Bolt Top Speed

Discussion in 'Bolt EV' started by JeremyK, Nov 20, 2017.

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  1. JeremyK

    JeremyK New Member

    What are your thoughts and GM's limitation of the top speed of the Bolt?

    Why 93 mph? It's not likely a mechanical limit of the electric motor. Guessing there is concern about discharge rate of the battery and/or overheating. Or perhaps, GM is just being conservative and testing out the propulsion system, before opening up more power in later versions/vehicle applications.

    Either way, I think it's a bit low. Even the Volt was "allowed" to go 101 before the electronic nanny kicked in. The way the Bolt is pulling at 90 mph suggests that it's good for MUCH more. Probably 120-130 mph, based on aero/hp figures.

    On a side note, my oversized snow tires (205/70/R15) allowed me to achieve a GPS verified 96 mph this morning, making mine perhaps one of the fastest Bolts on the planet. :)

    On a side note, my 2002 Hayabusa is easily tricked into exceeding its electronically limited top speed of 186 mph, by telling the engine computer that the motorcycle is only in 5th gear (not 6th). The ECU only pulls timing in 6th gear at a certain (high) rpm, thus limiting top speed. Could a similar strategy be employed with the Bolt or are modern systems more sophisticated/complicated to hack?

    Let's discuss.
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  3. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    My understanding is that most or all modern EVs have electronically limited maximum speed. EV motors are pretty powerful, and if allowed to run continuously at the motor's maximum speed I would guess that may damage the mechanical parts of the drivetrain, as well as overheat the battery pack and possibly some of the power electronics.

    I would guess that the waste heat generated by the battery pack and other parts of the EV powertrain, at a sustained 93 MPH, is about as much as GM engineers wanted the battery pack's cooling system to have to handle.

    The Bolt EV is intended to be a "city car". It's not advertised as a sports car or a high-performance car. There's no good reason for a top speed above what any sane person would drive on the Interstate. I think a top speed of something like 85 MPH should be sufficient. 93 MPH seems beyond what this car should need, altho that extra bit of top speed may be necessary for accelerating while climbing a hill, and the like.

    Beefing up the cooling system, and possibly also beefing up the power electronics, to allow the car to go faster, would add cost without adding significantly to utility. That would be a bad idea. Cars which are more expensive to make than they need to be, are less competitive in the marketplace.

    If you want a sports car, or a high-performance sedan like a Tesla, then buy one of those instead.
    Last edited: Nov 20, 2017
  4. Cypress

    Cypress Active Member

    It’s also a trade in gearing. Gear for high speed, or gear for efficiency at normal (legal) highway speeds and city driving, and lower end torque and acceleration.

    The Bolt has better acceleration from 50mph-75mph than a 300hp Dodge Charger, for example. But the Charger can dust the Bolt in top end.
  5. JeremyK

    JeremyK New Member

    It would seem that the Bolt is ALREADY geared for higher speeds (nearly as fast 30-60 as it is from 0-30). Compare to the Gen II Volt, which is actually slightly quicker to 30 mph than the Bolt, but considerably slower 0-60 mph. Gen I Volt is slower than either (at all speeds,) but can still drive at a sustained 101 mph, even in full-EV mode. Certainly, there are mechanical limits of an electric motor, but I doubt the Bolt is anywhere near those at 93 mph.

    If you look at the Model 3 specs., it's got a claimed top speed of 130 mph with a similarly sized motor, single speed "transmission", similar sized battery, etc and has even quicker 0-60 mph acceleration (5.6 seconds). I doubt the Model 3 has a larger heat exchanger or more robust cooling system for the batteries/motor. I just think Tesla tends to push their hardware to 99% whereas GM only allows the consumer to use 80% of the potential to protect against warranty claims. I doubt that battery chemistry alone is enough to account for differences in perceived capability between the two propulsion systems.

    Electric motors are generally less efficient as RPM increases (assuming full load), this means that unlike an ICE, the power will drop as RPM increases, while generating more heat. So, I absolutely understand why GM wouldn't allow SUSTAINED high speeds. However, it would have been just as easy to monitor motor and battery temperature and limit performance once a certain limit is reached, rather just prematurely limit performance based on velocity.

