Jc5 box questions>>

[dhay14]

hi guys,

here i am again with a performance question..

can someone tell me more about the final drive?
1. what does it effect regarding top speed and acceleration?
2. for a 400m drag car ( max 300bhp max) which JC5 box is better or combi of which ones?


Im running a turbo'ed f7r and will be mostly used for 400m sprints. its running a std willy jc5 now

reg

dhayone

[Yanoo_]

1, shorter FD (higher number) gives better acceleration but will decrease the top speed in all gears. Longer FD (lower number) increases the top speed but has negative effect on acceleration. Wheelspin may occur in lower gears with too short gear ratio despite LSD or sticky surface. Additionally, too short gear raitos may require an extra shift during the 400 m.

2, For drag race: first, you should know the torque and power curve of your car, second you should choose such gear ratios (overall ratio) which drop off the (nearly) max rpm to the region of max torque rpm. I guess your turbo'd engine has a constant torque curve in a given rpm interval. The rpm should be in this interval after you shift at (nearly) max rpm.
For street: that gives the most pleasurable driving when you shift at max power and the rpm is dropped off to max torque rpm (like in the Willy :wink:).

This is exactly why I made the 'Renault gearboxes' software. RG can help a lot if you want to choose a new gearbox or compile a new gear ratios for your car:

Left chart is the standard JC5-014 (with F7RA700, max Torque @ 4500 rpm, max Power @ 6100, tyre: 195/50 R15), the right one is the JC5-014 with shorter FD (4.5 instead of 4.067):

http://www.dp-automotive.hu/kepek/rgbx_jc5014.jpg

You can download the software from here: http://www.dp-automotive.hu/dpa_softwares.html

(it's Hungarian but maybe I will make the English version later).