Goose619
Posts: 1
Joined: Sun Nov 04, 2018 9:18 am

REX Acoustic sound dampening

Sun Nov 04, 2018 9:25 am

Hey guys I'm getting ready to pick up a used 2015 rex model and I 've heard some complaints about the sound of the ReX in the cabin.

I was wondering if anyone has tried lining the top cover in the trunk with some sound dampening vinyl?

Like this one: https://www.acoustimac.com/soundproofing-massloaded-vinyl-1lb50sf?gclid=CjwKCAjwsfreBRB9EiwAikSUHZrwHnbPxCyoUKm9ZTcxYR4eBxijh8_4OOm5W8KlC2d7_DHQphO2QhoCkgAQAvD_BwE

I think it can at least cut down on the sound a bit.

theothertom
Posts: 363
Joined: Mon Mar 20, 2017 6:08 am
Location: South Carolina

Re: REX Acoustic sound dampening

Sun Nov 04, 2018 1:13 pm

I don't think the sound is loud at all. I suggest you let the REx come on after you get your car and then decide.

i3Houston
Posts: 150
Joined: Thu Jul 12, 2018 2:30 pm

Re: REX Acoustic sound dampening

Mon Nov 05, 2018 8:13 am

Its not noticeable at all at freeway speeds; only at low speeds when no other cars/noises are around you can hear it.
TM3 Reservation holder/ 2015 i3 Rex

jfran2
Posts: 20
Joined: Tue Oct 30, 2018 4:20 am

Re: REX Acoustic sound dampening

Thu Feb 07, 2019 5:27 pm

FWIW, my 2014 i3 Rex didn't come with a parcel shelf. I ordered one from a salvage yard, and it helped considerably with the sound. At freeway speeds, I don't hear it at all on low speed, only when it kicks into medium or high.

bwilson4web
Forum Supporter
Posts: 652
Joined: Fri Apr 29, 2016 11:59 pm
Location: Huntsville, AL

Re: REX Acoustic sound dampening

Thu Feb 07, 2019 8:15 pm

Throw rugs?

Bob Wilson
20k/27k mi 2014 BMW i3-REx
10k/10k mi 2017 Prius Prime

MKH
Posts: 139
Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: REX Acoustic sound dampening

Fri Feb 08, 2019 5:02 am

Even at surface-street speeds, I can barely hear the Rex engine when it is on in my 2015. Wonder if, in the later models with the larger battery capacity, they have increased the Rex rev's, to provide more "juice" while running?
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 20 inch wheels, EVoInnovate EVSE

jadnashuanh
Posts: 4343
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: REX Acoustic sound dampening

Fri Feb 08, 2019 3:34 pm

The original REx was rated at 34Hp, someone said the new one is 38, so, yes, it might very well run a bit faster on the newer ones. Note, the REx rpm is not a fixed thing, it does change with load and how far 'behind' it is in keeping the set SOC. But, it doesn't rev very high until it gets over its initial warm up period.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

TheMK
Posts: 126
Joined: Tue Sep 18, 2018 8:57 pm

Re: REX Acoustic sound dampening

Fri Feb 08, 2019 5:03 pm

jadnashuanh wrote:The original REx was rated at 34Hp, someone said the new one is 38, so, yes, it might very well run a bit faster on the newer ones. Note, the REx rpm is not a fixed thing, it does change with load and how far 'behind' it is in keeping the set SOC. But, it doesn't rev very high until it gets over its initial warm up period.



I must preface this by saying that I have no backup/confirmation, just my own original research....

I believe that although the original REx was rated at 34Hp, somewhere down the line with an I-Step (vehicle software) update, BMW has bumped up the engine capacity in older models as well. We know that the engine it's self hasn't changed, rather the RPM at which it will run has. The original BMW i3 generates 25Kw (34HP) @ 4300 RPM [1]. Using test/measuring software (ISTA) on my i3, I have found that I can max out the REx at 4800RPM. Doing this requires a significant drop from the SoC hold point target, and also requires the vehicle to be moving quite fast. According to the W20 engine manual, the RPM isn't supposed to climb above 4300RPM but we do know that the W20 engine manual that's floating around on the internet is from the original 2014 release of the i3, and doesn't cover the upgrade. According to an i3 spec sheet dated 11/2017 [2], the output is now 38HP @ 5000RPM. I have only measured 4800RPM in my 2014, but if we look at the power and torque curves that are graphed in the W20 engine manual, we can see that the output at 4800RPM and 5000RPM is not very different at all (in fact depending on how you interpret the graph they may be identical), and both of those are certainly higher than the original 4300RPM amount.


Now the million dollar question is, was what BMW did legal? Both the 34HP, and 38HP systems are both Euro-VI compliant, so they should have no issue at all with EU emissions regulations, but what about US regulations? They might still be OK here too, the REx is rated as a SULEV here in the US, and as long as the software update version is still SULEV rated (it is, as we know from the official ratings on 2017+ models), then they should be OK here too.



[1] https://attachments.priuschat.com/attac ... Engine.pdf
[2] http://resources.mynewsdesk.com/image/u ... nioyut.pdf

Return to “BMW i3 Rex Specific Discussions”