Range at altitude

[Mach1E]

I can't say much about how much the thinner air reduces drag. Probably the physics behind it is pretty trivial and one could calculate that. But I think it wouldn't be very much.

I think the much more important point here though is that there is generally no negative effect of altitude on EVs, which is not at all the case for ICE vehicles. Combustion engines do significantly loose efficiency with increasing altitude due to the lower air pressure and less oxygen.

There is no free lunch though.

Yes- thinner air equals less wind resistance.

However it also typically means colder temps.

Colder temps can kill range.

Ideal setting for max range- high altitude and hot temps (80+ degrees).

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[Kamuelaflyer]

Except they do get to get away with using lower octane gas, at least. (Apparently this is controversial now as well, as I search it just now).

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[Mach1E]

Except they do get to get away with using lower octane gas, at least. (Apparently this is controversial now as well, as I search it just now).

Lower octane gas has more energy than higher octane gas.

 

[azerik]

There is no free lunch though.

Yes- thinner air equals less wind resistance.

However it also typically means colder temps.

Colder temps can kill range.

Ideal setting for max range- high altitude and hot temps (80+ degrees).

That’s exactly what I see. At 7400 ft if there is a difference I don’t see it because I’m usually driving slower because the cooler temps kill the energy off faster than the air can.

 

[xxiii]

Our summers here are typically in the 90s, and winters in the 20s, with occasional excursions into the triple or single digits.

 

[xxiii]

I was going to mention in my original, and decided not to, but I think I will now anyway:

My understanding is airplanes climb to 30-35,000ish feet because of efficiency reasons. even on short flights. Las Vegas is very near by (to me, SLC INTL) (in airplane terms) and yet they climb all the way up, only to almost immediately start descending again, paying whatever fuel cost it is to get an entire plane full of people and luggage 5 or 6 miles higher than they were, so it must be worth it. (some of it made up for on the way back down, I assume, shame that presumably planes don't currently have regenerative braking).

I understand on longer flights, but I was surprised last time I went to Vegas to discover this happened even on that flight (ah the age of wonders with my own personal GPS tracker that still works inside a mostly metal box). (I fly very rarely, so I still want a window seat and stay awake the whole time, but I digress, also this flight is only an hour, ignoring all the airport stuff).

I wasn't expecting this to happen and was curious how high we would actually get.

 

[Kamuelaflyer]

I was going to mention in my original, and decided not to, but I think I will now anyway:

My understanding is airplanes climb to 30-35,000ish feet because of efficiency reasons. even on short flights. Las Vegas is very near by (to me, SLC INTL) (in airplane terms) and yet they climb all the way up, only to almost immediately start descending again, paying whatever fuel cost it is to get an entire plane full of people and luggage 5 or 6 miles higher than they were, so it must be worth it. (some of it made up for on the way back down, I assume, shame that presumably planes don't currently have regenerative braking).

I understand on longer flights, but I was surprised last time I went to Vegas to discover this happened even on that flight (ah the age of wonders with my own personal GPS tracker that still works inside a mostly metal box). (I fly very rarely, so I still want a window seat and stay awake the whole time, but I digress, also this flight is only an hour, ignoring all the airport stuff).

I wasn't expecting this to happen and was curious how high we would actually get.

There's a big difference between battery electric vehicle efficiency and current generation turbofan engines on airliners. The parabolic flight profile you see on short flights isn't due to efficiency at altitude per se, it's due to the lack of efficiency when a turbojet aircraft stays in cruise longer at lower altitudes. Gas burned during the climb is significant, and gas saved during descent is even more significant, hence the seemingly suborbital altitudes and flight profiles compared to what would otherwise be a low 20s cruise altitude. The most efficient airplane for short hauls is usually a turboprop aircraft. The public doesn't like them though.

BEVs only work in 2 dimensions. The choice of altitude is nonexistent, it's whatever altitude the road is at. In an airplane altitude choice is up to the crew, the planners who have all the real flight planning programs and ATC and those are all competing interests. For a car there are no competing interests, it's whatever the road planners planned and built. Engine efficiency wasn't a consideration.

