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Discussion in 'News' started by dpeilow, Feb 23, 2010.
2010 Tesla Roadster Sport vs 2011 Porsche Boxster Comparison - Motor Trend
I'm constantly surprised as time passes how I've migrated away from my love of a good engine sound and towards the whine and wail of an electric motor. For me the spine tingling whistle of the motor picking up beats a V10 crackle.
Very nice. Seems like better weight balance and brakes would make up the difference in handling.
I'm glad MotorTrend likes the Roadster Sport.
That review was probably one of the best that I've read. It was pretty neutral and, I believe, shows that the Roadster is accomplishing Tesla's goal of proving to the "real-car" guys that just because a car is electric doesn't mean it can't be fun and hang with great sports cars.
Now if only they'd publish that as the cover story for this month's issue. :tongue:
Thats interesting.... I think the Porsche guy will always be a Porsche guy and you can't changes that.
It looks like the Roadster Sport faired well but I have a few questions that were not answered:
* Before its track runs was the Roadster fully charged?
* How many laps did they run before the Porsche guy mentioned it (Roadster) needing a charge?
* What were those sounds during the hard turns?
* Who won the drag race?
The Roadster was probably charged a decent amount since it was trailered there.
For the drag race, I'm pretty sure the Tesla won. On the sixth page of the article you see the Tesla has 12.6 sec @ 102.6 mph vs 12.7 sec @ 109.9 mph for the Porsche.
I don't know if they're role-playing, but the pro-Boxster guy comes off as a bit of an ignoramus. The whole "Ed Begley driving to Al Gore's house" or whatever he says. I mean, his anti-EV bias is pretty blatant, and it's like pulling teeth getting him to say anything nice about the Roadster at all. He doesn't even acknowledge the other guy's main point, which is that it's pretty incredible that an all-electric car is even in the same discussion with a Porsche Roadster. Even if the Porsche is slightly better for a cheaper price, the fact that they're comparable is amazing in itself.
YouTube - Comparison: 2010 Tesla Roadster Sport vs. 2011 Porsche Boxster Spyder
The drag race is @ 13:40
I wonder about track times. I know that the whole world is supposed to think The Stig is perfect and this guy certainly is no Stig but how can any driver expect to get decent times around a track without getting used to regenerative braking?!!
In theory you should always be speeding up or braking on a track but in practice there is a lot of coasting/ feathering/ lifting that would not count as either.
With the "engine braking" in the Roadster it would probably take a while perhaps days to get used to the characteristics of just that part of the car, let alone other aspects of handling a car with a 1K block in the center of mass.
That has got to mean a few seconds here.
And the article essentially pointed out that they obviously should have done the figure-eight venue first.
Configuring suspension geometry for efficiency is somewhat at odds with the configuration for ultimate handling. Are you racing for MPGe or lap time?
I think Tesla had to tend towards range optimization a bit more than Porsche.
Tesla handling fundamentals
Here is my advice based on experience with the Roadster and track driving in general:
In comparing the Tesla Roadster or Roadster Sport to other sports cars there are some basic fundamentals that define the handling characteristics of the Tesla that trace their roots back to a single thing: the Tesla is based on one of the most finely tuned/balanced chassis in the world but then adds about 800 pounds toward the back.
As a result, you have a few things that you really can't get around.
1) The brakes, which are the same as the Elise/Exige, were designed to stop a car that was 30% lighter. As a result you will have a harder time stopping in high-speed stuff and the brakes will fade more etc. etc.
One might then conclude that the best after market mod would be a big brake kit for the Roadster, but there are some problems with this: most importantly, braking is ultimately limited by the traction available in your front tires, and the front tires are very narrow. In the case of the porsche comparo, the Roadster Sport has 195mm wide tires and the Porsche's are 20% wider at 235. The problem is worse if you don't have the sports package and your front tires are 175mm wide. Bigger brakes certainly wont help with the standard setup. They might do something with the added grip of the 195mm AO48s (I never drove that particular setup) but the other problem is that the front wheels of the Tesla are 16" in diameter so there isn't much room for bigger rotors/calipers.
2) The lack of grip/contact patch in the front, combined with the weight in the rear, leads to a significant tendency to understeer (and the oversteer) in various situations. This is directly related to the above paragraph, and the only thing you can do about the understeer is put the wider, grippier AO48s up front, use the adjustable swaybars to tune out the understeer (I believe you should use the softer setting up front and stiffer in the rear but you should consult a tuner familiar with lotus chassis), and use camber adjusters. Camber shouldn't mess with efficiency (toe does) but dialing in camber will cause more wear in the inside track of the tire under normal driving which may cause you to replace the tires more frequently. Once you get the understeer under control be careful about oversteer!
Still, all of these tweaks will help things but they cant overcome the basic imbalance of car's setup. The Tesla will not handle as well as top sports cars but will try to make it up with the great acceleration.
Still, I would strongly recommend that anyone who likes to drive aggressively on the streets or on twisties (like Dr. Taras) should upgrade to the sports suspension and run the wider AO48s. The standard roadster is a bit scary at the limits!
(PS - the other reason the Tesla will not shellac ICE sportscars on racetrack comparos is that acceleration drops off notably after 60/70 mph. So the more long sections of the track, the more the Tesla will be at a disadvantage. Tesla's should compare well at tracks like Infineon but compare more poorly at fast tracks like Laguna Seca. The undersized brakes will compound this problem)
A flat battery pack along the bottom of the vehicle seems to be the way to go. It seems that is what they plan for Model S and some possible next generation Roadster. Lower center of gravity and less rear weight bias.
I still wish they would do a Roadster with a smaller battery pack. Less cost, less weight, better braking and better handling. Some people could make do with shorter range.
I don't think the roadster would be able to have the same performance with a much smaller battery pack. There was something on one of the tesla engineering blogs about that, if I remember right.
Tesla can do it safely if they lower the power output of the motor proportionally. The major problem with lowering the battery capacity is you increase the discharge rate of the battery, which affects life and may not even be safely possible. Current the Roadster discharges at about 4.06C (Sport motor 215kW, 53kWh).
The other way to do it is just to install fewer of the newer higher density cells and keep the same 53kWh capacity.
Less weight needs less power for the same performance (at least before wind resistance becomes the big factor). I don't know how much overall performance would suffer from a smaller pack, but reducing motor output would be at least partially offset by less overall weight.
I'm sure there are ways to do it (without dragging the thread into areas we have discussed before).
My boss, for one, has said he would buy one with half a battery pack for use as a 'toy'.
Switching to a smaller pack with higher power density cells could work from a performance standpoint. For instance, A123.
problem with using A123 cells is that you get half the range at the same weight off the bat. Make the pack half the size and now you are talking about 25% of the range. Its a tough sell to have a 60 mile car at close to $100K (Assuming a 13kWh A123 pack at $700/kWh)
Note that a 13 kWh A123 pack could easily drive a 215 kW motor since A123 is rated for up to 60C discharge (yikes!)