[scheherazade]

Originally Posted by farbmw

So what you are saying is if I increase my HP from 300hp to 450/500hp it is alright to go to a gear ratio from 3.08 to 3.46.

And did Rysandro calculate the gearing ratio right?

note : (smaller numbers are taller for a rear end)
3.08 is taller than 3.46
3.46 is shorter than 3.08




He's saying that if you boost the car (make more tq), you can afford to go with taller gears.

For the same engine power :
taller gears = slower accel, more top speed
shorter gears = faster accel, less top speed

If you have taller gears for more top speed, and make up the loss in accel with more boosting higher (more TQ), then you are win-win.

-scheherazade

[s2kpuddydad]

Originally Posted by farbmw

So what you are saying is if I increase my HP from 300hp to 450/500hp it is alright to go to a gear ratio from 3.08 to 3.46.

And did Rysandro calculate the gearing ratio right?

With most cars that boost for street use go to a longer gear like your 3.08 from a 3.46. The longer gear lets you stay in the boost longer before having to shift.

I am not the expert in the BMW world of performance so I can not give tech advice on what ratios work for your BMW. Rysandro seems to know the power band sweet spot and has given his input to what ratio may work best for your setup.

[Sniz]

Originally Posted by s2kpuddydad

With most cars that boost for street use go to a longer gear like your 3.08 from a 3.46. The longer gear lets you stay in the boost longer before having to shift.

I am not the expert in the BMW world of performance so I can not give tech advice on what ratios work for your BMW. Rysandro seems to know the power band sweet spot and has given his input to what ratio may work best for your setup.

this ^


on turbo cars you'll generally see people going to taller RD while supercharged cars often go shorter RD.

[scheherazade]

Or you turbo and go short - and switch to a dog box.

-scheherazade

[farbmw]

Originally Posted by scheherazade

note : (smaller numbers are taller for a rear end)
3.08 is taller than 3.46
3.46 is shorter than 3.08




He's saying that if you boost the car (make more tq), you can afford to go with taller gears.

For the same engine power :
taller gears = slower accel, more top speed
shorter gears = faster accel, less top speed

If you have taller gears for more top speed, and make up the loss in accel with more boosting higher (more TQ), then you are win-win.

-scheherazade

THANKS! I like the win-win scenario.

[farbmw]

Originally Posted by Rysandro

Depends on your mods, if you want have amongst the best times than the 3.08 FD is better. With a 3.46 you'll be seeing 126 MPH @ 7000RPM, but at 7000RPM the power will have fallen off quite significantly from where it was around 6000RPM.

With the 3.08 you are seeing 122 MPH @ 6000RPM and 132MPH @ 6500RPM in 4th gear, much better power band to finish the 1/4 mile than with the 3.46 gear.

Thanks for the info bro!

[Proper Motion LLC]

Originally Posted by farbmw

So what you are saying is if I increase my HP from 300hp to 450/500hp it is alright to go to a gear ratio from 3.08 to 3.46.

And did Rysandro calculate the gearing ratio right?

My numbers are correct for a 6MT with stock wheel/tire sizes. I don't know what a typical size would be for drag tires, but it won't make very much difference, maybe 2MPH at most.

http://www.wallaceracing.com/gear-speed.php

Keep in mind our stock wheel/tires have a 25.03 rear tire diameter.

[BerkTechnology]

Originally Posted by s2kpuddydad

Jason deleted my posts Sorry Jason if my posts came across commercial that was not my intention. I can not PM you as I do not have that privilege yet.

I'm not sure how to answer questions in this thread so I will be careful as best I can.

I'm not sure if OSGiken makes a LSD unit for the 330i You can call or email them to find out.

I would like to be a source of information to you guys and answer diff related questions if you have any. Please do not ask me to work on or give cost to having work done. I can answer tech questions and add my 2$ in on threads like everyone else

Hi Ben! Glad to see you on here! I too will give my vote of confidence with Ben's knowledge and service. Not only is he a diff installer but he can make crazy custom parts for those of you who have deep pockets. Ford 8" ring & pinion into a BMW diff? No problem!

[farbmw]

Originally Posted by Rysandro

My numbers are correct for a 6MT with stock wheel/tire sizes. I don't know what a typical size would be for drag tires, but it won't make very much difference, maybe 2MPH at most.

http://www.wallaceracing.com/gear-speed.php

Keep in mind our stock wheel/tires have a 25.03 rear tire diameter.