aardvark7
Posts: 13
Joined: Sat Jun 13, 2015 7:10 am

Maximum driving efficiency

Sat Jun 13, 2015 7:36 am

I'm curious and yet to find an answer relating to whether the settings available actually make a difference to efficiency, or if they are merely aids to help those who are 'heavy footed', so I hope someone might be able to help here. The exact answer will likely depend upon how Kia have implemented the system, but I have a nagging doubt as to the worth of using different settings.

Clearly, there are four options: D with Eco off, D with Eco on, B with Eco off, and B with Eco on, but what is the end effect on range and why?

Of course, there will be a 'most efficient' way to travel, that would take into account wind resistance, rolling resistance, and co-efficient of friction, but it would not be possible to use in the real world. For instance, I believe these 'cars' that try to travel the furthest on one gallon of petrol will accelerate at an optimum for the motor to a certain velocity and then coast until slowed to another speed, and then repeat the process. The record currently is 12,665 mpg...! No-one can drive like this in normal day-to-day life.

So, my question is, if you drive very smoothly with gentle acceleration and good anticipation, is it possible to achieve the same range in 'D with Eco off' as in 'B with Eco on'?

If so, what is the reason for even having B and Eco modes? For the life of me I can't work it out, other than to assume it is to help those with poor pedal control achieve the same as those who are very precise. Of course, Kia wouldn't ever admit to that, as they coud hardly sell on the basis of, "Don't worry if you aren't a good smooth driver, just use these settings and let the car sort it out!"

Also, part of this question hinges on just how much friction is involved with use of the brake pedal. For instance, if you have the same deceleration while using the car in B and no brakes as with the car in D and some brakes, is the regeneration exactly the same, or is some energy lost to friction braking?

Opinions and thoughts are welcome (but please no lectures or explanations about conservation of energy, as I'm fully conversant with that aspect!)

Birkeland
Posts: 68
Joined: Fri Dec 12, 2014 12:21 pm

Re: Maximum driving efficiency

Sat Jun 13, 2015 11:14 am

The laws of physics state that you use the same amount of energy if you accelerate fast or slowly. Also the same amount of energy is used to maintain speed, whether you have the car in ECO on or off. So in general, you are correct in your assumption that it really doesn't matter when it comes to increasing and maintaing speed. You may be right about the regeneration being more efficient when in ECO on.

All I have found, is that with ECO on, you reduce the power effect of the engine and AC/Heater with 20%. So your acceleration will be abit slower, and your Climate System will work with 20% less power avaliable. So all in all, I really don't see much difference.

I drive in B with ECO on, but my girlfriend who has absolutely no interest in driving efficient, gets even better milage than me. All she does, is putting it in D (with eco default ON) and using alot of brakes as she would do in a petrol car. I try to drive with one pedal, using B to decelerate to get the most recharge, but I am still not getting the milage she does.

The best way I have found to increase the milage, is to set the climate system to 22 degrees Celsius before driving when plugged in. This is the optimum temperature for the battery, so the battery pack will have the best possible temperature to work in. Does seem to work.
Owner of a 2015 KIA Soul Exclusive, Titanium Silver

aardvark7
Posts: 13
Joined: Sat Jun 13, 2015 7:10 am

Re: Maximum driving efficiency

Sat Jun 13, 2015 12:50 pm

Without wanting to be picky, I did say that I understand the pure physics of Newton's laws of motion and conservation of energy.

To go back to my point, your response seems to bear out my suspicion, that there is actually little point to the different settings.
If a driver can produce the same style of driving irrespective of settings and, by simply adhering to the most efficient method achieve the most miles, all the settings are nothing more than marketing junk!

notfred
Posts: 541
Joined: Thu May 07, 2015 2:28 pm

Re: Maximum driving efficiency

Sat Jun 13, 2015 1:21 pm

While you use the same amount of energy purely to accelerate quickly or slowly in a theoretical system, in the real world things will operate more efficiently (less losses e.g. to resistance in the wires) at certain energy flows.

aardvark7
Posts: 13
Joined: Sat Jun 13, 2015 7:10 am

Re: Maximum driving efficiency

Sun Jun 14, 2015 4:03 am

It seems that my desire to not have lessons in physics has not been understood, so I'll try a different tack.
Forget efficiency and driving style for the moment, but merely consider the physical nature of a device and compare it to another item in the Soul.

