How fast can you go "off the beaten path"? I was under the impression that this mod only helped at highway speeds?
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Aero wheels
- Thread starter richkae
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- Driving Dynamics Model S
JRP3
Hyperactive Member
As with any aerodynamic improvement, the faster you go, the more the benefit you will realize because air resistance (aka drag) increases with the square of speed, and therefore the power needed to push an object through air increases with the cube of the velocity.
Nice article here: Low-tech Magazine: The age of speed: how to reduce global fuel consumption by 75 percent
Formula and other info here: http://en.wikipedia.org/wiki/Drag_(physics)
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Nice article here: Low-tech Magazine: The age of speed: how to reduce global fuel consumption by 75 percent
Formula and other info here: http://en.wikipedia.org/wiki/Drag_(physics)
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Oh yes good point, except that a good portion of that particular trip is still on interstates (maybe half or so) so I could still realize maybe 15-20 miles of range which could come in handy if I am very close to the maximum range of the battery. That could make the difference between going out of my way to find a charger and stopping for over an hour, and not stopping at all.
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JRP3
Hyperactive Member
Chgd Up
Sig 1004
It will be tough to make a 200 mile trip on the 60kw pack. I'm not saying you can't do it, there are lots of hypemiling tricks to get you there but it is on the edge. There are a few things lithium ion batteries don't like and reduce their cycle life/capacity: being fully charged, fully discharged and getting hot. In GA you may be getting all three going at times.
Like some I'd try to steer you towards the 85kw pack, there may be some business case but the car is soooo much fun to drive and the bigger pack makes a big difference in this category.
At highway speeds it is all about aero so things like aero-wheels, self closing grill shutters(ala Mercedes CLA), etc make a difference; weight just doesn't have much impact. Take a look at these graphs particularly the second one for the roadster that decomposes the aero component. http://www.teslamotors.com/sites/default/files/efficiencyvsspeed_0.jpg
http://www.solarjourneyusa.com/Pictures/Whpermilevsspeed.jpg
Like some I'd try to steer you towards the 85kw pack, there may be some business case but the car is soooo much fun to drive and the bigger pack makes a big difference in this category.
At highway speeds it is all about aero so things like aero-wheels, self closing grill shutters(ala Mercedes CLA), etc make a difference; weight just doesn't have much impact. Take a look at these graphs particularly the second one for the roadster that decomposes the aero component. http://www.teslamotors.com/sites/default/files/efficiencyvsspeed_0.jpg
http://www.solarjourneyusa.com/Pictures/Whpermilevsspeed.jpg
It sounds like you're getting a 10%-15% increase at higher speeds (assuming those longer runs were done a higher speeds) which has got to be worth the current lack of aesthetic looks. I think carbon fiber disks/hub caps would be well worth it for the better look.
The shutters are a cool idea but if you look at them closely you can see they aren't all that aerodynamic. I think you'd lose back a lot of what you gained.
JRP3
Hyperactive Member
You could do a much more aerodynamic version of shutters and make them almost as flat as the pizza pans when closed.
Hmm, I'd question that. Not sure if you've gotten your car yet, but I've learned to chop a good % off the top. If you left your garage and got right on the highway and crept up to a 55MPH cruising speed, sure. But you've likely got stoplights and local streets before that, and that's where I find I bleed the most range. Granted, I'm a fast driver, but I've never come anywhere NEAR the EPA range on the 85kwh pack, let alone within 8 miles.
Stoplights and local streets are where I get the most EV range in my Volt. I very rarely have to actually stop, and the lower speed cuts aero drag.
Sounds like you are rushing up to stoplights, and slamming on your brakes. Try looking farther ahead, and never accelerate when you are not sure that you will not have to lift throttle for traffic.
GSP
Sounds like you are rushing up to stoplights, and slamming on your brakes. Try looking farther ahead, and never accelerate when you are not sure that you will not have to lift throttle for traffic.
GSP
Thanks, but no. I'm not the type to start braking for a stop light a mile back. I don't run up on stop lights, but I won't brake a quarter mile back either. Regardless, it takes energy to get moving again, and in the MS (especially the performance -- which I didn't get to drive like a grandma), unless you baby it off the line, you'll be pulling down 60ish wh until you get to 40 or so.
If I don't accelerate, what am I supposed to do? Stay at a stop until all lights for the foreseeable distance are green?
