After being coded, what is the real range at 75 or 80 mph?

I typically drive 80 mph on the highway. I like efficient vehicles, having owned a couple of hybrids and currently a diesel, but I certainly don't hypermile. What I'm wondering is, if the i3 is coded to be able to run the engine at 75% SOC, and if you have infinite fuel (due to carrying a gas jug and stopping for gas every so often), then in normal temperatures how long can the car maintain 75 or 80 mph before the SOC drops to ~10%? I would consider that the car's true real-world range but I have no idea what it is.

I found a YouTube video where someone reported that the 60Ah car could go at least 62 miles on electricity alone at a steady 80 mph, and with the engine running the charge level dropped fairly slowly, but I have no idea really what the rate is.

Alternatively, if anyone happens to know roughly how many kilowatts of power are drawn when going a steady 75 or 80 mph then I can calculate the expected range based on the engine's steady output (which is 22 kW I think...?).

The i3 is a city car, tall stubby and blunt, not designed as a highway cruiser; get yourself a Bolt, or wait a few years for a Tesla 3.

The original i3 REx's generator was a 34-Hp engine driven device. Given 34Hp, that's equivalent to 25.3Kw, but it obviously isn't 100% efficient. I do not know if they've tweaked the REx to produce more on later models.

People have said that you can maintain SOC while driving at around 60mph when running the REx on the level, obviously, less into a headwind or up a grade. ALso note that the REx doesn't always run at maximum output, depending on conditions, and might turn off at times as well. When you shut the car off, whatever SOC you have left is the maximum it will try to attain (unless you're into the less than 6% 'danger' zone) when you start up again.

CGameProgrammer said:

I typically drive 80 mph on the highway. I like efficient vehicles, having owned a couple of hybrids and currently a diesel, but I certainly don't hypermile. What I'm wondering is, if the i3 is coded to be able to run the engine at 75% SOC, and if you have infinite fuel (due to carrying a gas jug and stopping for gas every so often), then in normal temperatures how long can the car maintain 75 or 80 mph before the SOC drops to ~10%? I would consider that the car's true real-world range but I have no idea what it is.

I found a YouTube video where someone reported that the 60Ah car could go at least 62 miles on electricity alone at a steady 80 mph, and with the engine running the charge level dropped fairly slowly, but I have no idea really what the rate is.

Alternatively, if anyone happens to know roughly how many kilowatts of power are drawn when going a steady 75 or 80 mph then I can calculate the expected range based on the engine's steady output (which is 22 kW I think...?).

Click to expand...

My benchmarks:

• 463 mile - Charlotte NC to Huntsville AL: 40 MPG @65 mph, and; 44 MPG @55 mph, ~70F, night.
  ~80 miles - I-565 and I-65 benchmark, ~80F: 40 MPG @65 mph, day, preserves SOC
  ~80 miles - I-565 and I-65 benchmark, ~80F; 37 MPG @70 mph, day, preserves SOC
  ~80 miles - I-565 and I-56 benchmark, ~80F; 32 MPG @75 mph, day, loses 20% SOC per tank
  700 miles - Huntsville AL to Stillwater OK, night; 10 fill-ups, about 16 hours (some long breaks), 65-70 mph
  700 miles - Stillwater OK to Huntsville AL, day with AC; 10 fill-ups, about 13 hours, 65-70 mph

https://priuschat.com/threads/why-the-bmw-i3-rex.165584/page-10#post-2413276

My recommendation is use cruise control at 65-70 mph following a semi-trailer truck. There are trucking companies that run at 65 mph already. Let the dynamic cruise control handle speed and distance control. You'll have enough space to steer around road debris and it will be an easy ride. Expect to stop every 1 hour and 20 minutes.

Bob Wilson

Thanks for your help. I would never use cruise control or closely follow a truck but it sounds like the engine can effectively extend range pretty significantly if run concurrently and refueled often.

If you have the adaptive cruise control, following someone is easy and it will maintain the following distance you select including to stop if they stop. IOW, it's not stressful at all. I did not think I'd like it (it can be used as a 'conventional' CC if you wish), but have found it quite useful...enough so that I'd like it on my next car as well.

At 120 km-h, ( 74 mph ? ) , in winter ( heater ON and Nokian winter tire), quite flat country, i was loosing around 23% per hour.

2017+ models have a upgraded REX engine that can produce more kWh. It seems for the older models, ~70 mph is about the speed the REX can maintain without losing SOC, I'd imagine it must be higher in the 2017+ models.

gururise said:

2017+ models have a upgraded REX engine that can produce more kWh. It seems for the older models, ~70 mph is about the speed the REX can maintain without losing SOC, I'd imagine it must be higher in the 2017+ models.

Click to expand...

This isn't the first time that I have read this claim, but can anyone verify that the maximum power output (kW, not kWh) of the REx generator has been increased?

alohart said:

gururise said:

2017+ models have a upgraded REX engine that can produce more kWh. It seems for the older models, ~70 mph is about the speed the REX can maintain without losing SOC, I'd imagine it must be higher in the 2017+ models.

