What's the best expected mi/kWh and speed to achieve it?

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cctop

***
Joined
Jan 22, 2016
Messages
118
Location
San Francisco, CA
I know that energy efficiency relies on a lot of factors: terrain, temperature, wind, number of passengers, etc.

Given whatever assumptions you'd like to make for a real-world driving scenario (i.e. flat road, no wind, 72 degrees Farenheit, one adult driver, etc.) what do you think is the maximum expected mi/kWh for a 2016 SE and what MPH do you have to drive to achieve it?

Basically I'm wondering what scenario the VW engineers designed the car for optimal efficiency.

After 7 months with the car I'm averaging about 4.4 mi/kWh driving 18mph in hilly San Francisco.
 
In my own personal experience, with all peripherals and creature comforts shut off, except radio, during the daytime... doing 55 mph, sometimes a bit less, hardly ever touching the brakes, and driving smooth, in "D", paying attention to changes in elevation and coasting down hill when you can... my best has been 6.1 to 6.3 miles per kwh, starting and ending at the same location and elevation for the drive.

It can be done, but you need freeway or interstate on polished concrete, Bridgestone Ecopia 422 Plus tires set at 45 psi, and very, very smooth and steady driving techniques, with traffic that is accomodating on freeways or interstate. I try to get way far back behind a big truck, so cars that come up behind me know I am not the one impeding traffic, I can't drive faster than the truck in front of me, so they go around me.

You might have some luck heading south on 101 or interstate 80 to Sacramento and back, but not in town, in San Francisco. Way, way too many herd mentality drivers there with poor driving habits, driving combative instead of smooth. Just too many people there.
 
It's a tough question to answer because there are so many variables like you mention, but one thing I've learned is that smooth coasting with no turns at low speeds is really your best friend if you're looking at opimal efficiency.

I took a scenic drive down to Monterey this morning across varied terrain, temp was in the mid 60s, little wind or humidity, and I had radio and vents on but no A/C. The best stretch was definitely along the beach, eco+ mode, foot barely pressing on the pedal, coasting at 30 mph. I was seeing 8-10 mi/kWh here and it never dropped below 7. Another very good stretch was going from the beach to the highway, 45 mph, getting 6-7 mi/kWh.

It's really all about getting momentum and keeping it going. Starts/stops will drag your numbers down and going uphill will completely kill them.
 
cctop said:
After 7 months with the car I'm averaging about 4.4 mi/kWh driving 18mph in hilly San Francisco.

I would say you're doing very well, considering not just terrain but also constant stop and go.
 
I've had mine since January (2016 SE) and I average 5.2 mi/kWh. Washington DC is not as hilly as San Fran, which probably makes a difference. And although there's often plenty of stop-and-go rush hour traffic here, I live downtown and work just outside the city, so I usually avoid too much stop and go. I almost never drive above 60 mph, since I don't have a far commute, and most places I go you can't get going that fast even if you wanted to... that is DC for you. Going uphill really is noticeable when it comes to consumption, so you're probably doing quite well for SF.
 
~18 mph for 8 mi/kWh
(steady state on flat, smooth tarmac with no wind at 72f with no A/C or other accessories) :geek:

source
 
Thanks Verkehr! That's great data.

Are the numbers you quoted listed on this sheet? The closest thing I see is on p.2 in the box "Fuel Economy at Steady State Speed, 0% Grade" where it says 126.5 Wh/mi (7.9 mi/kWh) at 20mph.

I plotted the points on a chart:

http://imgur.com/GlvFfpM

It confirms the general knowledge that driving 80mph is about 50% less efficient than 60mph.

But I'm surprised how low the most efficient speed is, and also that efficiency decreases so linearly as speed increases.
 
We've averaged 4.9mi/kwh, 29mph here in the White Mts of NH over 2.5K miles. We always drive in the B mode little traffic :D . 2015 SEL
 
cctop said:
Thanks Verkehr! That's great data.

Are the numbers you quoted listed on this sheet? The closest thing I see is on p.2 in the box "Fuel Economy at Steady State Speed, 0% Grade" where it says 126.5 Wh/mi (7.9 mi/kWh) at 20mph.

