Efficiency Versus Speed

[Bombastinator2]

Nope, not yet; just had to go make sure. Totally even wear and decent amount of tread left.
Sentury Tourings and I'd guess they're at around 28k miles on em.

Sounds like I’m going 40 psi then

 

[LeftieBiker]

I've been running 40-42psi for over 10 years, now. No uneven wear at all.

 

[Gerhard]

In the city I drive at the posted limit, on the highway the limit here is 80 to 100 kmh I tend to drive 5 to 10 kmh over that so that I don’t annoy fellow drivers. My 40 kw car goes between 200 and 230 km on a charge before I get anxious.

 

[gmcjetpilot]

40psi. Avoid freeway with 65-70 mph. Range gies to pot. 55 mph limit OK but everyone is going 65 to 70 anyway. I try to take back roads 45-50 mph.

 

[cwerdna]

My 40 kw car goes between 200 and 230 km on a charge before I get anxious.

Battery capacity is measured in kWh, a unit of energy, not kw.

kW is a unit of power and a totally different metric.

40 kWh Leaf has 110 kW motor motor rating. Search https://usa.nissannews.com/en-US/re...d10c4d9207f2237-us-2018-nissan-leaf-press-kit for 110 kW.

 

[Gerhard]

Battery capacity is measured in kWh, a unit of energy, not kw.

kW is a unit of power and a totally different metric.

40 kWh Leaf has 110 kW motor motor rating. Search https://usa.nissannews.com/en-US/re...d10c4d9207f2237-us-2018-nissan-leaf-press-kit for 110 kW.

I am so sorry

 

[WetEV]

I suggested 40 psi to a mechanic and he said it would screw up my tire wear

I usually ran 40 PSI because it gave better tire wear and handling. Factory pressure is too low.

 

[LeftieBiker]

Just to illustrate how the door sticker pressure is part of the public mindset, I offer the following anecdote: a few years ago, I topped off the tires for my then-GF, who drove a mid nineties Corolla. I knew that she rarely checked her tires (one of the tires read 25psi, IIRC), and the 32psi sticker seemed at the bottom of normal to me, so I set them all to something like 36 or 38psi. When she found out, she went off like a bomb. She accused me of trying to ruin her tires, and then called her mechanic. The poor guy muttered something about trying to follow the door sticker, and hung up. I just reset them all to 32psi, and vowed never to work on her car again.

 

[nlspace]

No good deed goes unpunished, some folks you just can't help and let them run around on 25 psi tires...

 

[woeful]

Yes, Air resistance is proportional to speed squared (v^2), but the power to overcome it goes up by speed cubed (v^3).

...but the energy per mile needed to overcome air resistance is power divided by speed, which is back to speed squared. (v^3/v is v^2).

Power to overcome rolling resistance is proportional to speed, and the energy per mile for that is the same at any speed (power v^1, divide by v gives a constant).

Power to run heating, electronics, lights, etc is constant. Its contribution to total needed per mile decreases with speed (v^-1, or 1/v).

The most efficient speed is when the power needed to overcome air resistance is equal to those fixed loads. That's below 30 mph in daylight and mild weather, and below 40 mph even in the dark and nasty weather, with a bit of variation for windy conditions.

Going up hill doesn't affect the most efficient speed. Going downhill does, if the only way to keep the speed down is regeneration (around 80% efficient) or friction brakes (0% efficient).

 

[lorenfb]

Thanks! You reset the thread back to the correct physics.

 

[Bombastinator2]

One thing I like about electrics is they’re quick but not fast. For an ICE vehicle to be quick it also has to be fast. I don’t need a 160mph top end. I have no use for it. A low 0-60 can get me out of trouble though. My leaf has about the same top end of an average passenger car, but a 0-60 half of what an economy car has. Quicker than my old GTI which had a top end of 140something, which was totally useless to me.

 

[DougWantsALeaf]

My Leaf Plus is seconds faster 0-60 than my 1986 5L Tuned Port Injected TransAm, even with eco tires.