# What keeps EVs from their potential top speed?



## Siwastaja (Aug 1, 2012)

Technically nothing, it's just a matter of power, and a matter of market segments. It makes no sense to mass produce a vehicle to such power levels that only very few people want to use, but technically it's easy.

Tesla is a relatively cheap mass produced car, too, that's exactly their point. See Rimac for something more expensive and more powerful. There are also several DIY projects that aim for huge power levels (and hence top speeds).

ICE vehicles on the other hand need "oversized" engines to give decent acceleration at lower speeds.

Note that many ICE companies develop powerful track cars because they have the cash flow from selling normal cars. EV companies do not have that as of yet; if they were to produce such cars, it would need to be economically self-sustainable.


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## major (Apr 4, 2008)

mbman88 said:


> forgive me dearly if this is a repost of some post.. I cannot figure out a way to search for this kind of question. I've done Google searches before without finding any answer, just more ads.
> 
> So.. Why is it that Electric vehicles seem to have such a problem pertaining to their top speeds? Tesla Motors has solved that "speedy electric car" problem by creating a vehicle with equal power levels to typical consumer vehicles.. however, despite being FASTER than most non-electric vehicles in ACCeleration, the vehicle is still limited by its TOP Speed, even though most people aren't going to be concerned about it. Get an ordinary gear-head, however, and even though they will never be able to attain the top speed of any vehicle they enter without a 2 mile-long straight away, they will still judge the vehicle negatively if the top speed isn't high enough.
> Now PLEASE don't pick on Tesla motors here, I've seen this "top speed problem" show itself in ALL aspects of electric vehicle design. One of the worst is electric motorcycles. Apparently the Zero DS has a max speed of 100mph, again, not a problem for law-abiding citizens, but on the tracks this is a major and terrible thing. Motorcycles have a major flaw when it comes to their top speed not being as great as automobiles that have larger and higher-torque engines. Specialized racing bikes with large engines are made just because of this. So the real problem I see here is... electric motors are PLENTIFUL with torque availability.. so why is top speed so limited????
> ...


Hi mb,

You see the EV motorcycle in my avatar? In 2010 we set the FIM world record at 173+mph. In 2011 the new race bike set the SCTA world record at 215.960mph. It still stands today. Neither bike had a transmission. Both bikes were champion road racers with only chain ratio and fairing modifications. The 2011 record was accomplished at Speed Week in Bonneville. We were the first electric powered 2 wheeler to break 200mph. During that event, there were hundreds of passes on the short course (3 miles) and we were the second fastest barring none regardless of the number of wheels, power or fuel type or class. 

This June the same Lightning EV motorcycle was the fastest 2 wheeler by like 20 seconds in the Pikes Peak International Hill Climb. The gassers couldn't touch him. 

So I don't see any problem with EV speed 

major


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## toddshotrods (Feb 10, 2009)

Cost and intent. The top speed limits have been crossed, and by electric motorcycles.


The Lightning superbike has a world record at 215 and change, at Bonneville, with a recorded top speed of 218 and change. That's with an AC motor and single speed.
The Rocket dragbike also broke 200mph, at the drag strip, and in just under seven seconds; with a DC motor and single speed.
The only things stopping others from whatever top speeds are the cost of getting there, and the intent of the vehicle. Take a look at the prices of ~200mph production supercars - not exactly cheap. You can get there on a production superbike much cheaper, but it's still not common. Many of those vehicles, including ICE, are electronically limited with regard to top speed. I am from the ICE hot rod/musclecar world, and even with power-to-weight ratios that make Ferraris jealous, you rarely ever hear them boasting about 200mph top speeds. It takes so much more than just power to get there, safely, and there are so many other ways to enjoy the vehicles.


When you really get down to it, top speed numbers are nice marketing tools, that will never be realized by the average purchaser. I also doubt that, even with many serious performance enthusiasts, they account for much in actual sales. People oohh and ahhh, but soon forget when the cares of everyday life resume (a matter of seconds later).


So, if you're building a production vehicle, or a DIY personal commuter/toy, you make that decision based on how important top speed really is for your needs and desires - usually, not very. The money is almost always better spent on other things. Cost and intent.

As a simple matter of fact - the electric bike's numbers are there. It's a given now that they can go there. Cars are still behind a bit, but I don't think it's because they can't - it's more about _why_? Rimac, on paper, has the power and form - probably the same reason, _why_? I think their target market places more value on the paper specs and exclusivity, so they don't have an immediate need to prove it. Most supercars, in the hands of the owners, end up being ridiculously over-powered, over-pampered, ego machines.

I am embarking on the journey to go 200+ on my bike, and don't see any limits with available technology. The only real question is whether I want the number bad enough to make the investment of time and money to get there...


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## mbman88 (Feb 17, 2013)

Siwastaja said:


> Technically nothing, it's just a matter of power, and a matter of market segments. It makes no sense to mass produce a vehicle to such power levels that only very few people want to use, but technically it's easy.
> 
> Tesla is a relatively cheap mass produced car, too, that's exactly their point. See Rimac for something more expensive and more powerful. There are also several DIY projects that aim for huge power levels (and hence top speeds).
> 
> ...


hmmm... it seems that... this is..... the truth. It's interesting to see that Concept One car. Ultimate Aero never ended up doing anything with their Electric supercar. it was a 500hp supercar with optional 2 wheel drive or 4 wheel drive, a top speed of 208 mph. At least that was their goal. They never seemed to have made it. According to what I can see this concept One has been MADE but it hasn't been put into a production stage, therefore it's more or less a prototype. It's nice that it exists, at least.
Also it seems it's electronically limited to 189 mph.............. This somewhat brings the problem back into question once again. WHY is it electronically limited?? You'd think at first, Okay they limited it's top speed for safety.. but then you realize it's a $1 million supercar and most supercars aren't limited like that. Then what is their reasoning for limiting it? I can't find any more info..