Click to expand...

This isn't the first time that I have read this claim, but can anyone verify that the maximum power output (kW, not kWh) of the REx generator has been increased?

Click to expand...

I don't have a 2017, so can't verify; however, the combined EPA MPG of the REX engine went from 40mpg in 2016 to 35mpg in 2017. The logical cause for the drop in mpg is an bump up in output of the REX engine.

Hello people
I just woke up this morning wondering how does speed affect energy consumption on electric cars, i know they use more energy when you are going faster and have peak efficiency on significantly slower speeds than cars with IC engines but i was wondering if for example going 50 mph vs going 70 mph has more effect in percentage on range of electric car or on the IC car. Electric cars pay of if you drive a lot, but interesting fact is that electric car is most efficient compared to IC car in town - where you in general do less miles. Im traveling aprox 60 miles every day and i have prety good gas mileage on my IC car since its quite open road (and you could say i have heating included for that price ). If I had an electric car i would be no doubt exeptionally happy about it, but from my current standpoint how much is EV financialy justified? If i had the money i would buy one i3 right now, its really amazing car concept in my opinion and really stands out from other EVs in a good way, but im not really in the point where i can do stuff for the fun. So in my research of speeds effecting EV range vs IC range i bumped into this interesting topic, and i think if you analyze just one long roadtrip and you want do drive your i3 on REx in that case you are making your EV able to do that wich is great, but i dont consider it any more efficient than regular cars with IC engines - for comparison my I4 1.9l e36 series compact does 70mph with not more than 45 mpg. and average of my 60 mi travel is about 46mpg at the moment (i dont drive much more than 50 mph but have some driving in the city so it all blends in that avg. consumption). Also in the winter, with temperatures well below 0 celsius and not driving to an open road, mostly close to my town, letting a car warm up sometimes my mpg even drops to 33.
What do you think, would EV be good solution for my driving habbits? I do 7-10 thousand miles annualy

Drag is the biggest differentiator in energy consumption, and that increases at a V^2 factor...so at say 60 verses 80, 80-squared divided by 60-squared, you get 1.78x more drag at 80 verses at 60mph. That square factor means a small increase in speed increases the drag by quite a bit. It doesn't matter whether it's an electric motor or an ICE...

FWIW, the drag factor on the i3 is actually pretty good in comparison to lots of other cars. Not earth-shattering, but still better than most.

bwilson4web said:

CGameProgrammer said:

I typically drive 80 mph on the highway. I like efficient vehicles, having owned a couple of hybrids and currently a diesel, but I certainly don't hypermile. What I'm wondering is, if the i3 is coded to be able to run the engine at 75% SOC, and if you have infinite fuel (due to carrying a gas jug and stopping for gas every so often), then in normal temperatures how long can the car maintain 75 or 80 mph before the SOC drops to ~10%? I would consider that the car's true real-world range but I have no idea what it is.

I found a YouTube video where someone reported that the 60Ah car could go at least 62 miles on electricity alone at a steady 80 mph, and with the engine running the charge level dropped fairly slowly, but I have no idea really what the rate is.

Alternatively, if anyone happens to know roughly how many kilowatts of power are drawn when going a steady 75 or 80 mph then I can calculate the expected range based on the engine's steady output (which is 22 kW I think...?).

Click to expand...

My benchmarks:

• 463 mile - Charlotte NC to Huntsville AL: 40 MPG @65 mph, and; 44 MPG @55 mph, ~70F, night.
  ~80 miles - I-565 and I-65 benchmark, ~80F: 40 MPG @65 mph, day, preserves SOC
  ~80 miles - I-565 and I-65 benchmark, ~80F; 37 MPG @70 mph, day, preserves SOC
  ~80 miles - I-565 and I-56 benchmark, ~80F; 32 MPG @75 mph, day, loses 20% SOC per tank
  700 miles - Huntsville AL to Stillwater OK, night; 10 fill-ups, about 16 hours (some long breaks), 65-70 mph
  700 miles - Stillwater OK to Huntsville AL, day with AC; 10 fill-ups, about 13 hours, 65-70 mph

https://priuschat.com/threads/why-the-bmw-i3-rex.165584/page-10#post-2413276

My recommendation is use cruise control at 65-70 mph following a semi-trailer truck. There are trucking companies that run at 65 mph already. Let the dynamic cruise control handle speed and distance control. You'll have enough space to steer around road debris and it will be an easy ride. Expect to stop every 1 hour and 20 minutes.

Bob Wilson

Click to expand...

The semi-truck thing is a myth. Although it works in theory, in practice, you'd have to be too close to the truck where the risk isn't worth it. Thank you Myth Busters!

