Right this is why I have always wanted/expected 200lbs off the roadster (which, btw, might be possible with the new higher range pack anyway, which would be great - max possible weight improvement plus new cells), since that's my understanding as well. But didn't Elon say the car is "several" hundred lighter, not 200 specifically? I thought I heard him say that word. In which case, maybe the threshold isn't 200lbs.
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New Roadster Goodies for 2014
- Thread starter hjr
- Start date
Right this is why I have always wanted/expected 200lbs off the roadster (which, btw, might be possible with the new higher range pack anyway, which would be great - max possible weight improvement plus new cells), since that's my understanding as well. But didn't Elon say the car is "several" hundred lighter, not 200 specifically? I thought I heard him say that word. In which case, maybe the threshold isn't 200lbs.
dhrivnak
Active Member
Sure it is. Take a friend to the track and race with the friend and without. See the difference it makes. My findings are 200 lbs weight difference gets lost in the noise. Not saying there is not an improvement but that the improvement is small.
At an event I went to last year, there was a small but measurable difference in top speed @ 1/2 mile for the Model S with and without passenger. We're talking a few mph. The 1/4 mile times did not appear to be affected by a passenger. Probably Roadster is similar, but I've not tried it.
400 Mile Pack (Was New Roadster Goodies for 2014)
My findings are completely the opposite. My car comes alive when I'm the only one in it. It's way less impressive when I have a friend along. And significantly more impressive when the friend is a tiny Asian girl than when the friend is a fat guy.
200lbs is huge. That's nearly ten percent.
My findings are completely the opposite. My car comes alive when I'm the only one in it. It's way less impressive when I have a friend along. And significantly more impressive when the friend is a tiny Asian girl than when the friend is a fat guy.
200lbs is huge. That's nearly ten percent.
400 Mile Pack (Was New Roadster Goodies for 2014)
Realize that there are people who will pay on the order of a thousand dollars for Li ion car batteries to replace their standard lead acid 12v just to shave some 5lbs off the weight of their car. 200lbs weight reduction is almost unheard of without just tearing out all creature comforts, including seats. That's why I'm so excited about the possibility of huge weight reduction without compromising performance or comfort of the car. The roadster was always hampered by its enormous battery, that's why they spent so much on a full carbon body to try to offset it. It really should be a few hundreds pounds lighter. Which is possible with current tech. So that's why I want to see it happen so badly.
Realize that there are people who will pay on the order of a thousand dollars for Li ion car batteries to replace their standard lead acid 12v just to shave some 5lbs off the weight of their car. 200lbs weight reduction is almost unheard of without just tearing out all creature comforts, including seats. That's why I'm so excited about the possibility of huge weight reduction without compromising performance or comfort of the car. The roadster was always hampered by its enormous battery, that's why they spent so much on a full carbon body to try to offset it. It really should be a few hundreds pounds lighter. Which is possible with current tech. So that's why I want to see it happen so badly.
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Chowing down on pizza as I read this, and have a couple chocolate chip cookies for next. I guess I will just continue living without that stronger acceleration.
bonnie
I play a nice person on twitter.
Chowing down on pizza as I read this, and have a couple chocolate chip cookies for next. I guess I will just continue living without that stronger acceleration.
Hah! Had a couple second delay on this end for it to hit. Good one.
strider
Active Member
Yeah, we always laugh at the people spending thousands of dollars on replacing aluminum bolts w/ titanium when they could just go on a diet and get more weight savings. Every 7lbs is equal to one additional horsepower.Chowing down on pizza as I read this, and have a couple chocolate chip cookies for next. I guess I will just continue living without that stronger acceleration.
On the other topic, I have heard that the car is traction-limited off the line. Won't removing weight actually make that worse? Yes, it will corner better but it's 0-60 or 1/4-mile time may not move. That could explain what Doug has seen with and without passengers.
No, removing weight won't make it worse. When you have less car to push it takes less traction to push it. The normal force will be lower but the contact patch will be the same.
Lets crunch some numbers with these high rate C packs.
high rate C pack is 14.8v with peak of 117 amps, capacity is 1.3ah.
Existing ESS max peak (over estimated for safety margin): 500 Amps @ 400v.
400v/14.8v = Need 27 packs to meet the voltage requirements.
500A/117A = Need 4.2 (lets round up to 5) packs to meet the Amps requirements.