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## mbman88 (Feb 17, 2013)

major said:


> Hi mb,
> 
> You see the EV motorcycle in my avatar? In 2010 we set the FIM world record at 173+mph. In 2011 the new race bike set the SCTA world record at 215.960mph. It still stands today. Neither bike had a transmission. Both bikes were champion road racers with only chain ratio and fairing modifications. The 2011 record was accomplished at Speed Week in Bonneville. We were the first electric powered 2 wheeler to break 200mph. During that event, there were hundreds of passes on the short course (3 miles) and we were the second fastest barring none regardless of the number of wheels, power or fuel type or class.
> 
> ...


hahahaha, this is enlightening. However, doesn't this make you competition for the Killacycle?

Very impressive.


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## mbman88 (Feb 17, 2013)

toddshotrods said:


> Cost and intent. The top speed limits have been crossed, and by electric motorcycles.
> 
> 
> The Lightning superbike has a world record at 215 and change, at Bonneville, with a recorded top speed of 218 and change. That's with an AC motor and single speed.
> ...


Alright, so based on all the information, it seems there is no real limit at all, just a lack of motivation. Obviously, there is little practical reason to have a car go even 125mph top speed. But like toddshotrods said, it's mostly a marketing technique, and that marketing technique is what tears against those who make a stand AGAINST electric vehicles. Many Youtube channels who maintain a "Conservative" outlook pertaining to environmental aspects have a tendency of marketing the Big-Oil message. I live in a conservative area of the 'States and I know how much this message matters..

Pertaining to the Zero DS cycle, I did some research and it turned out to be that the Zero DS actually has a higher top speed than the one that it was being compared to in this video: " http://www.youtube.com/watch?v=Lej-KopK1tc " and it possibly has an electronic limit on top speed. 

If I had the capabilities I would start electric car racing circuits and the marketing that keeps racing alive.. Then there would be a true motive for high-powered electric racecars. I have a preference for Rally racing and Touring racing, and so for me it's essential to have a car look like a road car but be fast in order to do competition and time attacks. That is why I am so curious about this. This also explains a very important question I had about HP vs torque. Thanks everyone


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## toddshotrods (Feb 10, 2009)

mbman88 said:


> ...but then you realize it's a $1 million supercar and most supercars aren't limited like that. Then what is their reasoning for limiting it? I can't find any more info..


There can be different reasons a manufacturer puts electronic limits on their vehicles. To nail that down specifically, is hard without their input, and that's not so easy to obtain. Legal liability? Specific vehicle setup to make it stable and predictable at a given speed (note the ratio and fairing change Major cited for the Lightning bike)? Limits imposed by production tires, or other components? _Arbitrary_ numbers chosen by the manufacturer as being "enough" for the consumer?

The current fastest production car, the Bugatti Veyron SS, doesn't leave the factory capable of ripping off a 267+mph top speed - they limit it and it takes a special key or something to unlock it. I can't remember whether that's provided with the car, or has to be approved by them, but the point is they felt the need to place a limit (230-something I believe)...

It's often a purposed decision...


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## major (Apr 4, 2008)

mbman88 said:


> If I had the capabilities I would start electric car racing circuits and the marketing that keeps racing alive.. Then there would be a true motive for high-powered electric racecars.


http://www.diyelectriccar.com/forums/showthread.php?t=87629 

It's happening. And take a look at some of the EV 4-wheelers that ran PPIHC this year. Those are impressive machines.


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## Duncan (Dec 8, 2008)

*What keeps EVs from their potential top speed?*

Forgive me for something obvious

Tires!!!

If you want to reach 200mph on the road your tires have to be very special and I suspect the tire manufacturer would need to be involved in certifying that his tire were OK on your vehicle at those speeds


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## Rustybkts (Sep 27, 2009)

Although many others have answered this question, the answer is really simple.

ICE's need gears to ensure they can accelerate reasonably but also to keep revs down at high cruising speeds.
They also need to be overpowered for normal use as using an ICE at its maximum power for too long will destroy it.

An electric motor is comfortable to run at its maximum power for many years, indeed a huge number do so in industry.
It also only needs one gear up to its maximum revs but for higher speeds you would need two gears.

As no-one but Jeremy Clarkson uses speeds over 120mph, why bother?


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## CrazyAl (May 9, 2011)

Having a motor achieve high top speed is not an issue. There are other issues involved in making a car capable of driving at very high speeds. 

Duncan pointed out tires which is a very valid point.

Also, the faster you make a car, the better the chassis, suspension, steering, brakes etc have to be which means a bigger budget is required and better engineering is required.


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## subcooledheatpump (Mar 5, 2012)

Since someone mentioned Rimac, you should also consider the technical reasons. 

There are limits to electric motor speed (RPM) and the Rimac, like many production EVs has a fixed gear ratio. It may have over 800 kW peak power but that power may only come at speeds less than 200 MPH just to get better acceleration 

That could be one reason. So it might be possible to go a little faster with multiple gear ratios, but that complicates the setup, adds weight, friction, cost,etc. 

it is true going 200 MPH+ takes a special car. Tires don't last long at those speeds. I'd say the driver probably should have some experience as well. When you make a car that can go that fast you have to consider your customer's safety as well


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## toddshotrods (Feb 10, 2009)

I still think, just like the Lightning bike, a car can do 200+ without multiple gear ratios. Short of a purposed, wrinkle-wall tired, drag car you can't effectively use the kind of torque that comes with enough power to run 200+; electric or ICE. So, you move the power up to the RPM range that will put the car at 200+, and will likely still have more torque than you need to accelerate beyond the tires' traction limits. Most cars, street or race, that have the power to get there have to do a delicate balance of applying power until they're well into triple digits. They can often smoke the tires over 100mph.

The bigger question is still _why_? A minute after you run 200+ people have gone back to the cares of the world, and almost forgotten about it until the subject comes up again. Very few people (I happen to be one of them) obsess about this on a daily basis. Vehicles are ultimately judged on so many other factors, that you have to ask yourself, _why_? The cost is usually prohibitive (to actually do it, even with a vehicle that's capable), when weighed against the intended use.

