Very loud REX - any solutions?

[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

 

[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.

 

[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.

 

[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.

 

[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=desktop&v=arD_Cq_f6Fw&feature=youtu.be

 

[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

 

[SuperPoly]

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?

 

[Anonymous]

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.

 

[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

 

[Anonymous]

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

 

[alex29a]

Thank you so much MKH
I still want the rex, but in some dilemma.
Your rex is quiet. yet , which sounds very encouraging
However , the Rex tested was out in the cold, and had 2-3% charge,

A mechanic suggested that because it was cold, and with low charge, the moment
the engine powered up, Auto-choke kicked in and will be loud ? because the engine was on high rev.

Have you tried manually activating hold state of charge 1st thing in a cold winter morning and see if the noise is any worse
or if auto-choke takes over,

hopefully, once the engine warms up quick enough, and the engine quietens ( so I wish LOL) ,
and I will definitely go out and buy one.

 

[Anonymous]

Have you tried manually activating hold state of charge 1st thing in a cold winter morning and see if the noise is any worse
or if auto-choke takes over,

Could be what the mechanic said - just cold - could try letting it run and warm up to see if it is still loud.

Here, don't get much in the way of cold weather - today it is 50 F and sunny.

 

[JohnKelly]

"During my test drive at this deal, the battery was about 2%." This is beyond ridiculous. No person in their right mind would try to sell an EV that was not charged up and ready to go. This is like looking at a gas guzzler for sale with an empty fuel tank and a gallon of gas in a can in the trunk. The REX is designed as a back up, not a charging station. There is electricity available everywhere. The car should be plugged in BEFORE you do anything else. Then... take it for a long test drive. The REX is probably straining to charge the very low battery. Leaving a battery in a low state of charge can damage the battery. If you make an offer on this car, tell them you are worried about it sitting without charge on their lot and ask for documentation on how long it has been there.

 

[alex29a]

next time I view one, i will just use the manual steps above to start the rex up
never mind what temperature.
I believe, if the socharge is over 75% it rex won't work.? if so it can't be tested

 

[MagicCarpet]

Alex, correct the Rex does not run if state of charge is above 75%. It also wont run for mtce. if fuel level is below approx. 1/4. In this case you get bugged by display warnings until you relent and top it up so it can complete a 60 days 10 mins mtce run, then it shuts up for another two months. You can prevent further mtce runs by letting the fuel go below 1/4. code the warnings off if you dont like them. My WOF garage complains about the cobwebs in the tailpipe. I have to refuel once per year, oh the pain....

I have a 2017 96A/h Rex and if it is just doing a mtce cycle it starts so quiet inside the car I have to stop and listen to be sure it is really running. There is a perceptible noise when the battery is low or you need full power for sustained speed or hillclimbing. I agree that having it run around town the noise is similar to a scooter idling, from the outside. I've observed pedestrians as I pass by and nobody notices. The one in the showroom will run hard because they let the main battery get down too low.

When my car was delivered off the boat it did this due to low charge, I drove to the nearest DC rapid and fixed it before driving the 80km trip home. Its never run hard since, just every 2 months it wants to do a mtce cycle. Small inconvenience for peace of mind on long trips. If I bought a newer model, probaly would be BEV. The other factor to consider is elecrical faiures in the Rex EM system which will disable the car and less EV range with Rex versions.

 

[frictioncircle]

My WOF garage complains about the cobwebs in the tailpipe.

What is a "WOF garage"?

 

[alex29a]

Alex, correct the Rex does not run if state of charge is above 75%. It also wont run for mtce. if fuel level is below approx. 1/4. In this case you get bugged by display warnings until you relent and top it up so it can complete a 60 days 10 mins mtce run, then it shuts up for another two months. You can prevent further mtce runs by letting the fuel go below 1/4. code the warnings off if you dont like them. My WOF garage complains about the cobwebs in the tailpipe. I have to refuel once per year, oh the pain....

I have a 2017 96A/h Rex and if it is just doing a mtce cycle it starts so quiet inside the car I have to stop and listen to be sure it is really running. There is a perceptible noise when the battery is low or you need full power for sustained speed or hillclimbing. I agree that having it run around town the noise is similar to a scooter idling, from the outside. I've observed pedestrians as I pass by and nobody notices. The one in the showroom will run hard because they let the main battery get down too low.

When my car was delivered off the boat it did this due to low charge, I drove to the nearest DC rapid and fixed it before driving the 80km trip home. Its never run hard since, just every 2 months it wants to do a mtce cycle. Small inconvenience for peace of mind on long trips. If I bought a newer model, probaly would be BEV. The other factor to consider is elecrical faiures in the Rex EM system which will disable the car and less EV range with Rex versions.

============================================================================================================
Thanks MagicCarpet. :
1) keep the fuel below 25% to prevent mtce. do yo have the steps to code the warnings off? this is very useful. resume if needed for the odd long journeys. When it is convenient we can run mtce manually following the video posted above
2) ( elecrical faiures in the Rex EM system which will disable the car and less EV range) . Any particular electrical failure to look out for?

 

[MagicCarpet]

WOF garage means the Warrant of Fitness check, in England its called MOT (made orrible tea)

Alex, I just let the Rex do its thing, preferably during an out of town trip, it only runs 6 times a year which is probably the minimum for keeping the fuel fresh enough and the parts from rusting internally. I havent tried to code those alerts.

The electrical failure I mentioned which can only occur on the Rex comes up as a 'low insulation' type alarm and was caused from moisture condensing out inside the Rex generator - this depended on climate and whether the Rex got enough running to dry out the area. dealers would fix by replacing the generator but DIY can take steps and hope it self heals.
It seems pre - 2006 models suffered so later models probably OK,

 

[Arm]

If that REX was truly that noisy, then I suspect it wasn't taken very good care of. While it's not the smoothest or quietest thing, it's not super loud either.

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

 

[Timjohn]

The first time the REX fired up on my 2020 i3S I couldn't couldn't hear it. I was driving around town and the maintenance cycle started automatically and ran for 10 mins. Now the devil is in the details. Firstly, the REX engine will only fire up and rev above 3,000 rpm either when the demand for charge is high under certain operating and conditions of the battery level. Therefore if you are outside and at the back of the i3 it will be noisy and loud especially in a enclosed garage or close to a wall of a building with a battery sitting at 2%. Its programmed to rev (>3,000) to charge the battery.

REX adapts to what the car needs and will adjust its output under the following conditions:

1) At highway speeds (>60 mph) when the REX is programmed to Hold State of Charge (<75%) and the battery falls below this 75% level.
2) Battery level is <6% and you are driving at highway speeds.
3) The maintenance cycle has been manually enabled as in the case of an oil change

So I recommend to put your mind at ease with regards to the noisiness of an i3. Go out and take one for a test drive for more than a day. Get one with it programmed to hold state of charge (HSOC) and then drive it in the city and highway.

Trust me, you will forget about this issue because its a beautiful EV to drive. It's a great city car but most importantly its "fun".

Timothy