morpheus5039;674221 said:
me too using manual tranmission, mated with 4.1 FD...tat wat i surprise..mine should be higher rpm than urs at the same speed...y????? at the time i converted to manual, the guy told me is the same...i dont believed him....but...YYY???????? any sifu can explain to me????
i plan to put in the cams after the exhaust upgrade.
Sorry I thought mean you are using the Automatics now.
If that is the case, you are either using ZF S5-16, Getrag 240 or Getrag 260 gearbox. These are overdrive gearboxes with 0.8X 5th gear. Mating with 4.1 is correct. You can mate with 3.73,3.91,4.1,4.45 depend you want acceleration/top speed (Better fuel mileage). You can get stonger gearbox from metric mechanics of USA. Your final ratio should be 0.83 x 4.1 = 3.403
For mine the 5th gear is 1:1, can choose between 2.91, 3.07, 3.15, 3.23, 3.46. Mating with 4.1 for me is too short that I will have insane high rpm when cruising at 110km/h with 5th gear. My ratio will be 1.00 x 3.23 = 3.23
On 5th gear @ 3000rpm, using 245/40/18 tires, my actual speed should be 114.35km/h
Theoretical formula:
Wheel Speed at Rear Wheel = ( Engine Speed / Diff Ratio ) x (Tyre Circumference)
What is your tyre size? Some more you have to take into account that there is a variance betwwen actual speed and the speedometer, as the original speedo is calibrated for using 205/65/15 tires with 2033.7mm circumference.
Your rpm should be slightly higher than me. If you want to get lower than me then you should look for 3.73 rear diff, then you will have a total 3.0959 ratio.
