iMiEV Acceleration Times

[JoeS]

Over the past year I've learned some self-discipline when it comes to reading "professional" reviews of our iMiEV, as my blood would have boiled over long ago. Many reviews are inaccurate, biased, and certainly reflect an absence of basic math skills. I had no idea that there was such ignorance pertaining to electric vehicles or efficient driving, not to mention visual bias, amongst the "professionals". A recent article, which actually wasn't that bad relative to others, was particularly damning as pertaining to cold-weather range. I won't dignify it by providing a link to it. I mean, "The most range I ever saw on the in-car display with a full change (sic) was 46 miles" tells you something.

Anyway, in the midst of this article was the phrase "... leisurely acceleration - 15 or 20 seconds to 60." He goes on to say that he used Eco as his default mode. DUH, I guess he didn't floor it, and the difference between 15 and 20 seconds is significant.

Since I've always considered the iMiEV's acceleration quite lively and have never ever had a problem quickly getting up to speed to merge with our high-speed California freeway traffic, I'm very comfortable with the iMiEV's acceleration, not to mention our >80mph (130kph) top speed. But I don't have the numbers...

Does anyone have any acceleration numbers for our 2012 iMiEV (North American version), not just zero-60 but also transition intervals such as when passing other cars? While we're at it, how about lateral acceleration?

 

[Applewins]

I don't have acceleration times but I will say the acceleration from a stoplight is quite lively. I'll often out accelerate the vehicle next to me at a light without intentionally doing so. Acceleration is not a negative with this vehicle! I've read it will out accelerate the Prius. I'll let you know on that, my buddy at work has a Prius and we were going to line them up sometime soon.

 

[fjpod]

I don't have acceleration times but I will say the acceleration from a stoplight is quite lively. I'll often out accelerate the vehicle next to me at a light without intentionally doing so. Acceleration is not a negative with this vehicle! I've read it will out accelerate the Prius. I'll let you know on that, my buddy at work has a Prius and we were going to line them up sometime soon.

I own a 2010 Prius and a 2012 iMiev. While the iMiev has that silent rapid acceleration (which I sometimes think seems faster than it really is because it is virtually silent), the Prius can accelerate quickly as well. Remember, under hard acceleration, the Prius uses the ICE... AND... the electric motors. The car can move....although a lot of Prius drivers drive like grandmas to increase that mpg display on the dashboard.

 

[leec]

The international spec i-MiEV does 0-60 in 11.9 seconds according to Wired. The 2010 Prius does 0-60 in close to 10 seconds per Edmunds, but it does so far less efficiently due to the combustion engine.

A more reasonable comparison would be towards the subcompact Chevy Spark EV which might do an 8 second 0-60 given it's 400lb-ft of torque. We'll have to wait until it's reviewed to see if that holds up.

 

[MLucas]

I see it a lot like motorcycling, when I first got my bike - I thought it was blazing fast. Then as I got used to the burst of speed when I cracked the throttle, I lost that sense of acceleration. I had to use my eyes to see how easy it was to zoom past other vehicles. My boss in his Camaro tried to race me one afternoon after work, it didn't take much to out distance him. This is with a parallel-twin 650cc Kawasaki. Its the same way with my EV, the burst of speed was simply amazing from something so silent but now that I've gotten used to it - I have to go back to the eye-odometer to see the cars in my rearview mirror.

I don't understand those numbers in the reviews, its like they are reviewing some other car - like a golf cart they mistaken for the i-MiEV. I read one review where the writer said they had no place to put their toll ticket. I've never driven a car that had a specific spot for a toll ticket other than the ashtray. But, the i-MiEV does - right behind the drivers visor. Very handy for holding my Nexus card.

Most of this is spin, because I think a car like the i-MiEV is the every-person's electric vehicle. With incentives, its priced right - which probably scares the hell out of the petro companies and other manufacturers. If something like the i MiEV caught on, it could really make a dent some bottom lines.

