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What can be done to make electric cars have good high end acceleration

Discussion in 'Model S' started by theboom1, Apr 24, 2016.

  1. theboom1

    theboom1 Member

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    Ok there are many people that like to talk up 0-60 times but a lot of people care about what comes after 60, and the fact that the model s (and many other electric cars for that matter) sucks absolute crap after about 80-90 or from a roll. Not surprisingly, this is very apparent when in the quarter mile, the model s loses to cars that cant launch near as good. So what can be done to improve this?

    I know that battery technology will improve and get lighter and this will help with the fact that the model s weighs around 1000-1500lbs more than most of the cars it races so after your off the line and the extra traction and instant torque advantage goes away and the weight greatly hurts it.

    Also there is the fact that the power and the torque drops off greatly the faster you go. So to solve this could we not have a quick shifting 2 speed transmission like whats in the rimac? Maybe on just the rear axle or both, i don't know. I mean come on, both the rimac and most teams in formula e have more than one gear. A two speed transmission can be built to be very reliable and with very little additional mechanical losses. I know tesla first tried this with the roadster but i believe that they gave up on it because it couldn't handle the power. But with more that one transmission and when your not trying to send all the instant power through on trans like in the rimac, it works fine. I also wan't to point out that there are transmissions that can take the power: powerglides and turbo 400's running with 1000's of hp at the strip.

    Cooling issues can be solved right now, its just the fact that not many have built electric cars with the track in mind. The model s certainly doesn't have enough cooling.

    What I am saying is, is that the race doesn't end at 60, nor does it always start from a stop(like coming out of a corner at the track), and I would like to talk to people about how we can improve this because electric vehicles will dominate at some point and I want us performance people to be ready.
     
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  2. Skotty

    Skotty 2014 Model S P85

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    Transmission. But it has to wait until transmission manufacturers start taking electric vehicles seriously. Until then, they will just build more crap that falls apart.
     
  3. SR22pilot

    SR22pilot Member

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    I believe the original roadster had a two speed transmission. It had a very high failure rate due to the high zero rpm torque of the motor. Tesla retrofitted all roadsters with a stronger single speed transmission.
     
  4. Jason S

    Jason S Model S Sig Perf (P85)

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    Mostly I take offense at the following: "...and the fact that the model s (and many other electric cars for that matter) sucks absolute crap after about 80-90 or from a roll."
    False, and false.

    Goes very well at 80-90 and goes stoopidly fast from a roll (which I take to mean the 5-60 times). It is just limited to 130mph or so because that single speed transmission is spinning really fast at that point.

    Figure out what exactly you want to improve then manage to sell that to other people. Improving performance above the legal limit is simple not something most people care about.
     
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  5. ChadS

    ChadS Petroleum is for sissies

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    #5 ChadS, Apr 24, 2016
    Last edited: Apr 24, 2016
    More than 1 gear can help, but I believe the biggest issue is the power draw from the batteries. There are many factors that go in to battery selection, and a really high power draw is low on Tesla's list because they have adequate power for most drivers and all the demand they can supply so no need to chase after the racing set yet. Tesla optimizes for inexpensive energy-dense batteries with minimums for longevity, durability, etc.

    If Tesla builds capacity faster than demand, or if another company builds a race car, there are plenty of companies that build more power-dense batteries. Some racers already use them in EV drag cars. They are quite a bit more expensive. That's available now; in the future you can also put in a more-energy-dense battery with more energy, which should (though it depends on all the tradeoffs) have more power as well.

    Of course then you have to up-size all the cables, fuses etc as well. And the cooling as you pointed out. More expense, more complexity, more weight (at least for the same range, important to Tesla but not to racers who would keep it as small as possible for the race) for no sales benefit is why Tesla doesn't bother yet.
     
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  6. liuping

    liuping Active Member

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    Since the Model S is not a race car, and this topic is not really related to the Model S in any way, maybe it should be in the general Electric Vehicles forum, and not in the Model S forum?
     
