Differentials
10-20-2006, 01:49 PM
#11
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Originally Posted by BetterMakeWay' post='347181' date='Oct 20 2006, 02:46 PM
Confused...so that means that the steptronic is better at 1/4 runs or so?!
10-20-2006, 01:52 PM
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Originally Posted by AlexFW' post='347162' date='Oct 20 2006, 10:15 PM
Anyway ... 545i and 645ci have the same weight but with different differential there is a difference of 0.2s .
10-20-2006, 02:43 PM
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Originally Posted by EBMCS03' post='346873' date='Oct 19 2006, 09:18 PM
Ya it has to be the first and second gear ratio + rear differential which gives the Step the edge on acceleration.
Well with a higher final drive ratio you get less top end speed... maybe thats why BMW chose to give the manuals a higher final drive ratio... so they can drive faster on the autobahn...
Thats prob not the only reason... but a combination... RPM when crusing in 6th along with the avilability of a manual gear box that has the same gear ratios as a auto tranny so they changed the final gear ratio to make the crising rpms similiar?
Fuel Economy... we dont care but BMW does.. and needs to make them similiar also...
I dunno. just my guesses... thats all i can guess for now. brain is stuck and fried.
Well with a higher final drive ratio you get less top end speed... maybe thats why BMW chose to give the manuals a higher final drive ratio... so they can drive faster on the autobahn...
Thats prob not the only reason... but a combination... RPM when crusing in 6th along with the avilability of a manual gear box that has the same gear ratios as a auto tranny so they changed the final gear ratio to make the crising rpms similiar?
Fuel Economy... we dont care but BMW does.. and needs to make them similiar also...
I dunno. just my guesses... thats all i can guess for now. brain is stuck and fried.
The Steptronic cars should defineatly get the hole shot by looking at the gear ratios + they have a deeper first gear too. Once both Step and Manual/SMG shift into 2nd the Manual/SMG have the deeper transmission gears....I'd love to see a race/0-60 times with both cars in reverse!
From BMWUSA website:
Transmission
Standard gear ratios - I/II/III 4.06/2.40/1.58 :1
Standard gear ratios - IV/V/VI/R 1.19/1.00/0.87/3.68 :1
Standard gear ratios - Final drive ratio 2.93 :1
Automatic gear ratios - I/II/III 4.17/2.34/1.52 :1
Automatic gear ratios - IV/V/VI/R 1.14/0.87/0.69/3.40 :1
Automatic gear ratios - Final drive ratio 3.38 :1
10-20-2006, 02:47 PM
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Originally Posted by Heloha' post='347194' date='Oct 20 2006, 11:43 PM
The Steptronic cars should defineatly get the hole shot by looking at the gear ratios + they have a deeper first gear too. Once both Step and Manual/SMG shift into 2nd the Manual/SMG have the deeper transmission gears....I'd love to see a race/0-60 times with both cars in reverse!
10-20-2006, 02:56 PM
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Originally Posted by Heloha' post='347194' date='Oct 20 2006, 06:43 PM
I'm sure its all about fuel economy with the Step being more efficient overall. We with the manuals were probably compromised with the gas guzzler tax where BMW had to find a happy medium.
10-20-2006, 02:59 PM
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Originally Posted by ImolaRedM' post='347202' date='Oct 20 2006, 05:56 PM
The only thing that should make the step more efficient is the gearing. Torque converters are generally less efficient than direct gears.
10-20-2006, 06:47 PM
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Originally Posted by vegastrashed' post='346864' date='Oct 19 2006, 09:42 PM
I have been wondering why the manuals and SMGs have a lower final drive ratio (2.91) than a Step (3.46)? Znod and grogan545 both agree that the final drive ratio of the Step is a contributor for their excellent timed runs. Why can't BMW just outfit the manuals and SMG with the same 3.46 as the Step?
................. Manual/smg..ratio..Diff..overall ratio..steptronic..ratio..diff..overall ratio
Gear .................1..........4.06X2.93.....11.72... ...........1........4.17X3.38.....14.09
Gear..................2..........2.40X2.93.....7.0 3................2........2.34X3.38......7.91
Gear..................3..........1.58X2.93.....4.6 3................3........1.52X3.38......5.14
Gear..................4..........1.19X2.93.....3.4 9................4........1.14X3.38......3.85
Gear..................5..........1.00X2.93.....2.9 3................5........_.87X3.38......2.94
Gear..................6.......... .87X2.93.....2.55................6........_.69X3.3 8......2.33
Notice that gears 1 thru 4 the overall ratio for the step is higher than the manual/smg.A higher number means more torque multiplication,which means better acceleration.The differences for gears 1,2,and 3 are pretty significant which I believe accounts for the better times noted for the steps.Only in gear 6 does the manual/smg have an advantage,but since this is your cruising gear all it does is hurt your gas mileage.If you had the 3.38 gear in the manual/smg your mileage would suffer about 10%.You would also have many more revs/mile which causes more engine wear.I believe this is why BMW did not put the 3.38 in the manual/smg.The step has some losses due to the torque converter,but they are more than offset by the more favorable gear ratios.
10-20-2006, 06:54 PM
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Originally Posted by EBMCS03' post='347279' date='Oct 20 2006, 10:51 PM
Alright my assumptions and logical reasoning were close. 
10-20-2006, 09:45 PM
#20
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Exterior: 50% side windows / 35% rear window Formula One Pinnacle Series | Flat AMG hood emblem
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Wheels/Tires: Radenergie R10, Falken FK452 245/30/20, Yokohama ADVAN Sport 285/25/20
-----------------------------------------
2005 545i Sport SMG | Ti Grau | Schwarzes Dakota | Anthracite Maple | Logic 7 | Nav
Engine: Custom AFE CAI, Superchips ECU remap, Sprint Booster, RDSport Dual Exhaust Conversion with Quad Pipes and X-pipe, 3 resonators deleted, 90mm tips!
Exterior: M-Tech Aero kit | M5 Mirrors | M5 Rear Bumper | Trunk Lid Finisher | Vorsteiner decklid spoiler | 50% Formula One Pinnacle Tint
Suspension and Brakes: Bilstein PSS9 coilovers, JBT BBK: 16" cross-drilled rotors, 8 piston and 15" cross-drilled rotors, 4 piston
Wheels: VIP Modular VR 02 20x9F, 20x10R | Toyo T1R 245/30/20F, 285/25/20R
Lights: PIAA 4150K Xtreme White Plus fog lights, AIB v3
MOST IMPORTANT: Hardwired V1; =)
ED Date: 4/7/05, Re-delivery date: 5/21/05
Originally Posted by EBMCS03' post='347279' date='Oct 20 2006, 07:51 PM
Alright my assumptions and logical reasoning were close.