Another factor is perception. A vehicle can feel significantly different at 200, than it did at 180. When a magazine editor gets in your vehicle to do a review, you want him to stop writing before things start buzzing and shaking. So, if it will shake, rattle, and roll to 210mph, but feels like it's chiseled from granite at 180, you limit it to 180. Even though that person reading the article is likely never even going to make it into triple digits you don't want him/her to get the impression that your vehicle is of interior quality than the one that was electronically limited at its "granite point". Spending millions more to engineer the "granite point" out to 200+ is counterproductive, unless you're building a competitor to the Veyron SS - and that's still only one small reason those wealthy folk _might_ buy it.

Perception for EVs also goes to range. The faster you drive, the faster you start looking for charging stations, and take life off your pack. A common sense limit where the vehicle feels best, preserves the battery, and is still far above any real need, just makes sense.

Real life sucks sometimes...


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## mbman88 (Feb 17, 2013)

Rustybkts said:


> Although many others have answered this question, the answer is really simple.
> 
> ICE's need gears to ensure they can accelerate reasonably but also to keep revs down at high cruising speeds.
> They also need to be overpowered for normal use as using an ICE at its maximum power for too long will destroy it.
> ...


Similar to Jeremy Clarkson, us Americans are quite unreasonable people and tend to look at "electric vehicles" the same way he does.. we think they're little eco-toddler-toys (I've heard some of his comments that aren't publicized on his TV show, I've stopped liking his page on facebook because of them). Only when our Corvettes are being tossed around like toys will we see the light at the end of the tunnel... having a life-changing event occur. A guy in a Corvette might be beaten off the line, but then that Corvette's V8 starts pumping out serious power near its power-lines and catching up to that electric car. That's why we need motors capable of handling high electric input white putting up enough battery capacity to be able to actually create that input. 
Or, more simply of an answer, basically marketing reasons is all.


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## mbman88 (Feb 17, 2013)

toddshotrods said:


> They can often smoke the tires over 100mph.


Lingenfelter 1100hp Twin Turbo C5 generation Corvette   



toddshotrods said:


> The bigger question is still _why_? A minute after you run 200+ people have gone back to the cares of the world, and almost forgotten about it until the subject comes up again. Very few people (I happen to be one of them) obsess about this on a daily basis. Vehicles are ultimately judged on so many other factors, that you have to ask yourself, _why_? The cost is usually prohibitive (to actually do it, even with a vehicle that's capable), when weighed against the intended use.
> 
> Another factor is perception. A vehicle can feel significantly different at 200, than it did at 180. When a magazine editor gets in your vehicle to do a review, you want him to stop writing before things start buzzing and shaking. So, if it will shake, rattle, and roll to 210mph, but feels like it's chiseled from granite at 180, you limit it to 180. Even though that person reading the article is likely never even going to make it into triple digits you don't want him/her to get the impression that your vehicle is of interior quality than the one that was electronically limited at its "granite point". Spending millions more to engineer the "granite point" out to 200+ is counterproductive, unless you're building a competitor to the Veyron SS - and that's still only one small reason those wealthy folk _might_ buy it.
> 
> ...


hmmm these are all really good points. This has forced me to look inside myself and realize..... I'm into it solely for the "Daredevil" aspect. Despite the costs and ingenuity required, I thoroughly believe electric vehicles are a tier above gasoline-powered vehicles.. and while gasoline vehicles that are high-performance can easily outperform many electric vehicles, it really is just a matter of power and chassis capabilities. A fully, expensive R&D, developed electric supercar on par with the R&D of the Veyron and its miraculous W16 VR technology, should be capable of meeting the Veyron's top speed record WITHIN its first generation. I thoroughly BELIEVE that there is NO excuse to why an electric car currently does not hold the world-record top speed on land, outside of rocket-powered cars. It's simple to me, no one wants to prove that electric vehicles, due to their simplicity and thus higher capacities, are indeed a more capable machine. 
Industry, for example, has no problem admitting that electric motors are much more practical than their ICE counterparts. And not just for indoor equipment, but for machinery that hauls things such as forklifts. Electric motors are ideal for those situations since they provide high torque capability with very little stress upon the organic entities that are controlling them. 

I must have been about 6 years old when I first decided that I love speed. It's an obsession. Past paced video games are some of my favorites, including almost all racing games..

So.. that's the best I can do to explain why.


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## kennybobby (Aug 10, 2012)

*The technical reason is Bemf*

The back-emf generated by an electric motor is the limiting factor to top speed. When the bemf equals the battery pack voltage then you no longer have any headroom to push current thru the windings. No current = no torque.


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## major (Apr 4, 2008)

*Re: The technical reason is Bemf*



kennybobby said:


> The back-emf generated by an electric motor is the limiting factor to top speed. When the bemf equals the battery pack voltage then you no longer have any headroom to push current thru the windings. No current = no torque.


Then you just change the gear ratio, or increase supply voltage, or decrease the turns in the motor to go faster.


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## toddshotrods (Feb 10, 2009)

*Re: The technical reason is Bemf*

Again, there really aren't any technical/physical reasons why EVs aren't reaching their "potential top speed".



major said:


> Hi mb,
> 
> You see the EV motorcycle in my avatar? In 2010 we set the FIM world record at 173+mph. In 2011 the new race bike set the SCTA world record at 215.960mph. It still stands today. Neither bike had a transmission...
> 
> ...





toddshotrods said:


> Cost and intent. The top speed limits have been crossed, and by electric motorcycles.
> 
> 
> The Lightning superbike has a world record at 215 and change, at Bonneville, with a recorded top speed of 218 and change. That's with an AC motor and single speed.
> The Rocket dragbike also broke 200mph, at the drag strip, and in just under seven seconds; with a DC motor and single speed...






kennybobby said:


> The back-emf generated by an electric motor is the limiting factor to top speed. When the bemf equals the battery pack voltage then you no longer have any headroom to push current thru the windings. No current = no torque.





major said:


> Then you just change the gear ratio, or increase supply voltage, or decrease the turns in the motor to go faster.