I plotted the points on a chart:

http://imgur.com/GlvFfpM

It confirms the general knowledge that driving 80mph is about 50% less efficient than 60mph.

But I'm surprised how low the most efficient speed is, and also that efficiency decreases so linearly as speed increases.
Admittedly I make some assumptions with the most efficient speed, so bear with me as I explain my thought process - some German e-Golf (here at 5m28s), not sure if this is pre-production or otherwise, lists instantaneous consumption in kW. This car shows 0.3 kW load at rest in "ready" mode which helps explain worse efficiency at 10 mph than 20 mph despite guaranteed less aerodynamic drag. Noting similarities to the Nissan L3af motor, there should also be a few percent lower combined motor+inverter efficiency at low speed for the geared up single speed motor (see pg. 12), but as a percentage of 1.37 kW at 10 mph that is dwarfed by an assumed ~300w ancillary load. I plotted the same data as you but with kW and kW offset by 0.3 to factor out ancillary devices, and found consumption still more than doubled between 10 mph and 20 mph. So I believe there's some efficiency left below 20 mph and based on my experience found that to be 18-19 mph.

Note: the intercepts here are arbitrary but the scale helps show the Wh/mi inflection
nNzVHAP.png


PS: check out that government site's BMW i3 data for a really efficient crawler. 8.64 mi/kWh at 10 mph
 
Rsolaregolf said:
We've averaged 4.9mi/kwh, 29mph here in the White Mts of NH over 2.5K miles. We always drive in the B mode little traffic :D . 2015 SEL

Try only shifting into "B" mode when you need to brake, instead of all the time. You'll be surprised at the increase in miles per Kwh. Think of it like taking your TDI and shifting the stick shift from 3rd to 2nd gear to engine brake. With practice, you can judge speed and distance and hardly have to step on the brake pedal at all, using the "B" mode only. You can coast a lot farther in "D" mode and then only use "B" mode when necessary. Much easier on the car. More range per recharge. It takes a little bit of practice, but I find it worth it. Car still feels like a stick when done so.
 
wow great job Verkher!

Explains why I'm tooling along the diamond lane at 80 (And have people tailgating me) but I can visibly see the battery meter move.
 
JoulesThief said:
Rsolaregolf said:
We've averaged 4.9mi/kwh, 29mph here in the White Mts of NH over 2.5K miles. We always drive in the B mode little traffic :D . 2015 SEL

Try only shifting into "B" mode when you need to brake, instead of all the time. You'll be surprised at the increase in miles per Kwh. Think of it like taking your TDI and shifting the stick shift from 3rd to 2nd gear to engine brake. With practice, you can judge speed and distance and hardly have to step on the brake pedal at all, using the "B" mode only. You can coast a lot farther in "D" mode and then only use "B" mode when necessary. Much easier on the car. More range per recharge. It takes a little bit of practice, but I find it worth it. Car still feels like a stick when done so.

OK, I'll try that but we frequently need brakes due to the terrain. Leaving it in B make it a no brainer and we get up to 80 miles/charge even with the hills. So far the 110v charger has worked just fine for our needs but I'm always willing to save energy though our solar tracker produces more power than we consume even with our egolf.
 
Rsolaregolf said:
OK, I'll try that but we frequently need brakes due to the terrain. Leaving it in B make it a no brainer and we get up to 80 miles/charge even with the hills. So far the 110v charger has worked just fine for our needs but I'm always willing to save energy though our solar tracker produces more power than we consume even with our egolf.
I drive in D and then "downshift" with B but the people on vwvortex said that they get better efficiency driving in B mode exclusively.

I've also read that 240v charging is more efficient, so even though our solar also produces more than we use we still use the faster charger.
 
bizzle said:
Rsolaregolf said:
OK, I'll try that but we frequently need brakes due to the terrain. Leaving it in B make it a no brainer and we get up to 80 miles/charge even with the hills. So far the 110v charger has worked just fine for our needs but I'm always willing to save energy though our solar tracker produces more power than we consume even with our egolf.
I drive in D and then "downshift" with B but the people on vwvortex said that they get better efficiency driving in B mode exclusively.

