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MORE POWER

Discussion in 'Roadster' started by feelthesweetbeat, Aug 21, 2006.

  1. feelthesweetbeat

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    So... How will the aftermarket be able to make this more potent?  This makes Forced Induction obsolete, no more Air/fuel ratios, no more variable valve timing/porting, no more timing.  Any ideas for increasing the power/improving of this beast??!?!

    Things i can think of right now:
    -Batt cell rewiring (run parallel groups of 2 cells in series) to change the output voltage
        -which would require replace wiring to allow for higher current flow
        -add'l cooling

    -Motors with different # of coils (turns)
        -add'l cooling

    -Regenerative braking aftermarket units

    -Batt Voltage/amp control unit tuning

    -It'd be easy to implement a scramble power button if ya see fit

    Overall, i think tuning would become easier and would allow more people to perform mods on their own.  As a result, racing it would be cheaper enabling more people to compete competetively. 
     
  2. asdar

    asdar Member

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    I like the idea of more power and always loved tinkering with cars, but the thought of people tweaking the Tesla makes me cringe. I can just see some huge Lith explosion because someone threw some extra batteries in the trunk space and hooked it up, to get a few more miles.

    No matter if it was Teslas fault or not it'd be splashed all over the news, at least ten times the media the car got at launch.

    More power to you if you do mod it. I'd love to see a racing Tesla roadster.
     
  3. tonybelding

    tonybelding Active Member

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    I don't see many realistic options for tuning it. . . .

    Somebody on another forum mentioned experimenting with alternate motor windings, but I assume (and hope) he was joking about that.

    Chipping or re-programming the computer might be possible, but to me it would seem pretty scary considering how computerized this car is.  Also, it's not clear whether there would be much to gain from it.

    Changing the suspension should be pretty straightforward, and I could imagine something like the "sport package" that's available for the Elise.

    The other most obvious mods that people seem likely to do involve stripping weight off the car.  Any part you can replace with a lighter one, or anything you can remove, will improve performance.  If you were only going to use your car on the track, such things as the stereo and airbags could go, and you could swap in racing seats.

    And of course, you could remove batteries.  It has 900 pounds of batteries.  You might be able to remove half of those, and jettisoning 450 pounds would improve the performance quite a bit, and still have 100-125 miles of effective driving range.
     
  4. danny

    danny Administrator

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    the additionaly coils which you say will cool. does that increase power or just how long the batteries last or am i totally confused
     
  5. Joel1

    Joel1 New Member

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    That's just because none of us have any experience with it yet.

    A kid with a nitrous kit scares me more then someone with some extra batteries. Also this isn't like pouring alcohol in your gas tank. You can't just wire some things together. People performing mod's will have to be a little geeky. It's not like strapping a bigger carburetor on while drinking a 12 pack.
     
  6. feelthesweetbeat

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    increasing the number of coils (aka windings) in the electric motor would increase the strength of the beta field of the rotor thus increasing the amount of torque. As long as you keep in check how many amps youre drawing from the batts (by controlling the resistance of the circuit since the voltage is probably fixed) then changing the number of windings wouldnt be to disasterous. I guess you'd also need to balance the rotor (spinning part of an electric motor) after you increase the windings to ensure that it wont cause any harmful vibrations.

    Come to think of it, the "gas" pedal will probably be controlling the resistance of the circuit, therefore changing the "gas" pedal might actually make the car more powerful... seems weird.

    adding more windings also increases the length of the motors wiring, adding resistance and increases induced voltage within the coil, in turn, decreasing the voltage drop across the motors terminals and causes m... whatever theres alot to talk about. im gonna leave work now.
     
  7. stockey

    stockey Member

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  8. feelthesweetbeat

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    It looks like they are designed to act as the hub of a wheel and 150 extra lbs of unsprung weight per drive wheel is not a good thing in sports cars. It would be better if it was moved from the wheel to the center of the car and driveshafts added. 500 ft/lbs of torque per wheel is alot, not to mention the fact that each drive wheel can be independantly controlled eliminating the need for a diff. The transmission may also not be necessary due to electric motor torque curves. wow, very small drivetrain losses!!!
     
  9. Iamtherealwoody

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    NEW FOR THE SPORT SEDAN, AWD CONTROLLED BY THOSE HUB MOTORS, ONE PUSHING THE FRONT DRIVE SHAFT, ONE PUSHING THE REAR. oh my how nice would that be.
     
  10. tevvybear

    tevvybear New Member

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    I was reading up a thing today about how electric trains work. The modern ones don't use resistance to govern engine power, but instead the duty cycle of the input power.
    They do this because the power loss of a resistor would be huge!