It is completely a matter of cost and intent. BEMF, gears, or any other technical/physical concern aren't the reason.


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## evmetro (Apr 9, 2012)

I would imagine that if there was a market for ultra fast EVs we would see them. I like super fast cars, but am satisfied at my age with 100mph. Earlier in life, I lived in Europe where it was not uncommon to run 200kpm+ on the autostrada, so I would imagine that countries with those types of driving conditions will be where ultra fast EVs start showing up first.


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## Mark C (Jun 25, 2010)

Please don't forget the Tesla Roadster was initially designed with a 2 speed gearbox. It seems it was not up to the extreme torque demands of a high powered electric motor. Some very smart guys over there at Tesla, and they still decided to ditch the 2 speed gearbox and go with direct drive. They had a lot of resources to work with {though, like everyone else, not unlimited} and chose what they deemed the most reasonable compromise. 

And, don't kid yourself when someone advertises they made a "no-compromise" widget. There's always some kind of compromise.


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## Siwastaja (Aug 1, 2012)

Again, it's pretty simple --

If you design a car that can go high speeds, you are going to need a lot of power because of the drag which is not linear but exponential. This means you need torque.

When you have all that torque, it means that you have torque in _excess_ for lower speeds. Hence you don't need a transmission.

It's different when you have an undersized motor that has a top speed like, say, 40-50 mph. Then you can benefit from a transmission by increasing at least the acceleration at lower speeds while you cannot increase the acceleration at higher speeds or top speed.

OEMs do not use transmissions but DIYers may benefit from them in some cases. But the most usual reason is simply the fact that the transmission is already there and it works as the reduction gearing which is needed anyway. An RWD might go without because the fixed reduction is in the differential, but the ratio is usually not optimal. It may be 1:3 to 1:4 whereas the optimum would be something like 1:5 to 1:8 depending on case.


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## DavidDymaxion (Dec 1, 2008)

An ICE does have one advantage. As you work it harder, it gets more efficient (uses less fuel per horsepower produced). For instance, it roughly doubles the force needed to go 75 mph vs. 55 mph, but your gas mileage falls by less than 1/2. My ICE gets 21 mpg normally, that falls to about 6 to 7 mph on the track -- pretty amazing considering the car is making 200 to 300 hp on every straight and then you throw away all that momentum by braking hard for corners. It takes about 1/10 the hp to drive gently, but the fuel economy is only 3x better, not 10x better.

In contrast, an EV gets less efficient when you run it hard. The motor efficiency drops, the batteries sag more, I^2R losses get larger, Peukert or Peukert-like effects take a bigger bite out of battery capacity. I haven't run my EV on the track yet, but I'm sure the range will drop by a bigger fraction than the gas car does.


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## major (Apr 4, 2008)

DavidDymaxion said:


> ...For instance, it roughly doubles the power needed to go 75 mph vs. 55 mph, but your gas mileage falls by less than 1/2....


Where it would follow logic to see twice the fuel rate consumed to produce twice the power, that does not logically relate to half the distance per unit volume of fuel because the increased power results in increased speed covering greater distance per time.

In other words, you seem to mix to efficiency measures:

1) Fuel rate vs power output of the engine.

2) Fuel mass vs distance traveled.

You can not assume any direct proportionality between power and distance so doubling power would not even remotely suggest halving distance.

While there may be some validity to some of your statements regarding power plant efficiencies, I fail to see relevance to the thread topic.


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## EVfun (Mar 14, 2010)

O.k. So 68% of the fuel mileage at 75mph. I know that a Geo Metro doesn't drop from 50mpg at 60mph to 34mpg at 70mph. On the other hand, my EV range does drop from 20 miles at 60mph to about 14 miles at 70mph. The city range is an easy 30 miles, even driving it like I stole it. Speed kills... range!


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## toddshotrods (Feb 10, 2009)

Siwastaja said:


> Again, it's pretty simple --
> 
> If you design a car that can go high speeds, you are going to need a lot of power because of the drag which is not linear but exponential...





DavidDymaxion said:


> ...an EV gets less efficient when you run it hard. The motor efficiency drops, the batteries sag more, I^2R losses get larger, Peukert or Peukert-like effects take a bigger bite out of battery capacity. I haven't run my EV on the track yet, but I'm sure the range will drop by a bigger fraction than the gas car does.





EVfun said:


> ...Speed kills... range!





major said:


> ...I fail to see relevance to the thread topic.


It's another reason for placing an electronic limit on top speed. Especially if you are a manufacturer. The negative publicity of having people out running out of "juice", getting towed, and ruining battery packs, is not worth it - even if they're doing it legally at race tracks and simply fail to understand how much of a demand they're placing on the packs, how fast they will deplete them, and how much life repeated torture tests will take off of them. Especially magazine editors. In most of the EV tests I see by the big rags, it's clear they have little to no understanding of EVs, and are basing all of their assumptions on their ICE-related experiences. Whatever a well-built ICE car can do you push it relentlessly until you touch on its limits, usually with no consequences. If you run the tank empty, you just get more fuel and try again, and again, and again... EV enthusiasts, racers, and manufacturers tend to do more strategic, carefully calculated, testing to preserve the precious battery packs, short and long term. That kind of responsible use is not the forte of most with "dino mentality".

Just throwing out numbers, with no math to support it, if 220pmh is the actual top speed but the pack is depleted twice as fast at 220 as it would be at 180, limiting to 180 makes sense...

Imagine Top Gear with a Rimac Concept One that would do 220, no electronic "nanny", and a track rented for a day. If possible, they'd completely kill the pack and publish the results as real world evidence of a failure. Extreme example but I'm tryin to make the case for placing limits on top speed.


