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Speed drop at end of Baku straight

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#1 4ren

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Posted 01 May 2018 - 06:29

I noticed the speed of all cars (Mercedes included) dropped at the en of the main straight. The driver lifts off the throttle in a timed lap once he crosses the S/F line, but this happened during the race. I would think that the harvesting from the MGU-H would be enough to keep the batteries. The RedBulls were complaining about battery issues, and that makes me think that their battery was draining quicker than others. I wasn't aware of this speed drop until Baku, maybe because the straight is so long?

This is an example of a RedBull. It tops 320 kph but as it crosses the grid, speed begins to drop.



#2 thegforcemaybewithyou

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Posted 01 May 2018 - 12:15

What you see at the end of the straight is called derating. The MGUK isn't driving the wheels anymore after a certain point, only the combustion engine is. The energy that the MGUH can recover is now used to charge the battery instead of driving the MGUK (the wheels). This strategy of saving the electric energy for later use early on the next straight is done to keep the laptime loss as small as possible.


Example from a little simulation in Excel with a 800hp ICE, 120kW MGUK, 800kg car over a 1000m straight starting at 150km/h.


It takes the car 12.735s if it can use the ICE and MGUK all the time, the electric energy use is 1528kJ

Derating after 900m means 12.744s and 1394kJ

Derating after 800m means 12.771s and 1259kJ


So very little time is lost, but a significant amount of electric energy saved.



Edit: A video from Mercedes


Edited by thegforcemaybewithyou, 01 May 2018 - 12:22.

#3 4ren

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Posted 02 May 2018 - 20:32

Thank you so much!