    I'm looking into converting a car i own to electric in the near future, so i've been looking at how these things are done. (eg. i now know by Tesla's example, and a couple of other sources that 3 phase AC induction motors seem to be the way to go. - now i just have to make an appropriate 3 phase inductor, possibly utilising a variable gain buck-boost converter running at high frequency with a variable frequency and amplitude sin-wave generator to determine the ratio (either that or i make a microcontroller do all of the processing to determine the gain required - which i think is do-able)
     
  11. david_42

    david_42 Member

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    There's one fundamental point being missed here, all mass-produced cars are compromised in terms of weight, power, handling, etc at the altar of COST. The Roadster was designed to make as few sacrifices as possible. It is unlikely that anyone working on their own will be able to make noticeable improvements in ANY area. This is a little like when Chrysler came out with the 440 Six Pack. Very few street racers could improve on the engine, because Chrysler had already pack in the best after-market engineering available.
     
  12. TEG

    TEG TMC Moderator

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    One of the limiting factors is today's Li-Ion battery technology, and the desire to balance performance, durability and range.

    It could very well be in a couple of years that a better 18650 form factor Li-Ion battery could come out.
    You could directly replace the existing batteries in the ESS with different ones.
    (Or you could even use a different one today that has more current but less durability).

    If you knew how to reprogram the PEM, you could ask it to get the eMotor to make more horsepower.

    As with any race car modification program you would then start to stress the design limits of other components.
    Could the eMotor start to overheat? (maybe). Would the transmission be able to take the extra power? (maybe not)

    I am not sure how Tesla will relate to efforts to "hot rod" their vehicles for racing.
    Some car companies put together side teams to help racers know what is possible, and even provide different parts.
    Maybe someday Tesla can do something like that.

    For instance, see this:
    http://fyi.gmblogs.com/2006/05/same_company_new_tune.html
    ".... the aftermarket / factory-backed upgrade factor HAS to be considered.
    Look at all the rest ( even Dodge and Ford ) that have their own performance division...
    NISMO (Nissan),
    MUEGEN (Honda),
    MAZDASPEED,
    Mopar (Chrysler),
    SVT (Ford),
    TRD (Toyota),
    ...
    "

    Even low volume exotic car makers like Ferrari offer special "factory tuned" versions of their cars for racers.

    [​IMG]

    Maybe someday Tesla can get into that arena.
     
  13. AGR

    AGR Member

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    Does the car need more power or a few more gears (splits) in the transmission?
     
  14. TEG

    TEG TMC Moderator

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    What it really needs is less weight!

    If someone wanted to win a race, they could make a lighter ESS optimized for less range but the same power.

    That way the existing PEM, eMotor, transmission and all would already be up to the task. With less weight it would perform better.
     
  15. AGR

    AGR Member

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    Electric cars are inherently heavy due to the batteries. You reach a point where removing weight, while maintaining the safety of the car gets expensive.

    Do you raise the power, or add a few additional splits in the transmission, or on a commuter application us a CVT transmission.
     
  16. TEG

    TEG TMC Moderator

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    But the roadster carries a lot of extra battery weight to have a decent range.
    If you were willing to have less range you could make a less heavy pack that still produced the same eMotor power. Then you would get enhanced performance.

    I think the Roadster is already highly weight optimized. There isn't a whole lot more you could do other than shrinking the ESS.

    The eMotor torque curve is so wide and flat that you really don't need more gears. I don't think it would help you very much.
     
  17. AGR

    AGR Member

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    Most vehicles with an ICE have a 300 mile range under normal use, with the size of the gas tank adjusted accordingly to give a 300 mile range. The Roadster is at a 200 mile range under normal use.

    A vehicle with an ICE with a 1/4 tank will still deliver the same amount of power. A vehicle with an electric motor with 1/4 batteries will it deliver the same amount of power?

    Weightwise its all there...especially with the escalation in the price of Carbon Fibre, its getting costly.

    I am not an expert, to get electric motors to "torque up" I would conclude that you need to put volts and amps into the motor in direct proportion to the amount of torque required.

    How hot will the electric motor get? How do you cool it?

    With a simple transverse arrangement and a 2 speed transmission, it would seem that the electric motor is doing all the work, all the time, and putting a substantial load on itself and the batteries.
     
  18. TEG

    TEG TMC Moderator

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    The battery pack is arranged in banks to deliver various voltage and current capability.
    The type of batteries they currently use can be counted on to deliver somewhere about 3.5C (3 and a half times capacity)
    So with their 52kWh pack they can output up to 185kW (248hp).
    If you simply cut the pack in half, and everything else was the same, you would only be able to safely make 124hp max.
    ...but... If you used different batteries that could output more sustained current (e.g.: 7C cells) then you could restructure to still get 248hp, but for less time. To get batteries that could do that they would likely store even less energy per battery so your range would likely be less than 1/2 of the original.
    So, the tradeoffs are painful, but you might be able to make an ESS that weighs 1/3 less, can deliver the same eMotor power, but only goes for something like 90 miles. You could win a sprint race against a stock roadster, but would run out of charge much sooner.