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## MN Driver (Sep 29, 2009)

It takes roughly 80kw to maintain 133mph in a Tesla Model S based on the 3 or 4 seconds that this guy held the car at the limit. I'd imagine with a single speed gearbox that the cutback that starts scaling back power starting at 130mph is very close to the max safe RPM of the electric motor.
http://www.youtube.com/watch?v=gsQdwACgoXY

Hearing the wind noise reminds me of various cars that I've been in that get squirrely above about 100mph. Sat in a buddies early 90's Saturn SL2 at 100+ mph once, felt like riding in a boat through waves, a strange rocking sensation and I'd imagine it wouldn't take much to catastrophically disrupt the car at that point. I've seen videos on Youtube of where cars lose their grip on the ground and suddenly end up tail first. Most passenger cars have 112mph tires and the speed limiter on those cars matches that. Most production electric cars it seems to be a combination of max motor RPM and range concerns, maybe with a little pack stress(high C driving) as a concern too.

In the realm of DIY conversions, the Youtube videos with cars that barely hold highway speeds, even with some getting excited that it 'made it up to speed', are typically lead-acid conversions 144v or lower and the lower voltage plus voltage sag has their maximum power tapped out. With lithium we have less sag and also less people running low voltage systems that have the lack of power at a higher RPM where the power is needed on the highway. Since I'm a highway driver, I feel passing performance is critical and that's a factor for motor and voltage selection for me. I'm still not going to go faster than the speed rating of my tires though in any condition.


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## mbman88 (Feb 17, 2013)

From what I've gathered thus far, with some mild debate, the main problems seem to be related to A. the battery pack's sensitivity (manufacturers limit top speed due to the possibility that the battery pack will die and mean failure and thus mean bad publicity) and B. back EMF from motors which requires a secondary gear OR bigger battery pack to supply more voltage and thus more power. 

Regarding A: couldn't you prevent the battery pack from being damaged by "sandboxing" it behind capacitors? 

Regarding B: Do we need to manufacture a new type of motor which can dissipate back EMF? 
If the back EMF problem is dealt with in this way.. in other words, back EMF WASN'T a limiting problem, we wouldn't need more gears to remain closer to "high efficiency", and/OR we wouldn't need larger (read: heavier) battery packs to supply more power to handle the increasing demands. 

The nanocapacitor invention would alleviate the battery-pack-failure problem with high-speed EV "supercars", at least. 


Also, I must apologize as I am not an experienced person nor am I experienced in general and I feel like I'm communication with legends, here. lol.


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## toddshotrods (Feb 10, 2009)

mbman88 said:


> ...Regarding A: couldn't you prevent the battery pack from being damaged by "sandboxing" it behind capacitors?...





toddshotrods said:


> ...*The bigger question is still why?* A minute after you run 200+ people have gone back to the cares of the world, and almost forgotten about it until the subject comes up again. Very few people (I happen to be one of them) obsess about this on a daily basis. Vehicles are ultimately judged on so many other factors, that you have to ask yourself, _why_? *The cost is usually prohibitive (to actually do it, even with a vehicle that's capable), when weighed against the intended use.*
> 
> ...*A vehicle can feel significantly different at 200, than it did at 180.* When a magazine editor gets in your vehicle to do a review, you want him to stop writing before things start buzzing and shaking. So, if it will shake, rattle, and roll to 210mph, but feels like it's chiseled from granite at 180...
> 
> ...*Spending millions more to engineer the "granite point" out to 200+ is counterproductive*, unless you're building a competitor to the Veyron SS - and that's still only one small reason those wealthy folk _might_ buy it...



I'll leave "B" to Major.


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## Tesseract (Sep 27, 2008)

mbman88 said:


> ...
> Regarding B: Do we need to manufacture a new type of motor which can dissipate back EMF?
> If the back EMF problem is dealt with in this way.. in other words, back EMF WASN'T a limiting problem, we wouldn't need more gears to remain closer to "high efficiency", and/OR we wouldn't need larger (read: heavier) battery packs to supply more power to handle the increasing demands....


The back EMF in motors is what stops them from drawing huge amounts of power when unloaded. No free lunches. Word.


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## Brute Force (Aug 28, 2010)

Technically, an unloaded motor uses very little power. And a motor that has no back EMF uses none! And it produces just as much as it uses...



----------------

Now that I've got my snarky comment out of the way, speed = power, not torque. To be totally correct, the power required to push an aerodynamic load is proportional to the cube of the speed. Say you have car that takes 10 horsepower to push it 50 MPH. That same car will take 80 HP to push it 100 MPH and 640 HP to push it at 200 MPH. Gears ratios have no effect on the power required to push the car down the road.

Now consider that one horsepower is about 750 watts. So to push your car along at 200 MPH will take 480,000 watts. Basically half a megawatt. That all comes from the battery pack, capacitor buffers may help with a short spurt but in the end are of no help with this kind of continuous power draw.

Back EMF is the consequence of an electric motor producing useful mechanical power. Power in equals power out, your basic conservation principle. And power in electrical devices equals current times voltage. If the voltage is zero, no matter how much current you poor into it, the power will also be zero. And if you aren't putting any electrical power into the motor, you won't get any mechanical power out.

As Tess said, Nullem Prandium Gratuitum.


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## EVfun (Mar 14, 2010)

mbman88 said:


> Regarding B: Do we need to manufacture a new type of motor which can dissipate back EMF?
> If the back EMF problem is dealt with in this way.. in other words, back EMF WASN'T a limiting problem, we wouldn't need more gears to remain closer to "high efficiency", and/OR we wouldn't need larger (read: heavier) battery packs to supply more power to handle the increasing demands.


You want to make a motor that creates *less* torque? Power is power, you can measure it in horsepower or watts. 1 horsepower is equal to 745.7 watts -- you can do worse converting between the two, but never better.


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## major (Apr 4, 2008)

mbman88 said:


> Regarding B: Do we need to manufacture a new type of motor which can *dissipate* back EMF?
> If the back EMF *problem* is dealt with in this way.. in other words, back EMF WASN'T a limiting problem, we wouldn't need more gears to remain closer to "high efficiency", and/OR we wouldn't need larger (read: heavier) battery packs to supply more power to handle the increasing demands.


