Winter roadtrip - Santa Fe to Boulder and back

[dtbaker61]

Excellent trip report - very much appreciated. I don't normally road trip in the winter, but also have the SR battery, so this was super helpful.

I assume you sat in the car while charging? Heat on? What was the effect?

Thanks again!

sometime I sat in car, sometimes I went to nearby facilities or took a short walk to stretch legs. Leaving cabin heat on uses 2 kw when it is ON, so not a huge effect on charge time if you are charging at 80-100kw.

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[dbsb3233]

Have you noticed what your efficiency is at 80 mph? In my GT, I consistently get 2.4 mi/kWh in mild climate and no significant cabin heating.

It definitely drops at 80 vs 75, but there's so many other factors that it's hard to nail down quite how much. Excluding major wind, I see as low as 2.2 to as high as 2.8 on various stretches at 80 MPH, probably averaging about 2.5-2.6. I would estimate maybe a 7-8% lower MPK at 80 vs 75.

 

[mkhuffman]

I'd say 2.4-2.6 on relatively flat terrain at 80mph. but I don't have much flat. My average daily use is suburban/rural with some mountains and gravel thrown in. avg use hovers around 3.2 in summer, and 2.8 in winter

That's pretty good considering your aftermarket wheels.

 

[dtbaker61]

That's pretty good considering your aftermarket wheels.

winter tires are stock width and wheels. summers are an inch wider and open spoke w bad aero at highway speed

 

[kindofblue]

A slight digression please. What setting do you have to turn off the "cross traffic alert" when backing up with the bikes on the back?

 

[hartmms]

Perhaps I'm overthinking this. Do you have any data to show what the extra 50lbs of the hitch does to the efficiency? Maybe it's too small to measure. I'm debating adding a hitch, but was thinking about how I would use it for < 5% of the miles driven and doing the trade off comparison of just shoving my bike in the back of the car for the rare times I take it somewhere. Bike racks are sure convient when loading and unloading, but it comes at the cost of the 50lb hitch on the car for the rest of the time. I have a RAM 2500, so no need to tow anything with the MME except the bike rack.

Being only 3 hours from Sedona, it should be less rare for me to take the MTB up there, but that's a conversation for a different forum.

 

[SpaceEVDriver]

Perhaps I'm overthinking this. Do you have any data to show what the extra 50lbs of the hitch does to the efficiency? Maybe it's too small to measure. I'm debating adding a hitch, but was thinking about how I would use it for < 5% of the miles driven and doing the trade off comparison of just shoving my bike in the back of the car for the rare times I take it somewhere. Bike racks are sure convient when loading and unloading, but it comes at the cost of the 50lb hitch on the car for the rest of the time. I have a RAM 2500, so no need to tow anything with the MME except the bike rack.

The energy required to move an object is linearly dependent on its mass, so a 50 pound mass added to a 5150 pound mass (the car curb weight is about 4960 + 190 pound driver) will add less than 1% cost in energy, assuming there's no change in wind resistance.

 

[hartmms]

The energy required to move an object is linearly dependent on its mass, so a 50 pound mass added to a 5150 pound mass (the car curb weight is about 4960 + 190 pound driver) will add less than 1% cost in energy, assuming there's no change in wind resistance.

< 1% is not 0. I think I might be letting my day job cloud my judement. Even < 1% differences in energy usage can be a problem in computer chip design.

I sure hope I never get to 190 pounds. Maybe I should finally realize my desire to loose 25 pounds to offset the hitch weight.

 

[SpaceEVDriver]

< 1% is not 0. I think I might be letting my day job cloud my judement. Even < 1% differences in energy usage can be a problem in computer chip design.

I sure hope I never get to 190 pounds. Maybe I should finally realize my desire to loose 25 pounds to offset the hitch weight.

Agreed.

I've been down to 4% on a road trip, so a 1% improvement would not have gone unnoticed.

I could do with losing 25 pounds too (no, I'm not 190). A 0.5% savings over 31,000 miles is a free trip to the Grand Canyon!

 

[dtbaker61]

A slight digression please. What setting do you have to turn off the "cross traffic alert" when backing up with the bikes on the back?

there is a specific setting for cross traffic alert.... the problem is that it resets to default on every frigging time you turn off/on the car. I typically turn off all alerts and assists except 'blind spot alert'.

cross-traffic alert is the most annoying setting for me because it resets itself. I find the alerts more distracting and starling than the situation.

in my humble opinion, all settings should 'stick' when you set them.... only exceptions maybe blind spot alert which doesn't ding at you, and traction control which is probably safer most of the time for most people in most conditions when on.

are you listening @Ford Motor Company ?