The savings from using the adaptive cruise control, though, is real. IT is much smoother on maintaining your set speed and adjusting to traffic conditions than you'll ever be long-term. You might beat it short-term, but the attention and concentration required to achieve that would be quite stressful.

sipabit said:

. . .
The semi-truck thing is a myth. Although it works in theory, in practice, you'd have to be too close to the truck where the risk isn't worth it. Thank you Myth Busters!

Click to expand...

https://www.autoblog.com/2007/10/28/mythbusters-drafting-10-feet-behind-a-big-rig-will-improve-mile/

• 
  Drafting is a technique, usually used by race cars, to reduce drag by driving closely behind another car. Mythbusters did an episode about Big Rig myths that included a look at the drafting... myth? Does anyone really consider drafting a myth? Anyway, they found drafting increases your miles per gallon up to 39 percent at 10 feet distance away from a big rig. At two feet apart however, they found miles per gallon actually went down.
  
  The first part of debunking the drafting myth took the Mythbusters team to small wind tunnel to prove putting things in front of other things blocks wind. Good thing, too. I know I've always questioned stories of objects blocking the wind and can only be convinced by a wind tunnel experiment. . . .

Having wind tunnel data allows quantifying the effect. Manual drafting is nuts but we have dynamic cruise control which works just fine. There are some lighting conditions that can disable it but these tend to be relatively rare so revert to speed-managed cruise control and driver controlled distance.

Bob Wilson

sipabit said:

The semi-truck thing is a myth. Although it works in theory, in practice, you'd have to be too close to the truck where the risk isn't worth it.

Click to expand...

I try to avoid driving close to the rear of a large truck because of the road debris that they can launch. Paint and windshield damage can be the result. To be close enough for drafting to reduce drag would mean that one would need to be super alert to avoid driving over potholes, debris, etc. that could damage tires or wheels. Way too stressful for me…

A good safety rule to adopt is the 2-second rule...you should be no closer than 2-seconds travel time from the rear of any other vehicle in front of you. This gives you enough time to react, helps avoid road debris, and makes for much more relaxed travel. At 75mph, 2-seconds is 228'. Yes, if you leave that much space on a crowded highway, someone(s) will cut in front of you, but if you're talking safety, that's the magic number - 2-seconds. At 30mph, that becomes 88'. In typical stop and go traffic, you see people barely 20-30' away, which gives them all of a quarter of a second to react...most people don't, and is a common reason for rear-enders. Personally, I get antsy with less than a second trailing time/distance and generally try for 2-seconds when conditions merit it. 100' behind a truck at 75mph is, IMHO, not the smartest thing to do. On a track, a foot or two can work...on a roadway, that would be criminal.

bwilson4web said:

sipabit said:

. . .
The semi-truck thing is a myth. Although it works in theory, in practice, you'd have to be too close to the truck where the risk isn't worth it. Thank you Myth Busters!

Click to expand...

https://www.autoblog.com/2007/10/28/mythbusters-drafting-10-feet-behind-a-big-rig-will-improve-mile/

• 
  Drafting is a technique, usually used by race cars, to reduce drag by driving closely behind another car. Mythbusters did an episode about Big Rig myths that included a look at the drafting... myth? Does anyone really consider drafting a myth? Anyway, they found drafting increases your miles per gallon up to 39 percent at 10 feet distance away from a big rig. At two feet apart however, they found miles per gallon actually went down.
  
  The first part of debunking the drafting myth took the Mythbusters team to small wind tunnel to prove putting things in front of other things blocks wind. Good thing, too. I know I've always questioned stories of objects blocking the wind and can only be convinced by a wind tunnel experiment. . . .

Having wind tunnel data allows quantifying the effect. Manual drafting is nuts but we have dynamic cruise control which works just fine. There are some lighting conditions that can disable it but these tend to be relatively rare so revert to speed-managed cruise control and driver controlled distance.

Bob Wilson

Click to expand...

Drafting is effective in theory, but not in actual application. The point I was trying to make is that you don't really want to be that close to a big rig. Your chart clearly shows you need to be pretty close to have any sort of effect. The Myth Buster's episode concluded that it works but for it to work well enough to be worth it, you have to be within a very dangerous distance from the big rig.

We know drafting works in applications with cycling for instance where conditions are such that drafting is an expected routine. Riders even take turns drafting. You don't want to routinely hide behind a big rig though. Same effect, but very different conditions. Each to his own, but I don't want to be that close to a big rig just to save some gas mileage. Risk isn't worth it. Not to mention, the view sucks. The ride should be enjoyable. Keep it safe and have fun doing it. We already drive EV's. We don't really need to be saving bits here and there and exposing ourselves to exponential risk by being so close to a giant truck.

Dynamic cruise control is not drafting. Have you used dynamic cruise control?

Bob Wilson

There is a distinct difference between drafting and dynamic cruise control:

• Drafting is manually following another vehicle trying to stay in the burble and very tiring.
• Dynamic cruise control is an automated system that paces behind another vehicle.

I've done both and dynamic cruise control is distinctly different and safe.

Have you tried dynamic cruise control?

Bob Wilson