Back EMF (or as I refer to it: generated voltage) is not a problem. It is what makes electromechanical energy conversion possible. The power converted is equal to that generated voltage times the armature current. The last thing you would want to do is dissipate it 

Back on the topic of EV top speed. Sure speed kills range. With an EV, but also with a gasser. I saw a vid on the that Bugatti Veyron. I don't have the link and may be inaccurate, but what I recall was by the time it had accelerated to its top speed, it was basically out of gas. Or in other words; it uses a full tank of fuel to get to top speed. Therefore what is the usefulness of that top speed other than bragging?

So I don't see where this range issue is relevant to this thread topic. But I don't see harm in discussing it here either. Maybe we should consider a different EV: The bullet train. This is a vehicle designed for long range and high speed. And what propulsion system do they use? Electric  The fuel delivery system can be distributed along the route and not carried on-board. Try that with combustion engine 

Of course you have examples of the highest speed vehicles using combustion propulsion; jets, rockets, etc. And then there are vehicles which fall into the projectile class like bullets or rail guns. Here the electric wins out in the end. Ultimately, using electricity, those super colliders propel tiny vehicles to the speed light 

How's that for off-topic.


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## major (Apr 4, 2008)

zsnemeth said:


> A tank of gas last for 12 minutes at top speed. Start watching from 5:00.


Thanks. So it has a range of like about 40 to 50 miles, right?


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## DavidDymaxion (Dec 1, 2008)

Thanks Major for pointing out the error. I said "power" when I should have said "force." It turns out the math is right, and in the context of force the efficiency measures are not mixed.

Force ~ v^2

Force ratio ~ (75 mph / 55 mph)^2 = 1.9x more force to go from 55 mph to 75 mph to overcome aero drag

Energy = Force * distance

So for the same distance, twice the force (~40% more speed) means you need twice the energy per unit distance, or 1/2 the fuel economy if it scaled simply (but it doesn't, you get better than 1/2 the fuel economy).

Yes, yes, I know I left out rolling resistance to make it simple. Assume a really light, low rolling reistance vehicle with very bad aerodynamics. 



major said:


> Where it would follow logic to see twice the fuel rate consumed to produce twice the power, that does not logically relate to half the distance per unit volume of fuel because the increased power results in increased speed covering greater distance per time.
> 
> In other words, you seem to mix to efficiency measures:
> 
> ...


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## DavidDymaxion (Dec 1, 2008)

It's a small number of data points, but for fun let's look at the best on the Salt Flats. The Buckeye Bullet did a very awesome 315 mph on electrons! The ICE record is 450 mph for a wheel driven vehicle.

(450 mph / 315 mph)^2 = 2 (twice the force, and hence twice the energy)
(450 mph / 315 mph)^3 = 3 (three times the power)

It would be great to hear your thoughts on what the Buckeye Bullet would need to do to take the all time wheel driven land speed record.


major said:


> ... I fail to see relevance to the thread topic.


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## toddshotrods (Feb 10, 2009)

DavidDymaxion said:


> ...It would be great to hear your thoughts on what the Buckeye Bullet would need to do to take the all time wheel driven land speed record.


They posted three new Venturi motors on their FB page, which they claim will produce 1000hp each. No word on what they're using for inverters and batteries and how much they can pass to the motors.

For the record run Rizzoni said they had 1MW in the pack, but could only pass about half of that to the motors, due to inverter limitations.


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## dragonsgate (May 19, 2012)

DavidDymaxion said:


> It would be great to hear your thoughts on what the Buckeye Bullet would need to do to take the all time wheel driven land speed record.


A tail wind? As for top speed restrictions I have found speed limits and lurking cops to be a deterrent for my car reaching its limited capabilities. Excuse the noise but I thought would take a shot at giving some comic relief.


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## toddshotrods (Feb 10, 2009)

DavidDymaxion said:


> ...The ICE record is 450 mph for a wheel driven vehicle...


Speed Demon has a 439.024 record, and a top recorded speed of 462.##. (2000+ hp/1200+lb-ft) Is there a wheel driven vehicle faster? From what I remember, most of their issues have been mechanical, with stuff breaking, shredding tires, etc. The power is there for more.

They're shooting for 500mph, btw. BB3 is shooting for 400, the last I remember hearing them say. I need to try to poke my nose in CAR again soon.


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## major (Apr 4, 2008)

DavidDymaxion said:


> It's a small number of data points, but for fun let's look at the best on the Salt Flats. The Buckeye Bullet did a very awesome 315 mph on electrons! The ICE record is 450 mph for a wheel driven vehicle.
> 
> (450 mph / 315 mph)^2 = 2 (twice the force, and hence twice the energy)
> (450 mph / 315 mph)^2 = 3 (three times the power)
> ...


You have a typo in your second equation. ^2 ---> ^3.

The relevance I question is about power plant fuel efficiency and range, and top speed capability. Providing you can make the power and have a large enough fuel tank (or battery), what difference does it make 

Regarding the Buckeye LSR efforts; I'm pretty sure those boys know what they need. More power and/or less drag obviously. Says a lot that they think they can do it. Helps to have a few million in sponsorship 

Aside from things breaking mechanically one of the big obstacles is traction. With the 2-wheelers I heard one of the fastest ever talking that electric propulsion may have an edge due to the non-pulsating power delivery to the salt 

BTW Todd. In 2011 Paul set a record in excess of 200mph so was invited to the Red Hat Club banquet. He was gracious enough to take his crew guy and owner. There were several there who were in the 400mph chapter of the club. I forget the hat color. Not too many members though. And Bill Warner sat at the same table as we did. The first 300mph sit-on motorcycle and only one still. Sadly he was killed a few weeks ago when he crashed at 285. Reminds us all of the risk and guts it takes to accomplish these feats.