When you turn on the car and the home page appears, there is an icon saying 'ev' which, if touched, shows the 'ev' screen giving battery percentage, range, etc.
However, there is also a physical button which says 'EV' that, when pushed, leads to the exact same screen.

I think it reasonable to assume that either pressing or touching does absolutely exactly the same thing, albeit a different method.

Now, to go back to the 'D' or 'B' modes. If you were to be travelling in 'B' at a certain speed and completely took your foot off the accelerator you might see two bars of regen and come to a stop (more or less) by a certain point. If, however, you repeated in 'D' mode and took your foot off the accelerator and wanted to stop at the same point, you'd have to press the brake pedal. While doing so you'd see two blocks of regen also.

In summary, you have been doing the same thing initially and achieved the same result, but by two different methods. However, is there a physical difference?

If there is none, in particular relating to regen or friction braking being involved, then I do not understand the need for the two options (much as I don't really understand why there are two 'EV' button options!). I have seen nothing yet that persuades me there is a reason other than it being a driver aid for less capable people (although I do understand why a manufacturer couldn't admit that).

kiastormtrooper
Posts: 32
Joined: Sun Sep 13, 2015 5:21 pm

Re: Maximum driving efficiency

Sun Sep 20, 2015 2:53 am

Before I start, this is just "stuff I noticed," not official in any way.

Here's how I see the different setups:
B-mode -- much more efficient than than manual braking. Although you could emulate B-mode with manual breaking, you'd probably get RSI from all that. ;)
ECO-mode -- mainly prevents you from taking advantage of instant acceleration. It's been said to manage other things, but, on the EV/battery usage screen, I don't see a difference.

I don't think driving around in B and ECO permanently equate to maximum efficiency. Because of the lack of instant torque, I don't use ECO anymore, and it hasn't affected my numbers. I do use B most of the time, unless there's no traffic on the freeway, then I tap-coast in D. According to the dash's numbers, I average around 4.9. That's much better than when I was driving around in B and ECO, which hovered around 4.3.

Jeff42
Posts: 7
Joined: Mon Nov 23, 2015 1:42 pm

Re: Maximum driving efficiency

Mon Nov 23, 2015 1:57 pm

I assume eco mode vs. non-eco mode produce the same result if you don't accelerate faster than eco mode allows. I don't know that for certain, but it seems logical.

The efficiency difference between B and D modes would depend partially on what happens when you press the brake pedal. We can be pretty certain that decelerating by letting up the accelerator pedal never engages the actual brakes. However, when pressing the brake pedal it is not clear to me when it switches from pure regen to regen plus physical braking. If you press hard on the brake pedal the physical brakes will be engaged, but at what level of pedal pressure does it start? Without that knowledge it might be that driving in D and using the brake pedal more often might be less efficient.

kiastormtrooper, I like your idea of driving in D and coasting when possible. Logically this would be more efficient and your results show it is.

kiastormtrooper
Posts: 32
Joined: Sun Sep 13, 2015 5:21 pm

Re: Maximum driving efficiency

Mon Nov 23, 2015 3:08 pm

Jeff42, I have a slight update to that post, as I recently found out the energy consumption meter was giving me "optimistic" numbers because it was auto-resetting as a default. Since I turned off the auto-reset, my mi/kwh numbers have dropped and stayed around 4.3. I also found out that driving permanently in ECO was better than non-ECO, as I was able to squeak out an extra 0.1 mi/kwh over time.

I still shift between D and B, but it's all ECO driving now.
2016 Soul EV base model
Empire Black and White

fanbanlo
Posts: 177
Joined: Mon Apr 06, 2015 9:34 pm

Re: Maximum driving efficiency

Thu Nov 26, 2015 11:06 am

The only reason I switch to Eco mode is when my child is sleeping.

wrickcook
Posts: 148
Joined: Thu Nov 19, 2015 1:30 pm
Location: Seattle, WA

Re: Maximum driving efficiency

Tue Dec 15, 2015 4:32 pm

kiastormtrooper wrote:I still shift between D and B, but it's all ECO driving now.


Do you shift between D and B on the fly? Like if I were to keep it in B, but just before the highway flip it to D while going like 30?
It does not have a transmission, so I don't think it would have any issues. I have just been scared to try.
2016 Kia Soul EV+ - Shadow Black/Inferno Red

Return to “Technical Discussions”