Last Friday, I took my Tesla out to the local sports car track here in Colorado for some driving lessons and to see what the Tesla could accomplish. Below is a copy of what I sent to many friends last night. After that, I have some technical discussion and questions for this forum.
I took my Tesla out to the High Plains Raceway (HPR), to get some driving lessons from Michael Pettiford.
It was quite an interesting day. I got my first sports car, the Tesla Roadster, five days ago. Yesterday, I did my first day of track driving in it, and experienced a level of driving that I only knew about from a theoretical point of view. Let me tell you that driving the car on the track is an amazing rush and takes some real skill. I got a great introductory lesson from Mike, but still have a whole lot to learn. There are some videos from Mike and HPR at the end of this e-mail.
Getting power at HPR worked out well by taking my home High Power Charger (HPC) and connecting it in parallel with an RV owned by a former student of Mike's, Marsha Hubbel. This made it possibe for me to keep driving the car hard 20 minutes of each hour, my track time, and almost keep up with the charging the other 40 minutes. The Tesla was by far the quietest car there and got a lot of attention.
The day was great and my nephew, Andrew, came with me and took many pictures and videos. I did a quick selection of the pictures and a simple hard cut edit of the video highlights. See the pictures at Picasa Web Albums - Butch - Tesla at HPR and the video at Tesla at High Plains Raceway on Vimeo
Boy, is this Tesla fun!!!
For more info and videos of Mike Pettiford and HPR see:
* High Plains Raceway: High Plains Raceway | Your Colorado Performance Driving and Racing Future
* Go4It Services: Go 4 It!
* Mike talks about his driving school: YouTube - GO 4 IT Car Racing
* 9News Feature on HPR: YouTube - HPR Media Gran Prix - Governor Ritter Drives
* Accurate In Car View Simulation: YouTube - High Plains Raceway v2.0 - in car view M3 GT
I have several technical issues that I would like to discuss.
High temperature first on the PEM and then on the motor very quickly limit performance. HPR is, as they tell me, a fast, technical track. It is 2.55 miles long with the fastest cars doing that in 2:05 on Friday; that's 73 MPH, average. I don't know what my fastest lap, but it wasn't close to that. I am guessing it was more like 3 minutes or more. I am guessing that the mix of driving was, 20% coasting, 10% max braking, and 70% max power. The driving was a 20 minute session on the track out of every hour. Typically, the PEM hot warning would come on in 1 to 1.5 laps, then the motor hot warning would come on in several more laps with associated power reductions. As an example, on the highway straight away, with a fresh cool car, I could get 110 MPH, but with reduced power, all I could get was 90 to 95 MPH. As my instructor joked, when the popcorn is done (the car beeps), the Tesla slows down. When the Roadster is cool, it is competitive with most cars on the track, with the power limited, its a different story.
Obviously, driving 70% of the time at max power is very different than normal street driving, but it would be interesting to discuss how to get better cooling to the PEM for better track performance. The discussion on "Powertrain 1.5" at Tesla Motors - Engineering does not talk much about the PEM cooling. Is the PEM liquid cooled? If so, can we do something as crazy as carry some ice in the trunk and pass the liquid to the PEM through that first.
As you can see from my pictures, because my MC240 is back ordered, and I also installed a 50 Amp, 14-50, in my garage, I made my HPC into a large, mobile charger. It just fits into the Tesla trunk. With the 14-50 "Y" cable, I was able to share power with an RV very nicely and charged at 40 Amps all day.
Here are the data that I collected on charge state. I used Ideal Range (EPA) miles as my measure of charge state. See Picasa Web Albums - Butch - Tesla at HPR for these numbers.
I have two big questions. Why did the charge state change so much between the end of the drive to HPR and plugging in with the RV? Why did the charge rate slow down in the afternoon? I was using a charge current of 40Amps and "Performance" mode for each charge, and the voltage was between 240V and 244V for each charge.
This was pretty much as I expected. See Picasa Web Albums - Butch - Tesla at HPR On the drive to HPR, I wanted to conserve as much energy in the ESS as I could, so I drove out at 50 MPH, minimized regen by coasting down hills, etc. WIth that, I got, 218 W-Hr/mi, not bad. On the way home, I drove the 60 to 70 MPH and drove in a normal highway mode, getting 286 W-Hr/mi, as expected. On the track, with very aggressive track driving, I got 732 W-Hr/mi; again within expectations.
Has anyone else taken their Roadster out on the track?