MRF Solid Sub-Frame & Differential Bushings - A Night & Day Difference in Performance

[esquire]

Some of you are familiar with my build. Over the years, its become more and more focused on extracting maximum performance out of the car. (Full build thread HERE)

The first mod in that direction was KW Clubsports. Then an ESS VT2-625. Then I managed to get my hands on one of MRF's rare X-Pipe. Together that combo has made my car a bit of a freak in the horsepower realm, dynoing 581HP/377TQ on 91 Octane. (See MRF X-Pipe dyno gains HERE).

Its one thing to put down a lot of horsepower on a dyno. But its another thing altogether to get the same power down on the road, where traction, wheel-spin, and wheel hop come into play. Because of how much power I was putting down, first gear basically became non-existent. Accelerating from a dig, I couldn't hook up with the road without a lot of wheelspin. When I did finally hookup, my tail would either kick in one direciton or I'd get a lot of wheel hop, before the car could put down power properly. And even then, I'd have to short-shift out of first around 5k rpms before the car broke traction again. I began feeling like: "what's the point of my supercharger if i can't translate its power to real world results?"

I contacted MRF Engineering, who (as a lot of you know) is a shop that has made a name for itself for serious performance builds and track builds - i.e. serious project cars - and they recommended that I look into replacing the OEM sub-frame bushings and differential bushings with solid ones (Aluminum for the sub-frame bushings, Delrin for the differential bushings). They explained that the bushings would substantially improve how much power the car could put down, by minimizing wheel hop, car squat, and diff deflection

I was skeptical. How much difference could a hunk of aluminum or Delrin make?.....

Turns out... A LOT !!

Results:
Performance improvements were drastic. The way the car handles and puts down power now, is like night and day. Here are some of the many improvements I've noted. My car:

1. puts down A LOT more power now in first gear,
2. puts that power down much more reliably and predictably (which is very confidence inspiring),
3. puts that power down without nearly as much wheelspin or traction breaking in first gear, and eliminate wheelspin and traction breaking in second gear altogether (whereas before there was some),
4. gives me a lot more usable RPM in first gear (before I would have to short-shift out of first at 5k, now I can shift out around 7.5k RPMs).
5. wheelhop is eliminated
6. squat under heavy acceleration is eliminated
7. tail does not shift under heavy acceleration

The car should have come like this in the first place. It comes as no suprise, that subsequently BMW has begun putting these solid bushings in their other performance cars (including the M3 GTS, the new M5 and new m6). While I, personally, can't comment on the results for NA cars, the benefits are so universal that I have to imagine substantial improvements for NA cars as well. And NA people have said the same in other reviews. My car now feels much more sure-footed, planted, reliable, and most importantly, I have access to much more useable power from the line. If you care about performance, GET THIS MOD.


The Parts:
The sub-frame bushings are custom designed by MRF engineering, and C&C'd from solid aluminum. They're beautiful pieces. Too bad they're completely hidden from view once installed. Here is a pic:

MRF Aluminum Subframe Bushings




OEM Subframe Bushings

By contrast, the differential bushings are made of delrin - so they have just an infinitessimal bit more "give" than aluminum. Aluminum differential bushings are also available to those who really want them. Both the aluminum and delrin differential bushings (not the sub-frame bushings) are from Turner Motorsports.


Comments on NVH (Noise, Vibration, Harshness) -
This is a performance mod. As with any performance mod, there is a bit of a trade off in "comfort." People need to be honest with themselves about that upfront. Buy an exhuast, you get a louder car, and sometimes drone. Buy new shocks or a coilover kit, you get a stiffer less forgiving car. Buy a supercharger, you're gonna hear some supercharger noise. BMW dumbs this car down, and makes it more cushy for the masses. If you want to tap into the car's full potential, you have to get rid of some of BMW's "lowest-common-denominator" creature comforts. Luckily, the trade-off here is minimal.

The bushings do create a low volume whine above 40mph and 3k RPM for me. (Might be different for other people). Best way to describe the sound is that it sounds like the F1 car noise, but just on low volume. Its actually kind of cool. But if you're looking for dead silence - this is not it.

I have both the sub-frame and differential bushings so I can't pinpoint exactly WHICH of the two is causing the F1 type noise, but my understanding that it is strictly associated with the differential bushings and that the sub-frame bushings do not contribute to this noise.

For those curious about how prominent the noise is - its entirely imperceptible if you're listening to music, or if your windows are rolled down.

I will try to put a video up of the sound inside the cabin for those who are curious, sometime in the next few days.

The question I always ask myself on any mod is: "is what I'm gaining worth more than what I'm sacrificing?". With the solid bushings, the answer to me was an overwhelming yes. I can't communicate how truly pleased I am with the results.




