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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Lack of limited slip differential (LSD) in the 335i



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      07-28-2006, 10:42 AM   #89
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The E92 will not spend a lot of time on the track where a LSD would be useful.
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      07-28-2006, 11:19 AM   #90
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Quote:
Originally Posted by ksfrogman
That's a question that evokes a question. I didn't realize that this was the steptronic E90's diff, is it?

The upgraded performance open diff sold on Bimmerworld is a 3.64 for the 330i; stock ratio 3.15. For the 325i, they offer a 3.73 (instead of the OEM 3.23).

http://e90post.com/forums/showthread...ht=mods+matter
It probably is the differential typically used with the step. That is all cool. This is an old BMW tuning trick that has been used for a long time. Guys take the higher ratio diff from the automatic models and slap them on the manuals. It is a good way to do it since you are using OEM BMW parts... in my opinion, the only way to modify a BMW is to use OEM BMW parts from other BMW's
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      07-28-2006, 11:37 AM   #91
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Quote:
Originally Posted by epiphone3
It probably is the differential typically used with the step. That is all cool. This is an old BMW tuning trick that has been used for a long time.
Exactly.

Now the question is, why not use the 3.73 part from the 325i?
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      07-28-2006, 12:06 PM   #92
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Quote:
Originally Posted by mkoesel
Exactly.

Now the question is, why not use the 3.73 part from the 325i?
To be honest, the car will already be pretty violent with the 3.64 rear end. That is probably why.... with the 3.73 you would take much advantage of the fairly wide torque spread of the 330i power plant.

I have a buddy who swapped a US E36 M3 240hp 3.2 liter engine into a 1998 318is (I beleive it was geared at 3.75 or something) and the thing accelerated so violently that he was thinking really hard about getting a longer diff gearing (like 3.25) or something.
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      07-28-2006, 01:45 PM   #93
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I saw on this on Honda's website, which implies that the LSD will be available on the new Civic Si sedan.

What is a "helical type" LSD? Does it describe the type of gears or cogs that are utilized?

http://automobiles.honda.com/civic_si_sedan/index.aspx
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      07-28-2006, 04:10 PM   #94
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Quote:
Originally Posted by epiphone3
I do know how diffs work. I am a mechanical engineer and I made a LSD final drive system for my design project in University... thanks for the link though.

So the definition of EDL, by BMW, is:
Electronic Differential Lock (EDL).
The Electronic Differential Lock (EDL) applies brake force with the utmost precision to a rotating drive wheel up to a certain speed and then transfers the torque to the other wheel. An additional hydraulic pump is responsible for this transferral: if a pre-determined torque value for the wheels is exceeded, the pressure is rerouted via a magnetic valve to a faster-turning wheel, thereby braking it.

An open-diff works like this: if a wheel starts to slip (i.e. spin faster), the natural tendancy for the open-diff is to send more power to this wheel.

Moving forward, the EDL will slow that faster spinning wheel thus causing the open-diff to send more power to the wheel with grip.

An LSD will allow on wheel to slip a certain amount before transferring, typically up to 25% of the engine's torque, to the wheel with grip.

There is also the 100% M-differential found in the current M3. The M-differenatial is not a conventional LSD as it is essentially a clutch pack that can transfer power side-to-side. This one is so flexible that it can transfer up to 100% of the engine's torque to one wheel, unlike the typical LSD that can only transfer approx. 25%.

To me, the LSD that BMW would possibly put in the 335i, that is, a 25% LSD is basically six in one and a half dozen in the other when compared to the open-diff with EDL.

This is what I was trying to get at. While the open diff is technically open, all it does, really, is use a different method to transfer power than the complicated gear systems found in 25% LSDs. It seems simpler and, for the most part, as effective as a 25% LSD and cheaper (i.e. keep car cost down to allow lower price).

