Print 48 comment(s) - last by JediJeb.. on Jun 6 at 6:09 PM

Tesla Model S Signature starts at $105k

As if successfully completing the first commercial mission to the International Space Station and back wasn't enough, Elon Musk is also finding quite a bit of success with his electric venture: Tesla Motors.
Inside Line is reporting today that the Model S Signature Performance, the top-of-the-line trim level, is already sold out and Tesla Motors is no longer accepting pre-orders. Customers now wanting to purchase the Model S Signature Performance will have to be put on a waiting list.
Interestingly, the standard model is still available for pre-order and has a base price of "only" $57,400 before a $7,500 federal tax credit (President Obama wants to see that federal tax credit increased to $10,000). The Signature Performance, however, has a base price of $105,400.
The standard Model S comes with a 40 kWh lithium-ion battery pack (8-year, 100,000-mile warranty), can hit 60 mph in 6.5 seconds and has a top speed of 110 mph. Range is listed at 160 miles.

 Model S Signature at the Tesla Fashion Island Signature Weekend [Image Source: Tesla Motors]
The Signature Performance ups the ante with an 85 kWh lithium-ion battery pack (8-year, unlimited miles warranty). As its name implies, performance improves greatly with 0-60 times dropping to 4.4 seconds while the top speed increases to 130 mph. The maximum driving range of the Signature Performance is listed at 300 miles.
The first deliveries of the Model S Signature Performance will begin on June 22. Those who have ponied up for the standard Model S will receive their vehicles later this fall. Those who haven't already pre-ordered the standard Model S still have time to get in line; Tesla is still accepting $5,000 deposits for the vehicle.

Source: Inside Line

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Efficiency Sweet Spot?
By WalksTheWalk on 6/4/2012 2:34:57 PM , Rating: 2
Is there a general speed at which 100% EV vehicles generally operate at peak efficiency? I know it depends on the gearing too, but on average, most modern ICE cars fall in at about 60mph for peak efficiency.

RE: Efficiency Sweet Spot?
By Brandon Hill on 6/4/2012 2:39:59 PM , Rating: 1
Well, Tesla's driving range numbers are achieved at a steady state of 55 mph.

RE: Efficiency Sweet Spot?
By WalksTheWalk on 6/4/2012 2:46:39 PM , Rating: 2
Thanks! I'm sure 55mph is close to the optimal cruising state if that's what they base their measurements on. Just curious more than anything.

With that out of the way, these things look like a lot of fun, although out my price range to be sure. The torque on these things has GOT to be a treat.

RE: Efficiency Sweet Spot?
By Kurz on 6/4/2012 2:52:50 PM , Rating: 2
Those Numbers are achieved at 55 MPH but based on the gearing (1 gear transmission) I think to get the most out of the batteries you need to go around 30-40mph (If I remember correctly). So I bet the range at 30-40mph is a bit higher.

RE: Efficiency Sweet Spot?
By Jedi2155 on 6/4/2012 4:07:24 PM , Rating: 3
Top range is at 20 MPH where you could get 450 miles per charge.

- Traveling constant speed
- 85kWh battery
- Flat ground
- No wind
- Heat and A/C are turned off
- Sunroof and windows are closed
- Driver and cargo weigh less than 300 lbs.
- Tires are properly inflated
- Battery pack with less than a year or 25,000 miles of service

RE: Efficiency Sweet Spot?
By micksh on 6/5/2012 12:25:58 AM , Rating: 2
Once hypermilers realize that expect them to cruise at 20mph on interstate highways.

RE: Efficiency Sweet Spot?
By Kurz on 6/5/2012 3:46:59 PM , Rating: 2
Those people you see are either High or Old people.
Hypermilers drive by obeying the law and following safety standards and respecting the flow of traffic.

Hypermilier here 34-35 MPG on his car that gets 27MPG hwy EPA.

RE: Efficiency Sweet Spot?
By Jaybus on 6/6/2012 2:12:55 PM , Rating: 2
Here where? Try that in the mountains.

RE: Efficiency Sweet Spot?
By Kurz on 6/6/2012 3:21:49 PM , Rating: 2
RE: Efficiency Sweet Spot?
By Flunk on 6/4/2012 2:55:47 PM , Rating: 2
The motor's efficiency should be linear but because of wind resistance the slower you drive, the more efficient. Also you lose energy from over-braking because regenerative brakes are not 100% efficient.

It's not like a gasoline engine that needs to be spinning at a certain speed for max efficiency.

RE: Efficiency Sweet Spot?
By Kurz on 6/4/2012 3:08:27 PM , Rating: 3
There is an efficiency drop past a certain speed for Electric Cars.

RE: Efficiency Sweet Spot?
By testerguy on 6/6/2012 3:07:28 AM , Rating: 2
Specifically, the drivetrain is the main source of the inefficiency at lower speeds.

Also, constant energy losses like lights, cooling fans and pumps represent a higher percentage of energy at lower speeds, whereas at top speeds that same power draw represents less of an energy increase %.

RE: Efficiency Sweet Spot?
By Solandri on 6/4/2012 3:13:00 PM , Rating: 2
Peak efficiency for ICE vehicles (the speed at which you maximize mpg) typically falls at 40-45 mph, not 60 mph. Thus much to the consternation of urban planners, the way to make the country burn less gasoline is to raise speed limits in cities, and lower them on highways. Two very unpopular options.