    I think that is basically true with some little nuances to consider. What I am saying is that you could design a different battery pack that could weigh less, give the same volts & amps capability, but would run out of charge much sooner.

    With the wrong software they could make it so hot that things start melting.
    They air cool it, and probably push it pretty hard when doing full throttle at high speeds.
    They could get more cooling with liquid cooling, but they have avoided that probably due to safety, weight and complexity concerns.

    Huh? Don't you want to have the motor working hard all the time? That is how you get such great performance from a relatively low horsepower motor. (I say "relative" compared to other 0-60=3.9 cars)
     
  19. AGR

    AGR Member

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    TEG,

    Thank You for your response, its appreciated...in time the "electric knowledge base" will increase.

    A battery pack is similar to a gas tank, with software to control how the battery pack is used. Similar to a gas tank with software to control how the injectors use gasoline.

    A full tank (battery pack) is 185Kwh, as the battery pack loses charge the HP goes down. You can configure this battery pack to deliver power in a variety of ways as per the application.

    One way to configure the battery pack would be for a portion of the pack to run all the accessories, and another portion to run the motor. You could order a car with a "performance" - "cruising" - "commuting" battery pack formats.

    Usually when things get hot the durability / longevity is affected, on an ICE you would have a bigger radiator - oil cooler - dry sump with more oil - to cool down the motor. In the fashion that the motor is positioned(transverse) one side would be cooler that the other side. Similar to a V Twin in a motorcycle where the front cylinder operates at a lower temperature than the rear cylinder. The back side of the elctric motor with less air flow could be at a higher temperature.

    An ICE in a car has a longer life expectancy than an ICE in a Cigarette Top Gun boat, one is under partial load the other under full load. I would conclude that the design parameters of the electric motor are such that it can operate under close to full load for many many miles.
     
  20. TEG

    TEG TMC Moderator

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    No, that isn't right. Pack sizes can have different capacities, but the Roadster's is about 56kWh (or was that 52kWh?).
    That gives an idea of how much total energy charge it can store.

    They use the "C" value of the batteries to show how many time capacity they can output as continuous watts.
    So for simplicity sake lets say that the pack stored 50kWh, and the batteries could do 4C.
    Then the pack could output 200kW for 15 minutes, or 100kW for 1/2 an hour (at 2C)..., or 50kW for one hour (at 1C) (thus 50kWh). Using the battery C values isn't like direct math. You sort of "cheat" with shorthand that drops the hour rating to calculate the instantaneous output possible. The C factor is used to show max possible current draw, but the batteries are happier if you draw less current, so 4C capable batteries are given an easy time if you only need to draw 1C. Drawing current too fast can damage the batteries and shorten their lifespan.
    With the Roadster, if you asked the eMotor to make 185kW (248hp) continuously, a full pack would be empty in 18 minutes (56/185*60). People have done rough calculations predicting that the Roadster might need 110kW to maintain 130mph, so at 130mph (max speed) it may be able to travel about 65 miles ( (56/110*60)=30 minutes... (130mph*30/60=65 miles. )

    Probably not as much as you think.
    An "empty" pack still has a lot of voltage left. A full Roadster pack might output ~410Volts, and then down to 300Volts when considered empty. Even if they were trying to use max pack voltage all the time (which I don't think they do) they could still probably try to draw more amps from the cells even when their voltage is down. So, I don't really know how it works, but I suspect the power output from a full pack is not a huge amount different from a "so called" empty pack. With different programming they could probably extend the range even more, but then the pack is drained past the point where it damages the batteries and they don't want to take a charge again.

    You can read some more about their batteries here:
    http://www.teslamotors.com/blog2/index.php?p=39&
    http://www.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

    Well it isn't exactly modular and so easily reconfigurable on short notice, but with some re-engineering time it could be re-made for a different application

    They have a voltage converter that can lower the pack voltage to something appropriate for the accessories. So they don't need to segregate the pack as you say. Both the accessories and the drive motor share the same stored charge.

    Well, yes, that has been suggested, but so far they only seem to have the one pack offered.

    If you read up on the Lightning GT you will find that they offer different models with different packs. They have a high performance, short range version, as well as an "extended range" model with less performance.

    I am sure they are keenly aware of any such issues. I think there is a big fan and ductwork to get good airflow where it needs to be.

    Induction AC motors can be extremely reliable. They power most freight trains for instance (with a Diesel generator to provide electricity).
    If Tesla did all their homework the eMotor should last the life of the car.
     

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