Correct me if I am wrong.
Good write up, and yes you couldn't be more correct. For people who will drive their BMW's conservatively then the EDL really is the most effcient, sensable system. For those who are going to be initiating wheel spin more often a real LSD would be more effective. I think BMW has improved the DTC system since I had my 04 330i but I'm not sure. DTC will act as an EDL but without the engine management (kills the engine) of DSC. I'm not sure whether or not DTC will brake in an over/understeer situation like DSC, or if it has higher thresholds. I was very impressed with the LSD in my E46 M3 though, and I'm really not that anxious to go back to an open rear diff with DTC unless they've drastically improved it. If the 335i came with the LSD that's on the E46 M3 it would be much, much more desirable, IMO.
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      07-28-2006, 04:15 PM   #95
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Quote:
Originally Posted by epiphone3
It probably is the differential typically used with the step. That is all cool. This is an old BMW tuning trick that has been used for a long time. Guys take the higher ratio diff from the automatic models and slap them on the manuals. It is a good way to do it since you are using OEM BMW parts... in my opinion, the only way to modify a BMW is to use OEM BMW parts from other BMW's
I appreciate all this useful information. Thanks a million!
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      07-28-2006, 04:17 PM   #96
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Quote:
Originally Posted by mkoesel
Exactly.

Now the question is, why not use the 3.73 part from the 325i?
Bimmerworld has a gear ratio/rpm/speed calculator that is simply an Excel spreadsheet with formulas. I was tinkering around with this earlier today, but didn't have the chance to compare the data. I will post it later tonight hopefully.
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      07-28-2006, 07:25 PM   #97
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Quote:
Originally Posted by txusa03
I don't know anything about LSD. BUt my 330 e90 is wonderful to drive. How would a LSD improve my ride? Anyone care to chime in on this? If it was an option, I probably would bypass it due to the fact that I am happy with my current car option. I don't think I have driven a car with LSD.
A LSD is good for extremely tight corners under power (like autocrossing) and certain (rare) instances on the street. There is a corner near my house that I like to take fast that has a really serious elevation change. Due to the sport suspension being so stiff (and the pavement falling away underneath the right rear wheel as it rises under the left front wheel), the right rear wheel actually comes off the ground for a second when I am in the corner, and it spins.

The corner is only taken at about 8 MPH (hairpin), but it's pretty scary when the car has no thrust all of the sudden and the right rear spins and then chirps on the pavement. A LSD would not allow the inside wheel to spin.

I am pretty sure that even without the LSD, the traction control is catching the wheelspin it and applies the brakes to that wheel, but it takes a second to happen. Even my Jetta GLX had a LSD, but of course it was Front Wheel Drive which more than negated the advantage of the LSD.
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      07-28-2006, 08:02 PM   #98
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I put a 4.11 60/40 LSD on my 2002tii and the difference was incredible. With the standard 3.45 one wheel would lose traction, slowing the car down, and the when the tire got grip the engine would bog. With the LSD, you could control the car with power -- the gas pedal became a second steering wheel. It was so much easier to 'drift' when both wheels were spinning at roughly the same speed. My brother, who is a more accomplished driver than me, was able to do 360s in heavy traffic on slippery (preferably a little snow) surfaces with my car. It was screaming fun to race through the woods in northern Michigan, sun, rain or snow. If you got it stuck you could usually pick up the rear end and stick something under the wheels to get it going again.

So, while I suspect the E90 335 is a rather different sort of beastie than my old tii, I am anticipating putting her up on the hoist and swapping in a new Quaife, which I have never tried before. I promise an interesting DIY, replete with booze & drugs during the operation.
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      07-28-2006, 08:10 PM   #99
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Quote:
Originally Posted by Moderato
Good write up, and yes you couldn't be more correct. For people who will drive their BMW's conservatively then the EDL really is the most effcient, sensable system. For those who are going to be initiating wheel spin more often a real LSD would be more effective. I think BMW has improved the DTC system since I had my 04 330i but I'm not sure. DTC will act as an EDL but without the engine management (kills the engine) of DSC. I'm not sure whether or not DTC will brake in an over/understeer situation like DSC, or if it has higher thresholds. I was very impressed with the LSD in my E46 M3 though, and I'm really not that anxious to go back to an open rear diff with DTC unless they've drastically improved it. If the 335i came with the LSD that's on the E46 M3 it would be much, much more desirable, IMO.
Thanks!

Yes, DTC seems to leave the chassis control functions of DSC active but allows full engine power to the wheels. My dad's 330i only has ASC, so I don't have personal experience with the E46 DTC.

