The D and Auto

Tonight at 8:18pm, Tesla announced the D version of the Model S.  The D as many owners guessed stands for Dual motor or an all wheel drive version of the Model S.

An AWD version can really help sales in cold weather climates but also provides significant benefits over 2WD versions

1. Faster acceleration

Elon stated that the 0 to 60 will be 3.2 seconds with the P version of the AWD.  This number is really fast and even faster than my Roadster.  I have not been excited about the P85 because the acceleration was not nearly as smooth as the Roadster.  I hope to get a service loaner P85D in the future to check out the characteristics of this acceleration with two motors not just one.

2.  Top speed is higher.

This feature will probably be hard to take advantage of in most places outside of perhaps the German autobahn or very remote locations.

3.  Efficiency increases.

ICE cars become less efficient when you add AWD.  With the sophisticated electronics, the Tesla D is more efficient than a standard Tesla even with the increased weight of the second motor on the front axel!

The Dual Motor option for the S85 is $4,000 with no listed 0-60 performance increase.  The P85D is another $14,600 over the P85.  The P85D requires 21″ wheels, the tech package and smart air suspension.  The difference between a similarly configured S85 to a P85D is $26,600.  In a way I am glad this option was not available when I bought my car as that speed is very tempting.

Auto-pilot Announcement

Along with announcing the D, Elon announced some auto-pilot features that are in the cars that are currently produced.  He made it clear that these cars are not autonomous self driving cars.  The technology includes

  1. Forward looking radar that can see through fog, snow and sand.
  2. Cameras that with image recognition that can distinguish pedestrians and can read signs.
  3. 360 degree ultrasonic sonar that creates a protect cocoon around the car and is sensitive enough to see a small child or a dog.

With these features, the car can self park and automatically brake.  On private property, you can summon the car to you.

Although I am more excited about the speed of the D for roller coaster thrills, the auto pilot features are potentially more interesting for many buyers.



Model S on the Track

Laguna Seca Raceway

On The Laguna Seca Raceway

On July 20th, I drove my Model S on the Laguna Seca raceway in Speed Venture’s Refuel event designed for electric vehicles. Laguna Seca has a famous corkscrew turn and the course is banked by both sand traps and walls. Speed Ventures had set up the event for electric vehicles only although in-between were a few noisy ICE vehicles on the raceway.

For the price of $125 including a $30 helmet rental, you and about 50 other drivers are on the track for 15 minutes three times during the day.  According to what I have heard, this price is higher than other tracks in California that are less famous and located in places where land is cheaper.  Fifteen minutes on the first glance sounds quite short but it is sufficient given the intensity of the experience.

The time trial was an additional fee. They also provided electric hookups and Tesla brought eight superchargers.  The charging stations were intended for those who were participating in the time trial.

I had heard rumblings about “insurance” but decided to not investigate it.  One rumor was that supplemental insurance was only necessary for the time trial but some insurance companies may also consider Laguna Seca a “non-public road”.  I figured I would not drive extremely aggressively anyways and did not contact my insurance company.

I have a good friend who races regularly on these tracks so I had a very minor amount of prior knowledge.  I have always lived by the motto that life is not a spectator sport and only rarely have I watched any sporting events including car racing.  A number of other drivers mentioned they watched videos of the raceway prior to attending the event to familiarize themselves with the course.

The organization has mandatory briefings and debriefings as the rules of the road are a bit complex with several different flags that have different meanings; for example one flag indicates debris on the road.  A number of people taped their headlights down just in case of flying debris.

The instructor also used the analogy that racing is a lot like skiing or snowboarding.  There is speed involved but there is also a lot of skill and technique development.  Newer drivers have simpler turns and hit the apex of the curve later than more experienced drivers with more advanced techniques.  The instructor also provided instructions for what to do if you lose control of your car in different situations.

My Refuel Badge

My Refuel Badge

The first time out was quite overwhelming.  I wore both the rented helmet, the baklava and sunglasses and the combination was fidgety and difficult to adjust correctly.  The original list made it clear we needed to wear a long sleeve cotton shirt but that also felt hot and stuffy.  I also adjusted the cars setting to regenerative braking to be low.  I never drive with regenerative breaking low, so that major change was quite distracting the first time out.

I enjoyed my laps around the track.  Folks warned about curves where you couldn’t see the road below you but for some reason I barely noticed that area in particular.  Perhaps I did not react to these blind curves because I have driven on enough roads like that in real life.  I found that as soon as you negotiated a turn following the guidelines, the next turn was coming up very quickly giving no time to rest.  I definitely hit the blue and white striped area on the side once but did not have any real problems.  I have to admit I did not see all of the flags that were on the track the first round.  The track also had a series of numbered signs at every curve — three signs:  “1”, “2” and “3”.  I used these to gauge when to turn although he had not explained exactly what these signs meant.

Since I was in the beginner / inexperienced group, we were not allowed to pass on the first round.  After a few loops around the track, I felt a bit guilty as there were more experienced people behind me and decided to leave a few minutes early to allow them to enjoy the track.