    I highly suspect that the propulsion system of the Bolt is under-rated and its full potential is being held back for use in other platforms.
  6. JeremyK

    JeremyK New Member

    Some people prefer to go unnoticed, which is why I'd rather drive quickly in a neutral-colored, hatchback. The Bolt chassis and propulsion system are perfectly capable of doing 95% of what a Model 3 can do, at significantly less cost. Just need GM to let it loose.
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  8. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Hmmm, no, it is simpler and therefore less expensive, and likely more trouble-free, to simply limit the powertrain to what the heat exchanger can handle on a sustained basis. Furthermore, it makes much more sense from the standpoint of customer relations to do that. People don't like it when you do something they perceive as taking something back that you gave them or promised them.

    Just look at the negative reaction to Tesla limiting power in certain Model S's and X's, regarding repeated use of full-power "launch mode", and in overly frequent use of Supercharging. Altho Tesla has done the best thing for the customer in limiting maximum power to lower levels, to extend the life of the powertrain, still Model S/X owners complain and even file lawsuits to force Tesla to give that extra power back to them!

    Far better for Tesla to simply have made the available power level more limited from the start. But as you say, Tesla likes to push what its cars will do to the limit.
  9. Another thing to consider is motor design. Not all electric motors are created equally.

    Let's say you have a motor that is rated for a top RPM of 8,000. If spun up significantly higher, the rotor can actually expand enough to come in contact with the stator, thus bringing the party to a quick halt.

    Not saying that's the reason for the low top-end speed here, but GM engineers have been quite conservative with many other aspects of their design, and that may be the case here.
  10. rgmichel

    rgmichel Active Member

    I have been up to about 87 mph in my Bolt EV for a second or two, and it started to vibrate. I assume that was a wheel/tire issue. Its fine up to about 85 mph.
    WalksOnDirt likes this.
  11. I would consider having that checked out. Sometimes keeping up with traffic means hitting 80 mph or more, especially if you want to pop into the furthest left lane to pass. It's not hard to imagine bumping up against that top speed, at least momentarily.
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  13. rgmichel

    rgmichel Active Member

    While I couldn't possibly disagree, there is a tendency for some tire places to simply mess with the alignment, tell me its ok, then I end up with tire wear. For tire balance, some of them don't really spin the wheel fast enough to truly balance at 90 mph anyway. I have found vibrations at high speeds to be a bit elusive to fix, so unless the tires start wearing, I am just avoiding anything above 85 mph.
  14. For something like that I would avoid tire places (I avoid tire places anyway, after a number of bad experiences) and go to the dealer. It could be something fixable under warranty.
    Rex B likes this.
  15. rgmichel

    rgmichel Active Member

    I was actually talking about dealer experiences with a couple of Pontiacs that I owned for many years. I ended up going to a tire place in the end, and found that I could trust them more. I suppose my faith could be renewed..... The trouble with tires and wheel alignment issues, the results take a while to become evident if something is wrong. You end up with worn tires and a bill for new tires. However, I may try to have the wheels balanced, not cajoled into wheel alignment, and see how that goes.
  16. rgmichel

    rgmichel Active Member

    For those of us who live ways away from anything much that can be called a city this idea is a bit grating. The Bolt is a great long-distance car, so calling it a "city car" is rather restrictive to say the least. Its certainly not "exclusively" a city car, although it would do great in the city.
    Cypress and WalksOnDirt like this.
  17. I have to agree. I don't think GM intended the Bolt to be, or even thought of as being, a city car. Of course, it's not exactly a "highway cruiser" either -- just an all-round go-where-you-need-to-go kind of car.
    Cypress likes this.
  18. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Certainly the Bolt EV has enough range that it can be used as more than just a "city car". But that's the market it's aimed at. I didn't mean to denigrate the car on that basis. It's just a fact that the car was engineered more for city than highway driving. JeremyK said upstream "It would seem that the Bolt is ALREADY geared for higher speeds", but that does not jibe with what I've read elsewhere. The gear ratio is optimized for maximum range in city driving, not highway driving. Perhaps the inverter and other parts of the powertrain are, too.

    Here's what Eric Loveday wrote in one InsideEVs news article:

    Though Chevrolet focuses on the combined range rating of 238 miles, thanks to the EPA’s database, we can provide a more precise breakdown of the numbers in city, highway and combined format.

    The most notable figures is the Bolt’s 255-mile range rating in the city.

