MFactory LSD with 3.46 final drive review

[Obi Wong Kenobi]

Let me first say that I was a little skeptical of putting anything except an OS Giken, ATS/Carbonetic or Quaife in my 135i. I've had experience with all 3 brands, plus Kazz in my past cars and the LSD is a huge part of how the car feels navigating corners on the track and the twisties.

Enter MFactory with their excellent customer service and very fairly priced product:

http://www.1addicts.com/forums/showthread.php?t=943830

While surfing the forums and killing some time while at work, I started to read up on their thread. I can't lie, the price was the first thing that attracted me. For under a grand, I could get a forged helical LSD unit that would suit the needs of what I had planned for my 135i. A low noise, stealthy daily driver that was fun to drive. What really appealed to me was they had built pumpkins with a 3.46 final drive and LSD in stock for under $2000 shipped (if you send back your core). At that price, I bit the bullet and eagerly awaited my new purchase.

During the time, I was installing M3 arms front and back along with the BMW Performance suspension. Already installed is a Cobb V3 and downpipes. Even with those mods, I was having serious traction issues in first and second gear. Before getting any more performance mods, a LSD needed to be addressed.

Once all of it was done, the 135i honestly feels like a completely different car. Two years ago, I had a chance to drive the 1M and my 135i is coming close to what that car felt like. The MFactory LSD and suspension really transformed the vehicle. I've had about 4 full days of driving it with the LSD and I'm very impressed. Obviously, since the diff was already installed, I didn't get to see the quality of the item first hand. But knowing it's a forged unit and now my traction issues has been addressed, I'm a happy camper! I can now put the power down and more importantly, hang the tail out on command. That's something I never had a chance to do as well with my Cayman S or E46 M3 since low end torque was lacking. Not to say you couldn't do it at higher speeds... but that's a little more reckless around the city!

I'm sorry for the long winded review, but for my needs and as my daily street car, this MFactory unit is spectacular. I plan to try to squeeze in an autocross or two before the winter and visit some tracks next year and I'm confident this will help. If you're looking for a quality unit without breaking the bank, I believe MFactory should be high on your list of considerations.

[dcaron9999]

You did a good choice by selecting the 3.46 ratio. I did the same and went with a Quaife in March 2014 before MFactory had these units for our manual 135i's. I bought a used MY2007 3.46 ratio large pumpkin with bolted ring gear for $500USD, and Quaife + installation for another $1800USD. I sold my 2011 OEM pumpkin for $500CAD...

The 3.08 to 3.46 ratio upgrade really makes the car ready to pounce in any gear. This was a great upgrade for the track and even for the street. The DSC and e-diff wizardy (ie: rear brakes) hardly intervenes anymore, and the car is much more predictable at turn out and flat out acceleration. I actually turn everything off (DSC OFF mode) at the track now, but only once the tires are warm because I now have full confidence in the car. The present alignment on my 135i is also exactly where I want it. No more understeer, and a very faint controllable oversteer when the car is pushed really hard.

Alignment specs are 0 toe and -3.2*camber in the front, 3/32" toe in with -2* camber in the rear.

I may eventually get rear toe adjustable arms for easier camber and toe adjustments.

[3002 tii]

Normally I wouldn't consider putting a LSD into a daily given the cost/benefit but seeing how these are $700-800 less than competitors, it's definitely now worth it in my mind.

[wanganstyle]

Originally Posted by 3002 tii

Normally I wouldn't consider putting a LSD into a daily given the cost/benefit but seeing how these are $700-800 less than competitors, it's definitely now worth it in my mind.

Yes if you order a unit from M-factory it is only 2/3'rds the price of a new Drexlerif you wish to give up your core.
M factory also has a clutch type unit avail as well for someone with the time to tinker; It should be reasonably tune-able as well if you have the patience/resources to play with it.


BMW has made the 3,08 ring and pinion avail. brand new in BOLT on so that those with manual transmissions will have an option now; I just bought one + Drexler LSD unit

[BBursey]

Originally Posted by wanganstyle

BMW has made the 3,08 ring and pinion avail. brand new in BOLT on so that those with manual transmissions will have an option now; I just bought one + Drexler LSD unit

Do you have part numbers available for the 3.08 ring and pinion for our 135?

