Putting a license plate on that would be like putting braces on the mona lisa.
Tesla Roadster
661–670 of 729 posts
Re: Tesla Roadster
#662Has the 8 second quarter mile been confirmed to be done in stock trim (i.e., no special tires or other modifications)? The reason I ask is because that is EXTREMELY impressive. I tune EFI systems on race cars as a hobby, and any car in the 8 second range usually needs to run slicks or drag radials to have enough traction. Even all wheel drive cars (GTRs, DSMs, EVOs, etc.) usually run 4 slicks once they get to that sp…
> I tune EFI systems on race cars as a hobby, and any car in the 8 second range usually needs to run slicks or drag radials to have enough traction. Right, but you're comparing what is ultimately powered by the good old Karl Benz design from the 1880s, burning dinosaur juice, that has zero torque at zero RPM, needs to shift gears multiple times, and is about as responsive to control inputs as a cow munching on mariju…
Even if the difference was that drastic, none of that accounts for the fact that tires only have so much friction.
Re: Tesla Roadster
#663Earlier quoted context omitted.
God damn....that acceleration is almost cartoon-like. I'm kinda sad about the $200k price tag. I was planning on budgeting $125k for my next car in 2022. Obviously options have yet to be announced, but I'd really like to see a 100 kwh option for a cheaper price. That would give about a 300 mile range which would be plenty for me. Considering they announced 200 kwh as the base though, I'm not exactly holding my breath…
I think that the 200kwh battery pack is probably important for getting the instantaneous power out of the pack to hit their performance numbers. More battery cells in parallel = more current draw. The range is probably more of a bonus side effect of having enough battery cells to hit the power and acceleration targets.
Yep, this is why Tesla's current flagship is the P100D, rather than a P75D. The larger battery gives you better performance, even though it's heavier.
Re: Tesla Roadster
#664Re: Tesla Roadster
#665Earlier quoted context omitted.
Also I wonder how many times you can accelerate like that... maybe only once with full charge?
The Porsche CEO has been sorta claiming that but it doesn't make sense to me. The kinetic energy of your car at a given speed is the same, regardless of how fast you accelerated to get to that speed. Do batteries waste more energy when you drain them faster? They can't waste a large portion of battery capacity, because the heat from that much energy getting wasted would blow up the car.
All of the electrical systems waste more energy if you drain them faster. To drain them faster you need higher currents which lead to higher waste power. Waste power goes up with the square of the current (P=I^2*R). This is most apparent in batteries heating up due to their internal resistance. Here's [1] an 18650 lithium cells discharge graph at different currents.
Re: Tesla Roadster
#666Has the 8 second quarter mile been confirmed to be done in stock trim (i.e., no special tires or other modifications)? The reason I ask is because that is EXTREMELY impressive. I tune EFI systems on race cars as a hobby, and any car in the 8 second range usually needs to run slicks or drag radials to have enough traction. Even all wheel drive cars (GTRs, DSMs, EVOs, etc.) usually run 4 slicks once they get to that sp…
> I tune EFI systems on race cars as a hobby, and any car in the 8 second range usually needs to run slicks or drag radials to have enough traction. Right, but you're comparing what is ultimately powered by the good old Karl Benz design from the 1880s, burning dinosaur juice, that has zero torque at zero RPM, needs to shift gears multiple times, and is about as responsive to control inputs as a cow munching on mariju…
A couple of points:
1. A drag car does not start at zero RPM. The engine is probably over 4000 RPM and under load before the race even begins. In fact, many cars have to dial their launch RPM down because it ends up making enough power to lose traction from a dead stop. Look up "trans brake launch" to see what I'm talking about.
2. Your comment actually further confirms my skepticism of the Tesla not being able to maintain traction. If an unresponsive internal combustion engine powered car has trouble, imagine a car capable of shocking the tires even harder.
Re: Tesla Roadster
#667Re: Tesla Roadster
#668Earlier quoted context omitted.
> — its torque is also constant and available from 0 RPM I don't think torque is constant. The power is constant, and torque gradually decays as RPM increases as per the following equation: HP = Torque x RPM ÷ 5252 Most 1000 HP drag cars are in their power band from the time the driver lets go of the trans brake until the race is over (unless it's a stick shift, but most drag cars are automatic). Like any other conve…
"I don't think torque is constant." The torque is constant for the first 40% of the RPM, something like this: http://image.motorcyclistonline.com/f/30634938/122_0910_03_z... http://www.global-greenhouse-warming.com/images/TeslaTorqueg... The horse power increases gradually as RPM increases.
Interesting. Do they do that on purpose or is it due to how the motor works? It's so flat that It seems like they limit the torque on purpose, perhaps to prevent breaking things.
The almost perfect linear decline after the constant part is what I would have expected for an electric motor running with a constant power.
Re: Tesla Roadster
#669Earlier quoted context omitted.
oh please. they're putting money into R&D and into the ramp up. Your statement makes it sound like they're using the money to wipe their @$$es. No, they're putting the money to work. And if the analysts and shareholders didn't believe that, the stock would tank.
Very true. Belief - not actual results - is what is behind Tesla's valuation.
Is Tesla that different from Amazon 15 years ago?
Net income was flat but the revenue kept going up.
Re: Tesla Roadster
#670Earlier quoted context omitted.
Right but to hit an 8 second 1/4 you're trap speed is 170-190 depending on how fast your 1/8 mile was. There simply isn't even distance to accelerate linearly in 1/4 to hit 8 seconds without leaving the line like a bat out hell. The suspension on most of these cars is also far from normal. There's very few cars in the world which make an8 second pass on independent rear suspension. Most of these cars have straight ax…
Accelerating at 1.28g (41.25 ft/s2) for 8 seconds will get you to exactly a quarter mile. x = 0.5*a*t^2 = 0.5 * 41.25 ft/s2 * (8s)^2 = 1320 ft = 1/4 mi Under that acceleration, your final speed is 225 mph v = a*t = 41.25 ft/s2 * 8s = 330 ft/s = 225 mph
To clarify, it's 8.8 seconds, which is still absurdly fast, but that 0.8s makes a gigantic difference.