best rear-end ratio for 3.1L stroker?

[zredbaron]

ok, i've been reading this forum for over an hour now, and im hoping that there are others out there with the stoker who have tried various diff setups and can offer some advice from their experiences...

 

first, just to make sure my newbie impressions are correct, the higher ratio (ie 3.9 vice 3.364) the better the accelleration and lower top end, right? or is it more complicated than that?

 

i am leaning toward the 4.11 r200. thoughts? how vital is it to find a LSD? seems to me it would be crucial for high hp apps but since i have <250hp at the wheels should i still try to find one?

 

i intend to autocross mostly, perhaps roadrace down the road.

 

thanks!

 

oh, and what does "RBs" stand for?

 

-mark

[Guest MistressMotorsports]

You've pretty much got it that a higher numerical diff will yield more torque off hte line at the expense of top speed. This is a generalization that is true for most engines, although there are lots of exceptions. At your power levels, you won't have huge wheelspin problems, so the best bet may be to pick the ratio that will give you the best range of acceleration with the least shifting in an autocross (since that's what you want to do.) The autocrossers can chime in here, but your idea to use a 4.11 is probably very close, and should make the car a pretty good 2nd gear autocrosser. Maybe a 4.36 would be nice, but it really depends on your engine's rev range, tire size, and the speeds you need to reach. I road race with a 4.11 and a 225/50/15 tire. Don't know what trans you have, but a 5 speed will be a big help on the street with 4.11 gears, as it will improve milage and should give you more top speed. For autocrossing, an LSD will be extremely valuable as it will help put the power down exiting those really tight corners. An open diff would just let the inside tire spin and cost you some serious time. Best of luck.

 

Mike