Let me start off by saying that I consider the handling characteristics of the iMiEV to be very good and I have no problem tossing the car around while maintaining full control. The low CG of the battery and having it centered in the car certainly contributes to this solid and predictable feeling.
The following discussion is obliquely aimed at gathering more information for a future (and separate) discussion that Neutral plays in hypermiling. Bear with me…
I'm still driving a bunch of vehicles without even vacuum-assisted brakes, much less ABS and the brake-pedal-rate-detector in our iMiEV, and I am still trying to get used to the weird (to me) application of the Active Stability Control (ASC) system.
According to our manual, the "…(ASC) takes overall control of the anti-lock braking system, traction control function and skid control function to help maintain the vehicle's control.
is actively operating, I would perhaps describe the effect as a loud "juddering" and perhaps pulsating of the brake pedal (this I'm not sure of, as it's only kicked in once on me in a true panic-stop situation).Traction control
is described in the manual as "On slippery surfaces, the traction control function prevents the drive wheels from spinning excessively, thus helping the vehicle to start moving from a stopped condition. It also provides sufficient driving force and steering performance as the vehicle turns while pressing the acceleration pedal.
" This to me is interesting and perhaps a little scary, as that implies that both the drive motor and the steering are somehow being controlled.
Finally, Skid Control
is described in the manual as follows: "The skid control function is designed to help the driver maintain control of the vehicle on slippery roads or during rapid steering maneuvers. It works by controlling the electric motor unit output and the brake on each wheel
.", with a note stating that the skid control function operates at speeds of about 9mph (15km/h) or higher.
For those nervous about it, the good(?) news is that there is a convenient ASC OFF switch (have to hold it down for 3 seconds or more), which turns off both the skid control function and the traction control function. The manual suggests that ASC OFF can be activated when moving out of mud, sand, or fresh snow…
Now that we have the definitions, I had a disconcerting experience: I was going down a long sweeping high-speed curve (coming down out of the Santa Cruz mountains) going about 55mph with the iMiEV handling flawlessly under full control when I hit a rough patch on the road surface (not unusual with California's deteriorating infrastructure). No problem; however, the juddering ABS(?) and gawd-knows-what-else kicked in and noticeably forced the vehicle to slow down as I'm going around this curve in full control and gently accelerating. Have no idea if the ASC indicator turned on as I was concentrating on driving. Nothing untoward happened other than unnecessarily (in my opinion) slowing the car down and wasting energy. Now this bothered me, and even though Stirling Moss was one of the first race-car drivers to successfully apply braking on curves (you can look up "Trail Braking"), my own predilection with typically understeering conventional cars is to usually accelerate once I'm in the curve.
I'm relaying this as it is an unusual (to me) vehicle response and I guess it's a safety feature and I'm glad it is there for my wife. For myself, I need to take the iMiEV out on some deserted slippery roads or parking lots and play with it some more just to see what its limits are and how it responds both with and without ASC.
OK, so what does this have to do with Neutral and hypermiling? It's this: does anyone know how ASC is affected if the vehicle happens to be coasting in Neutral and hits a slippery patch on a bumpy curve?