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  7. Mike K

    Mike K Member

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    What he's getting at is that relative to off the line power, the Model S and X both are pretty wretched from highway speed rolling acceleration. You seem to think that's 5 - 60mph but in reality it's more along the lines of passing speeds on the expressway, so about 65mph here in LA.

    And he's right. They're all relatively slow from a roll and relative to their off the line speed, they are embarrassingly slow. There's a reason all the Tesla vs. Insertsupercarhere videos are all from a stop and not a roll and that's because from a roll the Tesla would get decimated by those cars and even from a stop you see them reeling the Tesla in quite quickly.

    I think the reason most don't care is because they're fast enough and because off the line power is what most people notice day to day. I've owned an M5 and a nearly 500hp 535. In both cases the cars accelerated so fast that I couldn't even top out a single gear on the expressway without earning myself a reckless driving ticket. So personally the Tesla's missing top end doesn't bother me too much. I wouldn't mind another 10 - 15% increase in power.

    What I really don't want is a transmission. I view the simplicity of these drivetrains as a huge selling point. I'd much prefer the car fall on it's face up top than have a multi-speed transmission in it.
     
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  8. SR22pilot

    SR22pilot Member

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    With the possible exception of a sports car I agree with not wanting a transmission. I do think people using the term "rolling start" should mention the speed. When used with respect to ICE cars it often means a 5 mph start which a Tesla is killer at but an ICE is hurt by since a 5 mph start means no launch control. Even at the 30 mph test often used to simulate country road passing the Tesla is no slouch. Autobahn passing is different. I haven't driven a Tesla under the last condition so I can't comment.
     
  9. ecarfan

    ecarfan Well-Known Member

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    In the real world everyday driving that everyone does -- except for on the Autobahn in Germany, which is a tiny fraction of all driving around the world -- an EV like a Tesla can outperform every vehicle except cars that cost much more and then the Tesla only loses at speeds which are illegal in most of the world. Yes, I know there are places, even in the US, where you can legally go over 80 mph. But 99. 99% percent of all miles driven in the US are at that speed or less. So this extremely minor disadvantage of EVs is inconsequential to almost all drivers. Don't exaggerate it.
     
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  10. McRat

    McRat Active Member

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    Racing and street driving are two totally different animals.

    Yes, you can make a >300 mph racecar that runs off electricity, yes you can win Pike's Peak in an EV.

    You cannot regen aero losses, hence you trash your range. You cannot have your battery last 8 years if you are going to heat it up to 300°F. You do not want to lose efficiency at low speeds by winding the motor for high speed operation.

    So yes, you can make electric racecars go fast. But no, you do not want one for street use anymore than you'd want a SuperGas drag car to drive to work.
     
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  11. sorka

    sorka Active Member

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    A P85DL makes 532 hp at the motor shaft(according to Tesla's specs and is pretty much in the middle of the KW power produced by the battery and the power we measure at the wheels with vbox's and dynos). It does 70-90 in 2.5 seconds which is just a little bit better than other cars that have the same power to weight ratio.

    A second gear would only help after 120 MPH, so yes, if you're driving on the Autobahn, a second gear would help. At speeds below that, you'll be slowing the car down by adding the extra mass of a transmission. The PD only loses 6% from driveshaft to wheels which is much better than any AWD ICE car on the market today. This is why a car that weighs 5000 lbs and only makes 532 hp can still manage a 70-90 pass that is faster than a car with a similar power to weight ratio in addition to the over head of gear shifts and the fact that an ICE isn't quite at peak power all the time between the shift point brackets.
     
