VWs Pikes Peaks EV

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NoDivergence
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Re: VWs Pikes Peaks EV

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Cold Fussion wrote:
Tue Jun 04, 2019 6:18 pm
From the exit of the corner just before the final straight to bridge takes the ID.R ~30 seconds (vmax=248, vbridge=242) while for the 919 EVO it takes ~21 seconds (max=369, vbridge=352). The 919 has basically a 100 km/h speed advantage along the entire straight, which is apparently 2860m long or ~14% of the track. There's 45 seconds between the two in overall laptime, so over ~14% of the track they lose ~22% of the their time difference to the 919, so the difference is proportionally larger than in the corners, but you would have to imagine they'd have to sacrifice a proportionally more corner speed in order to match the 919's vmax.
I looked at several corners that were traction/downforce limited rather than top speed. For example, at approximately 1 minute 6 seconds in the lap for the ID.R and 1 minute 2 seconds for the 919 Evo, the ID.R had a minimum speed of 122 kph. The 919 Evo was at 141 kph minimum speed... By the bridge, the 919 Evo was doing 220 kph whereas the ID.R is at 180 kph. The 919 corners faster, accelerates faster, and has a higher top speed. It's faster absolutely everywhere

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henry
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Re: VWs Pikes Peaks EV

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NoDivergence wrote:
Wed Jun 05, 2019 2:13 am
Cold Fussion wrote:
Tue Jun 04, 2019 6:18 pm
From the exit of the corner just before the final straight to bridge takes the ID.R ~30 seconds (vmax=248, vbridge=242) while for the 919 EVO it takes ~21 seconds (max=369, vbridge=352). The 919 has basically a 100 km/h speed advantage along the entire straight, which is apparently 2860m long or ~14% of the track. There's 45 seconds between the two in overall laptime, so over ~14% of the track they lose ~22% of the their time difference to the 919, so the difference is proportionally larger than in the corners, but you would have to imagine they'd have to sacrifice a proportionally more corner speed in order to match the 919's vmax.
I looked at several corners that were traction/downforce limited rather than top speed. For example, at approximately 1 minute 6 seconds in the lap for the ID.R and 1 minute 2 seconds for the 919 Evo, the ID.R had a minimum speed of 122 kph. The 919 Evo was at 141 kph minimum speed... By the bridge, the 919 Evo was doing 220 kph whereas the ID.R is at 180 kph. The 919 corners faster, accelerates faster, and has a higher top speed. It's faster absolutely everywhere
Not very surprising given the 919 is lighter and more powerful.
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Andres125sx
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Re: VWs Pikes Peaks EV

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hollus wrote:
Tue Jun 04, 2019 7:27 am
djos wrote:
Mon Jun 03, 2019 11:51 pm
Great lap. I think the vmax really hurt the Lap time as I don't think it was ever able to get above 270 kph.
It blinked 273 for a split second.
Interesting how at the beginning of the lap, the top speed was better in the middle of a long straight than at the end of the same straight. Something getting hot?
And then, by the end of the lap, the top speed was down to about 250km/h. Is that a less charged battery delivering a bit less power, or maybe more thermal stress, now accumulated over 5 whole minutes?
With electric motors nothing lowers perfomance because of hot. Batteries may degrade for the long term, and if it gets too hot you may demag the motor or even burn it, but perfomance is not affected by some overheating.

Actually the battery needs to be at least not cold to perform at 100%

But the power is affected with the battery voltage going down at the end of the battery capacity. Lower voltage, lower rpm for the motor, lower torque. With current Lithium batteries this drop is very small tough, with old Nixx batteries this difference was much more dramatic

Tommy Cookers
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Re: VWs Pikes Peaks EV

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Andres125sx wrote:
Wed Jun 05, 2019 7:06 am
....With electric motors nothing lowers perfomance because of hot....
rubbish !
increased resistive losses
fall in magnet performance

btw the 80% efficiency claimed in your previous post is actually about 55%
(60% of German electricity comes from thermal power stations)

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Andres125sx
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Re: VWs Pikes Peaks EV

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Tommy Cookers wrote:
Wed Jun 05, 2019 9:29 am
Andres125sx wrote:
Wed Jun 05, 2019 7:06 am
....With electric motors nothing lowers perfomance because of hot....
rubbish !
increased resistive losses
fall in magnet performance
Increased resistive losses are almost negligible, and fall in magnet performance only comes at very high temperatures which are not reached in normal conditions, only if extremely overheating the motor

Tommy Cookers wrote:
Wed Jun 05, 2019 9:29 am
Andres125sx wrote:
Wed Jun 05, 2019 7:06 am
....With electric motors nothing lowers perfomance because of hot....
btw the 80% efficiency claimed in your previous post is actually about 55%
(60% of German electricity comes from thermal power stations)
Rubbish! :roll:

If you are going to take into account electricity production, then you should do the same with petrol engines and take extraction, refining and transport into the ecuation too, dropping ICEs efficiency even lower than 20-30%