 

[Applewins]

I see it a lot like motorcycling, when I first got my bike - I thought it was blazing fast. Then as I got used to the burst of speed when I cracked the throttle, I lost that sense of acceleration. I had to use my eyes to see how easy it was to zoom past other vehicles. My boss in his Camaro tried to race me one afternoon after work, it didn't take much to out distance him. This is with a parallel-twin 650cc Kawasaki. Its the same way with my EV, the burst of speed was simply amazing from something so silent but now that I've gotten used to it - I have to go back to the eye-odometer to see the cars in my rearview mirror.

I don't understand those numbers in the reviews, its like they are reviewing some other car - like a golf cart they mistaken for the i-MiEV. I read one review where the writer said they had no place to put their toll ticket. I've never driven a car that had a specific spot for a toll ticket other than the ashtray. But, the i-MiEV does - right behind the drivers visor. Very handy for holding my Nexus card.

Most of this is spin, because I think a car like the i-MiEV is the every-person's electric vehicle. With incentives, its priced right - which probably scares the hell out of the petro companies and other manufacturers. If something like the i MiEV caught on, it could really make a dent some bottom lines.

I'd agree with everything you said except I have never felt that way about my motorcycle I own. With 181 horsepower, my Suzuki B-King never ceases to amaze me of the seemingly endless power of the hayabusa engine. Anyway, not on topic, but had to mention it. I'm loving every mile of our new MiEV and anxious to see how it performs with snow.

 

[sandange]

We just spent 2 days to dig ourselves out from 40 cm, 16" of snow and I can assure you the Miev does very well in the snow..

 

[Brian]

Does anyone have any acceleration numbers for our 2012 iMiEV (North American version), not just zero-60 but also transition intervals such as when passing other cars? While we're at it, how about lateral acceleration?

I used an app on my Motorola Droid X that is called CAR PERFORMANCE. It is free for anyone else to download to repeat the performance test.
My 0-60 time was 11.432 seconds. The app is terrific in that it will provide 0-20 time, 0-40 time, 1/4 mile time, and other neat stuff.

For comparison, here is a link to a site with 0-60 MPH times (and 1/4 mile times) for many vehicles. http://www.ssmoparmuscle.com/speedcomp.htm

My belief is that there are two components to the perceived performance experience.
1. The effortless torque. Being an electric motor, there isn't a powerband of torque that requires to engine to get to an optimal speed before the full potential power is available. The car feels faster out-of-the-gate because full torque is immediate and non-diminishing.
2. The silent acceleration. In an ICE, the driver is getting audible feedback from the engine and exhaust. Quicker acceleration means more sound. In an EV, the only extra sound may be a higher pitch from the motor and more road noise from the tires. It doesn't "sound" like you are accelerating quickly, so it visually appears to be going faster than previous conditioning from life in the ICE age.

 

[JoeS]

Brian, thank you for those measured numbers which corroborate my own seat-of-the-pants impression that the number was certainly less than 15 seconds.

Mitsubishi very purposely programmed the iMiEV controller to de-emphasize the initial acceleration spurt, providing a very smooth takeoff instead of one that would snap one's head back, thus undoubtedly sacrificing a bit of the 0-60 time. You can see the ramp-up on the power gauge as you floor it from standstill. As it is, the maximum current draw is limited to around 150 battery amps, which preserves battery life.

The same motors in the Mitsubishi awesome Pike's Peak race car IIRC have double the output of ours and I'm sure have almost-instantaneous full power application.
http://www.youtube.com/watch?v=G2Zp8DhyHME
Notice they hinted at varying power application to each of the motors on the rear wheels to improve handling in the future. So much interesting tuning can be done with electric race cars, and much of it with software!

As an aside and yet relating to acceleration, I own two Corbin Sparrows (electric with dc motor), one of which has a controller de-tuned for a long five-second ramp-up (wife drove that one for three years and was content with it). The other Sparrow's controller has no ramp-up and if one is not careful it will snap the huge Harley-Davidson drive belt on takeoff (both my wife and I have done that) instead of simply burning rubber.

