OEM FL5 RMM Measurements and Urethane Injection

[blueroadster]

Here are specifications and PICs for the OEM FL5 RMM. Weight is 1,364 grams or 3 lbs. It includes a 3mm insert shown in the first PIC and measured in the second PIC:

Other measurements:

Gap measurements:

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[blueroadster]

Using tried and true urethane injection to simply fill the cavities in the OEM RMM:

Note that you need to be very careful using 3M Windo-weld as it bonds immediately. If you happen to get any of it on your skin, nothing will remove it. It also has a Shore A of 55-60 where typical OEM motor mounts use a 70 Shore A hardness rating.

 

[HKSpeed]

I recently learned about this option, but I haven't seen/read any reviews of people who actually did it. I'm curious to see how yours turns out.

 

[blueroadster]

Inject the OEM RMM with 3M Windo-weld

Remove the stock insert and clean the RMM with dish detergent and a brush. Once completely dry, tape off areas on both sides where you do not want the urethane to be applied.

Apply clear packaging tape to seal off the other side to prevent the injected urethane from pushing out:

Put some gloves on and be careful when injecting the 3M Windo-weld. Whatever it comes into contact with will not be easy to remove. Flip the part over and inject urethane into the cavities on the other side.

Flip the part over and verify that the urethane completely fills against the clear tape:

Once verified, you can use a popsicle stick on the other side to smooth the surface of the urethane:

Let the part sit for at least 24 hours for the surface area of the urethane exposed to the air to cure. Urethane on the other side will remain wet as it is protected by the packaging tape. Tomorrow, I'll post an update on the next steps.

 

[HKSpeed]

After seeing your thread, I searched YT. I didn't find anything from an 11th gen Civic. I found this from a 10th gen Si. This guy injected all his mounts, then said the NVH was too harsh.

 

[blueroadster]

After seeing your thread, I searched YT. I didn't find anything from an 11th gen Civic. I found this from a 10th gen Si. This guy injected all his mounts, then said the NVH was too harsh.

Good heavens. Messy job and he went overboard injecting everything. I've always found it best to start with injecting the OEM RMM first and then gauge from there. The OEM RMM has a large rubber area where injecting softer urethane into the gaps does wonders. Most aftermarket RMM options use a smaller diameter polyurethane bushing that also have a higher Shore A equating to even higher NVH over simply injecting the OEM one.

On my previous FG2 build, I injected the OEM RMM with 3M Windo-weld and it helped reduce wheel hop significantly while not introducing excessive NVH. I later upgraded the motor mounts with ones from Hasport in a 62A instead of injecting the stock motor mounts. NVH was obviously higher but not bad IMHO. That car originally went from 178 wheel HP to 535 Wheel HP on 93 octane.

 

[blueroadster]

Here is a video of my previous FG2 during a dyno pull and tune at Evans with the 3M Windo-weld injected OEM RMM and Hasport 62A motor mounts installed:

As you can see, motor deflection was not entirely eliminated but reduced quite a bit over stock without excess NVH during idle or when the AC was turned on.

 

[jtlctr]

You can also buy liquid polyurethane in various hardness ratings from these guys:
https://www.suspension.com/diymmi

 

[blueroadster]

Next day and more PICs. Remove the tape on the side where the urethane has cured:

The urethane is very sticky so you are not going to get a buttery smooth surface. It is however flat and uniform without any air bubbles in it:

Next remove the clear packaging tape on the other side and use another popsicle stick to smooth.

Give that side another day to cure before removing the tape.

 

[blueroadster]

Tape removed from the other side. It still needs a few days to fully cure but will be ready to install this weekend.

 

[blueroadster]

I installed the injected RMM (a.k.a., torque rod). If you don't have a crows foot to torque the horizontal 19mm bolt when reinstalling, you can simply mark it to serve as a reference point prior to removal.

To remove the horizontal 19mm bolt, I found it easier to simply use a jack to push up on the rear of the front pipe to gain clearance. Old RMM removed and injected one installed. The vertical 17mm and horizontal 19mm bolts should be torqued to 69 ft lbs.

Here is the RMM that was removed. I have enough 3M Windo-weld leftover where I am going to inject this one as well.

 

[blueroadster]

As for impressions, I absolutely love it. Compared to the OEM RMM, there is no change to NVH. At idle and when the AC is turned on, you can feel a very slight vibration in the driver's seat and hear a slightly deeper engine/exhaust sound. There is no hum or vibration felt on the steering wheel at all in either case.

Under load and once moving, NVH is the same regardless of AC on or off. Everything feels more connected when driving and shifting. Wheel hop during launches is also gone.

Overall, I believe this is the best bang for the buck. Aftermarket inserts do not fill all of the voids in the OEM RMM. Injecting with 3M Windo-weld maintains the OEM rubber while filling the cavities with a 55-60 Shore A urethane.

Here is another thread discussing other aftermarket RMM offerings.

 

[blueroadster]

So two days after installing and sense then, the slight vibration in the driver's seat and sound at idle when the AC is turned on went away completely.

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