2021 Mexican Grand Prix - Autódromo Hermanos Rodríguez, Nov 05 - 07

[godlameroso]

They run Monaco level wing and get Monza level downforce.

Monaco level wings for Spa level downforce is probably more accurate. The air is thinner but it's not that thin, air density is reduced by ~30%, although that doesn't translate into 30% less downforce exactly. What matters is the relationship between the high and low pressure surfaces and the way flow is organized around the chassis.

If there's 30% less drag, then the air flowing under the car is also ~30% faster, meaning the velocity differential between the upper surface of the car, and the floor is not altered linearly.

Larger opening to the leading edge of the floor, may help around Mexico, Alpine style.

https://www.mclaren.com/racing/2017/mex ... uit-stats/

Mclaren themselves say otherwise, it's actually less downforce than Monza.

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

[godlameroso]

They run Monaco level wing and get Monza level downforce.

Monaco level wings for Spa level downforce is probably more accurate. The air is thinner but it's not that thin, air density is reduced by ~30%, although that doesn't translate into 30% less downforce exactly. What matters is the relationship between the high and low pressure surfaces and the way flow is organized around the chassis.

If there's 30% less drag, then the air flowing under the car is also ~30% faster, meaning the velocity differential between the upper surface of the car, and the floor is not altered linearly.

That's double counting - the drag is reduced because the density is reduced. It doesn't mean the air travelling under the car is going 30% too. The air is less dense all around the car and thus the mass conservation is maintained. Mass of air under the car is density*velocity*sectional area of the underfloor volume. If the density of the air going under the floor at the front (and coming out at the back) is reduced, the mass flow is reduced proportionally that's all.

Reduced air density leads to reduced drag and reduced lift/downforce and it does so linearly and proportionally. The equations are the same just with different coefficients (Cd and Cl).

I fear the day equations predict things as perfectly as you imply. Then I'd be out of a job.

[Tizz]

Monaco level wings for Spa level downforce is probably more accurate. The air is thinner but it's not that thin, air density is reduced by ~30%, although that doesn't translate into 30% less downforce exactly. What matters is the relationship between the high and low pressure surfaces and the way flow is organized around the chassis.

If there's 30% less drag, then the air flowing under the car is also ~30% faster, meaning the velocity differential between the upper surface of the car, and the floor is not altered linearly.

Larger opening to the leading edge of the floor, may help around Mexico, Alpine style.

https://www.mclaren.com/racing/2017/mex ... uit-stats/

Mclaren themselves say otherwise, it's actually less downforce than Monza.

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

Sources indicate that the atmospheric airpressure at 2000m is about 75% of the pressure at sealevel AND the relative amount of oxygen in the air decreases from 21% at sealevel to 16.5 % at 2000m. Meteo is not my thing but multiplying these two results in 40% less oxygen at 2000m. If that is correct, it is far more than I would have guessed. I guess they will cut some holes in the bodywork to suck in more air.

[godlameroso]

Ferrari will be very strong on the medium tire, not so much on the hard. They'll find it difficult to get the tire working in its sweet spot.

If they make the hard tire work it will be at the expense of the other two compounds.

How do you know ?

Probably did a few laps on the F1 game.

34 laps but the real track is so different from the game it's almost useless to compare. 2019 however painted a nice picture, extrapolating changes made to Firelli tires. Ie heavier and harder leads me to believe hard tires will be even more of a handful than they were in 2019.

Several drivers were complaining about lack of pace and grip on hards in 2019. Sainz Verstappen both Ferraris.

[DChemTech]

https://www.mclaren.com/racing/2017/mex ... uit-stats/

Mclaren themselves say otherwise, it's actually less downforce than Monza.

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

Sources indicate that the atmospheric airpressure at 2000m is about 75% of the pressure at sealevel AND the relative amount of oxygen in the air decreases from 21% at sealevel to 16.5 % at 2000m. Meteo is not my thing but multiplying these two results in 40% less oxygen at 2000m. If that is correct, it is far more than I would have guessed. I guess they will cut some holes in the bodywork to suck in more air.

it's not a multiplication - the 16.5% or thereabouts is the 'effective concentration' as it would be when comparing it with sealevel (more or less 0.75*21%). The oxygen fraction is actually very similar at different heights. Percentages just aren't very convenient - better use partial pressures

[Tizz]

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

Sources indicate that the atmospheric airpressure at 2000m is about 75% of the pressure at sealevel AND the relative amount of oxygen in the air decreases from 21% at sealevel to 16.5 % at 2000m. Meteo is not my thing but multiplying these two results in 40% less oxygen at 2000m. If that is correct, it is far more than I would have guessed. I guess they will cut some holes in the bodywork to suck in more air.

it's not a multiplication - the 16.5% or thereabouts is the 'effective concentration' as it would be when comparing it with sealevel (more or less 0.75*21%). The oxygen fraction is actually very similar at different heights. Percentages just aren't very convenient - better use partial pressures

Thx ! I take your word for it. It is still a bigger difference then I would have thought.

