Handling

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ZAPPED

New member
Joined
Dec 16, 2012
Messages
2
Well,

I just may inject a little maturity, experience, and wisdom to the i-MiEV discussion.

My first car was a Triumph TR3, the second a TVR 2500M. I’ve owned an E36 M3 Sedan (preferred by the factory racing team), a CTS-V (mistake), three Prii, a Cayman S, and an i.

Colin Chapman and Trevor Wilkinson would be ecstatic with the i. The wheels are pushed out to the furthest extremes of all four corners. Motor and transmission (and charger and inverter) over the rear driven wheels, with the battery mass located in the exact center of the vehicle. With a curb weight of 2579 pounds (less than a Tesla Roadster -2723 pounds), an extremely low polar moment of inertia, a low center of gravity (the batteries are hanging under the floor pan), and a front to rear weight ratio of 45/55 (identical to my Cayman), the i handles very well in transitions, and under steers (for the consumer’s safety) at the limit.

I think we will see a EV sports car built on the i chassis, one that costs closer to $30,000, not $110,000 (Tesla Roadster). Simply add more Kw for more torque, and a stiffer rear sway bar to reduce over steer. The i experiences wind buffeting due to a light weight cabin that is taller than it is wide. The structure is so tall that the driver experiences motion and tipping. A low slung sports car would easily eliminate that problem.
 
+1
Even though I'm partial to FWD having owned a Lancia Fulvia Zagato and a bunch of Saab Sonetts, the iMiEV allows itself to be thrown about with abandon, the only prerequisite being to turn off ASC.
Add a low-slung lightweight very aerodynamic body and we'd have a great car capable of over 100 miles/charge with our existing battery pack.
Perhaps the first step for Mitsubishi is: http://www.gizmag.com/go/8256/
 
After 6,000 miles, I'm extremely pleased with nearly every aspect of my i and especially love that it's RWD, but it's handling isn't one of my favorite things about it - I find it understeers nearly all of the time and severely so at the limit. If I could make a major change to any one feature, I think it would be to re-engineer the suspension both front and rear to make it handle better. If they were to ever make a sportscar version of it, the first thing to do would be to toss the entire suspension and start over with a clean sheet of paper

I suspect most of my disappointment though lies with the fact that my i shares a garage with my 1994 R package Miata and there's no comparing the handling of the two cars . . . . not even a teensy tiny little bit

I don't complain much though, because great handling was the entire reason behind the engineering of the early Miatas and every piece of the suspension was designed specifically with that in mind - No struts or torsion beams anywhere on that car, whereas with the i, great handling probably didn't even make the top ten list of what they were going for when it was engineered. True, all 4 wheels are indeed pushed to the extreme corners of the car, but that wasn't because they were trying to make it handle - If it was, they wouldn't have stopped there

The i is very good at what it does . . . . but when I get the urge to go for a sporting ride, I'll leave it in the garage! :lol:

Don
 
The height of the i makes it very easy to get in and out of. I like it this way as I use it as a city car only...for short stop and go trips. So besides the gas savings, cleaner environment, and less foreign oil, it is easy to park.

OK, I'll take a little more range, but leave the basic size and shape alone.
 
Oh dear, don't want to get into the perennial discussion of handling vs. roadholding, veering off into the differences between grip and adhesion and a zillion other subtleties. Enough on the Web about that already. http://en.wikipedia.org/wiki/Automobile_handling

Don, by every account the Miata is a superb-handling vehicle, with the differences amongst the MX-5's NA, NB, and NC extensively discussed elsewhere... I don't want to go there. Besides, I'm old-school, with my frame of reference being my own first car which was an Austin Healey 3000.

My bad, as perhaps I should have prefaced my remark by saying that we're simply talking about a tall econobox.

