jray3
Posts: 1635
Joined: Tue Dec 06, 2011 1:05 am
Location: Tacoma area, WA
Contact: Website

Tire pressure

Thu Mar 22, 2012 9:54 pm

:oops: Surely the pressure would be properly set from your dealer, eh? Well, I neglected to check up on their prep, and sure enough, the tires were set to a cushy 32 psi when Mitsu recommends 36 psi. Since I had a challenging 50 mile uphill highway run planned with a newby passenger yesterday, I went ahead and raised 'em to 50 psi to forestall her "range anxiety". What a difference! Feels like forever for coast-down, without a noticeable increase in noise or roughening of the ride on concrete highway. On fresh asphalt? Better than rails.
So, I drove 51 miles uphill to a meeting and arrived with two bars and 7 projected miles remaining. After a full recharge (all day meeting), the downhill return left me with four bars and 14 remaining miles. ON the way up I intended to stay at 55 mph, but spent plenty of time over 60.
To follow up on yesterday's 101 miles o fun that used 26 kwh from the battery, I did 64 miles today of mostly street travel on a single charge, using only 14 kwh (14 bars o charge)! Now that 62 mile EPA figure is looking reasonable after all!
3300 miles and counting!
PS- We had over an inch of snow on the ground this morning, and I pushed the front end through a few cold wet corners to test the effect of higher pressure. Tire scrub was not noticeably worse.
2012 i-SE "MR BEAN" 105,400 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

seattler
Posts: 22
Joined: Thu Aug 18, 2011 7:12 am

Re: Hypermiling the i-MiEV

Fri Mar 23, 2012 5:54 am

Last I heard about anyone driving an iMiev in the snow was Mitsubishi's promotional video!

What's the max tire listed on the tires? Was it 50psi?

JoeS
Site Moderator
Posts: 3736
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: Hypermiling the i-MiEV

Fri Mar 23, 2012 9:01 pm

Maximum pressure shown on the sidewall is 51psi. Mitsubishi recommends 36psi, front and rear, for the iMiEV.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

JoeS
Site Moderator
Posts: 3736
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: Tire pressure

Fri Mar 23, 2012 9:23 pm

jray3 wrote:So, I drove 51 miles uphill to a meeting and arrived with two bars and 7 projected miles remaining. After a full recharge (all day meeting), the downhill return left me with four bars and 14 remaining miles. ON the way up I intended to stay at 55 mph, but spent plenty of time over 60. To follow up on yesterday's 101 miles o fun that used 26 kwh from the battery, I did 64 miles today of mostly street travel on a single charge, using only 14 kwh (14 bars o charge)! Now that 62 mile EPA figure is looking reasonable after all!

jray3, your uphill drive of 51 miles is corroborating that distance as a comfortable limit for highway-speed excursions. I personally don't want to drop below two bars. Surprised you didn't do better downhill, but I figure you may have been in a hurry to get home... 26kWh/101miles=0.257kWh/mi, but you say that was battery-to-wheel and not wall-to-wheel(?). Glad you caught the tire pressure before your trip.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

jray3
Posts: 1635
Joined: Tue Dec 06, 2011 1:05 am
Location: Tacoma area, WA
Contact: Website

Re: Hypermiling the i-MiEV

Fri Mar 23, 2012 10:24 pm

Yep, that's battery-to-wheel from the guessometer. The ChargePoint station I used midday didn't output the kWh for some reason, only the elapsed time on charge. On the return trip I took a hillier, twistier route that was a mile shorter, but had more fun! The net elevation change was only 600 feet, but I'd wager several times that after the rolling hills.
2012 i-SE "MR BEAN" 105,400 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

JoeS
Site Moderator
Posts: 3736
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: Hypermiling the i-MiEV

Sat Mar 24, 2012 2:40 pm

Moving right along with the subject topic of hypermiling, let's talk about things that rob us of the small amount of energy we have...

Aerodynamics
Not much we can do here as it is designed-in. Mitsubishi tells us the Cd is 0.35 and they had not optimized this by, e.g., putting in a full-length underbody pan or wheel skirts or aerodynamic side mirror housings nor even building in a spoiler to keep the rear of the vehicle clean (see 1960s Saab station wagon). About all we can do is NOT put on a roofrack or bicycle rack ... I've been told that keeping the car clean and waxed does help.

