anyone tried the DINAN 3.91 Limited Slip Differential?

AtoB · 03-23-2008, 07:09 PM

i wondering how muck quicker it is.... a 1/10 faster.. more?
any of you math gurus have any way to calculate the difference from our 3.62 to the 3.91?

pbdm4k · 03-23-2008, 07:27 PM

c'mon man!

TECHNICAL FORUM!

AtoB · 03-23-2008, 08:31 PM

Quote:

Originally Posted by pbdm4k

c'mon man!

TECHNICAL FORUM!

i hear you... but it'll hardly get looked there. plus, i'm asking if anyone has done this mod... cut me a little slack here.

GP20 · 03-23-2008, 09:59 PM

Quote:

Originally Posted by AtoB

i wondering how muck quicker it is.... a 1/10 faster.. more?
any of you math gurus have any way to calculate the difference from our 3.62 to the 3.91?

3.91 divided by 3.62.

epbrown · 03-24-2008, 01:42 AM

It's much more common in the E46 M3 world, where conventional wisdom is that it shaves 2 tenths off your 0-60. You might look up Luminor on Z4coupeaddicts.com - Scott had this done almost immediately and raves about it, but he went with the 4.10.

I'm definitely doing this mod myself, but I'm still up in the air about which to get. If I continue with the Z4MC as my daily driver, I'm prety sure I'll go with the 3.91 gears as that will at least keep my highway mileage sane, while adding grunt in the first 4 gears.

If I get a daily driver after I sell my Z4 2.5i (I'm thinking E46 cab with hardtop for winter), then fuel costs be damned and in with the 4.10!

AtoB · 03-24-2008, 07:48 AM

Quote:

Originally Posted by epbrown

It's much more common in the E46 M3 world, where conventional wisdom is that it shaves 2 tenths off your 0-60. You might look up Luminor on Z4coupeaddicts.com - Scott had this done almost immediately and raves about it, but he went with the 4.10.

I'm definitely doing this mod myself, but I'm still up in the air about which to get. If I continue with the Z4MC as my daily driver, I'm prety sure I'll go with the 3.91 gears as that will at least keep my highway mileage sane, while adding grunt in the first 4 gears.

If I get a daily driver after I sell my Z4 2.5i (I'm thinking E46 cab with hardtop for winter), then fuel costs be damned and in with the 4.10!

thank you! this is the kind of info i wanted... i'm not sure i'm willing to part with the 3K... i know my wife isn't, she had dreams of a new floor in the kitchen. but i am playing twith the idea, and if by some miracle i stumble accross them deeply discounted... i want to have enought info to make a quick decision.

AtoB · 03-24-2008, 07:49 AM

Quote:

Originally Posted by GP20

3.91 divided by 3.62.

1.08? now what?

epbrown · 03-24-2008, 08:27 AM

I know what you mean about the money. I bought my oem CSLs on eBay and made one bid. I made a deal with myself that if someone outbid me, I'd skip the wheels and get the diff. When I won, it was like "Yes! Aw, man..."

Dammitt would likely be better at this, but the 3.91 gears should improve acceleration by 8%, the 4.10 by 14%, but acceleration is a curve and that doesn't allow for drag or whatever and blah blah blah.

My guess is that with the 3.91 the 0-60 times would rival the base 997 - the M has similar horsepower, weight, and gearing after the swap. The 911 has a taller first, but we have a higher redline. Definitely, it makes the Z4MC an even more impressive bang for the buck.

AtoB · 03-24-2008, 08:40 AM

http://www.z4coupeaddicts.com/showth...hlight=Luminor

this was helpful.... gave me some insight... and pause.
and who could blame you on the CSL's... they are GORGEOUS! on the M.
if i could find a reasonable set, i'd grab them. thanks again!

ac

Dammmittt · 03-24-2008, 11:01 AM

I would be helpful if I took the time to really understand how gear and differential ratios work...but I haven't...so whatever you say sounds good to me

GP20 · 03-24-2008, 11:31 AM

Quote:

Originally Posted by AtoB

1.08? now what?

If you want to find the difference in RPM when it's at 2000 with the 3.62. Then time 2000 by 1.08. If you want to find out the difference in WHP or torque, time the stock figures by 1.08. If you want to find out the difference in MPH at a certain RPM, time it by 1.08. Etc, etc. Same thing with the 4.10; (4.10/3.62).

