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Discussion in 'Model S' started by fiksegts, Mar 4, 2015.
Tesla Model S P85D vs Ferrari F12 Drag Racing
That Ferrari reeled it in, ran it down, and walked it like it was sitting still. Takes a lot of power to do that. Still bogged off the line like a 12 second Supra though.
The Tesla needs a secret weapon. Some sort of "nitrous/boost" like button that dumps full and direct power to the motors.
The Tesla did jump off the line nicely though.
Now if the Tesla weighed half as much? How much does the battery weigh? Not all that much. Start from there and build a car on that. Doesn't and shouldn't weigh as much as it does. It's built out of aluminum! Reminds me of the fiberglass Vette that only up until recently weighed far, far too much. If you strip the fiberglass off a Corvette; there is an aluminum Corvette underneath it!
How much does a non fiberglass Corvette weigh? I bet if it was skinned in aluminum it would weigh less than the fiberglass model.
It will be nice when Tesla decides to build a new Roadster. Hopefully they will take it to the limit; or at least offer up 2 or 3 versions of it. The base, the middle power, and the extreme. And it better be the fastest car in the world. They can get some timing lights installed on their test track and make it so.
PortaTree: Drag Race Timing Equipment, Drag Racing Equipment, Drag Racer Timing, Drag Race Reaction Time, Portable Timing Tree, Weather Station
I believe the battery is about 1,600 lbs. Still impressive what the P85D can do for the money given it costs $200,000 less but the Ferrari certainly is quick.
What I don't think many people realize is that AC induction motors start to induce "back EMF" as RPM's rose, and thus lose efficiency. It's not that Telsa is artificially limiting power at the top end, it's that there are challenges as the motor reaches those speeds...
How about a transmission of some sort to keep it out of the back EMF?
Yes. As I always like to say when I see these videos: "That Ferrari is lucky the Tesla doesn't have a second gear."
Now, if only someone could make a transmission that doesn't disintegrate under instantaneous peak torque. Tesla tried on the Roadster with several companies, Borg Warner included, but no one could pull it off. Materials science isn't quite there yet.
Likewise, if Tesla wanted to (and wasn't production constrained and actually could), they could make a 2 door, 2 seat version on the Model S platform. With the weight savings they could probably shave off a half second in the quarter mile and improve handling in the corners as well.
Thing is, they don't need to build that car as they sell every Model S, and soon Model X, they can make. A few years down the road maybe.
This place can build a gearbox to take the power: DODGE Gearing products I would either send them one of the attempted BW boxes from the Roadster or a picture of the shift mechanism.
Also have a look at this item from the 1960's: http://www.stangerssite.com/honeodrive.html
Then have a look at this item: https://www.gearvendors.com/
Also semi trucks have 2 speed rear ends on them.
I don't think back-EMF is the limiting factor with the P85D. I think it's the power output of the battery. The 85kWh pack can put out some serious power, but not for more than a few seconds. At that point it has to back off to protect the battery.
I don't have any technical info to back that up, but that's my hunch.
Want to see 3,000 amps pulled from a single battery?
Jump this video up to 1:06:24 to see it:
EVTV Friday Show - July 11, 2014 - YouTube
The first battery tested pulls about 1,000; it's the second one that does the 3k.
Wow.. I didn't think anyone here would still watch that guy's show after the comments he made about this forum and its members.
And the Tesla has no wheel spin off the line. To think that a 4 door sedan jumps a Ferrari till about half way down the track up to legal highway speeds makes the ICE racers a little sick to their stomach...
As an electric motor speed increases, the back-emf voltage (which is of opposite polarity) approaches the battery pack voltage level and opposes the current flow since there is less potential difference to force the current. Torque can be thought as proportional to current, so as the current gets reduced, so does the torque, which is the force that produces acceleration. 0-60, stoplight to stoplight, the electric motor wins on the street.
Yet, you can be cruising at 70 for 30 minutes only pulling ~20KW, so the battery will be relatively cool having been averaging only 1/4C... and if you floor it at those speeds you don't get nearly the torque you get at low RPM despite the battery being in a state where it can deliver max power for several seconds.
The motor simply can't develop the same torque it can at elevated speeds as it can at 0 RPM. This is illustrated by the power curves published for AC induction motors...