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      06-17-2010, 06:37 PM   #111
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Originally Posted by zamm3k View Post
this is something I've being looking to get. But damn.... dropping 4300 bucks for it is a bit..... well... too much
Good lord..
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      10-30-2010, 12:13 AM   #112
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What about rpm drops between gears?

I haven't read all of the posts on this thread, so I apologize if this has been addressed. I agree that a FD mod will not increase power, but in "race" conditions a higher differential ratio should narrow the rpm drop when shifting. This narrower drop should result in a high performance car staying in an rpm range that maximizes the horsepower actually used. If folks who purchase an FD mod are willing to drive at consistently higher RPMs, then they are probably experiencing more power because the car is developing more power at those elevated RPMs. Am I missing something here?

I just ordered a new DCT today and I'm toying with an FD mod because:

1. I think it will make the M3 feel a little like my close ratio geared down CBR1000rr
2. It will be more enjoyable around town
3. It's emission legal, (I think)
4. It's quiet
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      10-31-2010, 03:31 PM   #113
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There's a noticeable whine from the diff while cruising around
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      11-03-2010, 03:50 PM   #114
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Here's my real world experience with the 4.10 FD installed in my 2009 E92 M3 6MT. I've got around 14,000 miles on the 4.10 and well over 100 autocross laps. Other mods include the Active Autowerks exhaust, oiled air filter, Dinan springs, Dinan chip with 8600-rpm redline, UUC SSK and Dinan throttle bodies.

I don't do 1/4-mile races at tracks, I do occasional rolling start street races (but usually only up to around 100-mph) and I run BMWCCA sanctioned AX. AX is my main performance interest. It should be noted that I live at 5400-ft above sea level, so non-forced induction power adders are not near as effective as at sea level.

Around town the negatives of the 4.10 are poorer fuel economy and slight noise from the gears on the overrun. I expected these things going in and was only worried about the noise level. I can report that it's not bad at all and doesn't bother me, but I DO know it's there. My riders don't say, "What's that noise?", but it is more than stock. The advantages for street driving are in-gear responsiveness and acceleration in-gear. When I street race I hope to start at around 4000 rpm on the rolling start and use the full 8600 rpm redline and only shift once up to 100-mph. Squirting through traffic in 3d, 4th and 5th is clearly more responsive than stock.

If you look at those scientific charts, they're right. The gear ratios were not selected with this FD in mind, such that 1/4-mile time is actually worse, DUE TO THE TIME REQUIRED TO SHIFT. However, the in-gear acceleration can be better with the higher numerical ratio. Also, I'm able to space out my shifts a little more with the extra 200-rpm of redline that my car has.

AX is where the FD really pays off because, other than the 1-2 shift, the entire course is typically run in 2d gear. The 6MT has better acceleration than the DCT in 2d. The DCT will be faster on a road course, but the 6MT will be faster on an AX course.

Top priorities for AX speed are tires, then lightweight and wide wheels that reduce inertia and increase the contact patch and tracking width. Gearing and power come in distant thirds. I lean toward gearing, partly because my high altitude makes power VERY expensive to gain. Gearing is a known that won't be sapped by low oxygen density (my loss is around 16% vs. sea level). With my current setup (awaiting new, lighter 18" wheels and a switch to Dunlop Direzza tires) my car will spin its wheels anywhere on the course.

Anyway, I think that my case demonstrates there's no one absolute fastest answer. The answer is more like, "It depends on what you're doing." If you do standing start 1/4-mile races and that's important to you, then listen to the techno data. That is really, really true. Shifting time DOES cost speed. However, if you run events where shifitng is limited, you'll still want to minimize shifting time by either strategy or higher redline, or both, but it will not be as important to you as in a 1/4-mile event. A higher numeric gear ratio can be an advantage in events where there is little or no shifting.

I like the feel of the gearing with a 4.10 FD and I think it's quicker for AX.

Dave
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      01-16-2012, 02:29 PM   #115
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I found this thread on a search and it has proven to be most useful and also kind of what I expected. I was thinking of this mod on the m3 but given my experience on my s2000 and other cars, I expected this problem here too.

Let me chime in a few things:

a) When you do the differential mod, there is ALWAYS a trade off - simple engineering and math basics.

b) What you think you gain in "feel", you lose elsewhere in mileage, early shifting, more noise and chatter....

c) I did the diff/gear mod on my s2000 and found myself shifting much more often and on highway speeds it was ridiculous - I was going only 70 mph and the RPM's were in the 4000k range! The s2000 is already a loud car and doing this mod made it even worse.

I know the m3 is a more refined car but the side effects will be the same....

Guess I'm passing on this mod!
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      01-16-2012, 03:44 PM   #116
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Quote:
Originally Posted by s4play View Post
I found this thread on a search and it has proven to be most useful and also kind of what I expected. I was thinking of this mod on the m3 but given my experience on my s2000 and other cars, I expected this problem here too.