I recognize the necessity for Low Rolling Resistance (LRR) tires and accept the roadholding degradation that comes with them. Mitsubishi's use of unequal tire sizes is interesting, both by keeping the Rolling Resistance lower with the skinny front tires as well as their effect on handling, specifically understeer IIUC. They went to a lot of trouble to incorporate these very unique tires on our iMiEV.

Don, as you've pointed out in the past, the iMiEV's roadholding (and perhaps overall handling) could be altered and undoubtedly improved with different tires. That's been done successfully on the Gen1 Honda Insight, but I continue driving on the original LRR tires as efficiency is my priority with that particular car, just as it is with the iMiEV.

For myself, I had very low expectations of the iMiEV in either handling or roadholding. That's not what I bought it for, as its controllable electric drivetrain coupled with its wonderfully functional overall package were the deciding factors.

What I've been very pleasantly surprised by is the iMiEV's overall handling relative to my initial expectations. ZAPPED explained it nicely in his original posting on this thread.

Besides, not my area of expertise. 'Nuff said.
 
Joe,

I agree with nearly everything you said - I didn't buy it expecting great handling either and looking at it sitting there, I'm amazed that it handles as well as it does. It is a great around town econobox with emphasis correctly placed on good all around visibility, ease of entry and exit, comfortable room for 4 adults and spacious cargo room . . . . well, as much as you could reasonably expect for a car it's size anyway
JoeS said:
Mitsubishi's use of unequal tire sizes is interesting, both by keeping the Rolling Resistance lower with the skinny front tires as well as their effect on handling, specifically understeer IIUC. They went to a lot of trouble to incorporate these very unique tires on our iMiEV.
I kinda doubt they went to any trouble at all. It looks to me like they basically took an existing RWD ICE vehicle (and it's suspension, wheels and tires) and dumped in the battery, motor and trans and didn't change hardly anything thing in what became a completely different car, with a lower center of gravity, more equal weight distribution and a completely different drive system. Then, they made major changes by completely redesigning the entire body for the North America version, again not changing much of anything suspension-wise from the basic ICE they were building years ago

I understand they were likely trying to keep the costs down and they were probably trying to spend the money where they had to just to make a completely different, totally electric car, but I certainly wouldn't offer up any kudos for purposely designing a suspension just to fit this all new, low CG, less rear weight biased car - I don't think they did that at all. I think what we got suspension-wise was just enough to hold the wheels on the car and most of it was just carried along from the car it used to be. True, it didn't work out all that badly, but I don't believe a great amount of thought or engineering went into it - I think their time, efforts, engineering and money was all spent elsewhere

If they ever sell enough of them to recoup what they spent bringing it along this far, I expect the wheels, tires and suspension will get much more attention in the second generation car . . . . at least I hope so

Don
 
I guess the understeering can be helped. There is a switch to get rid of the nurse who controls the breaks and thrust.

Yesterday we tried melting snow for the first time and I was impressed. Snow was days old and melting. We found a lot of space were others did not dare going. Getting out again after hours of parking and late at night was no problem. Other cars got stuck with one wheel freewheeling.

Comparing my old VW Beetle and NSU Prinz 4 is not fair. They all had the engine in the back but the NSU was easy to control although oversteering and the Beatle was lost when it began swinging. All I could do was hit the breaks let it go turning and wait until it got to a stand still whatever directing it deemed apropriate to face. The i-MiEV would never lose its dignity as long as the nurse was watching.
 
My Bad,

I looked underneath my i and found each front suspension has a McPherson strut with the sway bar serving as the fore/aft locating link. The rear lacks a sway bar entirely, utilizing a three link DeDion tube/Watts linkage.

I think adding a rear sway bar would be entertaining.
 
With a F/R 45%/55% weight distribution, almost exactly the opposite of the Leaf, installing the same size tires, maybe 165R65x15, if a suitable low-rolling-resistance tire is available, would help tremendously with the i's overcautious understeering. If that's insufficient or not possible, then adding a rear anti-roll bar could reduce or eliminate the understeering, but a custom (i.e., expensive) anti-roll bar would likely be necessary.

