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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > M Series > E46 M3 (2001-2006)

E46 M3 (2001-2006)

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  #1  
Old 10-27-2008, 07:42 PM
blord1124 blord1124 is offline
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Location: Seattle
 
Join Date: Apr 2008
Posts: 27
Mein Auto: 2004 E46 BMW M3
M3 with Dinan 3.91 LSD

In my constant struggles to successfully find someone who has installed the Dinan 3.91 Limited-Slip Differential (LSD) in a NON-supercharged/FI E46 M3 - I failed. This is my post for the few people who are interested in doing it but were not able to find much information on it. Dinan has their sales-pitch on their website which I've read countless times... and the Z4M forums have a few postings about the Dinan 3.91 for THAT car... but not specifically the E46 M3. Here is my soliloquy...

I took the plunge. The only modifications I have are the Dinan short shifter, the Dinan D900-34M software and now the Dinan 3.91 LSD.

Naturally, I felt like everyone else does who owns an M3 and wants more power of it but could not justify dropping thousands of dollars for 20-30 bhp and 20lbft torque. I figured if I'm going to spend the money, i want to get a substantial difference; hence, the Dinan 3.91 LSD.

The bad new is that it's a 1200 mile break-in period. Once the mileage is met, I take it back in to get the differential fluid changed.... THEN, I can get after the throttle. Dinan specifically mentions that during the break-in period to keep the car 2/3 it's max speed in any gear and 2/3 throttle.

I CAN tell you without equivocation that driving away from BMW Seattle, I could feel a difference in the way the car drove. It feels more like a sports car. Simply put, you get through the gears faster. For those searching for the arithmetic:

3.62/3.91 = .9258

1-.9258 = .0742

.0742 X 100 = 7.42%

If you want to know the difference in RPM on a stock E46 M3 differential (3.62) vs. the Dinan 3.91 - take whatever RPM you want and multiply it by 1.074

In short, in the stock M3, I cruised at about 2700 rpms in 6th gear going 70 miles per hour. Now, in 6th gear, cruising at 70 miles per hour, I'm at 2900 rpms... only 200 rpms more at cruising speed... hence Dinan's "only a minor increase in engine speeds at cruise" (per their website www.dinancars.com).

Thanks to simple machines, I'm putting down more torque to the road which means attempting to squeeze whatever bhp and torque out of the engine in the future will be multiplied through (not by a whole integer, rather 2-8% increase in bhp/torque might be easier felt with the effortless leverage of the 3.91 final drive).

In 1170 more miles till break-in period is over, then... an update.
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Dinan D550-1001 Short-Shift Kit
Dinan D900-34M Performance Engine Software
Dinan D903-34M3 Stage 3 Engine Software
Dinan D903-34M4 Stage 4 Engine Software
Dinan D773-0462 3.91 Limited Slip Differential
Dinan D763-1600 High Flow Intake/Air Mass Meter Housing
Dinan D660-4604 Free Flow Exhaust
Dinan D760-3400 High Flow Throttle Bodies

Last edited by blord1124; 10-28-2008 at 11:10 AM.
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  #2  
Old 10-29-2008, 01:08 AM
MVF4Rider MVF4Rider is offline
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Location: Germany
 
Join Date: Aug 2008
Posts: 164
Mein Auto: Z4 M Coupe, E90 330xi
For sure this is the best "bang for the buck" mod to increase acceleration. Acceleration is all about torque delivered to the road, and the 3.91 final gear increases road torque by 8% in any gear at any rpm. Gearing is a torque multiplier (which is why engine torque without consideration to the gearing doesn't mean as much). I've seen conservative estimates showing as much as 3 to 4 tenths off a 0-100 km/h times with no other change. That's significant. Under full throttle, you'll shift sooner as the car will rev quicker, and theoretical top speed per gear is a little lower, but the car won't do its theoretical top speed anyway in 6th gear due to drag. I'm going to buy a E46 M3 next year (to go along side with my Z4 M) and I plan to do this mod as well as install a lightweight flywheel/clutch (street compound). Freeing up lost power also goes a long way toward increasing engine torque to the pavement.
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Last edited by MVF4Rider; 10-29-2008 at 01:24 AM.
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  #3  
Old 11-02-2008, 10:53 AM
blord1124 blord1124 is offline
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Location: Seattle
 
Join Date: Apr 2008
Posts: 27
Mein Auto: 2004 E46 BMW M3
An update...

She's fast... significantly faster... I still haven't had the car above 5000 rpms due to the differential break-in period (1200 miles) - but, it is fast... feels like a brand new car.

From here, I'm going going to get the car to breathe better via the Dinan intake/throttle bodies/exhaust systems/software and be done with it. I'll be 361 bhp and 281 ftlbs - but with the Dinan 3.91 LSD, it will be pretty dramatic (for a naturally aspirated S54 engine).
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Dinan D550-1001 Short-Shift Kit
Dinan D900-34M Performance Engine Software
Dinan D903-34M3 Stage 3 Engine Software
Dinan D903-34M4 Stage 4 Engine Software
Dinan D773-0462 3.91 Limited Slip Differential
Dinan D763-1600 High Flow Intake/Air Mass Meter Housing
Dinan D660-4604 Free Flow Exhaust
Dinan D760-3400 High Flow Throttle Bodies
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  #4  
Old 02-07-2009, 03:31 PM
Orthokid Orthokid is offline
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Location: Monterey
 
Join Date: Feb 2009
Posts: 1
Mein Auto: M3
So I'm sure you're past the break in period now. What do you think? I've been considering doing the gears for a bit now and would like a real world
Opinion? Thanks
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  #5  
Old 02-08-2009, 04:05 AM
PYGM PYGM is offline
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Location: Singapore
 
Join Date: Feb 2009
Posts: 4
Mein Auto: E46 M3
Hi, would love an update on this. Your thread encouraged me to go for the plunge!! I have an evosport 3.91 LSD on the way (three clutch with aysimetric ramps for street). Should be here in a week or so. My current LSD is clunking a bit so time for the upgrade. I have some performance box metrics from track use to do a proper comparison of performance improvements - but will only be able to do this a couple of months from now. My lightweight flywheel is already in.