  12. theboom1

    theboom1 Member

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    Take these for example which all off them have considerably less power than the model s:
    Audi RS7 Embarrasses Tesla Model S P85D From A Rolling Start
    Tesla Model S P85D Drag Races Porsche 911 GT3 from a Roll
    Video: BMW M4 vs Tesla Model S P85D rolling-start drag race shootout - Torque News

    In reality, racing from a roll is just as likely if not more likely than racing from a stop. I say this because how many times do you stop at a red light were you and the person you want to race are at the front with no one in front of you? When your at a stop, most likely there are many people around you. So even if your not racing and you want to feel the power, you don't have room to do it. Not so on the freeway where you much more likely to have a friendly race.
     
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  13. mikeash

    mikeash Active Member

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    Having driven much slower cars before I got my non-P non-D 85, I'm tremendously amused by phrases like "sucks absolute crap" being thrown around here.

    The 85's acceleration at all reasonable (non-German) highway speeds is pretty damned good, especially for a practical seven-seater family sedan. I often get comments from passengers about how effortless it is to pass at speed.

    I don't doubt that there are some cars which do better here, and I have nothing against improving performance in this realm, but I think a little perspective is in order.
     
  14. McRat

    McRat Active Member

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    #14 McRat, Apr 25, 2016
    Last edited: Apr 25, 2016
    RS7 = $130k USD before options, 11.4 ET
    GT3 = $131k USD before options, 11.2 ET
    P90DL = $119k USD before options, 11.1 ET

    A 1/4 mile is not a stoplight, nor are those speeds legal, safe, or just tickets in many countries.

    Drag racing in this realm occurs at trap speeds of 120-130 mph.

    The M4 is a few notches below, down where Challengers, Camaros, and Mustangs run except pricing.

    It would be interesting to watch the M4 deal with a old CTS-V which is a bigger, heavier, cheaper car. Both stick shift, both top gear, both 45mph from a punch, not the redline takeoff the M4 does in the video. "Roll on" contests do NOT mean pick your best gear. They mean you are cruising and you stomp on it.
     
  15. Uncle Paul

    Uncle Paul Member

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    Instead of two speed transmissions, maybe the solution is different gearing in each of the two motors. One for jackrabbit starts and one for higher end pulling power.

    I believe this, however is a made up problem. Due to Tesla's instant torque, it still passes much faster than most cars that need to take a few moments for their transmissions to down shift. This also shocks the driveline and can cause loss of traction.

    Believe the current Tesla configuration is the best for almost all driving situations.

    Tesla provides exceptional performance for the driving experience rather than to win high speed races.
     
  16. theboom1

    theboom1 Member

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    The original question was not asking whether or not high speeds is a good idea. It was about to improve high end acceleration as the model s and many current electric cars are very bad at.
     
  17. sorka

    sorka Active Member

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    #17 sorka, Apr 25, 2016
    Last edited: Apr 25, 2016
    The RS7 has more power than the P85D, 560 vs the P85D's 463. The only reason the P85D does as well as it does against the RS7 is because it's drivetrain loss is lower and it's powerband is wider.

    The other two cars are way WAY lighter.

    Oh, and that 463 hp the P85D has is only at 90% with max battery enabled. At lower SOCs it has less power. The lower the SOC, the lower the power.
     
  18. McRat

    McRat Active Member

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    OK, one more try. Yes, you can make an EV win high speed races.

    No, from an engineering standpoint, it's a stupid idea for a production street car today that by law must have an 8 year battery warranty.

    But if you freakin' insist, you can built one tomorrow. Do you REALLY want to race against this street legal EV? -

    This is for the standing mile record:



    It is faster than my 638HP ZR1 in the standing mile.
     
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  19. brianman

    brianman Burrito Founder

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    Source? Thanks.
     
  20. McRat

    McRat Active Member

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    It started with Hybrid batteries and rolled over to EV. 8 year, 100,000 miles Federal. Some states, like California, are even tighter.

    I'm not sure whether it's a mandate, a law, or qualifier.

    ie - Can a company get carbon credits without 8/100k warranty? Can it be exempt from emissions testing?

    But... I cannot find how it is controlled. All highway legal EVs are at least 8/100 in the US, and I don't believe that is a random number.
     

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