 

[dtbaker61]

The energy required to move an object is linearly dependent on its mass, so a 50 pound mass added to a 5150 pound mass (the car curb weight is about 4960 + 190 pound driver) will add less than 1% cost in energy, assuming there's no change in wind resistance.

nope....

adding mass doesn't really matter once you get it moving on flat ground as long as you don't change frontal area or drag coef. It matters when you LIFT mass, but you get it back when you go downhill. i.e. full car with cargo will kill your efficiency going up the pass, but you get most of the extra back going down.... the net will be pretty close to same distance on flat.

since a hitch (without a bike) doesn't add frontal area, and doesn't cause a measurable aero drag.... no difference in Energy use from the hitch alone. With bikes added however, there IS turbulence/drag which I'd estimate as consuming an extra 3-5% at 75-80 mph. you can back that all the way out to the exact figure if you have a CarScanner and drive a section of road at a fixed speed first with bikes, and then without, and note the difference in Power (kW) output.

It will not be easy to see....
lets say rolling resistance on a given stretch of road at 80mph = 20.0 kw without bikes & rack. you slip in the rack, load the bikes, and go drive that same stretch at same speed, same wind and conditions.... I'd guess you'll see power output closer to 21.0 kW



when accellerating... yes, there is a cost per pound added e=mv2
rotating mass is even more important... like on a wheel when you calculate the moment of inertia PLUS the forward linear accel.

 

[dtbaker61]

Agreed.

I've been down to 4% on a road trip, so a 1% improvement would not have gone unnoticed.

I could do with losing 25 pounds too (no, I'm not 190). A 0.5% savings over 31,000 miles is a free trip to the Grand Canyon!

going on a diet will not help avg rolling resistance at steady speed on a trip.... but reducing speed will. (wind resistance SQUARES with velocity)

losing weight might help at the drag strip. I seem to remember 0.1 sec per 100# lost in the 1/4mile given the same power output and same traction conditions. reducing wheel and tire weight matters even more since rotational mass adds moment of inertia when accelerating in addition to acceleration of mass straight ahead. This is why draggies go with the skinny light tires on the front (unless they are AWD and want the extra traction from front).

 

[kindofblue]

there is a specific setting for cross traffic alert.... the problem is that it resets to default on every frigging time you turn off/on the car. I typically turn off all alerts and assists except 'blind spot alert'.

cross-traffic alert is the most annoying setting for me because it resets itself. I find the alerts more distracting and starling than the situation.

in my humble opinion, all settings should 'stick' when you set them.... only exceptions maybe blind spot alert which doesn't ding at you, and traction control which is probably safer most of the time for most people in most conditions when on.

are you listening @Ford Motor Company ?

Thanks!

 

[SpaceEVDriver]

nope....

adding mass doesn't really matter once you get it moving on flat ground as long as you don't change frontal area or drag coef. It matters when you LIFT mass, but you get it back when you go downhill. i.e. full car with cargo will kill your efficiency going up the pass, but you get most of the extra back going down.... the net will be pretty close to same distance on flat.

This is true for a frictionless surface with only a single motion vector, but mass still matters on real-world vehicles. All accelerations (including turning, bumpy roads, passing, changing lanes, etc) involve mass and they're all linearly dependent on mass.

 

[dtbaker61]

This is true for a frictionless surface with only a single motion vector, but mass still matters on real-world vehicles. All accelerations (including turning, bumpy roads, passing, changing lanes, etc) involve mass and they're all linearly dependent on mass.

yes mass does matter for all accelerations.... that's why I said 'pretty much'. for instance on a bumpy road, acceleration up and down would take energy, but only change if the 'sprung weight' of wheels and suspension changed.

energy required to move the car at a steady state speed on the highway won't change much with added mass unless tires flex more and heat up.... hardly measurable

energy required to go up a mountain would increase as a % of added weight as potential energy required to lift the added mass , but 'almost' recover the potential energy coming down.

energy required to accelerate from a stop (or in any direction) would increase as a function of added mass to total mass until steady state speed is achieved. adding or subtracting 50#/4800# is going to be hard to measure on a trip when MOST of the time is relatively steady state velocity.

steady state velocity will have MUCH more effect than +/- cargo load on a road trip since drag on the (unchanged) frontal area increases as a square of velocity.

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