 

[aarond12]

Other car-focused sites have posted 0-60 times around the 11-13 second range, with one particularly ignorant article saying "15 to 20 seconds to get to 60" and "only 36 miles of range". :evil:

Skidpad results range from 0.68g to 0.75g from what I'm finding. I'm sure with some work finding wider rims and tires, that could improve significantly. Car and Driver has an amusing feature where they take a Leaf and add high-performance tires and get it VERY close to 1g!

http://www.youtube.com/watch?v=tOIAk8TA6b4

With rear-wheel drive, the Mighty Mitsu might be able to get pretty close to that with some sticky race tires. Of course your range will suck... :lol:

 

[Llecentaur]

I will try that android App if I find out where the ODB plug is (don't tel me it is under the swearing wheel?).

One encounter I have to share was with a a Porsche cayenne. As EV drivers, I think it is safe to say that we quickly learn to optimise the speed versus the flow of traffic and anticipate much more than an average ICE driver.

This driver was sticking to my bumper even if for about 5 minutes every acceleration, deceleration I had done was slow and early but particularly smooth and never missed a light or so compared to accelerating sharply everytime.

As soon as we came to a dual carriage road at the next stop he went to my right to overtake me, looking at me with disdain wearing my hat because I was cold, saving on the heating

I don't know why, just out of fun ,I decided to change the beat and put maximum power as the light went green, on a steep hill! Well he probably will grow to either hate little electric cars, because he did try but within the speed limits of the city he could not overtake or even show an advantage at all or he will go and buy an EV, probably a Tesla or Karma waiting to meet me again :evil:

The iMiev is a fun car to drive.

 

[MLucas]

I don't know why, just out of fun ,I decided to change the beat and put maximum power as the light went green, on a steep hill! Well he probably will grow to either hate little electric cars, because he did try but within the speed limits of the city he could not overtake or even show an advantage at all or he will go and buy an EV, probably a Tesla or Karma waiting to meet me again :evil:

The iMiev is a fun car to drive.

I had a similiar experience with a Cadillac SUV driver. I left the light normally but next to me I hear his engine roar as he tries to prove something to me. I punched it and I was able to get well ahead of him so that I could see his expression on his face. It was priceless.

BTW - the OBD port is below the steering column, trace that to the kick panel below the column and you'll find it.

 

[JoeS]

I continue to be perplexed by tests such as Edmunds and Consumer Reports which have shown 0-60 times to be 14.9sec and 14.7sec, respectively, and yet there are other tests which have shown the iMiEV to be more than 20% quicker (see above). I'm very comfortable with my iMiEV's acceleration. and have never had a problem getting up to speed quickly and matching Interstate speeds, often well above the legal speed limit. That said, I usually drive my iMiEV hard when the battery is close to full, and consciously diminish my exuberance with decreasing fuel gauge bars (perhaps my own ingrained response after driving lead-acid EVs for years). Until I validate my own subjective impression (that the iMiEV's 0-60 is around 12sec.) quantitatively, I'd like to put the following on the table:

I believe that our iMiEV's acceleration is dependent upon SOC. For example, if the battery is sitting at 20%SOC (e.g., fuel gauge at around 3-4 bars), the acceleration will be slower than if the battery is fully charged. Here's why:

a. Power is the product of voltage*current
b. Unsubstantiated, my impression is that the controller limits the maximum current draw out of the battery, regardless of battery voltage. As an aside, this current I had measured at a little over 150A.
c. Battery voltage, although fairly flat with Lithiums, nevertheless is a few tenths of a volt per cell lower when the battery is partially discharged. Multiply that by the number of cells, this becomes a significant number.

For example, say a partially discharged battery has lost 0.3v per cell:

0.3v*88cells = 26.4v loss, assuming no difference in voltage sag at full current between fully-charged and partially-charged
26.4v * 150A = 3960W less power delivered than at full charge.
At 1hp/746W, there is over five peak horsepower less available to feed the motor/controller.

Just for reference, here's some data and curve that can be considered typical for a lithium-polymer cell:
http://www.powerstream.com/lithuim-ion-charge-voltage.htm

Another variable is cell voltage sag as a function of current for various SOC. For example, in my other EVs the lead-acid voltage sag (percentage-wise) at a given current is far more when the battery is partially discharged than when it is fully charged.

