What is hwy mpg of REX?

[Pauli3]

If you start at 5% battery and drove 55mph on flat ground for extended period what would your mpg be?

 

[Lecram]

I did 120 kms at 110 km/h with the cruise control with 9% left in the battery.
And also 115 kms at 105 km/h cc from 90% with 12 kms left.
The app was telling me that I achieved 99% efficiency and zero regenerating.

In urban you will achieve better range if you use regen.

 

[Surge]

I did 120 kms at 110 km/h with the cruise control with 9% left in the battery.
And also 115 kms at 105 km/h cc from 90% with 12 kms left.
The app was telling me that I achieved 99% efficiency and zero regenerating.

In urban you will achieve better range if you use regen.

Sorry, can you clarify your observations?

You drove 120km at 110kph on REx alone? Ie, the battery level was 9% when you started and when you finished? That would be very impressive range for the REx at that speed.

And any observations at 120kph?

What temperatures have you driven? I'm curious what the REx only range would be at 120kph in -10C weather.

 

[Lecram]

It was an i3 Rex and the range was witn the use of the battery only. I didnt use the Rex there. I wil test it when i get mine on 16 May

Temp was about 16C

 

[MarkN]

The BMW i3 REx now shows up on the U.S. fueleconomy.gov web site. I was hoping the site would break out the city and highway MPGe since those aren't available on the Monroney sticker, but it doesn't that I see. But you can personalize the site's fuel cost calculation and use that to show city or highway MPGe by setting your driving to 100% city or 100% highway respectively. That gives:

City: 127 MPGe, 41 MPG with REx, 78 miles electric range, 160 miles total range
Highway: 107 MPGe, 37 MPG with REx, 66 miles electric range, 140 miles total range

For comparison, the i3 BEV has:

City: 137 MPGe, 89 miles range
Highway: 111 MPGe, 72 miles range

 

[Surge]

Thanks. Is the highway range done at 55mph?

 

[MarkN]

Thanks. Is the highway range done at 55mph?

You can see the test cycle speed graphs at http://www.fueleconomy.gov/feg/fe_test_schedules.shtml

 

[Ardie]

I haven't really bothered to calculate it, but the REx is a 35 hp engine.
Instead of attempting to figure in the drivetrain losses, wind resistance, temperature, existing battery level, climate control settings and phase of the moon for increased tidal pull,
I'll just recall that the REx is similar enough to a 1960's era Volkswagen Beetle (36 hp).
Since the Beetle got 35-36 mpg, I am using that figure for the i3, and I don't think it will be too far off.

As the (US) i3/REx has a 1.9 gallon gas tank, so I it ought to be good for 70-75 miles at the speeds that the Beetle drove (65 mph or so).
But I'm not going to run it totally dry to find out.

 

[uktechie]

As the (US) i3/REx has a 1.9 gallon gas tank, so I it ought to be good for 70-75 miles at the speeds that the Beetle drove (65 mph or so).
But I'm not going to run it totally dry to find out.

You can run it dry no problem.

 

[Surge]

So this is not quite the case. I have been driving a REx for two days and found that you cannot exceed 60 mph consistently with the REx running (and no usable battery charge).
Plus, any incline in the road and you will be below that speed. My car slowed to about 50mph on a very slight incline.

I was alone in the car with no luggage. The outside temp was a cool 16C.

This is by far the weakest point in an otherwise amazing car. It renders the REx a very challenging long distance driver. The REx is really only good to bail you out if you run out of battery.

Allowing the REx to be turned on or off manually, as in Europe is basically mandatory if you want to drive the car beyond the battery range on the highway.

 

[jadnashuanh]

My view of the REx, especially as implemented in NA, is that it is an emergency backup. Regular use in many situations will bring compromises. If you're willing to live with them, fine, but to expect full performance all of the time with depleted batteries and running on the REx for primary motive force, it is not going to happen. Keep in mind that the REx is essentially a 38Hp motor/generator, and there is some conversion loss while it makes electricity to drive the vehicle. It's in the same league as a Citroen 2CV or an original VW Bug once you've depleted the batteries. But, if you can keep your batteries above some minimum point (much easier in Euro zone with how they've implemented the REx), you won't notice anything except maybe a little more noise.