Thanks,
Bryan

[wanganstyle]

Originally Posted by BBursey

Do you have part numbers available for the 3.08 ring and pinion for our 135?

Thanks,
Bryan

Sorry, I do not. just ask your bmw parts counter, the cost is not for the timid as proper new BMW parts cost

[Grinchxvx]

you went 3.46 on a manual trans? how is that effecting gas mileage?

[darkrom]

Originally Posted by Grinchxvx

you went 3.46 on a manual trans? how is that effecting gas mileage?

Thats what I wanna know. I'm interested in acceleration over top speed, so this is something I'm strongly considering in the future for my 6MT. Its really the weakspot of the car. With JB4 on map 5 its far too powerful for an open diff.

[dcaron9999]

Originally Posted by Grinchxvx

you went 3.46 on a manual trans? how is that effecting gas mileage?

Yup. A couple of us did move from 3.08 to 3.46.
500 RPM increase in 6th gear at 110/120KMH (65-70MPH).
+1 liter/100Kms (+4MPG) fuel consumption bump on the highway.

[Grinchxvx]

Originally Posted by dcaron9999

Yup. A couple of us did move from 3.08 to 3.46.
500 RPM increase in 6th gear at 110/120KMH (65-70MPH).
+1 liter/100Kms (+4MPG) fuel consumption bump on the highway.

that's a little steep, I bet the fact that it feels faster and you want to floor it effects it more lol.

[Grinchxvx]

Originally Posted by darkrom

Thats what I wanna know. I'm interested in acceleration over top speed, so this is something I'm strongly considering in the future for my 6MT. Its really the weakspot of the car. With JB4 on map 5 its far too powerful for an open diff.

But what's worse? a open diff and roasting your 1 tire or a lower gear ratio making you roast both tires

[MFactory]

For start/stop driving, you'll actually get better fuel economy as less throttle is required to move the car. You will only see slightly less fuel economy on the highway.

So combined, you will probably not get any worse than normal, but you do you get the increased performance/acceleration

[flinchy]

Should be noted that 3.46 will actually slow down accel on stock frame, rb, vtt2 n54's and decrease traction more than anything else haha

[darkrom]

Originally Posted by flinchy

Should be noted that 3.46 will actually slow down accel on stock frame, rb, vtt2 n54's and decrease traction more than anything else haha

How so?

[wanganstyle]

Originally Posted by darkrom

How so?

combination of many things: please read I am not biased as I have changed the final drive to 3,46 on one car from original 3,23 (but this car is not turbocharged)

N54/55 engines are turbocharged, not Naturally aspirated

The final drive ratio is calculated in the mapping of engine and turbocharger spool up, the LOAD from the original 3,08 final drive is good for spooling up turbos - LOWER numeric final drive = more load to engine = more hot gas for turbocharger = go faster.

to compare from the BMW factory a e92 328i sport 6mt has a 3,73 final drive with almost identical zf 6 speed manual transmission. 335i/135i has 3.08 for 6 speed manual. Both engines are 3000cc; one is NA one is turbocharged.


boosted up catless 135/335 is already low on traction; Even with a LSD the car will be able to spin tires through 2nd gear on sheer power depending on driver/footwork/tire combination; changing the numerical ratio from 3.08->3.46 will create even less traction as the mechanical torque to the ground multiplier has increased. If you dont have traction issues then adjust the final drive to as high numerically as you feel like paying for fuel (adjust to MPG). for those who care about MPG; Stock BMW is absolutely the best for fuel economy.

For california cars a drastic change in Final drive ratio will cause the rolling load smog dyno test to be at a higher RPM and you MAY or may not pass smog.

[dcaron9999]

Excellent assessment from Wanganstyle.

The torque and power out of the curves and immediate acceleration response with the 3.46 diff is addictive though. May not be much "quicker" say from 0-60MPH or more, if you consider more frequent gear shifts with the higher ratio diff ...

You really need good grippy rubber in the rear, and nothing less than extreme performance street tires will do (RE11, ZII, AD08R, RS-3, PSP, etc)...

[flinchy]

Originally Posted by darkrom

How so?