So 27*5 = 135 packs needed, in 27S5P configuration, Cost be $2,504.25 per hobby king website.
High rate C pack 0.342 pounds each, so that's 46.17 pounds just for the batteries.
1.3ah * 14.8v = 19.24 watt hour, so 135 of them is 2.597 KWh.
Roadster gets what 300WH a mile? that be 8.6 miles.
That be a Fun 8.6 miles though
*note forgive any math errors, I didn't double check them.
It would not be a fun 8.6 miles. It would be a regular 8.6 miles.
On the racetrack you can easily consume 1200 Wh/mile. So you'd get a little over 2 miles of fun out of the pack.
That would actually be just fine for an autocross, but for driving on the racetrack you'd want a little bigger pack.
It doesn't need to be much bigger, because the car would go into power reduced mode due to heat after a few laps.
I'd want at least 10 or 15kWh for a track car.
If you could make an easy drop out and replace battery for the Roadster - it would be really cool to have two 12kWh 100 pound battery packs.
You get to the racetrack/autocross and then drop one out ( the one you used up to drive there ) and set it on the charger. You do a few fast laps, then come swap them.
One thing I was thinking of trying with the Model S - set suspension to Very High for drag race. More weight transfer at start due to higher center of gravity, then auto-lower by the time you get going fast. Not sure if it would make much difference, but might be fun to try.
Was going to do Race the Runway 2014 again this year, this time with the Roadster, but a scheduling conflict arose and I can't make it. Probably will do Luskville in the fall with the Roadster.
Was going to do Race the Runway 2014 again this year, this time with the Roadster, but a scheduling conflict arose and I can't make it. Probably will do Luskville in the fall with the Roadster.
JRP3
Hyperactive Member
Seems to me an easy fix for the air cooled Roadster would be a CO2 chiller spraying into the blower. Same thing should work on the heat exchangers for the Model S.
400 Mile Pack (Was New Roadster Goodies for 2014)
I had wanted to put a line about lowering air pressure in that last post, but I didn't because I was on mobile and I don't like typing a lot there. Roadster air pressures are already on the high side anyway for efficiency reasons. Wouldn't be hard to lower them a few psi and still have a more efficient car. And that's something you would want to do if you had a lighter car anyway. Either way, the tire is the same width, and is carrying less weight, which is a good thing.
I had wanted to put a line about lowering air pressure in that last post, but I didn't because I was on mobile and I don't like typing a lot there. Roadster air pressures are already on the high side anyway for efficiency reasons. Wouldn't be hard to lower them a few psi and still have a more efficient car. And that's something you would want to do if you had a lighter car anyway. Either way, the tire is the same width, and is carrying less weight, which is a good thing.
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spaceballs
Member
wiztecy
Active Member
The Roadster's recommended tire pressures are actually low, not high and can't even be inflated to tire's highest rating without having the TPMS complaining.
djp
Model 3 Performance
Interesting - how are you measuring that? I've found the rear tires wear in the center but not the edges when at the recommended 40psi, which would indicate overinflation. I'm running at the Comfort settings this season to see how that goes.
wiztecy
Active Member
The "low" I'm referring to is in relation to the AD08 / AD07 (rear) Max pressure rating of 51PSI that's listed on the sidewall vs the 40PSI Tesla recommends. I'd suspect if it was efficiency Tesla was purely after they'd pump the tires up to their max psi for lower rolling resistance. But in terms of rolling resistance the compound used in the AD07 tire was noted to be pretty good for low rolling resistance, especially the LTS (Lotus) version that the Roadster came stock with.
I usually run my rears around 37-38psi and happy with the wear, flat and even with a little more on the inside due to the -camber. Running the rears down really low since its summer, until I can see the rubber slightly transition to the belt then putting my new shoes on. So far 21,000 miles on the rear AD08s. I do feel that the Roadster is TC limited as discussed above about and that's why I was able to get so many miles out of my rear. When launching I feel the wheel slightly slips while the TC tries to negotiate the proper forces to apply the the drive wheel. I don't launch hard off the line and allow the Roadster to slightly roll before full acceleration.
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The inflation pressure depends on the weight of the car. The tire wall just lists the maximum pressure (cold) the tire is rated for. That has nothing to do with the ideal pressure. The ideal is that which provides uniform contact across the tread (assuming you are maximizing grip and wear rather then efficiency).
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