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## toddshotrods (Feb 10, 2009)

major said:


> ...The relevance I question is about power plant fuel efficiency and range, and top speed capability. Providing you can make the power and have a large enough fuel tank (or battery), what difference does it make ...


The topic of the thread is what keeps them from it. If range suffers terribly enough, it can be a reason people don't attempt it - to avoid the negative press, even when they potentially have the capability. Add to that things like a $42K  set of tires are wasted (in the case of the Veyron), and it becomes a question of whether or not it's even financially viable to attempt it. If it took a dozen attempts to reach it, you could have spent a quarter million bucks just in tires (if you used Veyron type custom/specific tires), and how much life might be taken from the battery pack by having been depleted so far, so fast? Even for testing, most people wouldn't consider it worth the effort, just to please a few hardcore speed junkies who won't even likely buy one. The rest of the public could honestly care less, after their eyes go back in their heads from hearing the magic 200 quoted.






major said:


> ...BTW Todd. In 2011 Paul set a record in excess of 200mph so was invited to the Red Hat Club banquet. He was gracious enough to take his crew guy and owner. There were several there who were in the 400mph chapter of the club. I forget the hat color. Not too many members though. And Bill Warner sat at the same table as we did. The first 300mph sit-on motorcycle and only one still. Sadly he was killed a few weeks ago when he crashed at 285. Reminds us all of the risk and guts it takes to accomplish these feats.


Wow. Reminds me of Elmer Trett the T/F motorcycle racer who was killed trying to get in the 5's, before his nemesis Spiderman (who pilots the Rocket bike, and his own 5-second ICE T/F bike).

Yet, I still want to give 200 a shot on Scrape.


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## DavidDymaxion (Dec 1, 2008)

Demonsgate: I did laugh! Something I do like about land speed and electrics is a high top speed tends to imply good range, unlike drag racing where a fast EV doesn't necessarily have good range. Also, the land speed guys tend to run narrow, high pressure tires, and have good aerodynamics -- stuff that is good for EV range.

Team Vesco has a 458 mph record, and has hit 470 mph, wheel driven.

http://www.teamvesco.com/

From my other post, other things being equal, the Buckeye Bullet team will need 2x the force and 3x the power to take the all time land speed record. I have seen the Buckeye Bullet up close, with some of the covers off. Would they have room for 3x the motors and inverters, and 2 to 3x the batteries? I would love to be proved wrong, but it is conceivable that ICEs will always hold the top land speed record due to inherent advantages.

A neat data point is the BYU light weight ( < 500 kg, or < 1100 lbs) streamliner. The battery pack is about the size of a golf bag, and it has exceeded 180 mph. Major's team lightning went 215 mph on a pack that comfortably fit on a motorcycle. So it looks like if 200 mph is your goal, it is quite doable electrically. 400+ mph... now there's the rub...

Major good point about picking up "fuel" off board, like many trains do. That is a huge advantage an ICE has over a battery electric, where both vehicles carry their fuel on board. The ICE gets 14/15 of its "fuel" from sucking in air. It would be very challenging to carrying enough air on board.



toddshotrods said:


> Speed Demon has a 439.024 record, and a top recorded speed of 462.##. (2000+ hp/1200+lb-ft) Is there a wheel driven vehicle faster? From what I remember, most of their issues have been mechanical, with stuff breaking, shredding tires, etc. The power is there for more.
> 
> They're shooting for 500mph, btw. BB3 is shooting for 400, the last I remember hearing them say. I need to try to poke my nose in CAR again soon.


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## toddshotrods (Feb 10, 2009)

DavidDymaxion said:


> ...
> Team Vesco has a 458 mph record, and has hit 470 mph, wheel driven...


Ahhh, I see. Now I get why Poteet and Main stress "piston engine" so much. LSR is interesting because of all the classes. Just pick a class, go faster, and become a record holder. I'm used to racing based on two or more competitors battling it out, and I don't process this right sometimes...






DavidDymaxion said:


> ...the Buckeye Bullet team will need 2x the force and 3x the power to take the all time land speed record. I have seen the Buckeye Bullet up close, with some of the covers off. Would they have room for 3x the motors and inverters, and 2 to 3x the batteries?...


All new car this time. I don't know whether the three motors are going in together or whether one or two could be spare(s). From the concept renderings, the new car (BB3) looks pretty long, so I suspect they're stretching it out for enough batteries for 400mph. Everything I have seen, so far, seems to follow what you've been saying with the math posted here, so they're obviously doing their homework. I wonder about the weight though, with current battery technology; maybe they'll get access to something "special".

The one thing I don't like is how much stuff gets subcontracted out. They boast and brag about their engineering programs and department, but don't personally take the reins and push the limits on things I would expect them to. That seems to fit with life, in general, here though - why push, when you can find a way to coast...  If anyone from OSU reads this board - there goes my way ticket back inside CAR. 







DavidDymaxion said:


> ...So it looks like if 200 mph is your goal, it is quite doable electrically...


Agreed, it looks pretty _easy_, from my vantage point. I have a friend who has been there on his ICE bike. I think I was close to 150 on a 'busa, but didn't have the room to keep going. That bike probably had 180 in it. I used to do 130-140 on my old ICE bikes, almost daily. On modern bikes, it's really pretty tranquil. I would imagine that 250-300 starts to feel a little on edge. I don't _think_ I'm going there...


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## major (Apr 4, 2008)

toddshotrods said:


> Agreed, it looks pretty _easy_, from my vantage point.


Tell me how easy it was after you've done it


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## toddshotrods (Feb 10, 2009)

major said:


> Tell me how easy it was after you've done it


Lol, I should have expected that!  It was much harder for you because you had to design for a competition bike, that had other concerns. I'm building an exhibition bike that has no other purpose than to satisfy my current whims. I also get to take advantage of the knowledge I've gained from observing your hard work - and hopefully pay you to help me figure out what I can't!  How do you think Mr DieHard-1MW-3000amps-DC ended up going high voltage AC? 

