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Thread: Autocross and range

  1. #1
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    Autocross and range

    I assume most of the autocrossers here trailer their vehicle to the autox and back, but I am curious what effect the actual event has on range. Say you start off with a full charge, what is the difference in range that it claims when the event is over?

    I plan on purchasing a Model S and there is of course no information on that for that vehicle at autocrosses yet so I ask here about Roadster experience on the matter just to get a general feel for what to expect.

    I hope to get the 300 mile battery pack. Since I enjoy autox, I would like to run the Model S at a few events, but I don't have a trailer. It looks like my local autox group does about half of the events at venues that are around 50 miles from me and the other half are at about 100 miles from me.

    If the charge / range burns down very quickly at an autox, it might not be feasible until I can find a way to trailer the car to / from events, but I hope I could make it out there and back. Also, I hope that charging stations will be a little more common here on the east coast once I get through the waiting line and the car is delivered to me... a short charge after an autox might be enough to get back home if the range is a little short after an event.

    So what reduction in range do the Roadster autocrossers experience for an event and what do they think about the distance I would have to cover before and after the event?

    Thanks!

  2. #2
    Roadster 919, S 2006 Doug_G's Avatar
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    Autocross really doesn't use much power; for me, I use more power driving the mere 15 miles to get there. Driving around cones consumes about a third what it takes to drive there, go for lunch, and drive home again.

    We typically get 7-8 runs, each of which lasts about a minute. Even if you were using energy at 3X highway driving, it's pretty hard to use very much power in that amount of time.

    I don't think 50 miles would be a problem. 100 miles x 2 is close to the total range of the car, especially if the highway is over 55 mph. I expect you'd need some juice for that.

    Driving on a track is a different story. I did a Race School once, and even though that was much less intense than, say, going lapping for a day, I got a power limit at one point (motor hot).

    The Model S should be a great track car. Everything is liquid cooled and the handling appears to be superb.

  3. #3
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    Thanks! That's great information. I look forward to running the car in an event. Hopefully I'll be able take advantage of how fun it should be on a track and participate in a track day at some point too. There's a great motorsport park in Kershaw, SC I haven't had a chance to visit yet (Carolina MotorSports Park). I'd definitely need to rent a trailer for something like that, but it'd totally be worth it.

  4. #4
    Driving around a go-cart track (PGP near Seattle) I was using between 900 and 1000 Wh/mile, so 3-4X normal driving. So, it takes quite a bit of it to drain the battery (which I managed to do, but it took all day of drive/wait for the car to cool/repeat).

  5. #5
    Old but effective Roger Reid's Avatar
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    My experience is that we loose 40 range miles per day per driver. 8 runs at .5 miles per run = 4 miles using up 40 range miles (you figure it ). Thats about 15 miles per gallon in cost compared to a ICE car. On my Corvette which I race, I reset the onboard fuel computer before an event and recorded 3 miles per gallon .

    The other issue is volts vs current. The higher the voltage the less current you use decreasing the heat generated (thanks Scott). So the higher the charge, the less heat is generated. When you charge to ranges above standard level (about 185 miles) you loose regen braking because there is nowhere for the energy to go because the battery is already near full. My son who races my 2.0 sport likes the regen braking so we start with the battery charged to the top of standard range. On a multi day event we charge to the top of standard range before the second day. If you drive 100 miles to the event, the best remaining range you could get is about 140. You will still get good performance (maybe not the best) when racing between 140 and 100 remaining range miles.

    So you shopuld be safe if the track is 50 miles away. At those tracke that are 100 miles away you might trailor it or go the night before and plug into the motel clothing dryer outlet. Motel 6 will leave the light on .

  6. #6
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    Thanks for the information guys -- I look forward to running the car in some events. Hopefully I'll be able to get a trailer solution for a track day at some point since there's a pretty good track (Carolina Motorsports Park) about three and a half hours away that the local autocross group sometimes sets up days at.

  7. #7
    At the go-cart track ( PGP ) where we've driven the Roadsters I gave them two Nema 14-50 outlets and they installed them for us.
    ( This is not an autocross, you get to drive for hours and can drain your battery without charging )
    With that, the Roadster is more convenient than a gas car, because they sometimes have to leave to get gasoline and we do not.

    When you have your car and your mobile connector - go to Home Depot and buy a couple Nema 14-50 outlets ( $7 ) or even better an RV park style enclosure with an outlet ( $26 ) and 50 amp breakers ( $15 - you can find out what they need and get those or just get one of each brand ) and donate them to the place if they will install them. You're out maybe $50 and now you have a place to charge.

  8. #8
    Roadster 919, S 2006 Doug_G's Avatar
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    Some of these places are very accomodating, and others are run by dinosaurs. You won't know which until you ask.

  9. #9
    Senior Member dhrivnak's Avatar
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    I had the opportunity to spend the day at a track last month and averaged 650 watts/mile almost 3x average. But the Autocross is only. 5 miles and 1/4 is well. 25 miles I four make MANY runs and still make it back with a half battery.

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