RE: Tesla Roadster: 'Quickest car in the world'

[RobDickinson]

fblm said:

RobDickinson said:

You think a 3 motor 200kWh car will be slower?

What's the battery capacity got to do with speed?

With Evs pretty much everything...

The bottleneck for power is the battery, motors are easy to do.

Getting power out of the battery is what limits the whole system, bigger battery, more cells, higher voltage, more power.

[JonnyVTEC]

Indeed. 200kWh allows 1MW of output discharging cells at 5 times capacity... 5C.

Doing the same with a 100 is far more demanding at 10C especially if the voltage sags and drives more current demand and heating.

I wonder if the roadster has upped the voltage of its HV system like the mission E is likely to.

[98elise]

RobDickinson said:

fblm said:

RobDickinson said:

You think a 3 motor 200kWh car will be slower?

What's the battery capacity got to do with speed?

With Evs pretty much everything...

The bottleneck for power is the battery, motors are easy to do.

Getting power out of the battery is what limits the whole system, bigger battery, more cells, higher voltage, more power.

KWh is the energy capacity, so its like saying a car is faster of you double the size of the fuel tank, so that's probably what he means.

As you say, depending on how the individual cells are configured double the energy means that the maximum possible current could also be doubled with no impact on the individual cells.

Essentially double the capacity means you can double the range, or double the max power drawn.

[canucklehead]

Hmph. 0-60 times are the party trick of electric motors: max torque at zero revs will do that for you. So, yawn.

And I guarantee you that you will not get 620 miles per charge if you persist in doing 0-60 in 1.9s or try to hit top speed regularly. Or indeed, drive it vigorously most of the time. Energy usage is energy usage, regardless of whether you're burning your fossilised dinosaurs in your engine or in a generating station miles away. You can sip it and eke out the range, or you can quaff lustily of performance and need to find more energy sooner. Physics is physics.

Oh, and don't forget that Tesla will eventually collapse under the weight of its debts. Or that Elon Musk is an irritating snake oil salesman.

[RobDickinson]

98elise said:

Essentially double the capacity means you can double the range, or double the max power drawn.

You actually do both...

Tesla are known to use specific cells (18650s), though a slightly larger one (2170 supposedly but rumours of a 44160) in the model 3 so this could be one of two sizes, or something new..

[RobDickinson]

canucklehead said:

And I guarantee you that you will not get 620 miles per charge if you persist in doing 0-60 in 1.9s or try to hit top speed regularly. Or indeed, drive it vigorously most of the time.

The veyron can manage what 12min at top speed, which is handy because the tyres are done in 15 min...

whats new here??

Edited by RobDickinson on Tuesday 21st November 19:57

[RobDickinson]

isaldiri said:

Actually I do. that 0-60 seems to be driving a lot of the hype but that's 1.4+g of acceleration. Now maybe Tesla will be able to have a custom tyre made for them in 3 years that can deliver that but there's no way a regular cup2 (918 tyre I believe) as used on the demo car is capable of that kind of acceleration. And if/when a tyre is capable of that, a decently powerful ICE nevermind hybrid will be able to do very similar times on the same tyre.

Did you watch the videos of the launch event when the roadster was doing ~2 second 0-60s all night? Where people who are used to 2.3 second 0-60s in the P100D were impressed?

P100D actually peaked as measured at 1.4g...

http://www.motortrend.com/cars/tesla/model-s/2017/...

Edited by RobDickinson on Tuesday 21st November 21:36

[RobDickinson]

anonymous said:

[redacted]

[Harrison-91xcg]

Psshhh old news. Remapped 535s have been doing 0-100 in 1 second since 2004

[isaldiri]

RobDickinson said:

Did you watch the videos of the launch event when the roadster was doing ~2 second 0-60s all night? Where people who are used to 2.3 second 0-60s in the P100D were impressed?

Did you see any independent vbox or gps type verification of sub2 second 0-60 launches? Because i sure didn't....

And again, you're ignoring that no Cup2 right now is going to be able to produce 1.4+g whether or not Elon Musk proclaims it can.

[RobDickinson]

No idea what rubber is on the p100d but as above motor trend tested it peaking at over 1.4g

wait that was
"245/35R21 96Y; 265/35R21 101Y Michelin Pilot Super Sport"

So no idea on cup2's , frankly who cares.

[anonymous-user]

RobDickinson said:

fblm said:

RobDickinson said:

You think a 3 motor 200kWh car will be slower?