I've also read that 240v charging is more efficient, so even though our solar also produces more than we use we still use the faster charger.
Driving in "B" mode deletes the coast feature. That can't possibly be more efficient than coasting on slight sloped declines, or coasting up to red lights or stop signs or traffic in front of you.
.
 
bizzle said:
Rsolaregolf said:
OK, I'll try that but we frequently need brakes due to the terrain. Leaving it in B make it a no brainer and we get up to 80 miles/charge even with the hills. So far the 110v charger has worked just fine for our needs but I'm always willing to save energy though our solar tracker produces more power than we consume even with our egolf.
I drive in D and then "downshift" with B but the people on vwvortex said that they get better efficiency driving in B mode exclusively.

I've also read that 240v charging is more efficient, so even though our solar also produces more than we use we still use the faster charger.


How many miles per kwh are they getting driving in "B" mode and recharging at the same elevation and location, every single time?
 
Interesting thing I noticed after reading that speed chart.

I decided to take the streets to work. Started with 30mi left on the meter.
Stopped after 7 miles. 20mph average and 6.7 mi /kwh (Probably the best as I normally get 4.0) AND 32mi left on the meter (Yes it went up!)

So going streets actually gets me more mi / kwh for sure. Though I do hate that it takes me 3 times the time to get to work..haha
 
JoulesThief said:
bizzle said:
Rsolaregolf said:
OK, I'll try that but we frequently need brakes due to the terrain. Leaving it in B make it a no brainer and we get up to 80 miles/charge even with the hills. So far the 110v charger has worked just fine for our needs but I'm always willing to save energy though our solar tracker produces more power than we consume even with our egolf.
I drive in D and then "downshift" with B but the people on vwvortex said that they get better efficiency driving in B mode exclusively.

I've also read that 240v charging is more efficient, so even though our solar also produces more than we use we still use the faster charger.
Driving in "B" mode deletes the coast feature. That can't possibly be more efficient than coasting on slight sloped declines, or coasting up to red lights or stop signs or traffic in front of you.
.
Around here there are no such things as slight sloped declines.Your basically going up or down fairly steep grades at least 50+% of the time. I tried using D and then B when needing to brake, so far it's a tossup as far as consumption is concerned. Driving in B for the short hilly trips we mostly do is certainly more convenient especially for my much better half. I'll keep researching this but won't mention it to my wife just yet. BTW we're both used to driving sticks.
 
There's pros and cons to driving with 'B' always active. On the plus side you'll definitely use regenerative braking more often. On the downside you'll sometimes un-intentionally brake and then have to accelerate. In such situations, it's better to coast.
 
Thanks, Verkher, for these efficiency results.

Reading the footnotes, it's interesting that

1.) the fuel economy steady states appear to have been done on the dynamometer, not on the track, and that they don't appear to give an ambient temp for the dynamometer test (the ambient temps for the track tests were 82-97 F, I believe)

2.) the fuel economy tests were done in Normal mode. I wonder how much better they would be in Eco or Eco +....
 
Kieran973 said:
Thanks, Verkher, for these efficiency results.

Reading the footnotes, it's interesting that

1.) the fuel economy steady states appear to have been done on the dynamometer, not on the track, and that they don't appear to give an ambient temp for the dynamometer test (the ambient temps for the track tests were 82-97 F, I believe)

2.) the fuel economy tests were done in Normal mode. I wonder how much better they would be in Eco or Eco +....

Eco and Eco+ modes are gimmicks. You can replicate all of that with a well tuned educated right foot, to do the exact same thing or better. All it takes is common sense and some will power to decide what is most important to you, driving for fun, or driving for maximum miles per kWh. At 60, retired, and not in a hurry, my priorities favor maximum miles per kWh and improving upon my personal best. Retired = no rush, no urgency. I let ambulance drivers do that for me if it's an emergency.
 
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