    To put this figure into perspective, the much heavier Model S 60D gets only 221.1 miles on the city rating chart and the 70D is rated at just 242.8 miles city. The Bolt’s 255-mile rating is also exactly the sames as the Model S 75D and just 4.6 miles less than the P90D.

    Where the Bolt fails to shine though is on the highway where its “disaster for aero” (Bolt designer’s words, not ours) coefficient of .32 comes into play.

    The Bolt is rated at only 217.4 miles highway, a figure that’s easily beat by every Model S (Cd of .24) and most of the Model X SUVs out there – except for the RWD Model S 60 (214.8 miles highway).

    Imagine what the all-electric Chevy could have accomplished with a more slippery design, optimized for an electric platform.
    Full article: "Detailed Range Ratings For Chevrolet Bolt EV – 255 Miles City"

    * * * * *

    I remember a post from someone who drives a BMW i3 REx, which has an all electric range far less than that of the Bolt EV. Just like you, he lived outside the city but was using it for his daily driver. And just like you, he was stoutly defending his car and reporting that it could be used for more than just city driving!

    I look at it this way: Just because an auto maker designed a car for a certain purpose, that doesn't mean it can't be used for other purposes. For example, auto makers don't design bog-standard sedans to haul trailers, but in the USA at least, that doesn't stop people from attaching 3rd party trailer hitches and towing with them.

    * * * * *

    So, just because GM designed the Bolt EV to be a city car -- or perhaps more precisely, designed it to be primarily a city car -- that doesn't mean it can't be used for a wider range of driving. It's just not optimized for highway travel, that's all.
    Last edited: Nov 23, 2017
  19. rgmichel

    rgmichel Active Member

    I could not possibly disagree with any of your points, Pushmi-Pullyu, some of which I have reproduced above. It turns out, I had no idea what market the Bolt EV was aimed at when i bought it. I just read consumer reports, figured that the range of this environmentally friendly car was excellent, acceleration and handling excellent, cargo space just what I needed, likely reliability good, service requirements virtually nil, infotainment right on the mark, costs virtually nil with the solar on my roof, and so it would fit all my needs - except for towing for which I will patiently wait for a new all-electric product; meanwhile I borrow my son's minivan for towing. I did read the "disaster for aero" article and looked around at all the disaster SUVs and pick-up trucks around me..... hmm. I considered the disaster for aero minivans and cars I have been driving for 50 years... hmm...

    A month after I bought my Bolt EV, I tested its long range driving abilities in an 880 mile round trip, fully loaded camping. The car was a pleasure to drive - one pedal, quiet, comfortable, fast, reliable, easy to charge in attractive places instead of the hole-in-the wall places by highways. Pure pleasure. Then I did an 1800 mile round trip through the northeast, CT to OH. It had long legs, loved the highways. By that time, I had done more miles on the highway than around home. I then did several 300 mile round trips taking guests to airports and so on. All in all a very impressive long-distance driver. The only caveat I would aim at long-distance drivers is to plan ahead for the location of chargers en route, with a backup plan, as there are not as many chargers as there are gas stations. I won't waste more space here talking about the excellent range figures I realized on these trips.

    Sure, the Bolt EV cannot do 900 miles in a day. There is just not enough time available to keep it charged for 900 miles in 24 hours, but 450 miles or 9 hours of actual driving is as much as I ever do, and it is a great car for those distances. When there are more chargers around, I believe 600 miles in a day might be possible - bit much for me because of driving time and charging time to a lesser extent.

    Comparing a Bolt EV to any new Tesla vehicle was not on point because when I was buying, Tesla was too expensive. A used one without the Federal tax credit and 50k miles on it was too expensive aswell. Even the model three might end up being more expensive than a Bolt, but I have not costed that vaporware yet. The Chevy Bolt beat Tesla to market with an affordable product aimed at real people who drive city, rural and highway, and rarely drive 900 miles in a day.

    It is still the ONLY available general purpose all-electric vehicle. Its not a city car, because that implies ALL it can do is potter around town with a low range, good efficiency, and can be parked easily. It can do that, but it IS also a long-distance car. Of course, if you specifically want to buy a car that can do 900 miles a day, and you need to go cross-country all the time.... don't buy a Bolt.