[Just_a_fan]

https://www.mclaren.com/racing/2017/mex ... uit-stats/

Mclaren themselves say otherwise, it's actually less downforce than Monza.

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

Sources indicate that the atmospheric airpressure at 2000m is about 75% of the pressure at sealevel AND the relative amount of oxygen in the air decreases from 21% at sealevel to 16.5 % at 2000m. Meteo is not my thing but multiplying these two results in 40% less oxygen at 2000m. If that is correct, it is far more than I would have guessed. I guess they will cut some holes in the bodywork to suck in more air.

Oxygen is the same as a percentage of the total volume of air at altitude but the effective amount (in terms of how much is useable by an organism / engine) reduces with altitude because the density with altitude (that's what the pressure reduction means) reduces i.e. each lungful/intake stroke of air has fewer molecules of nitrogen, oxygen, etc., in it.
http://www.altitudemedicine.org/physiology

[dans79]

Rayleigh scattering is well known.

Yep, it's shocking how many people don't know how much fine particulate exists in the atmosphere. moisture, volcanic ash, forest fire particulates, industrial exhaust byproducts, pollin, it's almost a never ending list.

[PlatinumZealot]

https://www.mclaren.com/racing/2017/mex ... uit-stats/

Mclaren themselves say otherwise, it's actually less downforce than Monza.

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

Sources indicate that the atmospheric airpressure at 2000m is about 75% of the pressure at sealevel AND the relative amount of oxygen in the air decreases from 21% at sealevel to 16.5 % at 2000m. Meteo is not my thing but multiplying these two results in 40% less oxygen at 2000m. If that is correct, it is far more than I would have guessed. I guess they will cut some holes in the bodywork to suck in more air.

Think about that figure though. Can humans survive comfortably on 40% of the oxygen that they normally breathe?

Hehe

Here I did the work for you.
https://www.iqair.com/us/mexico/mexico-city

In Mexico City, a cubic meter of air contains 212 grams of oxygen, while at sea level it contains 275. The combustion efficiency of a well-tuned car is 92 per cent, and in the DF 69 per cent, due to the higher altitude.

So the oxygen density in the air is about 77% versus sea level.

Also from other articles, the oxygen concentration inside the lungs of people is actually about 90% versus sea level.

Note for an F1 engine the combustion efficiency will not drop much due to turbocharging. The turbochargers will only spin faster to make the same boost.

[Ced]

Ferrari will be very strong on the medium tire, not so much on the hard. They'll find it difficult to get the tire working in its sweet spot.

If they make the hard tire work it will be at the expense of the other two compounds.

How do you know ?

Probably did a few laps on the F1 game.

[Mansell89]

I remember a couple of years back now someone talking about how traction and mechanical grip are highly important at Mexico, and that the straight line speed isn’t as important as it looks when you see the long straight on the layout.

When Red Bull have out performed Mercedes here on a couple of occasions and/or looked very fast here- usually when they’ve been off the pace overall in the season- have they been years where the RBR car has had particularly strong traction (ie those years where RBR held the edge at Monaco)?

Reason I ask is that when I watch the cars at Mexico, to my naked eye I think it might suit Ferrari, as I did with Monaco. It isn’t a fast flowing circuit like some of the European tracks where Merc have always been good, and I just wonder if they might cause a bit of headache to Merc and/or Red Bull this weekend?

[godlameroso]

I remember a couple of years back now someone talking about how traction and mechanical grip are highly important at Mexico, and that the straight line speed isn’t as important as it looks when you see the long straight on the layout.

When Red Bull have out performed Mercedes here on a couple of occasions and/or looked very fast here- usually when they’ve been off the pace overall in the season- have they been years where the RBR car has had particularly strong traction (ie those years where RBR held the edge at Monaco)?

Reason I ask is that when I watch the cars at Mexico, to my naked eye I think it might suit Ferrari, as I did with Monaco. It isn’t a fast flowing circuit like some of the European tracks where Merc have always been good, and I just wonder if they might cause a bit of headache to Merc and/or Red Bull this weekend?

If that's the case, McLaren will be strong as well.

[Zynerji]

I did predict McL and Ferrari on the podium here on page one for these reasons...

[SiLo]

Monaco level wings for Spa level downforce is probably more accurate. The air is thinner but it's not that thin, air density is reduced by ~30%, although that doesn't translate into 30% less downforce exactly. What matters is the relationship between the high and low pressure surfaces and the way flow is organized around the chassis.

If there's 30% less drag, then the air flowing under the car is also ~30% faster, meaning the velocity differential between the upper surface of the car, and the floor is not altered linearly.

Larger opening to the leading edge of the floor, may help around Mexico, Alpine style.

https://www.mclaren.com/racing/2017/mex ... uit-stats/

Mclaren themselves say otherwise, it's actually less downforce than Monza.

I spotted a typo. There is 25% less air not 75% less oxygen. But mistakes happen.

I think they meant to write that there is 75% of sea level Oxygen levels. Rather than 75% less oxygen. Anyway the point was that they run the highest downforce package and that they have less downforce than in Monza.

[zibby43]

This still the race thread?