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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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      04-26-2006, 01:20 AM   #1
visor
BMW, can I have some LSD please?
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Lack of limited slip differential (LSD) in the 335i

Just wondering what others think of the lack of a limited slip diff in the 335i.

Especially with 300 hp and 300 lb-ft, how are the rear wheels (which are exactly the same sizes/widths as 330i's SP) supposed to have traction with just only an open diff modulated by brakes (DSC/DTC).

I can't imagine trying to turn off DSC/DTC on this monster!
With max torque starting at a low 1300 rpm, that would be downright dangerous!

Even the IS350 has the option of LSD with the sports package.
Why, oh, why did BMW not include even the option of an LSD?

I know, I know, some of you will say BMW saves the LSD for the M variants, but at least give us an option for the Ultimate Driving Machine!
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      04-26-2006, 01:37 AM   #2
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Totally agree with you.

www.drexler-motorsport.com has some lim slip diffs for E87s and E90s so in the future maybe for a E92 too.
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      04-26-2006, 03:14 AM   #3
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SHIT PUT SOME BLEACH ON THEM TIRES AND WATCH EM SMOKE :rocks:
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      04-26-2006, 06:43 AM   #4
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BMW hasn't offered an LSD in the non-M models since the E36. And, at one time, it was actually standard on the 3 series coupe (E30 325is). That the 335i won't have one is practically expected.

Doesn't matter that much. You can buy an aftermarket unit and choose your own rear end ratio in the process.

Lexus does not offer an LSD in the 2nd generation IS - at least, if they do, I've seen absolutely no mention of it in their brochure, website, or press releases.
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      04-26-2006, 07:19 AM   #5
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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.
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      04-26-2006, 07:32 AM   #6
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Limited slips are great. They even out traction between the rear wheels, making power slides and life in the fast lane in general much more fun. Plus any low traction (snow, wet) conditions are easier to handle. The potential downside is the increased traction can put more stress on the drivetrain. So if there are any weak links -- transmission, mounts, etc. -- then problems are more likely. IMO, the 335si should come with DSG and an LSD. And without saying, the M-pack. That would be an effective S4 killer. If you don't want a V8 M3, that would be the ticket.
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      04-26-2006, 09:06 AM   #7
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I think visor nailed it when he said that BMW saves their LSDs for the M series. Otherwise, the 335i with an LSD and a little tuning would be too close to the new M3 for comfort. This is just like what Porsche has done with the Cayman. They don't want it to be able to outperform the 911, so they did not give it an LSD either. But, supposedly the Cayman has no problems in the handling department, so the 335i may be fine without one.
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      04-26-2006, 09:19 AM   #8
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don't worry, if you start to spin one of the rears the car will just kill power from the motor!

thanks DSC
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      04-26-2006, 10:48 AM   #9
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Quote:
Originally Posted by ward
don't worry, if you start to spin one of the rears the car will just kill power from the motor!

thanks DSC
And THAT is what the topictarter(and me included)don't want DSC interference or DSC offne (inside wheel) spinning, not having traction at all.
An LSD can make a rwd car tend to UNDERSTEER more when turning in the bend(2 rearwheels pushing the car into understeer first) , but you can floor it or lift off to get out of that situation depending on which state the car is in and how many HP the car has
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      04-26-2006, 11:00 AM   #10
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Quote:
Originally Posted by Hotan Braskey
But, supposedly the Cayman has no problems in the handling department, so the 335i may be fine without one.
LSD has absolutely no affect upon handling, per se - what it does affect is power delivery during corner exit. A LSD equipped RWD car distributes power to the rear wheels in such a way that maximizes traction, enabling the driver to use the engine's power to help rotate the car's rear axle - this basically means less understeer and more power to the ground when applying throttle, so the driver can effectively apply power sooner when exiting a corner. This can make a huge difference in lap times.

With an open differential, much of the power will be wasted on the inside drive wheel (which will spin without abandon) - increasing understeer and reducing acceleration. This isn't so much a problem in a fairly weak car like a 325i (I've seldom found a pronounced need for an limited slip in my 323i aside from some tighter hairpins), but with 300 hp and 300 ft-lbs of readily available torque, the 335i is really going to suffer for it.

Based on the numbers I've seen, a 335i with an LSD and a bit of minor suspension work has the potential to be an E46 M3 killer - but BMW isn't going to give it to us that easily. Nevertheless, anybody who actually takes the time to track their 335i will probably invest in the needed goodies at some point, so M3 drivers had better watch out.

The only real upside to not having an LSD (besides a reduction in the mechanical complexity of the drivetrain) is the fact that open diff equipped cars are more stable and easier to drive than LSD equipped cars - but, as we all know, stability (whether referring to cars, boats or airplanes) usually means an equally staid level of agility.
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      04-26-2006, 11:42 AM   #11
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Are there two conflicting views there?

