drag coefficient reduction to further increase range?

[cashcow]

Hello,

What do you guys think on tying to reduce further the rav4 ev's CD of 3.1 or 3.0 to increase range? Some modifications I could think of:

Rear Wheel Skirts
Front Wheel Covers/Moon Discs/Wheel Skirts (If that is what they are called on the front)
Full Boat Tail
Side Mirror or Mirrors? Delete
Front Grill Block of some sort? (Partial or fully /w electric adjustable cover)
Lowering the RAV4 EV (Suspension swap)
Weight reduction
Dual Motors (Ok not an aeromod but if they can be more efficient than 1 why not?)
Taping smooth all panel crevices?
Door Handle Delete or cover?
hood to windshield angle adjustment?

Any other suggestions?

 

[TonyWilliams]

Hello,

What do you guys think on tying to reduce further the rav4 ev's CD of 3.1 or 3.0 to increase range? Some modifications I could think of:

Rear Wheel Skirts
Front Wheel Covers/Moon Discs/Wheel Skirts (If that is what they are called on the front)
Full Boat Tail
Side Mirror or Mirrors? Delete
Front Grill Block of some sort? (Partial or fully /w electric adjustable cover)
Lowering the RAV4 EV (Suspension swap)
Weight reduction
Dual Motors (Ok not an aeromod but if they can be more efficient than 1 why not?)
Taping smooth all panel crevices?
Door Handle Delete or cover?
hood to windshield angle adjustment?

Any other suggestions?

This seems like lipstick on a pig ;-)

Lowering the car is really cheap and easy, and wheel pants and rear boat tail will probably have the most effect.

For weight reduction, how much money do you want to spend? ... and how safe do you want to be? Magnesium wheels, replacing glass with Lexan, removing roll up windows mechanisms, removing seats, removing front and rear bumpers (the real metal safety part, not the cheap plastic cover), removing the large (and heavy) crash bar under the motor, removing air bags, etc, all have a price of lost functionality and lost safety.

I think if you want a really aerodynamic car, I'd start with something else.

 

[TeCKis300]

Lower it and put some narrow/skinny wheels and tires on it.

The stock wheels and tires are the same size as the ICE RAVs. Would be pretty easier to go narrower.

 

[cashcow]

Hey all,

Tony you are on point as always. I went to ecomodder and asked around. They agree that because the car is so aerodynamic already I'd need big aero mods to see any noticeable difference in millage gains. That meant Full Boat Tail and also four pants, or skirts, on the wheels! The biggest benefit though was definitely the boat tail though and that it had to be full 'size'.

I think weight reduction would be the last thing to do because I always carry my camping gear with me and I camp pretty often. I threw it in there just because I figured it would get mentioned. Definitely it ever were to happen I'd pretty much would have to just strip the rav4 ev down to 'naked' level.

Any suggestions on suspension swap options? I know the guys that did the pikes peak run lowered their rav4 ev quite nicely. I did look around before on the gas rav4 forum for suggestions on suspension options and there are some threads about people lowering their rav4s. Not that many and some had mixed results and one guy having to cut the suspension coils? I believe. Plus I am not sure if the extra weight of the rav4 ev would mess with the new lower suspension

I recall seeing the mitsubishi MIEV and the tires were the size of a bicycle! I wasn't sure how that thing would handle on turns. I like taking turns.... How safe it is to go narrow tires? Risks? The guys at ecomodder did mention narrower tires too. Those tires could help with the skirts since the tires on the rav4 ev right now stick out the wells so the skirts would have to be more oval rather than flat.

Any guesses on what kind of increase in range I could see with a full boat tail, 4 skirts, and low suspenion? Stock range in the rav4 ev is about 103 mix 109 in extended mode and 93 in standard? Is this correct? I saw the 200 mile club and it seems with some hyper miling techniques and really favorable winds you can go up to 150s. I think there was only 1 person that did 200 miles?

Went to tirerack and punched in the rav4 ev. There apparently are some low rolling resistance tires. Not sure if they are any narrower but being lower resistance would there be any benefit at all?