Let me chime in a few things:

a) When you do the differential mod, there is ALWAYS a trade off - simple engineering and math basics.

b) What you think you gain in "feel", you lose elsewhere in mileage, early shifting, more noise and chatter....

c) I did the diff/gear mod on my s2000 and found myself shifting much more often and on highway speeds it was ridiculous - I was going only 70 mph and the RPM's were in the 4000k range! The s2000 is already a loud car and doing this mod made it even worse.

I know the m3 is a more refined car but the side effects will be the same....

Guess I'm passing on this mod!
Comparing the 4.10 mod in the M3 to some unstated ratio change in a S2000 is faulty logic. Just because you overdid it in your S2000 doesn't mean that this is a bad mod in an E92 M3.

There is NO CHATTER added with the 4.10FD. Noise increase is moderate enough that my wife doesn't notice it. Gas mileage change is proporsional to the ratio change.

If you're looking for better mid-gear response below 90-mph or if you plan to autocross a 6MT and it's legal in your class, this is a good mod, particularly if you combine it with an 8600-rpm redline.

If you want to decrease your 1/4-mile time, then this may not be a good mod, because it'll add a shift near the end of your run, unless can raise the redline enough.

It's not for everyone, for sure, so consider your usage before jumping on it.

Dave
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      01-16-2012, 08:19 PM   #117
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Quote:
Originally Posted by s4play View Post
I found this thread on a search and it has proven to be most useful and also kind of what I expected. I was thinking of this mod on the m3 but given my experience on my s2000 and other cars, I expected this problem here too.

Let me chime in a few things:

a) When you do the differential mod, there is ALWAYS a trade off - simple engineering and math basics.

b) What you think you gain in "feel", you lose elsewhere in mileage, early shifting, more noise and chatter....

c) I did the diff/gear mod on my s2000 and found myself shifting much more often and on highway speeds it was ridiculous - I was going only 70 mph and the RPM's were in the 4000k range! The s2000 is already a loud car and doing this mod made it even worse.

I know the m3 is a more refined car but the side effects will be the same....

Guess I'm passing on this mod!
I've just never, ever, ever understood the "shift more often comments". From rest I use first gear. At speed I use top gear (7th in my M3, but I also have an S2k) unless I'm going less then 35, which is quite rare. I don't skip gears. So, the only opportunity to "shift more often" is when down shifts are required for acceleration. An FD mod makes this less necessary.

I have a 4.44 rear in my S2k, and I shift slightly LESS than with the stock 4.10. In reality, the amount of shifting is almost identical, but there are rare occasions when I don't downshift due to the 4.44 when I might have with the stock 4.10.

The S2000 is faster in every scenario with the 4.44. I have copious pbox data to support this. This, of course, does not apply directly to results obtained with a different ratio in the e9x M3.
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      01-16-2012, 08:26 PM   #118
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I've got the 3.45 (DCT of course) and couldn't imagine the car without it. I think it's the perfect ratio for the DCT in a track setting, as the added torque coming out of corners is an advantage but it is an expensive mod and definitely pushes the boundaries of the placebo effect. I always geared up on my bikes and just love the peppier feel of the car as well, on top of helping the low torque problem :
J/k
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      01-18-2012, 01:58 PM   #119
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Without the 3.62 diff I would have sold my M3. sorry but 0-20mph on a stock M3 dct feels the same as a 328. I raced a stock dct and pulled every time 1-2 car lengths up to 100mph. Also for all you weirdos who keep trying to convey that it is not faster...stop crying! who cares, we are happy and you are strangely upset???
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      01-18-2012, 02:19 PM   #120
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I agree my s2000 feels "quicker" with the 4.44. gears - but it topped out way too early and I lost too much highway cruising speed for the gain to make sense as a DD.

At 70-80mph on the freeway, I was turning well over 4000rpm in 6th gear which just does not work for a DD (track car maybe).

I do have one question, it seems the m3 is various gear offerings:

4:10
3:62
3:45

(why all the variations? Does the 6-speed manual and DCT have different options?)


thanks!
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      01-18-2012, 04:03 PM   #121
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Yes, the 3.62 & 3.45 replace the stock DCT diff of 3.15. The 4.10 replaces the 6MT diff of 3.85.
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      01-19-2012, 01:30 AM   #122
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FYI, I run at 3500 rpm going 80 on my DCT, not bad at all on the highway with the 3.45.
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      01-20-2012, 11:52 PM   #123
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Quote:
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FYI, I run at 3500 rpm going 80 on my DCT, not bad at all on the highway with the 3.45.
Did you do any 1/4 mile tests? I'm curious as to what they may have been before and after the diff mod. I have not replaced my Diff on my M3 yet but was considering this mod.
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      04-01-2014, 01:15 PM   #124
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I haven't heard much about other people's experience, but I'm lining up a bunch of work on the rear-end for me E92, turner bushings, uprated sway bar, etc. I also figured I might as well go for broke and ordered a 4.44. Currently waiting for it's arrival from Germany.

I'm now torn on LSD units, whether or not to change out the M variable for a ramping setup...
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      04-01-2014, 02:02 PM   #125
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I haven't heard much about other people's experience, but I'm lining up a bunch of work on the rear-end for me E92, turner bushings, uprated sway bar, etc. I also figured I might as well go for broke and ordered a 4.44. Currently waiting for it's arrival from Germany.

