustable aerodynamic device on each car (typically the rear wing on most cars), as well as blanking for the cooling ducts and radiators. Increased wing angles reduces top speed. Increasing the cooling openings reduces top speed.

So teams have a window to play with. If you compare the Porsche 963 cars at Spa, the #38 car only reached 311.4 km/h in qualifying. The #5 Penske car reached 313.2 km/h. The #7 Toyota reached 317 km/h, but the #8 Toyota only reached 313 km/h. The 51 Ferrari reached 315 km/h but the 83 Ferrari only reached 313 km/h.

So the ACO has to have a reference point for the aerodynamic configuration to know if they are truly balancing top speed, or if one team is just reducing the wing angle and blocking off cooling inlets while another uses a higher wing angle and more cooling openings. Otherwise a team who wants to game the Le Mans BOP would simply run their highest downforce settings at Spa and claim their top speed is low.

[Adam43]

Originally Posted by Articus

@Adam43, do you have an opinion on the lack of a reference driver weight in the regulations? Does this not corrupt and/or manipulate the BOP process or do you think the FIA accounts for this somehow?

The drivers in the hypercar class vary in weight anywhere from 60 to 75 kg. The Porsche motorsport website list Julian Andlauer at 60kg. They list Michael Christensen at 75 kg. This is a 15kg difference in driver weight. This is larger than the size of an average BOP adjustment.

Since the BOP weight does not include the driver, this means that larger drivers make their cars slower than the lighter drivers. When we are comparing cars like the Toyota, Ferrari, Alpine, Porsche, how can BOP be designed without this consideration? Also, why are the larger drivers being punished?

Interesting point. The relative difference in weights of drivers and cars.

I don’t class it as a BoP issue. For me it is the philosophy of what they want to do with driver weights.
The relative driver weights is the same if you’ve got BoP or a simple minimum weight.

Maybe it is making it harder to measure performance, but maybe they allow for this.

Some series compensate for driver weights. Often a single seater thing and other series don’t. Even if you simply correct for driver weights there is still an advantage to being lighter as you get more ballast to tune with. Although some regulate where this can be.

If there was a safety concern then I’d be worried, but it’s OK. Car safety isn’t being compensated. Driver’s aren’t dangerously dieting. The pros are super fit and relatively light, but healthily so.

If they changed to compensate for driver weight it would be interesting for they do it. Average of all drivers? Additional weight added or removed in seats in pit stops? Penalties! How do they consider weight loss in a quadruple stint? Not insurmountable, but equally I can see why they steer clear!

[Adam43]

Originally Posted by Articus

It wouldn't make sense to me that the ACO would use the top speeds in Spa directly to make the power gain table at Le Mans so that may be an explanation for why Lamborghini and Toyota do not correlate.

I think there is an explanation. Each team makes a choice of how much downforce and cooling to run each weekend within their setup window. The regulations permit a single adjustable aerodynamic device on each car (typically the rear wing on most cars), as well as blanking for the cooling ducts and radiators. Increased wing angles reduces top speed. Increasing the cooling openings reduces top speed.

So teams have a window to play with. If you compare the Porsche 963 cars at Spa, the #38 car only reached 311.4 km/h in qualifying. The #5 Penske car reached 313.2 km/h. The #7 Toyota reached 317 km/h, but the #8 Toyota only reached 313 km/h. The 51 Ferrari reached 315 km/h but the 83 Ferrari only reached 313 km/h.

Tat'


So the ACO has to have a reference point for the aerodynamic configuration to know if they are truly balancing top speed, or if one team is just reducing the wing angle and blocking off cooling inlets while another uses a higher wing angle and more cooling openings.

Yes, that could be why. To a certain extent I tried to compensate by averaging the cars from one manufacturer. Lamborghini data is the worst here.

The ACO will have a better understanding and knowledge of this.

I was pleased that it was Spa before. While not perfect (no track is), it is probably the most Le Mans representative of all. Also, nowadays, there is much less variation here. No special Le Mans bodywork. Or special non Le Mans bodywork!

Your point is valid and could be why the correlation didn’t work for Toyota and Lamborghini. It was damn fine for the others.

A silly point, I meant to do square of the speed as drag increases with that. Just for fun. Although over a narrow range it is fine to do a linear relationship.

[Articus]

I also have been playing around with the BOP information after each event but have not had anywhere to share. I joined this forum a very long time ago and had forgotten that I was a member. It's nice to see there is a place where I can ramble with others about the BOP table.