GOODYEAR
INTEGRITYPassenger All-Season

Size: 225/65R17 101S
Sidewall Style: Blackwall
Low Rolling Resistance: Low Rolling Resistance Technology
UTQG: 460 A B
Qty:
Per Tire:
$126.45

 

[TonyWilliams]

Any guesses on what kind of increase in range I could see with a full boat tail, 4 skirts, and low suspenion? Stock range in the rav4 ev is about 103 mix 109 in extended mode and 93 in standard? Is this correct? I saw the 200 mile club and it seems with some hyper miling techniques and really favorable winds you can go up to 150s. I think there was only 1 person that did 200 miles?

This is what you have to beat:

 

[cashcow]

Hey Tony,

I feel like I'm already at a disadvantage here carrying around all of my gear and other things inside . I reset that energy usage meter history thing on 10/22/16 or so because it kept saying that I get 2.2 mile/kwh. I thought it was just the previous owner's driving but now that all the past history is gone I am still seeing 2.2 miles/kwh. That is very low if you ask me . I'm starting to wonder just how much weight my rav4 ev is carrying plus I always drive around one of my family members with me. I was expecting more around the 3.X something range. I love using neutral and always drive around slow meaning 5mph under speed limit and fwy 55 or 54. Should I even be paying attention to the energy monitor/trip information?

Also, I got a question that someone asked me at ecomodder:

How much heat does the engine or it's capacitors produce? Block the grille.

That is something I wouldn't know how to answer as I don't know. I know the rav has a radiator and it looked big from what I saw in a collisioned rav4 ev. Just wonder how much cooling it really needs?

Oh yeah, wish I could find a road that stretches on and on for ever at 45mph on a perfectly level surface my rav4 ev already has some degradation though being a 2014 model . maybe if i get lucky and toyota replaces my pack

 

[TonyWilliams]

I doubt that there is anything wrong with your car. If you are getting lower consumption numbers (increased consumptionrate) based on steady speed, you might be:

1) Not driving at a steady speed (you must use cruise control)
2) Driving up hill
3) Driving into a head wind
4) Have different tires, or underinflated tires
5) Driving with a cold battery
6) Driving on wet / snow / contaminated roads
7) Left a dog strapped on the roof (see the original movie Vacation)

If you are just driving around "using neutral" (not at a steady speed) or whatever you're doing, I guess you know how much energy that takes now!

Around town driving for me is definitely in the 2.x range. When stretching range, I'm looking for high 3.x at 55-60mph.

Range is simple consumption rate multiplied by stored usable energy.


You can test the battery capacity with the procedure that I outlined elsewhere.

 

[cashcow]

1) Not driving at a steady speed (you must use cruise control)
Okay, maybe this is it. I should use Cruise more often, but the thing crashes if I engage it too fast and it can get annoying fast in the city. I do mostly city driving and sometimes getting cruise control just right before a light can be a hassle ( I don't like speeding up fast. I like doing it slow). I'm going to have to see just how much my speed fluctuates with my foot too .

BTW, wouldn't be better if CC was more focused on energy rather than speed? WIth hills up and downs you aren't really doing any steady energy draw as the machine tries to keep speed steady. Wouldn't be nicer if you could set it to consume X amount of killowatts for a steady draw?

2) Driving up hill
Part of my city driving do involve hills, but when I come back down I mainly use N and D or B if I get caught off by a red light. Really try not to use the physical brakes here or accelerate.

3) Driving into a head wind

This one could be another factor I haven't really taught about it much. Not that windy around here but the weather now does involve winds. Maybe they are stronger than I thought!

4) Have different tires, or underinflated tires

Will have to check if these tires are the same. Never thought about that. I had the tires at a steady 40 psi the past months and just now it went down to 35 psi. I checked monthly. Bumped them last night to 44 psi.

5) Driving with a cold battery

I sleep in my rav4 ev on ( i camp out in it) over night so I have a feeling the battery is plenty warm to start the day. I mean I do shut the car off sometimes, but maybe for an hour or so. Does the bat get cold that fast? How long does it take to warm it up? I charge at public places so lv2 charging is included on a daily basis for me. Though the thermal management system is not on while charging. you are so evil toyota why?