I enjoyed the second round a lot more when we were allowed to pass (and to be passed).  The driver in front of you waves to you with the hand out the window with the an arm gesture to the left or right.  Both front windows are required to be lowered while racing.  When I got on the track I allowed a number of people to pass me.  And then I basically had the track to myself for the rest of the session until near the end when I caught up to a couple of cars.  At the debriefing a number of people had said they were in a traffic jam.  Perhaps there were simply too many people on the track at a given time.  I normally really don’t like to drive near other people even when just cruising down the freeway.

Right after my second drive was the EV parade lap.  All electric vehicles could participate and drivers and passengers were not required to wear a helmet.  This little loop around the track was nice and an alternative for people who don’t want to actually race.

The third session was about four hours after the second one.  I did not feel compelled to wait around for the last session.  I enjoyed the second one a lot but that was quite a long period to wait.

I’m sure for many folks driving on Laguna Seca’s racetrack would be on their bucket list.  I took advantage of this opportunity to try something exciting.  I enjoyed it a lot but I doubt I will do it again. I have been a lifetime skier and have snowboarded a few times.  I love speed but I don’t particularly care to turn unless it is a beautiful medium mogul run, which unfortunately don’t exist much anymore in California — skiers and boarders these days prefer groomed runs.  I found that a racetrack was more about turning than speed and it would take me a while to develop the skills to get a true thrill out of acceleration.

When talking to others at the track, someone suggested perhaps I’m more of a drag racer!  Many years ago I remember going ridiculously fast on the autobahn in a rental Volkswagen and a number of times I have driven very fast on extremely remote desert roads where you have great visibility and few cars.  I do enjoy driving on twisty roads but for me I really like simple speed.

More experienced drivers commented on that the Model S does limit power after racing hard for a few laps.  The battery cooling is not set up for track use, so the algorithm does not kick in early enough.  Probably a firmware change could fix this.  I was so concentrated on driving I have no idea what my top speed was or whether I hit any power limits.

In Line for the EV Parade Lap to Begin

In Line for the EV Parade Lap to Begin

Drive Unit / Motor / Rotor

Sarah Schumm, Tesla Rotor Machinist

Sarah Schumm, Tesla Rotor Machinist

On an excursion to Yosemite, I happened to  meet the machinist who built my Model S rotor. Her name is Sarah Schumm and she built and machined all the rotors till around serial number 5,000.

This wonderful chance meeting has lead me to discuss the electric motor of the Model S.  As I mentioned previously, I have a degree in Electrical Engineering.  I have to admit my least favorite class was Electromagnetics but that was largely due to both a very poor professor and a bad book.

Electric cars are driven by very simple magnetic principles.  Anytime electricity runs through a wire, a magnetic field surrounds that wire.  By turning on and off electricity on different places around a cylinder, the magnetic field can essentially move in a circle.

An electric motor contains two parts:  the fixed outside stator (represented in grey below) and the rotating rotor (in yellow and purple) with the magnetic polarities of north (N) and south (S). The rotor is very simplistically a large magnet. The accelerator causes a series of electrical pulses along the stator to generate a moving magnetic field.  The rotor will respond by trying to line up the magnets as the magnetic field moves along the stator over time.

Very Simplistic Motor

Very Simplistic Motor

The stator has various wires in different locations.  By controlling the electricity in these fixed wires, the magnetic field can essentially move in a circle causing the stator to physically rotate clockwise.  In the first circle, a electricity through a wire creates a south pole magnetic field.  The bottom of the stator with the matching pole is repelled by this field, and the upper north pole is attracted to the field causing the magnet to turn clockwise as in the second picture.  The stator then turns on a different wire further along the circle to continue the movement of the rotor causing an additional turn in the same direction.

This example is very simplistic.  The actual rotor that Sarah machines for both the Model S and the upcoming Model X is also much more complex that one large magnet. The Model S uses a 3 phase four pole alternate current (A/C) system.

To learn more about the actual motor, you can read an official Tesla whitepaper about the Roadster’s motor.  Or watch the following discovery channel video.

An electric motor is more efficient than a gas engine.  An electric motor simply has less moving parts.  By eliminating the engine, an electric car needs no fuel, engine-oil, spark plugs and emits no exhaust.

Another driver has been blogging about his Model S during the same period I have.   With 30,000 miles he has had four drive units replaced.  Since this blogger is Dan Edmunds of the car website he has received a fair amount of attention.

The drive unit contains the motor, some simple gears and the inverter.  When the car is built the drive unit is completely sealed.  So when anything goes wrong with any of those components, the whole unit needs to be replaced.

I think his experience is somewhat unique.  A poll occurred on the Tesla Motors Club Forum that found 61 other owners have had their drive units replaced with eleven having repeat replacements.  Most of the owners report just simple noise issues not catastrophic failures.

There is no way to statistically compare this data in any accurate way.  But from my observations, the problems with inside edge tire wear seem to be a higher level of concern amongst the owners.