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Track Day at Pacific Grand Prix

Discussion in 'News' started by tomsax, Mar 21, 2010.

  1. tomsax

    tomsax Member

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    #1 tomsax, Mar 21, 2010
    Last edited: Mar 21, 2010
    On March 17, six Seattle-area Tesla owners joined the Evergreen Lotus Car Club for a track day at Pacific Grand Prix, the new smaller track next to Pacific Raceways in Kent, WA. The folks at Pacific Grand Prix were excited to have a bunch of Tesla show up. We were treated to unseasonably nice weather, clear and sunny except for a brief hail storm.

    Trevor Cobb of the ELCC did a wonderful job of organizing the event and we really appreciate his invitation to the Tesla cousins.

    ampitup.jpg
    (photo courtesy of David Caley)​

    The track is 30 feet wide and 0.8 miles long. It's used for go cart rentals as well as track days for full size cars. As you can see from their web page, the track is all about turns with just a couple of short straightaways, so the speeds are kept under control. There were no timers on the track, so it was all about learning the track and improving your own driving. I did some autocrossing in the mid-90's, so this was somewhat familiar territory, although less forgiving of big mistakes. (The day went fine, the only notable off-course driving was a Lotus driver who sprayed dirt all over the track with no harm done to car or driver.)

    A couple of months ago, the Pacific Grand Prix folks attended a Seattle Electric Vehicle Association meeting to let the community know they are supportive of EVs. At that meeting, Daniel Davids, long-time local EV advocate and now president of Plug-in America, offered up some tips to the group from his extensive track-driving experience. So, when I got the email from Trevor inviting the local Tesla owners to join in on their track day, I offered to Daniel that we could split the driving if he'd give me some pointers. He accepted.

    We arrived at the track at 8:00 am, drivers meeting at 8:30 and the first group hit the track at 9:00. The second group was the six Roadsters. We got 15 minutes of driving, then about an hour wait between runs.

    I took the first run and Dan talked me through it, helping me to improve on each lap. Between runs Trevor offered up some helpful tips also. On the second run, Dan showed me what a Roadster can do with a skilled driver behind the wheel. It was a little frightening at first, then I could see that he knew what he was doing and that I was in a for a real treat. Dan just swept through the turn combos where I was struggling with the steering wheel. He made everything look smooth and easy, except for figuring out how the passenger is supposed to hang on through all of that lateral acceleration without a steering wheel to grip. After seeing it done well, my run in round 3 was greatly improved.

    Depending on the driver, each run was consuming between 3 and 7 ideal miles per driven mile. On my first tentative run, I used 21 ideal miles in 7.5 actual miles. Rich, an accomplished track/autocross driver, used 36 ideal on that same run. Dan managed to burn 35 ideal miles on the second run, even though he exited the track after only 5.2 miles.

    It was also fun to compare the recent energy use screens between me and Dan. Here's mine after the third run:

    graph_tom.jpg

    You can see I averaged 761 Wh/mi over the last five miles after the cool down lap and exit from the track. In normal driving, the average is more like 260 Wh/mi, with occasional green spikes for acceleration, but here it's solid green with dips for occasionally getting off the pedal. Doing the math from the trip meter says I used 841 Wh/mi for that run. Now, here's Dan's graph from the second run:

    graph_dan.jpg

    There is no letting off the pedal for Dan, at least not for long enough to show up on the graph, and the graph is pegged at 999 Wh/mi. Doing the math from the trip meters says Dan averaged 1,423 wH/mi on that run.

    There was supposed to be 240V charging at the track, but there was a problem with that circuit, so we searched out all of the 120V outlets around the track and charged as much as we could. Even with that little charging, I had plenty of charge for the 25 miles home when I had to leave around 3:00, I could have easily stayed for the last run. Others who had a longer drive were charge constrained and had to leave early. The track folks are very open to getting better charging installed, so future events should be easy for everyone.
     