Pics from the Installation:









As you can see, the Sub-Frame comes out for this install. Luckily MRF Engineering has some very expensive custom tools at their disposal (being a performance oriented shop) - and can get what would otherwise be a very long install, done relatively quickly. That saves us (the consumer) money and time. Unsurprisingly, other shops that aren't quite as performance oriented just don't have these tools. This month alone, I understand Malek has already done 8 (!) of these installations. And all of their reviews appear to be universally as glowing as mine. Probably a good reason for that.



Best,
- esquire

[tmntmn]

Very detailed review about the subframe upgrade!, been reading a lot of forum member with SC m3 upgrade their subframe recently.

I'm trying to keep my car N/a and was wondering if its worth it to do the upgrade.

[esquire]

Originally Posted by tmntmn

Very detailed review about the subframe upgrade!, been reading a lot of forum member with SC m3 upgrade their subframe recently.

I'm trying to keep my car N/a and was wondering if its worth it to do the upgrade.

That's really a question of whether you feel your car is capably putting power down in first gear. Part of that has to do with how much power you have. Part of that is also how aggressively you drive. Some members are making a good amount of power NA, I would say this mod is for them. Some members also like to mash the pedal off the line, I would say this mod is also for them.

Like I mentioned in my post, there are several NA cars out there who have done their bushings, and I believe they have all had positive things to say about the mod.

[BarryC]

Nice review! Regarding wheel hop - did these mods eliminate or reduce it?

Thanks!
BC

[BESTNDA416]

More and more I read about this the more it keeps pushing me to buy these. Thanks for the great review

[esquire]

Originally Posted by BarryC

Nice review! Regarding wheel hop - did these mods eliminate or reduce it?

Thanks!
BC

I have yet to experience any wheel hop whatsoever

[Someone?]

Sweet, great info, isnt there some companies that make super hard but not soild differential bushings? How long did it take and what was the Total cost?

[schnell325]

Wonderful review. You've made up my mind 100%.

May I ask the price of the sub frame bushings and the diff bushings?

PM me if you wish

[spdy330]

Sounds expensive.

[JEllis]

SWEET review!

[flipm3]

Incredible review as always.

If it's possible to make a video, that would truly be appreciated!

[esquire]

Originally Posted by flipm3

Incredible review as always.

If it's possible to make a video, that would truly be appreciated!

Will do !

[schnell325]

Originally Posted by esquire

Will do !

I'll reply tomorrow!!

[Wendall]

Originally Posted by Pertplus

Love mine! And I don't notice any whine!

My whine is faint. Actually, I would like it louder! Its sounds like a baby F1.

[flipm3]

Originally Posted by esquire

Will do !

Thanks! I truly enjoy your write ups on the forum.

Originally Posted by biggynuts01

My whine is faint. Actually, I would like it louder! Its sounds like a baby F1.

I want a F1 Baby!

[esquire]

Originally Posted by Pertplus

Love mine! And I don't notice any whine!

Pert, did you get both the subframe and the differential bushings? Goes to those that the noise is so faint that on some cars its completely non-existent.

Originally Posted by Pertplus

I do notice a lot of stiffness. But that's all coming from my lower pants region whenever I drive this MRF built monster

Lol.

[Brian0473]

Would be interesting to see before/after performance measurements, i.e. 0-60, 60ft. times, 1/4 mile, to see what the actual improvements are to acceleration.

[Malek@MRF]

Sasan,

Glad you are enjoying your new bushings.

For those wondering if this is only for Supercharged cars, the answer is a resounding no. The Sub-frame bushings equally benefit the naturally aspirated cars as all the same rear end problems are still present. The forced induction guys simply notice more of a grip difference in comparison to the N/A guys because most N/A cars don't have traction issues in comparison to SC'd cars.

All the other benefits are identical.

[klammer]

I've gone delrin (they felt like metal to me) subframe bushings and I'm NA and just did this as my car sees a lot of track time. Did a rear sway install at the same time (that I've subsequently snapped at the bar ,not end links ) and can say I love the solid, responsive feel of the back end and that the whole car just feels that much more responsive and communicative at the limit. Did a 1700 mile round trip days after install with the wife and kids (out to VIR last year) and felt no difference cruising around and neither did my wife. Stayed away from the diff upgrade as I've heard that's what adds the most NVH, (besides the engine ones) and have never once done launch control and don't plan on it, so subframe for me...great writeup

[Leonardo629]

esquire, can PM me the total cost for this mod?

[esquire]

Leonardo, just reach out to Malek@MRF. He can get exact figures to you

[schnell325]

Sent my order.