I can say, however, that when climbing a very snowy, slippery hill, I switch to DTC and the differential seems to very effective a switching power from side to side and keeping the car going straight as an arrow.

The diff in the M3 is quite amazing and would be a great chassis addition to any car... however, I am sure that most people buying 3 series BMW's would be choked at the increased price of 3-series cars if they were to include such a sensational piece!
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      07-28-2006, 08:11 PM   #100
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Quote:
Originally Posted by ksfrogman
I appreciate all this useful information. Thanks a million!
Anytime! I love the sound of my own... ummm... typing!
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      07-28-2006, 08:27 PM   #101
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Quote:
Originally Posted by epiphone3
The diff in the M3 is quite amazing and would be a great chassis addition to any car... however, I am sure that most people buying 3 series BMW's would be choked at the increased price of 3-series cars if they were to include such a sensational piece!
Good point. That's why BMW should make it a 1K option. I'd pay it!
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      07-28-2006, 08:53 PM   #102
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Hi everyone,

I'm new to this forum as you can tell from the number of posts I've made. I've searched but can't find the information I'm looking for, please help.

I'm an avid autocrosser, my previous car was a '04 E46 M. Anyway, I've been looking for a LSD for my new e90 330i and can't seem to find one. Perhaps the car's too new? Or perhaps I'm looking in the wrong places. Please help me locate a vendor/supplier that may be able to help me with a LSD.

Thanks...
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      07-28-2006, 09:01 PM   #103
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Quote:
Originally Posted by Moderato
Good point. That's why BMW should make it a 1K option. I'd pay it!
+1

Cheaper than 2k for a Quaife, and the security of warranty besides. I would also be happy if they bundled it in a ZHP/si/M-sport package.
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      07-29-2006, 12:32 AM   #104
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Quote:
Originally Posted by epiphone3
I do know how diffs work. I am a mechanical engineer and I made a LSD final drive system for my design project in University... thanks for the link though.

So the definition of EDL, by BMW, is:
Electronic Differential Lock (EDL).
The Electronic Differential Lock (EDL) applies brake force with the utmost precision to a rotating drive wheel up to a certain speed and then transfers the torque to the other wheel. An additional hydraulic pump is responsible for this transferral: if a pre-determined torque value for the wheels is exceeded, the pressure is rerouted via a magnetic valve to a faster-turning wheel, thereby braking it.

An open-diff works like this: if a wheel starts to slip (i.e. spin faster), the natural tendancy for the open-diff is to send more power to this wheel.

Moving forward, the EDL will slow that faster spinning wheel thus causing the open-diff to send more power to the wheel with grip.

An LSD will allow on wheel to slip a certain amount before transferring, typically up to 25% of the engine's torque, to the wheel with grip.

There is also the 100% M-differential found in the current M3. The M-differenatial is not a conventional LSD as it is essentially a clutch pack that can transfer power side-to-side. This one is so flexible that it can transfer up to 100% of the engine's torque to one wheel, unlike the typical LSD that can only transfer approx. 25%.

To me, the LSD that BMW would possibly put in the 335i, that is, a 25% LSD is basically six in one and a half dozen in the other when compared to the open-diff with EDL.

This is what I was trying to get at. While the open diff is technically open, all it does, really, is use a different method to transfer power than the complicated gear systems found in 25% LSDs. It seems simpler and, for the most part, as effective as a 25% LSD and cheaper (i.e. keep car cost down to allow lower price).

Correct me if I am wrong.
Alright, you asked for a correction and here it is...

Your references to electronic diff lock and variable M-diff lock are one and the same. It is just a limited slip diff with an electromagnetically controlled piston/clutch pack that adjusts the amount of torque split between the two driving wheels. If you search EDL and variable M-diff lock on BMW's technology website, you get the exact same photos with very similar descriptions.
http://www.bmw.com/generic/com_04/en...tial_lock.html
http://www.bmw.com/generic/com_04/en...rent_lock.html

The EDL/variable M-diff lock works within the housing of the rear LSD differential to manage wheel-slip by varying the amount of pressure (most other LSD have a fixed pressure and hence a fixed torque transfer) on the clutch pack against the side gears to control the amount of power transferred to the non-slipping or outside wheel.