6) Driving on wet / snow / contaminated roads

No snow and only rained I think once last month. Not sure on contaminated.

7) Left a dog strapped on the roof (see the original movie Vacation)

Thank god I don't have a roof rack! or a dog for that matter

Not sure what to believe anymore. The energy monitor page/history keeps saying 2.2kwh mile average but today I did a drive up hill in a hurry (I was late.. ) and it was about a 10 mile drive. When I shut the vehicle off I saw the reading on the instrument cluster (Not the monitor stuff) and it said 2.8 miles/kwh average. So I don't know what to believe I had to use sport mode too for part of the drive. I thought it be much lower like 1.1 but got 2.8. was surprised. I still don't get why it says 2.2 miles.kwh but I will have to keep an eye on the numbers in the instrument cluster because these say different things.

 

[cashcow]

All right. Here is what I got so far. I did 5 trips of different length and it included going up and down hills. The energy info trip memory thing keeps saying an average of 2.2 mi/kwh, but I now started to record the numbers you get when you turn off the rav4 ev:

First Trip: Mixed Hills trip.
2.6 mile trip
01:16 Trip Time. I was parked in a parking lot for a while before taking off...
3.6 MI/KWh
68/100 <- Eco Coach points

Second Trip: DOWN Hill Trip.
3.1 Mile Trip
00:17 Trip Time
7.0 Mi/KWH
78/100 Eco Coach Points

Third Trip: GOING BACK UP THE HILL
4.1 Mile trip
00:22 Trip Time
2.6 mi/kwh
81/100 Eco Coach Points

Fourth Trip: Short one with a tiny hill then flat.
1.5 Mile Trip
00:11 Trip Time
3.4 Mi/KWH
72/100 Eco Coach Points

Fifth Trip: Bit of Flats and some bit of down hill-ish.
1.8 Mile Trip
00:09
3.6 Mi/KWH
78/100 Eco Coach Points.

So looking at these numbers it doesn't seem like I am close to 2.2 mi/kwh average that I keep seeing on the screen. I wonder if the whole sleeping in the rav for 8hrs + while its on is throwing off the energy monitor?

 

[TonyWilliams]

You can't make mileage comparisons on short little jaunts. Sorry, but it's an exercise in frustration.

Also, how in the world would you expect to get 65mph STEADY SPEED in ANY city environment? When the range chart has 65mph, it means 65mph from START to FINISH (like over a 40-140 miles).

For around town driving, it "is what it is".

To get 3.4 miles per kWh at 65mph, I proceed onto the freeway (only 2 miles away) and my consumption could be any value at that point, depending on which way I went, how cold it was, etc. I wouldn't even waste my time looking at it.

But, at about the 20-40 mile mark into the trip, I want to see close to 3.4, or at least some lower number that is steadily ticking up every handful of miles... 2.8.... 2.9.... 3.0, etc. I may need to start slowing down to 60mph (if 3.4 is the number I need to make it to the next stop).

If 60mph doesn't do it, then I slow to 55mph and starting making a Plan B for a charging stop.

You are really looking for trends. A lower value consumption increasing upward at 55mph or 60mph is a good sign. Stay at the lower speed until 3.4 is reached, then maybe speed up to 65mph. If you are at 55mph for 40 or 50 miles and the consumption is decreasing, it's time for drastic action. Is the cabin heater on? Low tire pressure? Headwind? Plan B required to charge?

If I really, really need a consumption value, I start at a speed that is 5-10mph below the target. For a needed 3.4 rate, I might start at 55mph until a see a solid 3.4 for 10 miles or more, then bump up to 60mph, and maybe 65mph by the 20-40 mile mark.

If you hit update on the consumption meter, whatever value is in there divided by into the miles driven is the kWh burned, for example:

142 / 3.4 = 41.8kWh

Conversely, starting out with a fully charged brand new battery at 70F or warmer driving will go:

41.8kWh * X.X miles per kWh = autonomous range

I can assure you that your battery is not new, however. Estimate 10% degradation until you do a proper test.