AtoB · 03-24-2008, 12:45 PM

Quote:

Originally Posted by GP20

If you want to find the difference in RPM when it's at 2000 with the 3.62. Then time 2000 by 1.08. If you want to find out the difference in WHP or torque, time the stock figures by 1.08. If you want to find out the difference in MPH at a certain RPM, time it by 1.08. Etc, etc. Same thing with the 4.10; (4.10/3.62).

uhhh... maybe i'll just stick with a set of CSL's. i finally figured out 'offsets' recently....

this will probably cause my head to pop off. thanks though.

Dammmittt · 03-24-2008, 01:28 PM

Quote:

Originally Posted by AtoB

uhhh... maybe i'll just stick with a set of CSL's. i finally figured out 'offsets' recently....

this will probably cause my head to pop off. thanks though.

Really? Would you like to explain it to me...never did figure that out...

AtoB · 03-24-2008, 01:46 PM

Quote:

Originally Posted by Dammmittt

Really? Would you like to explain it to me...never did figure that out...

now you're just being mean.... do you want to lose your place in line for my RPI scoop?

Dammmittt · 03-24-2008, 03:20 PM

No...I'm actually being serious...I have zero clue about offsets...the only thing I can tell you is that the Z4Ms have very similar (exact maybe?) offsets compared to the M3.

RCNet · 03-24-2008, 03:43 PM

Here's a really good thread on everything differential. http://www.bimmerfest.com/forums/sho...d.php?t=237063 It includes info and tables with speeds and rpms on different setups with rear ends and wheel size.

If you look closely you'll see "Doubting Dammmittt" involved in the conversation, so he's holding out on you. I think knows more than he's letting on.

vachss · 03-24-2008, 04:51 PM

Before you get *too* excited about differential swaps, remember that the non-M Z4 3.0si Roadster has a 3.23 rear while the 3.0si Coupe has 3.46 - a 7% difference yet they get essentially the same 0-60 time. If you ever have to upshift the diff swap may buy you less than you think.

Dammmittt · 03-24-2008, 06:00 PM

Quote:

Originally Posted by RCNet

Here's a really good thread on everything differential. http://www.bimmerfest.com/forums/sho...d.php?t=237063 It includes info and tables with speeds and rpms on different setups with rear ends and wheel size.

If you look closely you'll see "Doubting Dammmittt" involved in the conversation, so he's holding out on you. I think knows more than he's letting on.

I forgot about that...just cuz I'm an engineer doesn't mean I know EVERYTHING

jarrow · 03-24-2008, 06:17 PM

Does changing the differential have any effect on the speedometer?

Dammmittt · 03-24-2008, 06:26 PM

Quote:

Originally Posted by jarrow

Does changing the differential have any effect on the speedometer?

I don't think so, the speedo gets it's speed by measuring wheel rotations.

AtoB · 03-25-2008, 08:02 AM

Quote:

Originally Posted by vachss

Before you get *too* excited about differential swaps, remember that the non-M Z4 3.0si Roadster has a 3.23 rear while the 3.0si Coupe has 3.46 - a 7% difference yet they get essentially the same 0-60 time. If you ever have to upshift the diff swap may buy you less than you think.

that is what i'm starting to conclude.... not worth the money and sacafice.