How is the Dinan? What is it like as a daily driver? What about hard usage? Also, do you have smg and has this experience changed for you?
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  #6  
Old 02-08-2009, 11:34 AM
blord1124 blord1124 is offline
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Location: Seattle
 
Join Date: Apr 2008
Posts: 27
Mein Auto: 2004 E46 BMW M3
update on Dinan 3.91

In short, the 3.91 (in my case, Dinan) is really what the M3 should have had in it stock. Perhaps fuel efficiency was the biggest reason why they didn't do so... I'm not sure. With the stock differential, I found the 5th gear (manual transmission) to be pretty useless. With the 3.91, I use 5th gear all the time. It feels even more like a driver's car. First gear is NOT useless at all. I never start in second.

Getting through the gears happens faster... 4th gear on the highways is much more fun.

First gear under full throttle will snap you back significantly harder. Naturally, the increase in torque to the road means with the DSC off, you will find your tires spinning earlier in the RPM range.

It's tough to say how this has affected my gas mileage... It's a lot more fun to drive, so, naturally, I'm on the throttle more lowering the gas mileage anyway. During the differential break-in period I'd get 20-22mpg where as with the stock differential I'd get 22-25. Due to the fact the car is more fun to drive, I find myself in the 16-18 range more often (post differential break-in period).

Most people don't do this modification due to:
1) not knowing what is is, or what it does
2) thinking the only way to increase performance is via adding engine upgrades
3) the cost

Dinan says it best: it's the best way to make the most dramatic difference to the E46 M3 while keeping it naturally aspirated.

Because of torque multiplication, any performance modifications done post 3.91 LSD will be slightly more dramatic than they otherwise would under the stock differential.

Which lightweight flywheel did you get? I'd appreciate it if you could PM me or repost about the difference (if any) that you got with the lightweight flywheel.

Thanks and enjoy the 3.91 when you get it!
__________________

Dinan D550-1001 Short-Shift Kit
Dinan D900-34M Performance Engine Software
Dinan D903-34M3 Stage 3 Engine Software
Dinan D903-34M4 Stage 4 Engine Software
Dinan D773-0462 3.91 Limited Slip Differential
Dinan D763-1600 High Flow Intake/Air Mass Meter Housing
Dinan D660-4604 Free Flow Exhaust
Dinan D760-3400 High Flow Throttle Bodies
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  #7  
Old 02-08-2009, 09:20 PM
PYGM PYGM is offline
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Location: Singapore
 
Join Date: Feb 2009
Posts: 4
Mein Auto: E46 M3
Thanks for the really quick response and update! The waiting, its like Christmas!!

I opted for the Rogue Engineering set up in the end. As I have an SMG, I didn't want to compromise too much on the gear change experience. Neither did I want to increase the noise in the cabin too much. RE used to sell the Performance Clutch System stating that it was OK for SMG but, since I have had it fitted, I have not been able to find any support for this! None the less, the fitment works and it is hard to find a more suitable alternative that strictly supports SMG.

The biggest difference I found was the clutch biting response. This is the first time I have had a competition clutch and, as it bedded in, I had to get used to the snatching that occurred. It still snatches a little in reverse.

The other thing was that the car was much freer revving than before. I think, with the combination of the 3.91 Diff and the LSD, the car will respond much more like a bike than a car!!

With the flywheel lightened by approx 60%+ there is a distinct loss of kinetic energy so the car bogs down a little at the lights when you are trying hard to accelerate. I am hoping that the LSD + light flywheel "package" will counteract this and make the whole car launch well. Its not that the car is no longer capable (far from it), it is more a driver adaptation requirement to compensate for the lack of kinetic energy.

The biggest documented drawback for lightweight flywheels is the chatter and noise. This really hasn't been too much of an issue. There is enough sound proofing in the E46 M3. Also, the RE flywheel does not seem to clatter much at all. The only increased sounds I get are when pushing hard, and also letting off the gas in 5th gear. The sprung hub really seems to work well on this.

On balance, it was a really good upgrade, and part of the greater plan for the car. My clutch needed replacing and the car was much more responsive through the clutch engagement than it was before.

http://www.rogueengineering.com/Merc...gory_Code=LTWF

___________________________________
E46 M3
Upgraded: 200 Cell Sports Cats, Groupe M Air intake, Stoptech BBK w/ Hawk Track Pads, HIOP ECU Upgrade, Bilstein PSS9's, H&R Swaybars, RE Lightweight Flywheel and Competition Clutch, RE Strut Bar, Evosport power pulleys.

On the way: Evosport 3.91 3 way clutch with 30/70 Asymmetrical Ramps
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  #8  
Old 02-18-2009, 08:26 PM
drmillerM3 drmillerM3 is offline
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Location: Louisville, kY
 
Join Date: Feb 2009
Posts: 4
Mein Auto: '04 BMW M3
A guy in our CCA chapter had 4.10 in his e46 M3 that he tracked. It was quite fast.
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  #9  
Old 12-26-2011, 04:30 PM
M3Guy M3Guy is offline
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Location: Greensboro NC
 
Join Date: Sep 2011
Posts: 20
Mein Auto: 2004 M3
Old post I know but I recently put a 3.91 Dinan in my M3 with Rogue El Diablo exhaust (waiting on my AP headers to come in). Big difference for sure. A must upgrade.
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