Apples to apples please

Tommy Cookers
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Re: VWs Pikes Peaks EV

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Andres125sx wrote:
Wed Jun 05, 2019 10:31 am
... Increased resistive losses are almost negligible, and fall in magnet performance only comes at very high temperatures which are not reached in normal conditions, only if extremely overheating the motor ....
+100 deg C will increase armature resistance (so resistive losses) by 35 - 40%

+100 deg C will reduce magnet flux density by 5 - 20%
correspondingly changing torque constant and voltage constant (analogous to mechanically changing gear)
and magnetic field strength is reduced by the magnetic field produced by current flow - this is 'armature reaction'
(enough AR can wholly or partially permanently demagnetise the magnets - high temperature isn't necessary)

changing torque constant and voltage constant will need closed loop eg rpm control
to give the motor when hotter the necessary greater current for a given torque demand
to give the motor when hotter the necessary greater voltage for a given rpm demand
and there will be some cost for this paid by the battery and/or what comes between the battery and the motor
Last edited by Tommy Cookers on Wed Jun 05, 2019 2:42 pm, edited 1 time in total.

bill shoe
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Re: VWs Pikes Peaks EV

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Andres125sx wrote:
Tue Jun 04, 2019 6:55 am
bill shoe wrote:
Mon Jun 03, 2019 10:24 pm

Also, would be interesting to know the total energy used for these kinds of record-setting runs for all the types of cars that attempt them (petrol-only, hybrid, and elec-only). Is elec-only similar to petrol-only or are they way different?
Considering engines efficency is below 40% (being optimistic) while EVs motors efficiency are above 80% (being conservative), you can bet they´re way way different and electric only need just a small fraction of the energy
True, so I'll narrow my definition of energy to "delivered" energy which is the positive torque energy delivered to the wheels. My hypothesis is that electric cars will still be more efficient because they have less delivered energy available and therefore have been designed to go fast more efficiently than the petrol cars.

I think it's almost inevitable that a well-designed unlimited electric hillclimb/time-attack car will be more efficient than a modified racecar like the 919. The largely-petrol 919 was designed to a set of rules that essentially mandate inefficiency as a way to control speed. But my inner engineer still wants to see the numbers.

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Andres125sx
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Re: VWs Pikes Peaks EV

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Tommy Cookers wrote:
Wed Jun 05, 2019 1:06 pm
Andres125sx wrote:
Wed Jun 05, 2019 10:31 am
... Increased resistive losses are almost negligible, and fall in magnet performance only comes at very high temperatures which are not reached in normal conditions, only if extremely overheating the motor ....
+100 deg C will increase armature resistance (so resistive losses) by 35 - 40%

+100 deg C will reduce magnet flux density by 5 - 20%
correspondingly changing torque constant and voltage constant (analogous to mechanically changing gear)
and magnetic field strength is reduced by the magnetic field produced by current flow - this is 'armature reaction'
(enough AR can wholly or partially permanently demagnetise the magnets - high temperature isn't necessary)

changing torque constant and voltage constant will need closed loop eg rpm control
to give the motor when hotter the necessary greater current for a given torque demand
to give the motor when hotter the necessary greater voltage for a given rpm demand
and there will be some cost for this paid by the battery and/or what comes between the battery and the motor
+100 deg C, that´s a huge increase for an electric motor. Do you know what´s the temp it´s reaching into the ID?

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Morteza
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Re: VWs Pikes Peaks EV

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It broke Nick Heidfeld's all-time record in an MP4/13 [which was 41.6].
The VW did it in 39.9!
"A fool thinks himself to be wise, but a wise man knows himself to be a fool."~William Shakespeare

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jjn9128
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Re: VWs Pikes Peaks EV

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Found this when trawling the twitters. Nice view of batt box and motor, plus that HUGE diffuser and cooling path!!!
Image Photo @wordsbymt
#aerogandalf
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Cold Fussion
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Re: VWs Pikes Peaks EV

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Morteza wrote:
Fri Jul 05, 2019 11:39 pm
It broke Nick Heidfeld's all-time record in an MP4/13 [which was 41.6].
The VW did it in 39.9!
https://youtu.be/8il5ohB8FYk
Not sure what the justification is for banning F1 laps anymore considering how on edge that time looked.

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jjn9128
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Re: VWs Pikes Peaks EV

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Cold Fussion wrote:
Wed Jul 17, 2019 9:18 am
Morteza wrote:
Fri Jul 05, 2019 11:39 pm
It broke Nick Heidfeld's all-time record in an MP4/13 [which was 41.6].
The VW did it in 39.9!
https://youtu.be/8il5ohB8FYk
Not sure what the justification is for banning F1 laps anymore considering how on edge that time looked.
Safety. Watch Heidfeld's lap by comparison. F1 cars are so much stiffer and lower riding than a car designed to run on public roads. That said I can see a limit on EVs coming too.
#aerogandalf
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica

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Morteza
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Re: VWs Pikes Peaks EV

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"A fool thinks himself to be wise, but a wise man knows himself to be a fool."~William Shakespeare