The easy part is that the parts exist. I am exploring options, but can simply purchase a motor/inverter package, can easily fit a couple/few choices for enough battery for Scrape's limited sprints, and started with a liter-class sportbike chassis...

Compared to trying to figure out how to get a multi-purpose car there, this feels _easy_.


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## spoland (Aug 9, 2012)

mbman88 said:


> So.. Why is it that Electric vehicles seem to have such a problem pertaining to their top speeds?


I would say it is a matter of cooling.
ICEs have very efficient cooling that gives then a sustained power that is the same as their peak power. Thereby they can accelerate for a long time period which is needed to obtain a high top speed, and also sustain that top speed.
Electric motors usually have a peak power that is much higher than their sustained power. So their peak power can be used for short, powerful accelerations but not for the longer accelerations that are needed to obtain and sustain a high top speed.
If electric motors had more efficient cooling their peak power could be used for longer time periods and even be sustained. Then EVs would have higher top speed.


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## mbman88 (Feb 17, 2013)

major said:


> Back on the topic of EV top speed. Sure speed kills range. With an EV, but also with a gasser. I saw a vid on the that Bugatti Veyron. I don't have the link and may be inaccurate, but what I recall was by the time it had accelerated to its top speed, it was basically out of gas. Or in other words; it uses a full tank of fuel to get to top speed.


Yep. I can verify this with daily driving habits. If I drive faster through traffic I'm out of gas sooner. That's an excellent argument.


Capacitors would indeed have been useful for short bursts, but I wasn't necessarily thinking about Top Speed when I recommended them, it just popped in my head as an idea. In my opinion it seems that to make a quick EV without using Capacitors is potentially insane since you could guarantee that he battery pack will be destroyed much sooner than it needs to be. But his only applies to acceleration, temporary. 

From what I can tell, our current EV technology means we've already done it wrong. Using Lithium Ion cells is really a matter of demand, not choice. Gas is getting expensive and scarce.. and while Lithium Ion type batteries are superior to the non-Lithium range of batteries, they still have the chemical-cell problem and will be inevitably damaged by electric propulsion *unless they are large enough batteries*. A superior, battery-like capacity, capacitor is what is needed to make more reliable energy-packs. The limitations on Top Speed seem to be directly related to manufacturers preventing their battery packs from being overly used and damaged... and I do not disagree with this. The more EVs deal with problems then the worse their image is. In this respect it is worth not having a "bragging rights"-high top speed since you are avoiding a media frenzy of battery pack failures... however... I think that battery pack failures are still going to be a problem until we develop a superior energy-pack technology such as Nanocapacitors.

And.. I understand that it's impractical. But that isn't my point. It's all about the bragging rights. It's not about Ego, not mine anyways. It's about proof, evidence. I've already said it but I will clarify. We are thickheaded "power-hungry nutcases" and we need to be proven wrong. The EMF thing was just a question, for some of you. It has been answered. And thank you. No need to continue with that. 
Technically, with "Major" and his motorcycle I can already see that the stuff has been proven. But some thickheaded nuts still believe that an electric truck cannot be invented because of whatever reasoning that they think they have. That's an easy one to disprove since there are obvious examples of powerful electric trucks that haul better than ICE counterparts. But societies work by mass opinion, and the current mass opinion of ours (USA) is that electric motors and batteries are LESS overall powerful than ICE engines, which is obviously untrue since the electric systems are more efficient.


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## kennybobby (Aug 10, 2012)

Capacitors are passive electrical components that hold energy according to 0.5*C*V^2, but don't create or generate any energy on their own. 

But your original question then seems to be more related to the "fuel" and energy storage aspects rather than the factors that limit the speed in electric motors. 

Gasoline: a gallon has a volume of 231 in^3, weighs 6.2 lbs, and in a non-reversible chemical reaction involving oxygen has an energy content of 111,000 BTU or 32.51 kWh 

Batteries: a 100 AHr lithium iron phosphate prismatic has a volume of 136 in^3, weighs 7.72 lbs, and using a reversible chemical reaction has an energy content of 1092 BTU or 0.32 kWh. http://www.electriccarpartscompany....25-in-150-69-207-mm-br-772-Lb-35-Kg_p_41.html 

So it would take 772 lbs of batteries (x 100) to provide the same energy content as 1 gallon of gasoline. 

The top speed of an EV is not so much limited as it is a design solution involving the trade off of range versus top speed for the amount of 'fuel' or energy that you carry onboard. If you don't care about range you can make a dragster with high top end speed. 

When your 'fuel' weighs so much then you're not going to get both range and top speed in the same design package, because weight has always been an enemy of speed.


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## DavidDymaxion (Dec 1, 2008)

Don't forget the gas car throws away around 80% of its energy as heat, and the electric car throws away much less. 772 lbs of lithiums will take a conversion much further than a gallon of gasoline will. For instance, on about that much weight of lithiums Jack Rickard's cars go 100+ miles -- much further than a gallon of gas will take them.

Weight is the enemy of acceleration, but can actually help top speed. The fastest stock bodied car ever, a Pontiac Firebird, went 300+ mph. I was told the car had the frame rails filled with lead and weighed something like 8000 lbs! At high speeds, rolling resistance is a small part of your loss, it's mostly air resistance. The weight helped hold the car down for traction. So if you want to go as fast as possible in the 1/4 mile, make the car light. If you want to go as fast as you can on the Salt Flats, don't worry about the weight (indeed, adding some could help!).


kennybobby said:


> ... Gasoline: a gallon has a volume of 231 in^3, weighs 6.2 lbs, and in a non-reversible chemical reaction involving oxygen has an energy content of 111,000 BTU or 32.51 kWh
> 
> Batteries: a 100 AHr lithium iron phosphate prismatic has a volume of 136 in^3, weighs 7.72 lbs, and using a reversible chemical reaction has an energy content of 1092 BTU or 0.32 kWh. http://www.electriccarpartscompany....25-in-150-69-207-mm-br-772-Lb-35-Kg_p_41.html
> 
> ...


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