There's even more than what wanganstyle said

the torque/power curve of a high boost small turbo N54 means you don't shift at redline for max acceleration in gears 3+... more like 6100/6200

by shortening the effective gear ratio of the car, you're increasing how often you need to shift, and reducing the width of your (limited) power band..

there's calculators you can use to simulate it.. but basically, a stock frame (besides the upcoming SUPERRB/VTT2+) at max boost/power will get better acceleration with a 2.56 ratio over a 3.08 or 3.46

however it will FEEL faster going the shorter gearing, even though the reality it's several tenths slower and much harder to control.

[dcaron9999]

Originally Posted by flinchy

There's even more than what wanganstyle said

the torque/power curve of a high boost small turbo N54 means you don't shift at redline for max acceleration in gears 3+... more like 6100/6200

by shortening the effective gear ratio of the car, you're increasing how often you need to shift, and reducing the width of your (limited) power band..

there's calculators you can use to simulate it.. but basically, a stock frame (besides the upcoming SUPERRB/VTT2+) at max boost/power will get better acceleration with a 2.56 ratio over a 3.08 or 3.46

however it will FEEL faster going the shorter gearing, even though the reality it's several tenths slower and much harder to control.

Im still loving my Quaife 3.46 diff, and its very smooth and predictable at the track. I assume the MFactory 3.46 LSD is similar. You do have to be smoother with your throttle inputs when turning. If you apply a little too much pedal, you just need to "lift" - its very easy to get it back under control with the LSD ...

Im getting a custom tune done for my Cobb AP3. PTF (protuningfreaks.com) tailors a map specific to your Diff ratio, tire category and tire size. This is interesting and may address what you mentioned about turbo load ...

Im pretty impressed with the way the power is delivered and handled with my Quaife at the track currently, but allways looking for that extra gain and even smoother delivery if possible. Will see how well PTF addresses this for my setup versus OTS maps ...

[MFactory]

Boost goes by rpm, which does not change. Longer gears = stay in boost longer, is a myth. If that was the case, why even change gear?!?

Acceleration goes by speed, not distance. A shorter geared car will always accelerate faster to 100mph than a longer geared car, regardless of how many times you need to change gears (which isn't any different anyway. It's only 200-300 rpm difference). Do you want to be quicker to 100mph than everyone else (i.e acceleration), or quicker to cover a mile (i.e top speed)?

What people need to realise is, a shorter geared car is NOT about the rpm difference (and therefore when you need to shift), unless you are deliberately fine tuning you gear ratios for a track car. For 90% of you, a shorter geared car is about Torque Multiplication. Say you had 400lbft:

3rd Gear is 1.58 ratio. Torque to the ground is 400 x 1.58 x 3.08 = 1946lbft

If changed to the 3.46: 400 x 1.58 x 3.46 = 2186lbft

That's a 12% increase in torque throughout the entire rev range. It has nothing to do with shifting gears quicker or slower, nothing to do with what modifications you've done to your engine. It is a 12% increase no matter what you do to your car.

The only disadvantages to a shorter gear ratio are:

1) Traction. If you can sort out the traction (better tires, better chassis setup etc), then this isn't an issue
2) Top Speed. This is why you should use a gear calculator, to see if what you end up with is sufficient

Obviously there is more to this, but this is it explained very basically.

[PeteA]

Personally, I feel 3.46 to be far too aggressive for the N54/N55. There is already PLENTY of torque down low from the engine. Touching these ratios is better for an engine which doesn't have much low down torque....say the S54/S65 for instance.

The 3.08 is well suited to the chassis / engine / turbos. This is even more so the case when you tune them to a higher and more linear torque curve. The 1M has a 3.15 final drive ratio and many of the owers feel that even on a stock tune the 1st gear is next to useless.

If you're keen on 0-100km/h times, the 3.08 ratio only requires a single gear change to get there on the 6MT.

[MFactory]

Basically, what I'm saying is, all the final drive change does is give you more torque. If you are worried about having too much torque, then why bother to even modify/tune your car in the first place other than doing chassis or cosmetic mods? A good tuner will be able to tune your power curve more linear. A great tuner knows how to tune the power curve based on what the gearing of the car is like. Unfortunately, a lot of tuners don't have a clue about this.

If you were worried about the "rpm/speed" aspect of the final drive change, then changing wheel/tire size does the exact same thing; but everyone still does it

[ASAP]

Everyone here is aware that 3.46 is the stock auto final drive right? lol

It works perfect...