LSD 3.08 > 3.46 (Gas Mileage?)

NocturnalEVO · 12-02-2014, 06:31 PM

Hey all,

For all the guys who have a 6MT and swapped to an 3.46 LSD, I'm wondering if you guys can comment on how your gas mileage is afterwards.

After doing some reading/researching, I'm reading a lot of people ended up dropping ~2mpg or so based on having the RPM's rev higher while cruising on highway.

I went with an 3.08 MFactory unit (on order), but not gonna lie the 3.46 seems so much more enjoyable.. but afraid of seeing my 21mpg turn into 19mpg lol

Thanks in advance guys!

WilliamS · 12-02-2014, 07:07 PM

Well math would dictate about a 10% change in gas mileage, so if you are getting 20 mpg you would get 18mpg. Not a huge hit. There are other factors at play but thats a decent rule of thumb.

Miller335 · 12-02-2014, 07:33 PM

With as much torque as we have even with stock turbos is a shorter ratio worth it? Esp 6 speed, we lose so much time shifting.

C.Pop · 12-02-2014, 08:06 PM

It would certainly take 3rd gear up a notch.

Some guys have reported improved mileage but just around town, not highway. Maybe something to do with better mech advantage. I've heard 2-3mpg loss on the highway.

ferocity02 · 12-02-2014, 08:08 PM

Quote:

Originally Posted by WilliamS

Well math would dictate about a 10% change in gas mileage, so if you are getting 20 mpg you would get 18mpg. Not a huge hit. There are other factors at play but thats a decent rule of thumb.

I don't think that is a decent rule of thumb. +10% RPM does not translate into -10% MPG. In some cases, gearing up can improve MPG since you would be "bogging down" the motor less, or running at a more efficient operating point. At least that's what I've seen in the Chevy LS world. The end result of a gearing change depends on many many factors, mostly how you drive it and the time spent in city vs. highway. But I'm curious to see what results there are from the BMW world.

NocturnalEVO · 12-02-2014, 11:10 PM

Yea hoping some guys who have the setup can chime in and share their results

Island Road · 12-03-2014, 01:37 AM

I have the setup and made the switch. You loose about 2mpg on the highway but it's a lot of fun for sure and when u are actually on a track (not strip) makes a difference.

MFactory · 12-03-2014, 02:13 AM

What it loses on highway mpg, it more than gains back for traffic light mpg. Gas mileage isn't just about rpm, but also about load/throttle.

It really just depends on what type of driving you do and, of course, your right foot (trust me, most of the mpg hit is because you are actually enjoying the increased acceleration. This normally wears off after a while when you go back to regular driving habits)

Icewall · 12-03-2014, 06:41 AM

mfactory 3.46 in my car. about 2mpg loss.

I like mine but bought it so I could go single turbo.

NocturnalEVO · 12-03-2014, 01:43 PM

thanks for chiming in people!

Asides from the decreased mpg, another concern I had was increased exhaust noise since I'll be revving a little higher on the highway to cruise at 65-70mph

Have you guys found that an issue as well?