  2. TEG

    TEG TMC Moderator

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    Thanks for the summary!
    (I like the picture you included.)

    Sounds like the new "P.C." term.
    "Q: Suffering from range anxiety?"
    "A: Oh, no I am just charge constrained today!"


    Did any of the Battery/PEM/motor temp monitors give you any power limits during your day?
     
  3. tomsax

    tomsax Member

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    I know you're being facetious, but I think it's different. Range anxiety is the worry of being stranded with a dead battery, but Tesla gives us such good information about the state of charge that we know what we can get from the car.

    This was a very unusual case where we were using the battery at 7 times the normal rate and stuck with three 120V outlets for six cars. We still had a lot of fun and people with longer drives knew what they could do and leave a comfortable margin for getting home. The people who bailed early missed the nearly two-hour wait for the fourth round caused by the driver who spewed dirt and grass all over the track, so that turned out well for them.

    I saw the motor temp edge one blip into the yellow, as did others. I didn't hear anyone say they got the power reduction warning. It might be different on a hot day, but hopefully we'll have some 240V charging available by summer which will help with cooling the battery pack between runs.
     
  4. TEG

    TEG TMC Moderator

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    By the way, I had done a little bit of Autocross in the early 90s too.
    I was using an Rx7 not totally set up for track use, but doing OK with it. But every time a certain guy showed up with his Rx7, he would turn in much quicker times around the course. Finally I asked if I could get a ride with him to see how he did it, and I was surprised to experience a "bucking bronco" ride where it seemed it was either full acceleration or full braking and not much in between. From hearing about road course driving, I was more used to a smooth/steady approach which I guess is oriented more towards avoiding brake fade, saving fuel for distance, and other such things that don't matter so much on such a short / tight course used for autocross. I guess to do autocross right you have to be willing to beat the *(&@# out of your car to get the most out of it.

    I bring this up because of your 1,423wH/mi observation. I could imagine something like that on the autobahn with the petal to the floor for a while, but how on such a slow, tight track do you do that without having a bunch of dips for coast, and drops for braking. All I can conclude is that the on/off was so frequent that the readout just had to average them on each sample. So, in reality it was probably more like 3kwH/mi frequent acceleration mixed with short bursts of heavy braking.

    I wonder how a Roadster would do in a tractor pull, where low end torque really rules the day?! ...But seriously, if a Roadster tried to drive fast up a very extreme grade or push something heavy at the MPH where it makes max HP, I wonder how high it could theoretically get on the wH/mi chart. Possibly not something we want to ever test as it wouldn't be nice to the drive-line and batteries.

    Well, it sounds like you had another fun day out with your Roadster(s). Thanks again for sharing.
     
  5. bolosky

    bolosky Member

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    Yes, my motor went overtemp on each and every run, usually after about 4 laps (in performance mode, of course). When that happened, it said that it was limiting torque (not power).

    The PEM and battery didn't seem to get that hot, though.

    After one of the runs, I looked at the temps, and the motor was at 148C, which seems quite toasty.

    I also twice got an "Internal resistance warning," which didn't seem to do anything except pop up the screen. I sent logs to Tesla, but I didn't get around to doing it until yesterday, so I haven't heard back from them yet.

    I was pushing it pretty hard (for me), but the highest energy usage that I got was somewhere in the mid 900 Wh/mile range, so it was well below the people who actually knew what they were doing.

    I have a 2010, non-sport.
     
  6. ChadS

    ChadS Petroleum is for sissies

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    It's obviously hard to compare with different drivers...but do you have a feel for how the Teslas compared to the Lotuses on that track? The Tesla is obviously faster, but the Elise is lighter and that track is all turns, so it should have been a good place to compare them.
     
  7. DrTaras

    DrTaras R254->R725->S1364-->X769

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    Tom-
    Great post... loved the pix of the comparo of the graphs!
    NJoy! --Ian :wink:
     

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