If I don't accelerate, what am I supposed to do? Stay at a stop until all lights for the foreseeable distance are green?
efxjim
Member
Don't plan too close to the edge. 3 years from now when your pack has aged the trip will not be possible.
ChadS
Last tank of gas: March 2009
Yes, 200 is definitely possible. So is 230; I've done a full-range trip in my Tesla. If you go downhill or get a tailwind or go really slow, you could possibly get over 300.
But if you really want to get somewhere (as opposed to just seeing what the car will do), I would never PLAN a trip like that. My rule of thumb is to always reserve 1/3 of your range to handle really bad weather. Or, if the weather's good, to travel at the speed you really like. In a 60kW car I would never plan a trip with more than 139 miles between charging stations. (A lot of numbers behind that thinking are HERE).
Of course, on the day of the trip, if the weather is really good and you won't go too fast, you might decide you can go more than 139 miles. And you will probably be right, but you never know if you will hit a headwind, or if the charger at the other end will be blocked, etc.
Road trips in an EV can be stressful if you push the range. As long as you've got a charging station within 2/3 of the range of your car, though, it should be no sweat.
I'm right there with ya.
"Dude. The S is great. Finally a decent range. You can just drive it. None of this hypermiling crap."
<time passes>
"You don't get 150 Wh/mi.? You must be a lead foot."
How times change.
I don't have my car yet (I have to finalize by 2/8.) It's interesting, this particular trip is exactly 200 miles (from Alpharetta, GA to Sevierville, TN) it's about half interstate/well traveled state routes and half through the mountains (blue ridge parkway).
There are alternate routes that are almost all interstate but longer (up to 259 miles via I-75.)
I would take it as a challenge to be able to make the trip with no stops in a 60kWh. But I would want to plan it out the wazoo because running out of charge in the mountains would be no fun at all!
But, shouldn't it be easily doable starting on a full range charge, on a nice spring day, with the wheel covers, and sticking to ~45mph mostly?
I think the main key is keeping the speed down -- as that would drastically improve the range.
This is really more of a fun mental exercise at this point as I will more than likely end up getting the P85.
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By the way, I had not noticed this before, but there is a really cool range calculator that lets you plug in speed, temperature, whether the AC is on, etc.
http://www.teslamotors.com/goelectric#range
On a 70F day, going 55mph highway, WITH AC on, in a 60kWh this calculator is saying I can get 224 miles!
Is this just marketing BS or is it real?
ChadS
Last tank of gas: March 2009
45mph would add about 26% to your range (whereas 75mph, a speed most people asking range questions are interested in, subtracts 26%) so yeah that's a very big help. At that speed you'd be gaining very little from the wheel covers; but if the weather is good (70, clear and dry, no big winds) and there's no net elevation change, I would think you could make it.
Tesla's calculator seems pretty accurate for what it considers. But it does not include elevation changes, winds, or road conditions like standing water.
Tesla's calculator seems pretty accurate for what it considers. But it does not include elevation changes, winds, or road conditions like standing water.
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Babylonfive
Power12
Couldn't you solve all the 'I like it black" or "I like it with spokes" personal subjective aesthetics issues by making it clear? What about a polycarb disk with a ridge carved in it on a CNC, which matches the 19" or 21" wheel exactly? Then add j-hook screws and recessed acorn nuts to tighten to the j-hooks. This would be clear, so you'd see the regular wheel. If heat were a problem, you could route some small but useful slots - more air for cooling but a little less savings.
I think this is very interesting.
I think this is very interesting.
I've never seen a polycarb anything stay clear if it was actually used. You'd probably make a new one every six months or so as the old old one became translucent with scratches and such. An opaque one would be fine and would likely last several years.
Babylonfive
Power12
Here was what I was thinking. A disk of polycarbonate, still clear to make installation and positioning easier.
A quarter-inch deep concentric slot cut along the edge, to fit into the edge of the 22" wheel - I measured it and the outer face ring is about 22.5" in diameter.
Then five quarter-inch holes each countersunk to allow a panhead sexbolt to connect with the J-bolt underneath.
You could even try heavy-duty tie-wraps.
A quarter-inch deep concentric slot cut along the edge, to fit into the edge of the 22" wheel - I measured it and the outer face ring is about 22.5" in diameter.
Then five quarter-inch holes each countersunk to allow a panhead sexbolt to connect with the J-bolt underneath.
You could even try heavy-duty tie-wraps.
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