Why don't the teams use their 2017 cars on selected tracks?

[J.A.W.]

https://www.engineeringtoolbox.com/docs ... ensity.png

Baku is ~sea level?

Or maybe even a bit denser..

[jjn9128]

this amateur pilot has never known surface pressure outside the range 995-1015 millibar
throughout flight you need to know this pressure and confirm it to others - as altitude measurement is based on it

Hollus is correct, you're not seeing big pressure changes because pressure decreases as altitude increases - reducing the density of air - while temperature reduces with altitude (depending how high you're flying but amateur pilot would suggest low altitude) - increasing air density. Baku is at a fixed altitude


Having looked it up track temp in 2017 was ~56C (air 26C), this year it was ~27C (air 25C) - that's a 30C difference at track level, but only 1C air.

[Just_a_fan]

I have another question:
If the Porsche 919 EVO is able to beat an F1 car, why doesn't any team use the Porsche 919 EVO to compete in F1?

(I'm assuming this thread is just for nonsense questions, sorry if my interpretation is wrong.)

Because it's not an F1 car and doesn't meet any of the rules governing F1...except the bit about a car being a 4-wheel vehicle.

A nonsense question still requires a sensible answer

[J.A.W.]

this amateur pilot has never known surface pressure outside the range 995-1015 millibar
throughout flight you need to know this pressure and confirm it to others - as altitude measurement is based on it

Hollus is correct, you're not seeing big pressure changes because pressure decreases as altitude increases - reducing the density of air - while temperature reduces with altitude (depending how high you're flying but amateur pilot would suggest low altitude) - increasing air density. Baku is at a fixed altitude


Having looked it up track temp in 2017 was ~56C (air 26C), this year it was ~27C (air 25C) - that's a 30C difference at track level, but only 1C air.

Pretty sure that T-C, by "surface" - means ground-level.. & Baku is, AFAIR, actually below sea-level..

[jjn9128]

this amateur pilot has never known surface pressure outside the range 995-1015 millibar
throughout flight you need to know this pressure and confirm it to others - as altitude measurement is based on it

Hollus is correct, you're not seeing big pressure changes because pressure decreases as altitude increases - reducing the density of air - while temperature reduces with altitude (depending how high you're flying but amateur pilot would suggest low altitude) - increasing air density. Baku is at a fixed altitude


Having looked it up track temp in 2017 was ~56C (air 26C), this year it was ~27C (air 25C) - that's a 30C difference at track level, but only 1C air.

Pretty sure that T-C, by "surface" - means ground-level.. & Baku is, AFAIR, actually below sea-level..

Aaaaah yes. The point remains though - I would say he's probably not flying when air temp is 0C, and depending where he lives 30C may be unheard of (it's very rare here in the UK) - so the pressure/density change won't be as big as a 30C swing. I would say Hollus was confused about track and air temp - so the front wing and floor are probably close enough to have a sharp temperature gradient when track temp is 30C higher than air as it was last year - and experience density difference - but the rest of the car probably won't be... except the rear wing which has 400C exhaust blowing onto it... are we properly off topic now?

[jjn9128]

How do you explain cars getting slower in Barcelona, when the race is held in Summer, compared to the faster times they achieve in Winter? And Barcelona has high down force corners too!

Can I ask when you mean about times getting slower? Since 2014 laptimes at Barca have been reducing by 2-2.5s per year. Laptimes are slower in qualifying than testing because the tyres Pirelli take to winter testing are <2 steps softer than they take to the race - good for the cold temps (softer tyres have lower operating temps) and those headline grabbing times (fastest time on the hypersoft was over a second quicker than the fastest on the supersoft). Also as colder air is denser dowforce increases by the same as drag - colder/denser air also gives more power and means the cooling system has to work less hard (they can blank the cooling - brakes and rads - to save drag).

[wesley123]

How do you explain cars getting slower in Barcelona, when the race is held in Summer, compared to the faster times they achieve in Winter? And Barcelona has high down force corners too!

Because Barcelona is a high downforce track, and Baku is not.

Before coming to Baku in 2018, after 12 months from last race, the cars have gone through 12 months of development and the winter development. Plus, the power units have evolved and got better in terms of overall power. The tyres have gotten a step softer, which should have better grip, albeit less durable. If you compare the loss due to halo and the lower temperature to the factors I mentioned, it should still be a positive difference in performance. Yet, the cars are slower by a second! While Ferrari was faster by 2 tenths, Mercedes is slower by 1.1 seconds!

My hunch is, the tyres have taken away great deal of performance from the cars. In an effort to make the tyres less durable, it seems like Pirelli has created tyres which are far lower in grip, despite being in right temperature window.

No, the issue is that it was two months earlier. The general rule in that is that if it is earlier in the season, it's colder. The track was significantly colder, and the wind in between buildings doesn't help.

It has never happened that the cars have gotten slower from one season to next, while the regulations have stayed same. In my opinion, halo has added 6 kilos of weight to the car, but hasn't greatly changed the aero performance of cars. Actually, many teams expressed concerns when the nose regulations changed from 2014 to 2015 and admitted to have lost a lot of downforce, including Mercedes. But the cars still were faster in 2015, than in 2014. Throughout the last season when teams were trying halo, no one made statements about their aero being affected.

Have you considered the possibility that the cars aren't actually slower? It's weird to conclude the cars are slower when they were quicker in the first three races of the season

[Tommy Cookers]

the Engineering Toolbox plot that Hollus has shown is for air bounded in a particular way

ie it might be true of Baku if all the world's atmosphere fell by 20 deg when Baku's does
but Baku's air is bounded by the 99.999999999% of the world's atmosphere that does not really track Baku's temperature

if the Hollus argument was true ......
distance athletics would be dominated by cold air temperature - as 20 deg cooler air would give 7% more oxygen per lungful


(plot's boundary condition is equivalent to whole Baku-area column of atmosphere fenced-off from the rest of atmosphere ?)

[Greg Locock]

If the local air temp directly affected the local air pressure linearly then the air pressure would drop dramatically overnight.

[NathanE]

Isn't that why it's hard to stay awake at night?

[Greg Locock]

hohoho

here's a graph of atmospheric pressure in melbourne for the last week



and here's the temperature



hard to pick a 24 hour cycle in the pressure.

[Greg Locock]

Having said that there might be a bit of a peak at mid day, but nothing like 10/300*1000 =30 millibar

[jjn9128]

Having said that there might be a bit of a peak at mid day, but nothing like 10/300*1000 =30 millibar

Wasn't the original point about air density ()... not pressure ()...


Not that I'm not enjoying the graphs and analysis

[Greg Locock]

Oops, beg your pardon! P/(density*Temp) is a constant. In a day P ain't changing much so yes the density must change inversely proportional to the absolute temp. Sorry, wandered off down a blind alley.

[Tommy Cookers]

denser air will mix and/or run downslope of course
ok Baku is already downslope - but consider elsewhere eg Silverstone
and there's wind of course

considering aero forces aka 'density altitude' you can't assume density from temperature without pressure
however the Baku case had the temperature fall and the pressure rise - both increasing density
and the absolute humidity probably decreased with the temperature fall - further increasing density (H20 is lighter)

so I must apologise to Hollus for saying he was mistaken

differences in air density and humidity could in principle have quite large effects on engine power with these engines

EDIT
Greg's data shows a trend of pressure and temperature rise and fall together over days - and London data has the same pattern

broadly temperature and pressure rise and fall together and so air density changes little in the long term

though interestingly pressure isn't responsive to seasonal temperature differences (as I thought from 'experience')