Rolling Resistance
Again, this is designed-into the vehicle, with rolling friction hopefully minimized with appropriate bearings and zero-drag brakes and efficient low-friction motor and drivetrain. About all we can do is pump up the low-rolling-resistance tires, noting that the factory recommends 36psi and the maximum load noted on the sidewall is at 51psi. Even though I run higher, far be it for me to recommend anything other than what the manufacturer specifies.

Weight
Simple: keep it light and empty. DO NOT CARRY ANYTHING SUPERFLUOUS in the car. Trailer hitch falls into this category. Go on a diet yourself. Drive by yourself and want to be extreme? - take out the passenger seat, and you'll have more cargo room as well if you need it. What the heck, take out all the other seats as well. :roll:

Regeneration and Brakes
We already talked about this, but I feel I need to repeat it: use regen ONLY if you need to slow down; otherwise, regeneration sucks valuable kinetic energy from the vehicle. Applying the brakes is even worse: as an experiment, you might practice driving as though you had no brakes and simply apply them when you're down to 5mph.

Other Energy Consumers

HVAC - the onboard heater is a terrible waste of battery power, but if all you do is short trips and don't need to hypermile, then by all means stay comfortable. The seat heater is an excellent low-power alternative. I don't know how much energy the air conditioner consumes, so I don't know how much of a hit the battery pack takes with it, but it can't be good. Where I live I'm lucky and can get by with simply opening the windows (even though that is not good from an aerodynamic standpoint).

Lights - I haven't quantified how much the driving lights, headlights, etc. consume, but those are necessities anyway. About all I intend to do is remove the fuse from my driving light circuit once summer comes (unless someone can point out to me that they're legally needed). My car has the foglamp switch which doesn't work on the driving lights... or else I'm confused.

Radio and accessories - the one or two amps at 12V is probably negligible in the overall scheme of power consumers, so I wouldn't worry about it.

In the next installment I'll talk about what I believe to be the biggest range-limiting hit the iMiEV takes: aerodynamics - and what we can do about it safely while driving. Future topics will include acceleration/deceleration, cornering, dealing with hills, dealing with traffic, and simply examples of real-life driving situations.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

jray3
Posts: 1635
Joined: Tue Dec 06, 2011 1:05 am
Location: Tacoma area, WA
Contact: Website

Re: Hypermiling the i-MiEV

Mon Mar 26, 2012 1:16 pm

SWOT, but my odometer just rolled 3400 miles while still a week short of 3 months of driving. This 'second car' has certainly proved to be our prime mover! :mrgreen:
2012 i-SE "MR BEAN" 105,400 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

leec
Posts: 67
Joined: Mon Apr 09, 2012 10:20 pm

Re: Hypermiling the i-MiEV

Fri Apr 13, 2012 12:42 am

A sensible firmware modification would set "D" mode driving to only regen when you touched the brakes. It would also be nice to have an indication when mechanical braking was applied, so you could train yourself to ride the edge of regenerative braking without wasting energy heating up the brake pads.

Of course, modifying the firmware of one's car would certainly void the warranty. It would be nice if Mitsubishi would allow some kind of hidden override switch to enable this feature, though.

Is there any difference between the zero pedal regenerative braking in the "D" and "Eco" modes already?

rokeby
Posts: 31
Joined: Thu Dec 29, 2011 12:51 pm
Location: Ballamer, Merlin

Re: Hypermiling the i-MiEV

Fri Apr 13, 2012 3:24 am

One tool for those trying to max their MPGs in a Prius is the ScanGauge II.
It plugs into the OBD II port and is easy to use.

Using custom programmable X-Gauges you can monitor HV battery in/out puts,
temps, and a bunch of other metrics.

Has anyone mounted a ScanGauge and got any of the X-Gauges to work?

jennrod12
Posts: 229
Joined: Sat Feb 11, 2012 8:51 pm
Location: Santa Clara, CA

Re: Hypermiling the i-MiEV

Thu Apr 19, 2012 3:04 pm

I was coasting the other day and I moved the gearshift into "R" by mistake! I noticed the indicator on the dash and immediately moved it back to N, then D. I don't know if I actually put my foot on the accelerator at that time or not! Nothing happened, though, nothing at all. But I'm not going to try it again on purpose.

Jenn
2012 Diamond White i-MiEV ES
with green racing stripes and hubcaps (thanks to WeeJohn)
Santa Clara, CA

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