Quote:
An LSD can make a rwd car tend to UNDERSTEER more
Quote:
With an open differential... increasing understeer
I've felt what seems to be more understeer with an LSD (noticed this on small roundabouts), but with ways to get round it (power or lift off) as RobinHood said. With an open diff, couldn't it become unstable if you suddenly get the inside wheel spinning - is there a weight distribution that may spit the back out (into a slide, but one with more of the drive being wasted than if there was an LSD). I think the LSD makes the transition to oversteer more gradual and you can then keep on the power.
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      04-26-2006, 11:53 AM   #12
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Quote:
Originally Posted by JonMad
Are there two conflicting views there?




I've felt what seems to be more understeer with an LSD (noticed this on small roundabouts), but with ways to get round it (power or lift off) as RobinHood said. With an open diff, couldn't it become unstable if you suddenly get the inside wheel spinning - is there a weight distribution that may spit the back out (into a slide, but one with more of the drive being wasted than if there was an LSD). I think the LSD makes the transition to oversteer more gradual and you can then keep on the power.
JonMad indeed! It's a bit logical thinking. And driving/ feeling it too. But it's not a point of view actually, it's just pretty logical: 2 rearwheels pushing the car into understeer first(into the bend) instead of one(without a LSD)wheel only, actually not doing anything with the car. After the UNDERSTEER you can play more with the throttle(midcorner and out of the bend) and have enough traction to get out of that bend. Drive a E46 M3 without DSC/DTC and it becomes very clear.

Last edited by Robin_NL; 04-26-2006 at 12:14 PM.
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      04-26-2006, 11:56 AM   #13
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Are you agreeing or disagreeing, I can't tell I was agreeing with you, I think!

I'd like to try an E46 M3 but for now I will have to stick to my LSD-equipped MX-5.
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      04-26-2006, 11:59 AM   #14
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Quote:
Originally Posted by JonMad
Are you agreeing or disagreeing, I can't tell I was agreeing with you, I think!

I'd like to try an E46 M3 but for now I will have to stick to my LSD-equipped MX-5.
LOL, I'm agreeing with you man

Even a F50 has understeer
http://www.kicken.com/funnyfiles2/ww...rari.crash.mpg
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      04-26-2006, 12:00 PM   #15
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that's what I thought
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      04-26-2006, 12:08 PM   #16
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Quote:
Originally Posted by stressdoc
Limited slips are great. They even out traction between the rear wheels, making power slides and life in the fast lane in general much more fun. Plus any low traction (snow, wet) conditions are easier to handle. The potential downside is the increased traction can put more stress on the drivetrain. So if there are any weak links -- transmission, mounts, etc. -- then problems are more likely. IMO, the 335si should come with DSG and an LSD. And without saying, the M-pack. That would be an effective S4 killer. If you don't want a V8 M3, that would be the ticket.
100% agree with you across the board. I'd LOVE to have LSD on the 335i. I wish it was standard. And of course, have those other 2 options as well, the DCT/ZSG and an M-pack. This would make the car complete! However, I'll take it as a 95% fit anyway, still very excited by everything it has to offer!
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      04-26-2006, 12:29 PM   #17
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I know you guys want these cars to be race cars, but they are not. I mean I have had real race cars with posi and such and it takes some skill to drive them. The back wheels are spinning like mad with over 500 hp and a locker in the a$$. We are talking about BMW's that are luxury cars aren't we? Not a seat with a gauge cluster, a 500+ ci motor and a tubbed rear end to hold all the tire.

LSD. LOL I had one on my Jeep for off roading. They do work pretty well.

This car I built had quite a bit of HP and some really skinny tires. Talk about breaking the tires loose. From a rolling start it went pretty good though.

http://www.corvetteforum.net/classics/curtis/
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      04-26-2006, 12:42 PM   #18
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For a good time, go to:
http://www.quaifeamerica.com/
and check out their ATB dif
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      04-26-2006, 03:00 PM   #19
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Just go straight then
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      04-26-2006, 03:33 PM   #20
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Quaife rules.
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      04-26-2006, 03:35 PM   #21
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wait Max torque is at 1300RPM??? HOLYYYY!!!
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      04-26-2006, 04:18 PM   #22
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Quote:
Originally Posted by Robin Hood
JonMad indeed! It's a bit logical thinking. And driving/ feeling it too. But it's not a point of view actually, it's just pretty logical: 2 rearwheels pushing the car into understeer first(into the bend) instead of one(without a LSD)wheel only, actually not doing anything with the car. After the UNDERSTEER you can play more with the throttle(midcorner and out of the bend) and have enough traction to get out of that bend. Drive a E46 M3 without DSC/DTC and it becomes very clear.
That's basically what I was trying to say - I was talking about corner exit, not entry. Sorry for any confusion.
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