Tezta

On evosports site there is an MKB sport differential in the drivetrain section. What kinds of 0-60 gains will one see? Anyone using this item?

JamE55

I'd say probably mid to high 4's

Tezta

Serious? that's awesome for $4,800

JBrady

Changing gear ratios increases the torque at the tire to road interface but reduces the speed which can be attained in each gear. The gains are felt as more thrust for each gear.

What MBZ car/engine combination do you have?

Sleestack

I have the MKB 3.07 differential package in my CLK. Definitely a nice upgrade for those who want their car to feel quicker through the gears. I will being going back to a stock differential because my car's hp and torque will be a bit excessive for the 3.07 diff. My differential package should be avaialable.

Tezta

If i choose to go with a sport diff. it would be on a W211 E320.

Sleestack i read some old posts about your car, did the differential take like some 2 months to be installed or something?

Mach430

Tezta,

The differential can be installed within a day. You would probably want to choose a 3.27 (3.07 stock) for your w211 E320. This will substantially help the acceleration of the car, but alone, will not bring it anywhere near the 4 sec mark. I would recommend combining it with our underdrive pulleys to help add some low-end power.

Sleestack

No, the differential was installed during my first round of tuning, which was with Oberklasse. That round of tuning took about 2 months.

Tezta

Thanks Ben.

How much would it affect highspeeds? I know the car will have an electronic limiter of 131mph so would it matter much?

Mach430

You would notice it at any speed.

Sleestack

I think you are asking about it's affect on top speed. Unless you remove the Vmax limiter, you won't notice it's affect on top speed... but you will get to 131mph quicker.

Tezta

Thanks sleestack.

Denlasoul

Any negative aspects to consider with a diff upgrade?

SiLvaC32

you will be at a higher RPM for crusing speed on the highway.

Mach430

Which translates to lower fuel economy and more engine work.

Ted Baldwin

............the guys at Bergwerks said that the differential change can drop .4 secs from your 0-60 time of a non modified V6 MB. I have thought about doing this. With the added power froim a s/c I wonder how much more than .4 secs can be shaved off.

Ted

Ted Baldwin

Also, Sleestack..........How high will the car rev at crusing speed on the high way? Is this an audible rev that disturbs passengers?

Ted

drdave

remember that times to 60 mph for example may not be improved if the car needs to do a "2nd" gear change...most cars will pull to 60mph in second gear. if the new rear gear ratio is very aggressive, then second gear may only rev to perhaps 55 mph.

i would imagine the car would feel more spirited in regular driving and perhaps the 1/4 mile time would be improved as well, but the actual "time" to 60mph may not improve at all.

i have also heard of cars (specifically lexus gs400/430) hitting the rev limiter because the computer is not calibrated for the different rear gear?

dr dave

Tezta

Ted,

Which setup at bergwerks will shave .4 off the 0-60 time? Their site has like percentage of gear reduction not the final drive ratios. Are we talking 3.27?

I am curious too about the S/C Diff combo.

JBrady

The differential gear is almost the final ratio before the power meets the road. Tire diameter is actually the final but lets just talk engine, tranny and diff.

I do not know what your transmission gear ratios are (if someone has them I will give more specific data) but in general... here are the facts. I will use Lexus data as I have that and it can be applied similarly to ANY car.

Engines make power and torque. Power is effectively fixed whereas Torque can be multiplied (drivetrain losses do apply) . This is what the tranny and diff actually do. The Lexus V8 makes about 310 lbs of tq at the engine. Here are the transmission ratios: 1st=3.357, 2nd=2.180, 3rd=1.424, 4th= 1.000, 5th=0.753, and the differential=3.26.

So, the engine (at 4000rpm, torque peak) is making 310 lbs/tq, this is multiplied by 1st gear (3.357) which yeilds 1041 lbs/tq (310 x 3.357) at the transmission output (minus losses) at a tranny output RPM of 1192rpm (4000 / 3.357) this is fed to the differential and is multiplied again with an output of 3394 lbs/tq (1041 x 3.26) at an output rpm of 365rpm. Now, the actual drivetrain loss (including tire loss) on this package is 22% so the actual road torque is 2647 lbs/tq @ 365rpm. When you correct this back to the engines rpm you get a NET engine rating of 242 lbs/tq at 4000rpm.

Confused yet?

The whole point I am making is that torque is multiplied by the gearing of the drivetrain. Changing the gearing will either increase or decrease the torque at the tires. Most people are completely unaware that their cars have so much torque at the wheels but it is true.

Now, the tradeoff of gearing is RPM is reduced. If you change from 3.07 gears to 3.27 gears your torque goes UP 6.5% and your engine RPM goes UP the same amount for any given vehicle speed in each gear. You will also shift 6.5% sooner at redline in each gear. If your old differential ratio was making 2647 lbs/tq, add 6.5% and your output with the new gearing is 2819 lbs/tq.

Will the car be quicker? Yes, definitely. It will be quicker in each gear. However, since it is shifting sooner there will be a small window where the old combination would have an advantage. This is the vehicle speed that the old combo was still in 1st gear but the new combination is in 2nd gear (and for each changed ratio for all the gears).

0-60mph may be quicker or slower. If a modified car must shift into 3rd to reach 60 and it could previously do it in 2nd... it may not be quicker to THAT specific time. Howerver, it WILL be quicker in each gear to redline.

This is a somewhat confusing and complicated concept but the above will hopefully help. I will get more detailed if there is interest here.

BTW, a common gear upgrade on the Lexus V8 cars is a 3.77 ratio. This is a 15+% increase.

Tezta

Jbrady thanks for the info, it is a bit confusing

Here are the MB E320 gear ratios if they help any.

3.95,2.42,1.49,1.00,0.83 diff 3.07

max test speed for each gear is:
38,62,100,131,131

Ted Baldwin

Which setup at bergwerks will shave .4 off the 0-60 time? Their site has like percentage of gear reduction not the final drive ratios. Are we talking 3.27?

...........yes 3.27

Ted

nukblazi

Just a statement made by someone who had changed their rear diff. Hope it is helpful. He installed 3.67:1 from a C200 in his C230 Coupe. Stock was 3.27:1.

Sleestack

His statement regarding only being able to change the diff. on manual transmissions is wrong. You do have to make modifications to the ECU, however, the MKB differential is a complete package.

JBrady

What is your tire size?
What is your redline?
What is peak HP at what RPM?
What is peak TQ at what RPM?

I can calculate for 3.27s but you may want to go a bit higher... other ratios available?