03-23-2008, 07:09 PM	#1
AtoB Major 112 Rep 1,262 Posts Drives: Z4M Join Date: Jan 2007 Location: Boston iTrader: (3)	anyone tried the DINAN 3.91 Limited Slip Differential? i wondering how muck quicker it is.... a 1/10 faster.. more? any of you math gurus have any way to calculate the difference from our 3.62 to the 3.91? Attached Images
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03-23-2008, 07:27 PM	#2
pbdm4k Lieutenant Colonel 74 Rep 1,689 Posts Drives: 2010 335d Join Date: May 2007 Location: North of the Border iTrader: (3)	c'mon man! TECHNICAL FORUM! __________________ 2010 BMW 335d "Ha! She wants the D." 2006 VW Jetta 2.5 Once upon a time... '03 VW GTI, '99 Audi A4 1.8TQ, '00 VW Jetta 1.85T, '09 BMW 335i xDrive, '04 BMW Z4 3.0i, '01 Audi TT 1.8T, '04 Volvo S80 2.5T
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03-24-2008, 01:42 AM	#5
epbrown Colonel 60 Rep 2,128 Posts Drives: BMW M Coupe, Porsche Boxster S Join Date: May 2007 Location: Chicago, IL iTrader: (0)	It's much more common in the E46 M3 world, where conventional wisdom is that it shaves 2 tenths off your 0-60. You might look up Luminor on Z4coupeaddicts.com - Scott had this done almost immediately and raves about it, but he went with the 4.10. I'm definitely doing this mod myself, but I'm still up in the air about which to get. If I continue with the Z4MC as my daily driver, I'm prety sure I'll go with the 3.91 gears as that will at least keep my highway mileage sane, while adding grunt in the first 4 gears. If I get a daily driver after I sell my Z4 2.5i (I'm thinking E46 cab with hardtop for winter), then fuel costs be damned and in with the 4.10!
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03-24-2008, 08:27 AM	#8
epbrown Colonel 60 Rep 2,128 Posts Drives: BMW M Coupe, Porsche Boxster S Join Date: May 2007 Location: Chicago, IL iTrader: (0)	I know what you mean about the money. I bought my oem CSLs on eBay and made one bid. I made a deal with myself that if someone outbid me, I'd skip the wheels and get the diff. When I won, it was like "Yes! Aw, man..." Dammitt would likely be better at this, but the 3.91 gears should improve acceleration by 8%, the 4.10 by 14%, but acceleration is a curve and that doesn't allow for drag or whatever and blah blah blah. My guess is that with the 3.91 the 0-60 times would rival the base 997 - the M has similar horsepower, weight, and gearing after the swap. The 911 has a taller first, but we have a higher redline. Definitely, it makes the Z4MC an even more impressive bang for the buck.
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03-24-2008, 08:40 AM	#9
AtoB Major 112 Rep 1,262 Posts Drives: Z4M Join Date: Jan 2007 Location: Boston iTrader: (3)	http://www.z4coupeaddicts.com/showth...hlight=Luminor this was helpful.... gave me some insight... and pause. and who could blame you on the CSL's... they are GORGEOUS! on the M. if i could find a reasonable set, i'd grab them. thanks again! ac
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03-24-2008, 11:01 AM	#10
Dammmittt My favorite sign. 169 Rep 4,333 Posts Drives: 2007 M Coupe Join Date: Dec 2006 Location: Der Autobahnen iTrader: (0)	I would be helpful if I took the time to really understand how gear and differential ratios work...but I haven't...so whatever you say sounds good to me __________________ 07 ///M Coupe (Premium Package) Black Saphire Ext. Imola Red Int. Best Website EVER!
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03-24-2008, 03:20 PM	#15
Dammmittt My favorite sign. 169 Rep 4,333 Posts Drives: 2007 M Coupe Join Date: Dec 2006 Location: Der Autobahnen iTrader: (0)	No...I'm actually being serious...I have zero clue about offsets...the only thing I can tell you is that the Z4Ms have very similar (exact maybe?) offsets compared to the M3. __________________ 07 ///M Coupe (Premium Package) Black Saphire Ext. Imola Red Int. Best Website EVER!
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03-24-2008, 03:43 PM	#16
RCNet Woof!! 5 Rep 111 Posts Drives: 2006 Ti Silver Z4 M Coupe Join Date: Apr 2007 Location: SW Washington iTrader: (0)	Here's a really good thread on everything differential. http://www.bimmerfest.com/forums/sho...d.php?t=237063 It includes info and tables with speeds and rpms on different setups with rear ends and wheel size. If you look closely you'll see "Doubting Dammmittt" involved in the conversation, so he's holding out on you. I think knows more than he's letting on. __________________ 2006 Ti Silver Z4 M Coupe 2009 Deep Sea Blue 535i xDrive Sports Wagon
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03-24-2008, 04:51 PM	#17
vachss Captain 55 Rep 815 Posts Drives: Z4 Coupe Join Date: Jan 2008 Location: Ventura County, CA iTrader: (1)	Before you get too excited about differential swaps, remember that the non-M Z4 3.0si Roadster has a 3.23 rear while the 3.0si Coupe has 3.46 - a 7% difference yet they get essentially the same 0-60 time. If you ever have to upshift the diff swap may buy you less than you think.
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03-24-2008, 06:17 PM	#19
jarrow Private First Class 6 Rep 150 Posts Drives: 2004 Z4 3.0i Join Date: May 2007 Location: Webster, NY iTrader: (5) Garage List 2004 z4 3.0i [2.00]	Does changing the differential have any effect on the speedometer?
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