GoldiE46
Posts: 17
Joined: Wed Dec 02, 2020 9:43 am
Location: District of Columbia

Re: Ran the REX for the first time....

Thu Dec 03, 2020 10:23 am

I guess you are lucky:) I've owned two and both are/were loud. Not that I am complaining, it's generator and it should be expected.

jadnashuanh
Posts: 5149
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Ran the REX for the first time....

Thu Dec 03, 2020 11:04 am

The REx rpm, and thus the general sound level, will vary considerably depending on the current SOC on the battery, and the amount of energy it thinks it needs to supply. It can go from barely at idle to its maximum speed, and the sound level will change. The vehicle also adjusts the REx some due to the speed of the vehicle in accordance with the other mentioned parameters. It's trying to keep the sound level down, so normally, will slow down as you do unless the battery level is way below where it is trying to maintain.

Probably the worst case would be when the level was below 6% SOC, and you were climbing a long grade at speed with things like the seat heaters, cabin heating, rear window defroster all going at full blast (some of those might get turned down or off by the computer in this case).
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

Pahaska
Posts: 63
Joined: Thu Jul 30, 2020 11:49 am

Re: Ran the REX for the first time....

Tue Dec 22, 2020 5:37 pm

After living with a big exclamation point on the display and having to constantly reset a message saying the REx is due for a maintenance cycle, the REx finally ran on its own. It so happened that I had a string of days where the most I drove was to the mail pavilion and back, all of a mile and a half, and used almost no battery. This morning I had to do a 20-mile round-trip supermarket run. The REx finally fired up right on arrival at the market. I shut down rather than keep it noisily running while waiting among other cars for social-distanced delivery in the rear hatch.

The REx fired again when I restarted and ran most of the way home. The only time I heard it was when I briefly lowered a window to wave at a friend. I arrived home with 70+% battery.

Steve999
Posts: 12
Joined: Wed Nov 07, 2018 7:03 pm
Location: CA

Re: Ran the REX for the first time....

Tue Dec 22, 2020 10:44 pm

Has anyone tossed a thick blanket in the trunk to see if it dampens the REX noise a little? There doesn't seem like much sound insulation from the metal "engine hatch" to the cabin area, but I'm not sure if that's the only source. Maybe a good experiment to try (I think I'll have to dig around my closet...).
2015 i3 REX Gigaworld, Tech Package

User avatar
MKH
Gold Member
Posts: 706
Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: Ran the REX for the first time....

Wed Dec 23, 2020 5:26 am

There doesn't seem like much sound insulation from the metal "engine hatch" to the cabin area,
The 'floor' of the cargo area that sits over the metal engine/motor cover has fairly thick sound-deadening material on the underside. I can barely hear the REx at all when it is running. Check the metal cover hold-down bolts. The cover is fastened down with bolts going through a Neoprene Nut. If they are over-tightened when the cover is replaced after an oil change, the Neoprene Nut will split, and the bolt will be just sitting held in place by the top half of the split neoprene nut, but not holding down the cover ( (ask me how I know), or the bolt will be missing entirely, either of which could make the cover loose and vibrate when the REx is on, if enough of those fasteners were compromised or missing.
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch 427 wheels, EVoInnovate EVSE

Pahaska
Posts: 63
Joined: Thu Jul 30, 2020 11:49 am

Re: Ran the REX for the first time....

Wed Dec 23, 2020 7:49 am

I have never heard the REx running with windows up except once between buildings where the sound was reflected.

Deutsch100
Posts: 135
Joined: Mon Sep 30, 2019 2:28 pm

Re: Ran the REX for the first time....

Wed Dec 23, 2020 9:46 am

I used my REX a couple of days ago, and when it is running on "low speed", I can barely hear it (if at all). When REX kicks into "high", then I can hear it, but it sounds like a scooter or small motorcycle outside or next to me, but it is still not loud or obnoxious inside the cabin. If I roll the windows down, you can of course hear more, but still not bad.

Oddly, my 2019 REX was a wee louder than my 2020 REX....but I think I had a "bad" 2019 in terms of sound insulations. In my 2019 the front doors rattled and the dash too and many times the moonroof covers. My 2020 actually feels like a BMW :)
2020 i3S Rex; Capparis White

agzand
Posts: 2
Joined: Tue Dec 22, 2020 3:00 pm

Re: Ran the REX for the first time....

Mon Dec 28, 2020 9:48 am

The REX is significantly down tuned from its scooter application. In the BMW 650 scooter it makes 60 hp at 7750 rpm. In the i3 REX it makes 38 hp at 5000 rpm. So in i3 even at max rpm it is in a relatively relaxed state of operation.

jakecturner
Posts: 6
Joined: Wed Nov 01, 2017 5:43 am

Re: Ran the REX for the first time....

Fri Jan 08, 2021 12:37 pm

I can barely hear mine. With the radio off, I can only really hear it when doing 80mph on the toll way. Even then, it is barely audible over the wind noise.

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