 

[Scooby24]

Just chiming in to say forced induction engines still suffer overall power losses with altitude. To compensate for lower density air, pressure is increased. Higher pressure is going to push the turbo to be less efficient, produce more heat, and lower the knock resistance. But the overall losses are much less than NA which is vacuum dependent. In either case your car only needs xx torque to drive the vehicle at any altitude and the throttle just needs to open a bit more to make the necessary torque. The fuel needed is fixed to maintain target AFR and scales appropriately based on MAF and or MAP readings in combo with O2 sensor..so mpgs in an ice should be about the same if not a bit better because you overall have less fuel demands with higher throttle events.

 

[Fixbear]

I had a 83 T Bird Turbo coupe. 2.3 liter 5 speed that had 19 pounds of boost and a waste gate. On trips to RI monthly, I got 29 MPG on a nice day and 42 when it was raining. So apparently the moisture had a factor in the efficiency.

 

[4sallypat]

So if you drive below sea level altitudes like Death Valley, CA at -300ft below sea level, your range is decreased ??

 

[Thor2j]

So if you drive below sea level altitudes like Death Valley, CA at -300ft below sea level, your range is decreased ??

In an electric car yes. Drag is drag. If temps are the same.

 

[Scooby24]

I had a 83 T Bird Turbo coupe. 2.3 liter 5 speed that had 19 pounds of boost and a waste gate. On trips to RI monthly, I got 29 MPG on a nice day and 42 when it was raining. So apparently the moisture had a factor in the efficiency.

Humidity has the opposite effect on efficiency. Humid air slows down the fuel burn (lower in cylinder temps, higher EGT due to the fuel's inefficient in cylinder burn, and worse knock resistance. I've never observed a benefit to humid air....except when I was making it humid with methanol injection

 

[Fixbear]

Humidity has the opposite effect on efficiency. Humid air slows down the fuel burn (lower in cylinder temps, higher EGT due to the fuel's inefficient in cylinder burn, and worse knock resistance. I've never observed a benefit to humid air....except when I was making it humid with methanol injection

Yes, but when you add water to the combustion, it adds power. Look at the F4-5 or FG-2 Corsair. I had the car for 5 years and monthly traveled for drill weekends to either Brunswick, ME or Davisville, RI from the NY Adirondacks. Problem with the car was it needed plugs every 3000 miles and at 80,000 miles tires. 395 tires were $500 each back then. And it would light the tires up in 3rd gear when the boost came it. It easily would do 160 MPH. But only a four banger. Ford didn't make to many of them, as it was to prove the motor for aircraft use. The first of the aerodynamic design's. NASCAR made them raise that body design 2 inches over the field in 84.

 

[Scooby24]

Yes, but when you add water to the combustion, it adds power. Look at the F4-5 or FG-2 Corsair. I had the car for 5 years and monthly traveled for drill weekends to either Brunswick, ME or Davisville, RI from the NY Adirondacks. Problem with the car was it needed plugs every 3000 miles and at 80,000 miles tires. 395 tires were $500 each back then. And it would light the tires up in 3rd gear when the boost came it. It easily would do 160 MPH. But only a four banger. Ford didn't make to many of them, as it was to prove the motor for aircraft use. The first of the aerodynamic design's. NASCAR made them raise that body design 2 inches over the field in 84.

Adding water to charged intake is an entirely different impact as that's rapid IAT decrease due to evaporation and the temp decrease is offsetting the impact of additional humidity. Methanol accomplishes this even more dramatically than water alone and I was adding 10+ degrees of additional timing on top of maxing out my turbo and not seeing any knock and my EGTs were a solid 2-300 degrees lower.

 

[Fixbear]

I'm quite familiar with Methanol and Nitro methane. I worked at a speed shop in the 60's. High point was with Don Garletts and Swamp Rat II at the 68 winter nationals. He actually said it was make or break in the final round and mixed 70% nitro. Top came off the 426 hemi.

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