    I remember, vividly, driving my son's beautiful 2014 Honda minivan after a month or two driving my Bolt EV. That switch was truly amazing. The necessity to wind the thing up before it would actually react to the accelerator pedal was dumfounding. How could I have ever liked this van? Of course, I soon re-learned how to drive an ICE machine, but it remains amazing to recall how bad it felt in that first few miles. Score another for the Bolt EV - one pedal driving, regenerative braking... and so on...

    There is reliability and technical information that is worth having before you buy a car, and there is second-guessing of engineers and salesmen that is not worth much. Into the latter category, I put the the gossipy pronouncement that the Bolt EV is a "disaster for aero", with its resultant implication that consigns the Bolt EV to city imprisonment.
    Cypress likes this.
  20. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Yeah, it was unfair of Eric Love to compare the Bolt EV to a Model S. I quoted that article because it made the point I wanted to make, but I wish I had been able to find a quote that didn't mention Tesla. Comparing a ~$95,000 "premium" liftback sedan to a ~$39,000 (average sale price) 4-door hatchback isn't appropriate. People in the market for a nearly $100k car are likely not going to be cross-shopping the Bolt EV.

    Good point. The Bolt EV isn't a "disaster for aero" compared to the average car; it's just that it's not as streamlined as (some) other plug-in EVs.

    But the counterpoint here is that GM didn't consider the coefficient of drag to be that important, and that is one of several indications that -- again -- they designed the Bolt EV to be primarily a city car. If GM thought the highway range was important, they would have designed it to have lower drag.

    Well, since you bought one and you're driving it, you certainly have an informed opinion on the subject. However, just because you're not using it as a "city car" doesn't mean it wasn't designed primarily to be one.

    Quoting from an review of the Bolt EV:

    After just a few weeks in the fleet, our long-term 2017 Chevrolet Bolt has become a staff favorite. It's an excellent city car with above-average range (as far as compact electric cars go)...​

    [emphasis added]

    Full article: "2017 Chevrolet Bolt EV Long-Term Road Test"

    Obviously we're not going to agree on this point, Rgmichel, but I'm going to continue to use the term "city car" for the Bolt EV, because that's how it's described by those who know more about cars than I do.
    Last edited: Nov 24, 2017
  21. rgmichel

    rgmichel Active Member

    After 50 years of driving all sorts of cars, and reading all the rubbish in motor magazines, I can only be amused at your articles of faith, lack of skepticism, and blithe acceptance of the opinions of those writing therein. Even Consumer Reports is prone to glib statements; more so in the last decade or two as they have convinced themselves that their job is harder than it used to be.

    Its going to be interesting in the coming five years to see how market share of electric cars will fare, irrespective of what the pundits say while second guessing engineers and salesmen. Its the sales figures that count, and its GM's master stroke that impresses, as they correctly judged the markets with a car that performs so well and sells exactly to match their production targets. What GM does over the next few years is a key, although I am not forgetting Tesla, a company that appears to be on a fast track to success.
    Cypress likes this.
  22. I think the term "city car" can have a pejorative sense when applied to the Bolt, as though it's being implied that it's less capable than it really is. I'd be happy to reserve it for use describing more apt vehicles (hello, Mitsubishi iMiEV!). :)
    Cypress, rgmichel and WalksOnDirt like this.
  23. Pushmi-Pullyu

    Pushmi-Pullyu Well-Known Member

    Wow! I thought we were having a friendly discussion.

    I'm not sure why you have gotten emotionally involved in an argument over semantics; over a mere label. I certainly don't have any emotional investment in what category people want to pigeon-hole the car.

    In fact, I'm amused at the varying descriptions, from "compact SUV" to "subcompact hatchback" to even, bizarrely, "small wagon", for the Bolt EV. I find equally amusing the arguments over whether it is "really" a compact or a mid-sized car. Obviously none of those are exact terms, and again arguing over which category the car belongs in is merely a semantic argument over the label, not the reality of what the car is or what it can do.

    I don't consider the term "city car" to be a pejorative, but rather a descriptive label. If you do consider it to be a pejorative... well, I guess that's your problem, Rgmichel, given the consensus or near-consensus from various auto reviewers that it is a city car, and your rather strange efforts here to deny that reality.

    It's certainly not my problem!
    Last edited: Nov 24, 2017

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