RE: Efficiency Sweet Spot?
By Mathos on 6/4/2012 4:29:27 PM , Rating: 2
Actually not really true. Peak efficiency for ICE depends on the engine. It has more to do with the RPM that the motor is being ran at, than the speed of the vehicle. Which is why we've starting moving towards 5-8+ speed tranny's instead of the old 3 and 4 speeds that were popular for a long time. Peak efficiency is generally achieved at 2000-2500 RPM, as that is generally the range where you're going to have access to most of the engines torque and power, while still using fairly little fuel.

This is why in most vehicles, if you pay attention to your RPM monitor, if you're not bulldogging it, and speeding up at a good steady pace, you'll notice that your tranny always shifts gears to try and keep you in that RPM range.

RE: Efficiency Sweet Spot?
By Mint on 6/4/2012 5:11:35 PM , Rating: 3
Unfortunately, most engines are producing too much power at the peak efficiency operating point to be useful for cruising.

Speed matters a lot more than running the engine at optimal efficiency. If you need 20hp to cruise at 60mph but only 6hp at 30mph, that 40% reduction in energy needed per mile will be more important than, say, 30% engine efficiency at 20hp vs 25% at 6hp.

Here's an example BSFC chart I googled:
Sure, peak efficiency is at 2500RPM and ~70% throttle, but if you only need 10kW, the optimal efficiency is around 1100RPM and 50% throttle.

RE: Efficiency Sweet Spot?
By Jedi2155 on 6/4/2012 5:42:23 PM , Rating: 2
It also varies a lot depending the auto cycle. The Atkinson cycle on the Prius offers a very linear BFSC:

RE: Efficiency Sweet Spot?
By JediJeb on 6/6/2012 5:06:59 PM , Rating: 2
I had a 79 F150 with a 400CID engine and it got terrible mileage at 40-45mph but almost doubled once you hit 55-60mph(not that the difference between 9mpg and 18mpg is that wonderful). The crazy thing was you got 18mph on the highway if it was empty, or if you were carrying 1000 pounds of load in the bed. I really do miss that truck.

RE: Efficiency Sweet Spot?
By WalksTheWalk on 6/4/2012 5:55:32 PM , Rating: 2
I was merely taking my anecdotal evidence with the vehicles I've driven (mix of V6, I6 and I4 engines) where a reasonable cruising speed of about 60mph is close to the most efficient based on the computer's calculations of mpg. I've made trips at 55/60/70/75mph and generally see that about 60mph is the best. The engine's RPM is somewhere around 2,300-2,500rpm at 60mph in the newer vehicles and they all have am overdrive gear.

For older vehicles back in the 90's, early 00's it was about 50mph so it seems like manufactures are cluing into the fact that people drive faster than 50-55mph and better efficiency should be geared towards 60mph.

RE: Efficiency Sweet Spot?
By Jedi2155 on 6/4/2012 6:14:30 PM , Rating: 2
My general rule of thumb for maximum efficiency in a ICE is 40/50 MPH and up is worse. For EV's its 20 MPH and up is worse. Variations differ depending on auxiliary loads and size of the engine with idea that the larger the engine generally the faster you should be traveling to make up for other losses. Please correct me if this assumption is a poor one.

RE: Efficiency Sweet Spot?
By JZavala on 6/4/2012 6:50:26 PM , Rating: 1
not to be mean or anything, but you just showed your age. the reason cars from the early 90's were better at 50mph was because highway speed limits were lower. being in the ~55mph range. and before that, even slower.

RE: Efficiency Sweet Spot?
By Jaybus on 6/6/2012 2:31:47 PM , Rating: 2
Now you show your age. :) They were lowered to 55 by the 1974 Emergency Highway Energy Conservation Act as a response to the 1973 OPEC oil embargo. Before that federal law, it had always been up to the states, and was 70 in most states. The federal law was repealed in 1995 and speed limits are again set by each state.

RE: Efficiency Sweet Spot?
By Mint on 6/5/2012 2:37:14 AM , Rating: 3
Manufacturers can't change the laws of physics. The fact is that you need more mechanical energy per mile at 60mph than at 50mph or 40mph. If a car is most efficient at 55-60mph, then it must waste a lot more energy at lower speeds than its competitors due to poor gearing, high friction, big engine, etc.

An efficient car will always get better mileage cruising at 45mph than 60mph.

RE: Efficiency Sweet Spot?
By JediJeb on 6/6/2012 5:21:50 PM , Rating: 2
Best efficiency for the engine is normally near its peak torque rpm. Above that you may have more power, but are using more fuel proportionally, and below you are getting less power but using more fuel proportionally. If the engine would produce power in a linear ratio to the amount of fuel burned then it would be a simple matter of getting more efficiency the slower you drive(in a vacuum on a frictionless surface as in all the college physics assumptions lol). Since almost no drive is over completely flat roads, then you reach a point to where driving slower costs you too much fuel when you have to travel up a hill, since if you were moving faster you could cruise up the hill letting your momentum carry you over.

My example in another post where I had a truck that got terrible mileage at 40mph versus what it got as 60mph is a good example of how real world results don't match up with theoretical assumptions.

"Young lady, in this house we obey the laws of thermodynamics!" -- Homer Simpson

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