Adding to this is the possibility that the iMiEV controller cuts back as battery charge depletes - for example, we know it does this dramatically when the battery is near-empty, but perhaps it does it along the way as well in order to preserve battery life?

Does anyone have any data available for the exact cells used in the iMiEV?

My conclusion is that to show off the IMiEV's capabilities, acceleration performance tests should be carried out with the battery fully charged.

As an aside, when talking about acceleration for an ICE (Infernal Combustion engine), I usually think in terms of torque rather than power. But since torque = (power)*(angular speed), if we decrease peak available power, at any given motor rpm we thus have proportionally less torque available to accelerate the vehicle. Further confusing the issue is that motor torque is usually proportional to motor current (not to be confused with battery current), and I don't know what our motor controller is doing when converting our dc power into ac drive power. I don't think we need to go there, but here's a brief ICE discussion relating to this: http://danielmiessler.com/study/horsepower/

 

[gatedad11]

This is an interesting discussion, on a technical level, and I am uniquely UNqualifed on a technical level to discuss with any scientific facts. However, I can state, as everyone else can, that this car has excellent pickup. In every case, co-workers who have taken rides with me have commented on the quick pickup of this car from a stop. Truthfully, who cares what the magazine writers think about the acceleration? On a day to day basis, real world, this car drives very nicely. That's all that I care about. Of course, the car takes an unecessary beating in reviews, and gives an innacurate view of the car, and that's not fair. Mitsubishi, like Nissan, just has to get people to take EV's for a ride, and people quickly change their perceptions of what they can really do.

Lou

 

[aarond12]

90% of my driving is city driving. However, I will take occasional short jaunts on the freeway, mostly to save time. (Some of the streets here in Dallas are at odd angles making it difficult to get somewhere without using the freeway.)

Tonight, to save time, I jumped onto the freeway. I had a long in-ramp, but it was uphill. It took about 80% of the power meter to get me up to 60MPH, the slowest speed I dare drive on the freeway. I would consider the power "adequate". I've had the car up to 75MPH on the freeway and it did a good job. I don't have much doubt the car can do 81MPH.

 

[Don]

I don't have much doubt the car can do 81MPH.

It will - Uphill, downhill or on level ground. Plenty of power, but it's limited to 9900 motor RPM . . . . which is 81 mph. Occasionally it will flash 82, but that's it

Don

 

[JoeS]

As I just posted elsewhere: if the heater was ON during acceleration and performance tests, then of course the car is going to be slower, as the BMS limits the maximum total current draw out of the battery!

Let me summarize:

UNLESS THE HEATER AND AIRCON ARE TURNED OFF AND THE BATTERY IS FULLY CHARGED, THEN ANY ACCELERATION TEST RESULTS DO NOT REFLECT THE CAR'S CAPABILITIES. Those should be standard test conditions for any electric car acceleration tests, just as setting tire pressures and identifying altitude and ambient temperature and windspeed/direction and all the other those other standard factors which can affect the outcome ...

 

[jray3]

bump-

Yesterday morning brought stereotypically soggy streets to the Tacoma area, but that is no impediment to full acceleration from a stop light in the i. However, the Corvette that found himself shrinking in my rearview could not cope so easily, as I watched him lose traction twice while trying to catch up! i flashed the brakes once and eased off at 40 mph, moving into the other lane to quietly declare victory and taunt no further, but was amused when that balding boomer decided not to catch up to me after all of his hard work, despite the 45 mph speed limit!.... :mrgreen:

 

[Barbagris]

It's an old thread, but...

Just for fun, I was playing with CanIon. It logs data, and then can be imported on a spreadsheet.

My 0-100 km/h is near 13 sg, with about 50% SoC.

Seems that can not do much more testing at full throttle! :lol:

 

[JoeS]

Barbagris, wonderful! Now, to repeat this same test on a smooth level windless road at 100% SoC. My contention is that the motor current is limited so the higher voltage should result in more applied power and thus better acceleration and lower 0-100km time.