 

[TonyWilliams]

So looking at these numbers it doesn't seem like I am close to 2.2 mi/kwh average that I keep seeing on the screen. I wonder if the whole sleeping in the rav for 8hrs + while its on is throwing off the energy monitor?

Did you hit "UPDATE" on the consumption page?

 

[cashcow]

Hi TOny,


That is pure genius! I never thought about watching the Mi/KWH # and adjusting cruise control speed to be sure you can reach your destination! I'm going to have to safe keep your post and read it a couple of times so it sinks in well.

I hit the update button then some weeks later I hit the clear button. I actually just found out what the problem is:

Your Mi/KWH Number decreases when the rav4 ev is sitting still not moving. Even in P! I hit the reset button again and watched the average Mi/kwh number fluctuate. It was actually in the 3.5 mi/kwh during most of my trips. Then.... I went to the bank and left the rav4 ev on for my mother so she could use the electronics and a/c. Then I came back and the number had dropped to 3.3 mi/kwh.

So when I noticed that I decided to do some paper work on the rav4 ev while watching the number and sure enough it gradually dropped to around 2.8 mi/lkwh.

That means that every time I camp out in my rav4 ev for 8 + hrs over night my average mi/kwh number is constaly decreasing.

That is not cool.

Need to leave your rav4 ev on for your family? Mi/KWH number drops.
Need to step out of the rav4 ev just for a couple of minutes to buy something? Mi/KWH number drops.
Need to camp out in your rav4 ev because it is just the cool thing to do with an EV? Mi/KWH number drops!

Not a problem if you don't step out of the rav4 ev and leave it on for whatever reason.

Not really an issue unless you always get caught up in heavy traffic or something

I feel that this is unfair. I don't get why my average mi/kwh # should drop if I leave my rav4 ev in P standing still for my family or whatever else. Toyota is so frustrating. Of course you can just reset the value every time or watch the values you get when turning off the rav4 ev (On the speed meter screen bit I believe this one is current for the current trip only?).

Heck I guess you can just turn it off everytime you are at a stand still in heavy traffic like an ice engine (So it the ice doesn't consume gas just standing still) just this time you are doing this so the motor or the whole system doesn't drain electricity thus causing your average mi/kwh to decrease. I feel ripped off!

 

[miimura]

I would be much more outraged if the car did not account for all the energy used. Let that sink in for a minute.

 

[TonyWilliams]

I would be much more outraged if the car did not account for all the energy used. Let that sink in for a minute.

Yes, what I was thinking. The consumption data is just simple math. I absolutely DO NOT recommend turning the car off and on at every stop sign. That is a lot of needless wear and tear on the contactors.

 

[TonyWilliams]

That is pure genius! I never thought about watching the Mi/KWH # and adjusting cruise control speed to be sure you can reach your destination! I'm going to have to safe keep your post and read it a couple of times so it sinks in well.

Don't "chase the needles" as we say in aviation. You are making educated guesses as to what your consumption rate will be, and making methodical SMALL and infrequent changes to speed.

I use 5mph increments, but I've done 2-3mph corrections, too.

 

[cashcow]

Big Thanks Tony

I switched to using the incorporated reading in the speed panel (Where the odometer is) for the live energy draws during speed. This feels better than having to look at the big screen on the side and I have been adjusting my speed to match current best economy or aiming for better. Things are making more sense now.

When I spoke about all th energy draws being accounted into the driving efficiency it made me think for a second of the equivalent of a 'gas pump kill switch' that convention ICE hyper milers use at a stop sign. Basically not wanting the ice engine idle and drawing gas so thinking the same on electric car not drawing energy while in too heavy of traffic or when stopped at a long light.

Anyway but you are right the contractors are not like a gas pump and would likely be more expensive to change. SO! I guess this is just something we will have to live with. I would have at least liked for toyota to give you a separate reading. One that accounts for the millage and one that accounts for everything but that is just me. I'm happy with my rav4 ev just not so happy with toyota sometimes

 

[TonyWilliams]

The overhead on a warm day is very small. Like a few amps, while the car can pull 530 amps in Sport mode acceleration.

On a cold day with a cold battery, obviously it can pull up to 6kW with the battery heater going.