With its weight concentrated low (probably a relatively low center of gravity despite its height) and a mid-engine design (low polar moment of inertia), the i could be made to corner quite well.
 
ZAPPED said:
...I think we will see a EV sports car built on the i chassis....

6485401205_332557ea33_z.jpg


Mitsubishi Sport Air
 
In line with this thread's topic:

Can you imagine being a suspension engineer for Mitsubishi and telling management that they need to put in some seriously-skinny non-standard front tires on this vehicle? It must have taken some pretty compelling arguments (handling? rolling resistance?), but the net result works well, IMO. Converting to four identical fatter tires may result in 'unintended consequences' (and I don't mean the 'obvious' reduced range). :roll:

Sorry, after a year of driving the iMiEV, I now don't buy into the understeer allegation with the stock tires in place.

First of all, with the overly-sensitive (in my opinion) ASC (Active Stability Control), it is all but impossible to get anywhere close to the adhesion limits of this car - it just starts auto-correcting. Best example to demonstrate this is to have your foot off the accelerator in 'B' on a sweeping downhill curve with a rumpled road surface while traveling fairly fast - what happens is the car suddenly both releases regen (which I personally really don't like) and starts selectively applying the brakes. You can't detect understeer nor oversteer as the car doesn't let you get there.

Now, turn off ASC and do the same thing. In my opinion the balance is neutral with neither understeer plowing nor oversteer aft end swinging out.

For me driving daily on my twisty curvy roads, the car is simply a joy to fling around the corners (much to my wife's dismay). I would hope some of our Forum members would enter the iMiEV in some autocross/gymkhana competitions to demonstrate this. That centered and low-down battery pack contributes to the car's stability, with its low polar moment of inertia allowing it to easily twitch through S-curves while accelerating hard. The statements by certain car reviewers that the car "feels tippy" are sheer nonsense unsupported by the facts, which a static stability test would quickly quantify and hopefully disprove.

Flame suit on. ;)

Edit: Oops, forgot to mention that I'm running 60psi in my tires, which Don had pointed out is probably a bit unsafe and with a minimal improvement in rolling resistance over the tire maximum spec of 51psi. Mfg. spec. is 36psi for both front and rear.
 
JoeS said:
Can you imagine being a suspension engineer for Mitsubishi and telling management that they need to put in some seriously-skinny non-standard front tires on this vehicle? It must have taken some pretty compelling arguments (handling? rolling resistance?)
They had some very compelling arguments, so I'm sure it was a pretty easy 'sell'. I doubt rolling resistance was even discussed, but it was surely done in an effort to make the car handle the city environment it was designed for, no doubt about it. Much like a modern Porsche, it really needed the larger rear tires just to keep the rear end behind the front end :lol:

Remember, this was all designed for a car a foot shorter, 3 inches narrower, nearly 700 pounds lighter and extremely rear weight biased compared to our iMiEV . . . . and it had half the power. Truly a 'city car' designed neither for speed or handling

Drivetrain
The i has a "rear-midship" engine mounted just ahead of the rear axle, a highly unusual configuration in a small car where front-engine design has dominated since the 1970s. The 3B20 three-cylinder powerplant has an aluminium cylinder block, a displacement of 659 cubic centimetres, and incorporates double overhead camshafts with MIVEC variable valve timing in the cylinder head. Initially only an intercooled and turbocharged engine was offered, until a naturally aspirated version was introduced for 2007.

Suspension, brakes and tires
MacPherson struts are used in the front suspension, and an unusual three-link De Dion tube/Watt's linkage is used in the rear. Front discs with anti-lock braking (ABS) and electronic brakeforce distribution (EBD) are standard across the range. In common with many other mid- or rear-engined vehicles its fifteen-inch wheels have uneven-sized tires, 145/65 on the fronts and wider 175/55 on the rears, in an effort to minimize the chances of oversteer caused by the rear-biased weight distribution.