This should not be confused with the E90/92's DTC that works external to the open differential and is essentially an extended function of ABS that detects wheel-slip and uses braking to transfer power to the non-slipping or outside wheel.

I'm no mechanical engineer and I've never installed or designed any LSD's, but this is my understanding. Can anyone else help us out?
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      07-29-2006, 01:58 AM   #105
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Okay, here's the comparison with my existing set-up vs the performance one. From what I can tell, there will be a 500 rpm difference when comparing equivalent speeds between the two set-ups. The charts also show that when were dyno testing our cars in fourth gear, we were hitting about 131+ mph near redline.
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      07-29-2006, 08:06 AM   #106
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ks,
with that step-up in ratio, its still pretty streetable. I am running a 3.63 in my 325 (got a $$new$$ one last year) and its at the cusp of being too short. With 6 speeds though, highway cruising is fine, and makes 6th a useable gear.

You will like it. They dont call a differential swap the "poor mans supercharger" for nothing!

edit: on topic, DTC is in no ways comparable to any proper LSD or M-Diff. With all the torque the 335 is going to be making, LSDs in these cars are going to make for a much better enthusiast driving experience.
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      07-29-2006, 08:13 AM   #107
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Quote:
Originally Posted by visor
Alright, you asked for a correction and here it is...

Your references to electronic diff lock and variable M-diff lock are one and the same. It is just a limited slip diff with an electromagnetically controlled piston/clutch pack that adjusts the amount of torque split between the two driving wheels. If you search EDL and variable M-diff lock on BMW's technology website, you get the exact same photos with very similar descriptions.
http://www.bmw.com/generic/com_04/en...tial_lock.html
http://www.bmw.com/generic/com_04/en...rent_lock.html

The EDL/variable M-diff lock works within the housing of the rear LSD differential to manage wheel-slip by varying the amount of pressure (most other LSD have a fixed pressure and hence a fixed torque transfer) on the clutch pack against the side gears to control the amount of power transferred to the non-slipping or outside wheel.

This should not be confused with the E90/92's DTC that works external to the open differential and is essentially an extended function of ABS that detects wheel-slip and uses braking to transfer power to the non-slipping or outside wheel.

I'm no mechanical engineer and I've never installed or designed any LSD's, but this is my understanding. Can anyone else help us out?
There was no need to correct epiphone3. He understands how the systems work perfectly and even stated all you just said in his original post.
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      07-29-2006, 09:36 AM   #108
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Quote:
Originally Posted by RichP
ks,
with that step-up in ratio, its still pretty streetable. I am running a 3.63 in my 325 (got a $$new$$ one last year) and its at the cusp of being too short. With 6 speeds though, highway cruising is fine, and makes 6th a useable gear.

You will like it. They dont call a differential swap the "poor mans supercharger" for nothing!

edit: on topic, DTC is in no ways comparable to any proper LSD or M-Diff. With all the torque the 335 is going to be making, LSDs in these cars are going to make for a much better enthusiast driving experience.
Wow. You have a 3.63 in your E90 325? I imagine the car needs to be "worked" a little more when it comes to shifting, but the acceleration should be much stronger.

Oh, and are you sure it's a 3.63? I know that BMW actually makes a 3.73 as well.
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      07-29-2006, 01:33 PM   #109
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Okay... just to clarify.... I haven't taken my car on the autocross yet (just completed break in). When I do autocross it, should I leave the DTC active or off? There apparently two level's of "off" for the DTC - push the DTC once or push and hold the DTC for 3 seconds. Which will give me the most traction?

Wish September was already here.... our next autocross is in September.
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      07-29-2006, 01:38 PM   #110
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Yes, I am sure. Its the PN for the 330 automatic (I didnt want to really go nuts with the 3.73) You do have to work the shifter a little more, but its supersuper short. My E46 I went from a 2.93 to a 3.38 (about the same ratio increase) and I found that is about the limit of upgrade before it gets "too short" Of course, the E46 didnt have a 6th gear, which made highway driving a little tedious.

If you upgrade your diff, its quite a bit more torque to the ground, assuming both wheels have grip, which is the focus of this talk, lol.

I am considering perhaps rebuilding one of my diffs (I still have the stock) with a LSD in it for the 335 ill get once this lease is up next summer.

LSD+335 turbo+software = all you need.
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