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

[jjn9128]

when calculating aero forces you can't assume density from temperature alone
have we been given the pressures in the Baku case ?

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

This is an interesting topic... trying to relate the data to the original post and why the cars were slower at Azerbaijan this year:
Data for this years race, 29/4/18 - race 4-6pm:

Data for last years race, 25/6/17 - race 5-7pm:


Air temp this year was ~15°C for the race, last year was 29°C dropping to 25°C. Barometric pressure this year was 1020mb vs 1011/1012mb last year. Wind is really interesting, this year was ~55kph dropping to ~43kph but with gusts up to 68kph vs 15-23kph last year - and the direction was NNW in both cases. Looking at the circuit map that's a cross wind on the long start-finish straight - that gusting cross wind really messed with the cars coming out of T16 onto the straight this year.



So temp is ~15°C cooler and air pressure ~10mb higher - so air density 5.9% higher this year. Higher density and cooler conditions would help engine and cooling performance, but would increase aerodynamic drag. The gusting wind would play havoc with the aerodynamics. Cooler temperatures and the lower sun from the earlier race (I think it was cloudier too) meant track temperature (as mentioned earlier ~30°C lower) was lower so they also struggled getting all the tyre compounds (even the softest) into the correct temperature window.