12-02-2014, 06:31 PM	#1
NocturnalEVO Stock 173 Rep 1,275 Posts Drives: 2009 E92 335i Join Date: Dec 2006 Location: Long Island, NY iTrader: (8)	LSD 3.08 > 3.46 (Gas Mileage?) Hey all, For all the guys who have a 6MT and swapped to an 3.46 LSD, I'm wondering if you guys can comment on how your gas mileage is afterwards. After doing some reading/researching, I'm reading a lot of people ended up dropping ~2mpg or so based on having the RPM's rev higher while cruising on highway. I went with an 3.08 MFactory unit (on order), but not gonna lie the 3.46 seems so much more enjoyable.. but afraid of seeing my 21mpg turn into 19mpg lol Thanks in advance guys! __________________ '09 E92 335i (6MT) Jet Black/Coral Red '11 E90 328i XDrive (6AT) Jet Black/Saddle Brown (wife's car) '06 Evolution IX MR (sold) '06 R6 Anniversary Edition (sold)
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12-02-2014, 07:07 PM	#2
WilliamS GoofBall 55 Rep 1,055 Posts Drives: 2008 E92 N54 Xdrive Join Date: Jun 2012 Location: Tampa, FL iTrader: (2)	Well math would dictate about a 10% change in gas mileage, so if you are getting 20 mpg you would get 18mpg. Not a huge hit. There are other factors at play but thats a decent rule of thumb.
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12-02-2014, 07:33 PM	#3
Miller335 Colonel 295 Rep 2,189 Posts Drives: 2007 E92 Join Date: Oct 2013 Location: Portland, OR iTrader: (0)	With as much torque as we have even with stock turbos is a shorter ratio worth it? Esp 6 speed, we lose so much time shifting. __________________ 2007 E92 335 6MT w/335is clutch FBO MHD E60 Wedge map 49k miles
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12-02-2014, 08:06 PM	#4
C.Pop First Lieutenant 65 Rep 385 Posts Drives: 335i Join Date: May 2013 Location: AZ iTrader: (0)	It would certainly take 3rd gear up a notch. Some guys have reported improved mileage but just around town, not highway. Maybe something to do with better mech advantage. I've heard 2-3mpg loss on the highway. __________________ 2007 E90, 6MT, VRSF 7" FMIC, RR DP's, Vargas Stage 2+ (19t unclipped), CP-e Charge Pipe/Tial BOV, BMS DCI, Fuel-it! Stg 2 LPFP, E66, 118k+ miles Brentuned
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12-02-2014, 11:10 PM	#6
NocturnalEVO Stock 173 Rep 1,275 Posts Drives: 2009 E92 335i Join Date: Dec 2006 Location: Long Island, NY iTrader: (8)	Yea hoping some guys who have the setup can chime in and share their results __________________ '09 E92 335i (6MT) Jet Black/Coral Red '11 E90 328i XDrive (6AT) Jet Black/Saddle Brown (wife's car) '06 Evolution IX MR (sold) '06 R6 Anniversary Edition (sold)
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12-03-2014, 01:37 AM	#7
Island Road Major 196 Rep 1,327 Posts Drives: 335i Join Date: Mar 2011 Location: Boston iTrader: (5) Garage List 2008 335i [10.00]	I have the setup and made the switch. You loose about 2mpg on the highway but it's a lot of fun for sure and when u are actually on a track (not strip) makes a difference. __________________ 08 AW 6MT \| MHD \| Wavetrac LSD 3.46 \| AE Quad \| VRSF DP'S \| VRSF 7" IC \| DD Hood / Diffuser\| Mtech Front / Rear\| BMW Performance Splitters / Spoiler \| Wheels 18lb 18x9 SQ \| Hexon RR550 \| TFT Inlets
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12-03-2014, 02:13 AM	#8
MFactory Major 678 Rep 1,475 Posts Drives: E92 M3 Join Date: Feb 2014 Location: San Dimas, CA iTrader: (2)	What it loses on highway mpg, it more than gains back for traffic light mpg. Gas mileage isn't just about rpm, but also about load/throttle. It really just depends on what type of driving you do and, of course, your right foot (trust me, most of the mpg hit is because you are actually enjoying the increased acceleration. This normally wears off after a while when you go back to regular driving habits) __________________ - Specialists in Automotive Carbon Composite Technologies. Website: www.ctecarbon.com Official Partners: MFactory Competition Products, Porsche Cup Experience, Ferrari S.p.A, BYD Auto, Honda Racing Corporation, Three Five (555) Motorsport
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12-03-2014, 06:41 AM	#9
Icewall Private 1 Rep 90 Posts Drives: black 135i Join Date: Jul 2013 Location: Clark, nj iTrader: (0)	mfactory 3.46 in my car. about 2mpg loss. I like mine but bought it so I could go single turbo.
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12-03-2014, 01:43 PM	#10
NocturnalEVO Stock 173 Rep 1,275 Posts Drives: 2009 E92 335i Join Date: Dec 2006 Location: Long Island, NY iTrader: (8)	thanks for chiming in people! Asides from the decreased mpg, another concern I had was increased exhaust noise since I'll be revving a little higher on the highway to cruise at 65-70mph Have you guys found that an issue as well? __________________ '09 E92 335i (6MT) Jet Black/Coral Red '11 E90 328i XDrive (6AT) Jet Black/Saddle Brown (wife's car) '06 Evolution IX MR (sold) '06 R6 Anniversary Edition (sold)
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