I'm now torn on LSD units, whether or not to change out the M variable for a ramping setup...
What kind of mods do you have on the car?
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      04-01-2014, 02:14 PM   #126
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What kind of mods do you have on the car?
Currently:

6MT (should clarify)
Dinan pulley & intake
BPM Tune Stage 1
Ultimate Clutch Pedal

Awaiting install:

Turner Solid Al Sub-Frame Bushings
Turner Solid Al/Delrin Diff Carrier Bushings
RD Sport Rear Sway
Adjustable Toe Endlinks

Near future:
CAE Shifter
UUC DSSR
Al/Delrin Engine/Tranny mounts

I'm walking a fine line in regards to pulling the trigger on a weld-in cage in the next 12-18 months, I already drive the car very little. I'm simply torn about the LSD carrier, the diff will be open and disassembled, should I swap it out for something a bit more fun? In the future I'll add a cooling-circuit, however a full race unit is a bit extreme for the current time being.
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      04-01-2014, 02:21 PM   #127
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Quote:
Originally Posted by sterile stork View Post
Currently:

6MT (should clarify)
Dinan pulley & intake
BPM Tune Stage 1
Ultimate Clutch Pedal

Awaiting install:

Turner Solid Al Sub-Frame Bushings
Turner Solid Al/Delrin Diff Carrier Bushings
RD Sport Rear Sway
Adjustable Toe Endlinks

Near future:
CAE Shifter
UUC DSSR
Al/Delrin Engine/Tranny mounts

I'm walking a fine line in regards to pulling the trigger on a weld-in cage in the next 12-18 months, I already drive the car very little. I'm simply torn about the LSD carrier, the diff will be open and disassembled, should I swap it out for something a bit more fun? In the future I'll add a cooling-circuit, however a full race unit is a bit extreme for the current time being.
I asked about the mods because I can generate a simulation of your results based on actual dyno files in the Dyno Database. With those mods, I'd say you're around 355-360 whp. I'll see if I can find something in that territory and generate some simulations comparing this FD to stock and 4.10. It will give you an idea what kind of performance you can expect with the 4.44 FD mod.
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      04-01-2014, 03:41 PM   #128
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Quote:
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I asked about the mods because I can generate a simulation of your results based on actual dyno files in the Dyno Database. With those mods, I'd say you're around 355-360 whp. I'll see if I can find something in that territory and generate some simulations comparing this FD to stock and 4.10. It will give you an idea what kind of performance you can expect with the 4.44 FD mod.
Wow! Thank you very much. I most certainly didn't expect for such extensive research as that, but sincerely appreciate the thought and would be delighted to see the comparisons!
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      04-01-2014, 03:55 PM   #129
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The 4.44s are going to be to short, I wouldn't go beyond a 4.10 rato for the diffy. Also, tire spin is a problem with 3.85s. Imagine with 4.44s I hope you are running drag radials everywhere you go.

I think the 4.44s will actually make you slower as time in gear will be quite a bit less unless you raise the rev limit. As far as which LSD to run I would contact diffsonline, this is where most vendors get their diffys.


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      04-01-2014, 04:32 PM   #130
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Quote:
Originally Posted by Novus View Post
Yes, the 3.62 & 3.45 replace the stock DCT diff of 3.15. The 4.10 replaces the 6MT diff of 3.85.
There used to be some awesome discussion in some threads from back in the day with PencilGeek, not sure if it can be dug up somehow. I think DCT guys should stay away from the 3.62 by all means. The 3.45 works well with the DCT and most 6MT guys that went with the 4.1 seem to love it.

FYI: I believe you would get the same/similar torque multiplication if you ran an 18" wheel with 265/30 rather than the stock 265/40series tire and see if you like it before you do the diff conversion. Your speedometer would be off but you should see about a 8% increase in torque. The DINAN will give you 6.5% but the tire swap is a cheaper route and easier.
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      04-01-2014, 04:36 PM   #131
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The 4.44s are going to be to short, I wouldn't go beyond a 4.10 rato for the diffy. Also, tire spin is a problem with 3.85s. Imagine with 4.44s I hope you are running drag radials everywhere you go.

I think the 4.44s will actually make you slower as time in gear will be quite a bit less unless you raise the rev limit. As far as which LSD to run I would contact diffsonline, this is where most vendors get their diffys.


Dave
I've come across a bit of tire spin tales with the 4.10, however for track purposes and appropriate compounds, I'm optimistic that it will suffice, particularly with a 275/30 or 285/30 application. If not, the choice will definitely add to the lively-nature of the car. I'll reach out to diffsonline for sure, in the meantime, I'm looking for any feedback from individuals that have gone with non-factory units, OS GIKEN, QUAIFE, DIFFSONLINE, etc. Thanks for the guidance!
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      04-01-2014, 05:02 PM   #132
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There's a noticeable whine from the diff while cruising around
yeah and it sounds AMAZING
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