Any real limit to running REX?

[alohart]

In reality, whether BEV or REx suits you better depends on your circumstances and, to an extent, your location. I've owned my 120Ah BEV for more than 18 months now, and I've never had a situation where I would have needed to use the REx engine - so for my circumstances it would simply be a waste - weight carried around everywhere without any useful purpose.

Exactly our situation. For over a decade, we have used our i3's for what BMW designed them, to be a megacity vehicle. We've never road-tripped them, so a REx would have been a waste. I am very happy to be done with ICE maintenance and problems.

 

[louisgrenier]

You can go to a small airport and buy 100ll (low lead) they don't allow corn lcker in aviation fuel yet. Good stuff for small engines that sit a lot like lawnmowers in the great white North

Are you sure the Rex does not have a catalyser? I use 100LL on everything i can that does not have a catalyser. Like my generator, old cars, even mixed in chainsaw, but i never tried in the Rex because i was thinking it have a catalyser. I would surely use 100LL if it does not have a catalyser

 

[louisgrenier]

You can go to a

 

[mojo]

Are you sure the Rex does not have a catalyser?

The REx engine does have a catalytic converter. "An air-gap-insulated exhaust manifold enables the catalytic converter near the engine to heat up quickly through minimal heat losses."

 

[Whereitis]

I find the Rex to be the only thing that prevents extreme anxiety every time I go more than 10 or 15 miles in a day in the i3. My 14 Rex typically shows about 60 e-miles in the summer but only about 40 in the winter, and with the heat on and if I drive the slightest bit aggressively (which I tend to do a lot), that winter e-range quickly drops to 25 or less. Yes it's a 10 year old car and the HV battery has obviously degraded some, but even on short trips, I often find the e-range down to single digits by the time I get home. With the Rex, I just don't care. So what if I need to put half a gallon in it the next day? Without the Rex, I would never be able to stand the stress of wondering when I'll be stranded with zero charge. Just my own experience.

 

[unL33T]

Because of the way that the REx is decoupled from the wheels, it seems unlikely that its total use could be expressed in miles.

I was playing around with an OBD reader the other day and there was indeed a reading for mileage on the REx. Mine said just over 11000 km. The car has 117000 km on it. There was also a running hours reading for the REx but I can't remember what that one said.

To answer the original question, most I have done is 300 km each way. I had to fill up ~4 times each direction and hold the brake while I got out to fill while the car was running. The car gets very poor fuel economy on the REx. 9-10L/100km. I keep 3x5L jerry cans in the frunk so occasionally I just lock the brake with a modified clamp/expander and dump in a whole can.

 

[I3drivei3]

I was playing around with an OBD reader the other day and there was indeed a reading for mileage on the REx. Mine said just over 11000 km. The car has 117000 km on it. There was also a running hours reading for the REx but I can't remember what that one said.

To answer the original question, most I have done is 300 km each way. I had to fill up ~4 times each direction and hold the brake while I got out to fill while the car was running. The car gets very poor fuel economy on the REx. 9-10L/100km. I keep 3x5L jerry cans in the frunk so occasionally I just lock the brake with a modified clamp/expander and dump in a whole can.

May I ask why you lock the brake while refueling? I am assuming this keeps the car "on" and allows you to see something that you couldn't see with the car off. Thanks.

 

[mojo]

I was playing around with an OBD reader the other day and there was indeed a reading for mileage on the REx. Mine said just over 11000 km. The car has 117000 km on it.

It does make you wonder how they could calculate that - given that the REx engine can be running while the car is stopped? Maybe they have some algorithm that does a calculation based on the total number of revolutions and the total runtime, or number of revolutions and distance traveled while the REx is running? There's zero chance of finding out - not something that BMW is ever likely to document for a mere owner...

 

[unL33T]

May I ask why you lock the brake while refueling? I am assuming this keeps the car "on" and allows you to see something that you couldn't see with the car off. Thanks.

Otherwise the car turns off which resets your Hold State of Charge setting to whatever your current charge is instead of whatever it was when you first enabled it. The car loses about 3% of battery per 10 km at highway speed even with the REx running. It will also keep charging with the REx until you are within 3% of the original SoC if you hold the brake.

 

[Whereitis]

I was playing around with an OBD reader the other day and there was indeed a reading for mileage on the REx. Mine said just over 11000 km. The car has 117000 km on it. There was also a running hours reading for the REx but I can't remember what that one said.

To answer the original question, most I have done is 300 km each way. I had to fill up ~4 times each direction and hold the brake while I got out to fill while the car was running. The car gets very poor fuel economy on the REx. 9-10L/100km. I keep 3x5L jerry cans in the frunk so occasionally I just lock the brake with a modified clamp/expander and dump in a whole can.

It surprises me to see you got such poor Rex fuel economy. I tested this when I first got the car. Starting out with a full 2-gallon tank and the HV battery already reading zero e-miles available, I went for a 120-mile round trip mostly on the highway, with the Rex running the entire time of course. It required two refills during the drive (the one after I was almost home for just over a gallon), and I calculated it was getting about 38mpg purely on Rex. Based on your numbers, you got about 24mpg (10L = 2.64G & 100k = 62m), considerably less. Have you done this again to confirm your mileage?