What's the battery capacity got to do with speed?

With Evs pretty much everything...

The bottleneck for power is the battery, motors are easy to do.

Getting power out of the battery is what limits the whole system, bigger battery, more cells, higher voltage, more power.

Ok I see what you're saying. At this point in EV development, battery capacity and car performance have roughly improved at the same time so a bigger battery is roughly analogous to more performance, especially for the same battery architecture. Going forward the max draw and thermal management of smaller capacity batteries will improve beyond the performance of todays higher capacity ones. The EP9 already pulls 1MW from an 82kWh pack making capacity a very poor yardstick for power output even today. If the roadster is a 1MW car why not say it's flippin fast because it's got 1MW/1300bhp? No arguing with that!

[isaldiri]

RobDickinson said:

No idea what rubber is on the p100d but as above motor trend tested it peaking at over 1.4g

wait that was
"245/35R21 96Y; 265/35R21 101Y Michelin Pilot Super Sport"

So no idea on cup2's , frankly who cares.

You realise a g peak is exactly that. A spike. Means bugger all especially on a gps recorder. sustained g's are much more relevant.

[RobDickinson]

fblm said:

If the roadster is a 1MW car why not say it's flippin fast because it's got 1MW/1300bhp? No arguing with that!

The only real data we have is its 10,00nm torque and 200kWh battery. Working on the model s data that does indeed work out to ~1300bhp but who knows.

I'm thinking the 3rd motor is geared for higher speed somehow so as the main 2 motors drop off at 14-18k rpm this one picks up the slack.

[ntiz]

I wonder if this will have same problems as the p90 and p100 with if you do too many flat out launches they turn off the launch mode to protect the battery and the same if you do to many high speed runs?

[RobDickinson]

isaldiri said:

You realise a g peak is exactly that. A spike. Means bugger all especially on a gps recorder. sustained g's are much more relevant.

So? if you can peak at 1.4g you can if you have enough power and control, sustain it..

[Talksteer]

jsf said:

RobDickinson said:

Have Ferrari ever remotely upgraded a cars performance?

Tesla has.

They also have a 7 seater saloon that can do 0 to 60 in 2.28 seconds.

You think a 3 motor 200kWh car will be slower?

Define upgrade.

If you mean unlocked more of the already built in capacity, that's not really upgrading.

0-60 means jack st to how a car performs as a driving experience. If that's all you've got you haven't got much worth owning.

The performance upgrades were achieved by data collection from the fleet which allows conservatism to be reduced in terms of battery discharge and motor temperature.

However a good example of the upgrades was the creep function. Owners who were used to auto boxes asked on the forums if they could have it creep forward like they do.

The feature was coded in a few days and released that weekend.

[anonymous-user]

canucklehead said:

Oh, and don't forget that Tesla will eventually collapse under the weight of its debts.

It's only got about 6bn in debt. The problem is their cash drain (down from 5 to 3bn since just august). If model 3 is further delayed they are going to run out of cash. If they can get it together by the end of q1 they'll be fine but it's going to be tight. Given the problems they've already overcome volume production isn't exactly rocket science.

[RobDickinson]

I think they have until about July/august burning cash at the rate they are, seems vin numbers for model 3 have gone up recently and they have opened the order system to people who have put deposits down.

[anonymous-user]

Talksteer said:

jsf said:

RobDickinson said:

Have Ferrari ever remotely upgraded a cars performance?

Tesla has.

They also have a 7 seater saloon that can do 0 to 60 in 2.28 seconds.

You think a 3 motor 200kWh car will be slower?

Define upgrade.

If you mean unlocked more of the already built in capacity, that's not really upgrading.

0-60 means jack st to how a car performs as a driving experience. If that's all you've got you haven't got much worth owning.

The performance upgrades were achieved by data collection from the fleet which allows conservatism to be reduced in terms of battery discharge and motor temperature.

However a good example of the upgrades was the creep function. Owners who were used to auto boxes asked on the forums if they could have it creep forward like they do.

The feature was coded in a few days and released that weekend.

If that is the culture in the business then expect to see some blowback when a bug gets into the software. You would be horrified if the mainstream car makers had that kind of product testing culture. That's fine when releasing a new software update to a PC, but this thing is a 2 tonne killer if it goes wrong.

It sounds very much like product development testing is being carried out by car owners, they are skipping the usual testing stage a mainstream would do. That will bite them in the arse.