I decided to do something interesting which was to calculate a weighted average power to weight ratio for each car based on the Le Mans BOP. The reason for the weighted average is to approximate the average power-to-weight ratio over the entire lap at Le Mans, considering there are two reference power numbers, one above and one below 250km/h.

For this method, I watched an onboard lap from last year's event and estimated around 60% of the lap spent above 250km/h. So to compute the average power permitted by the regulation around the full lap, you simply take a weighted average of the two power figures where the weightings are 60% to the above 250km/h value and 40% to the below 250km/h value.

The formula is below



You can adjust the weightings as you like.

Once you compute the weighted average power level, you can compute the weighted average power-to-weight ratio. I have shown all values in the table below and included the 2023 Le Mans power-to-weight figures for returning cars (excl. Peugeot) for comparison.




According to the weighted average calculation, Toyota and Ferrari both seem to have increased power per kilogram compared to last year. Porsche less. You can see that in the figures for the below 250kph, above 250kph, and the weighted average tallies for 2024, compared to 2023.

It is difficult to understand the meaning so far. A cursory glance would suggest Ferrari was somehow a minor beneficiary (from 0.478 last year to 0.482 average this year) but that Toyota is a significant beneficiary going from 0.474 to 0.485 power to weight ratio. Porsche on the other hand had their performance potential reduced from 0.492 to 0.490. Perhaps it reflects what it takes to keep Toyota competitive vs all of the performance that Ferrari and Porsche have unlocked over the winter? Either that is the case, or Toyota will run away with it.

[Articus]

Also, I learned something interesting. The Lamborghini is currently unable to reach the BOP weight that it has been assigned. It is stated in their second episode of the youtube documentary for the program. In Qatar the excess weight was said to cost them 0.5 sec compared to the minimum weight they were allowed by the BOP (1041kg). The car is homologated. I don't think they can change anything without the usage of jokers. The car is in need of a significant diet.

The only thing the ACO can do for them currently is to give them more power which is why they have 519kw below 250km/h to improve their acceleration. The limit of the category is 520kw. There is hardly any room to increase the power more and this does not help with the braking and cornering. I expect them to continue to run off the pace on most circuits until they can properly reduce the car's weight. I wonder if this failure is the reason that Giorgio Sanna was fired. They homologated an overweight car.

[Articus]

And a direct comparison of Spa 2024 vs the Le Mans weighted average power to weight ratio.



Relative change vs Spa with Porsche as the reference:

[TF110]

Originally Posted by Articus

Also, I learned something interesting. The Lamborghini is currently unable to reach the BOP weight that it has been assigned. It is stated in their second episode of the youtube documentary for the program. In Qatar the excess weight was said to cost them 0.5 sec compared to the minimum weight they were allowed by the BOP (1041kg). The car is homologated. I don't think they can change anything without the usage of jokers. The car is in need of a significant diet.

The only thing the ACO can do for them currently is to give them more power which is why they have 519kw below 250km/h to improve their acceleration. The limit of the category is 520kw. There is hardly any room to increase the power more and this does not help with the braking and cornering. I expect them to continue to run off the pace on most circuits until they can properly reduce the car's weight. I wonder if this failure is the reason that Giorgio Sanna was fired. They homologated an overweight car.

Interested in the real weight of the Lamborghini then. Is it stated anywhere by them what they actually weigh? Perhaps they will use an update to produce a car that can make the weight. I don't know if they have to use a joker or not but they'll have to get on top of it!

[Truckosaurus]

For driver weights, I don't think you can do much about it in a series where each car has multiple drivers - as even averaging it out over 2 or 3 drivers still gives an advantage when the lightest driver is in the car.

You can't really be bolting on ballast during driver changes.

Also, differences in driver weights is minimal compared to the difference between a full tank of fuel and an empty one.

[tomcug]

Originally Posted by TF110

Interested in the real weight of the Lamborghini then. Is it stated anywhere by them what they actually weigh? Perhaps they will use an update to produce a car that can make the weight. I don't know if they have to use a joker or not but they'll have to get on top of it!

I remember that this weight issue was already mentioned during the pre-homologation testing. They said they must have still worked on minimal weight and it turns out they failed! Also a strong hint that most of these cars don't carry much ballast (if at all) to reach 1030 kg and that's something that was discussed here before.