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Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 5:14 am
by alex29a
I want a REX because it makes sense especially at this early days of EVs
with range, and charging practicality issues.


I was viewing a 2018 i3 Rex at a dealer's Yesterday,
the 94Ah had low charge and the REX was running immediate up powering up.
It sounded so loud like I was literally standing next to Road Works


I was thinkomg Is this how the REX works, or there is a fault in this particlay i3?
Surely , it is the 21st century, someone can come up with a much quiter small
petrol engine. even a miniatre 4-stroke if need be. just to drive an alternator.

I occasionally have to go out to work before 6am or sometimes return home
around that time or earlier
I can see me reversing into my drive and the REX comes on
My neighbours miles around are going to love me


Or is there a way to disable it permanently, and only enabling it for
long journeys

I love the i3, so I am still considering getting one, IF, that rattling sound problem can be resolved


Thanks in advance

Re: Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 12:15 pm
by SuperPoly
Could you give a decibel reading from the NIOSH app (dBA and dBC)? A video might also be useful, but phones typically add some compression.

I have driven two REx models extensively, a 2018, and my 2017. The REx on both was extremely muted, all but inaudible at highway speed. I think there is something wrong with your car.

Re: Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 12:19 pm
by JohnKelly
Your REX should not come on automatically unless you are below about 8% battery, or it needs to run a maintenance cycle from not being used for about two months or so. In any event, they are NOT very noisy when sitting unless it has been run very hard for a while and then you stop.... whereupon it will try to catch up the state of charge it was engaged at. Usually the REX will shut off when you pull up to a stop.

Re: Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 12:21 pm
by JohnKelly
Also, that dealer must not want to sell the car if they don't keep it fully charged while on the lot.... either that, or they are just ignorant about EVs.

Re: Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 2:44 pm
by alex29a
I can't guess the decibel it is very loud. pretty much like what road works sound with the hammer drill going , when you are about 30' away.

this link gives a fair demo
https://www.youtube.com/watch?app=deskt ... e=youtu.be

Re: Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 2:55 pm
by alex29a
During my test drive at this deal, the battery was about 2%. As soon as he powered up the car ( every time) the REX came on with this non-stop rattling.

I might still buy the car IF
1) the range extender trigger can be adjusted or reduced to 2% instead of 5-6%
2) when the maintenance cycle starts it off, it can be stopped immediately, with no further run
or
3) Disable the REX Completely, and only re-enable it whenever I want . very occasionally on long journeys

superpoly - I have not bought the car yet becase of the noise.
i didnt even want to test drive it

is it not supposed to be this loud?
or will it mute after a while ? thanks

Re: Very loud REX - any solutions?

Posted: Mon Nov 22, 2021 6:50 pm
by SuperPoly
alex29a wrote:
Mon Nov 22, 2021 2:55 pm
During my test drive at this deal, the battery was about 2%. As soon as he powered up the car ( every time) the REX came on with this non-stop rattling.

I might still buy the car IF
1) the range extender trigger can be adjusted or reduced to 2% instead of 5-6%
2) when the maintenance cycle starts it off, it can be stopped immediately, with no further run
or
3) Disable the REX Completely, and only re-enable it whenever I want . very occasionally on long journeys

superpoly - I have not bought the car yet becase of the noise.
i didnt even want to test drive it

is it not supposed to be this loud?
or will it mute after a while ? thanks
The REx kicks on at 7%. It's already a compromise since the car cannot deliver peak power at 7%. In Europe the cars have an option called 'Hold State of Charge" to turn on the REx at 75%. That is much safer. Most US owners "code" their car with an app called Bimmercode to add this option.

I really don't know why the REx is loud with that car, but I am extremely sensitive to noise and the REx cars I have driven were quiet. Quieter than a luxury ICE car.

Can you get a longer test of the car running on gas?

Re: Very loud REX - any solutions?

Posted: Tue Nov 23, 2021 2:29 pm
by MKH
I might still buy the car IF
1) the range extender trigger can be adjusted or reduced to 2% instead of 5-6%
2) when the maintenance cycle starts it off, it can be stopped immediately, with no further run
or
3) Disable the REX Completely, and only re-enable it whenever I want . very occasionally on long journeys

1. It is adjustable a bit with Bimmercode, i think, but not down to 2%

2. When the maintenance cycle starts, it runs for 10 minutes. If you stop the car before the 10 minutes, the REx will restart to complete the maintenance cycle next time you start the car. No way to change this.

4. No way to easily/safely disable the REx.

Sounds like you need to buy the BEV i3 model without the REx to begin with.

Re: Very loud REX - any solutions?

Posted: Wed Nov 24, 2021 3:09 pm
by alex29a
Thanks for all your kind help.
The Rex provides peace of mind. just the wretched noise. If maintenance decides tocome on in a build up area in heavy jam. it will p-off everyone
in the vicinity. and i get dirty looks. if not car jacked.

I will look around and see if there is a way of disconnecting it by pulling out a plug . and re-connect only in dire situations
if possible, that will be perfect

Re: Very loud REX - any solutions?

Posted: Thu Nov 25, 2021 7:43 am
by MKH
First, look around and see if you can test drive another i3 with the REx engine - there is a procedure to be able to start the REx anytime, for emissions testing. When my REx is on, from in the car I can barely hear it - I actually have to look at the dash display to decide if it is running or not. The car you are looking at buying may have a bad/loose/broken muffler on the REx. It's a 650 scooter engine, it shouldn't be very loud running.

https://www.youtube.com/watch?v=Jbr1xJNnAQ4