For the underpowered Tokyo city car it was designed for (which probably seldom saw 50mph) the minimal suspension made pretty good sense. For a larger, heavier EV cruising down the PCH at 65 mph, not so much

Now . . . . . Can you imagine being a suspension engineer for Mitsubishi and recommending that they keep this exact same set-up in a completely new car which is larger, wider, heavier, has a much closer to 50/50 weight distribution and more than twice the engine torque?? (The standard I car had 42 ft/lb, the turbo had 65 and our iMiEV has 133). If any suspension engineer thought this was a good idea, I'm pretty sure he would have lost his job before the sun went down! But, seriously, I doubt any Mitsubishi suspension engineer had any hand in this - I suspect it came directly from management as a cost cutting measure. "We'll stick an electronic ASC system on it (that the original car didn't have) which won't let it understeer quite as badly as it does without it, and hopefully nobody will notice that the suspension was designed for a completely different car"

I'm pretty shocked (and really disappointed) that it seems like they just took an existing automobile and converted it into an EV with so little thought as to what they were changing. Size, weight, C/G, F/R bias and power. The iMiEV is so much different in so many ways, yet they didn't make ANY changes to the suspension. How much more would it have cost to properly set up the now 2600 pound EV? Surely much less than it cost to completely redesign the body to add a foot of length and a few inches to the width just for the North American market. I'm all for keeping costs down, but this borders on the ridiculous, IMO

Show me any other 2600 pound car which uses 145/65 tires - There ain't one

What I can't imagine is . . . . how they actually managed to get a 2600 pound car with 145/65 tires past the Feds in the USA - Now that seems improbable. Put four 200 pound adults and some cargo in it and now you have a 3500 pound vehicle riding on 145/65 tires :shock:

Saving a few bucks here wasn't a great idea, IMO

Don
 
acensor said:
peterdambier said:
There is a switch to get rid of the nurse who controls the breaks and thrust......
Where is that switch?
Low on the dashboard on the left of the steering column (I believe). I think it's near the small handle that opens the L1/L2 charging door. It might have the icon of a skidding car on it. My car is parked 42 floors below in our parking garage, so it's not simply a matter of my walking a short distance to my garage to take a quick look, but you should be able to find this switch if you kneel down with the driver's door open and look at the lower dashboard area.
 
on a RHD car it is in the small group of controls that alter the headlight height and the mirror adjustment - between the steering column and the door - where the number 12 is on this diagram:

inst-controls.png


Maybe a LHD car is just a mirror image of this layout?
 
Oddly, our 'Bonnet Release Lever' is in the same exact place as it is in your car - Over on the far right, even though all the rest of the controls were moved to the left

Don
 
Thanks Bleepy and Art.

If I understand right Mitsubishi's idea in making it possible to disable that electronic stability control wasn't to enable you to push the car closer to the edge when whipping around corners for sport ;) , but for certain conditions such as an ice driveway where you might be able to muddle your way out of or up a slight slope if you disabled that feature that's being a bit too clever for its own good?

Did I get that right?

Alex
 
acensor said:
Did I get that right?

I think you did - my 1st Prius got stuck on a waterlogged field because the traction control could not be disabled. I'm sure if I'd been able to spin the wheels it would have started moving. Luckily there was a tractor on hand to tow it out.
 
ADMIN, got another one ^.

There's no way Mitsubishi would say that button is for "sport". If it was, they would have a sport mode. They're lawyered up pretty well, as evidenced by some of the warnings in the owner's manual. For one, don't shift into neutral while driving because you lose throttle input, not because it may cause damage to the car.

Turning off ASC in snow is fun, though. I needed to turn it off the other day to make it up my brother's driveway.

(off topic) Is it possible to take the headlight adjustment switch out of an i-MiEV that has it and put it in a US i-MiEV? The servos and gearing are on the headlights, but is the wiring and circuitry in place under the dash?
 
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