Tuning a drexler limited slip differential (lsd)

[Adam P]

Recently the team acquired a drexler lsd. As many of you may know the drexler lsd for fsae has different acceleration and decceleration ramp angles that dictate different lock up percentages. We have only run the car with the diff set in the stock position. Does anybody know what changing the position would do to the handling of the car? Is there anyway to calculate the changes that need to be made? Or is the only way to got out testing?

[Z]

Originally posted by Adam P:
Does anybody know what changing the position would do to the handling of the car?
Adam,

I hear the Drexler is quite expensive, $3-4,000?

Given you don't seem to know how it works, or how it will affect your car's handling, why did you buy it? http://fsae.com/groupee_common/emoticons/icon_confused.gif

Were you just after the bling? http://fsae.com/groupee_common/emoticons/icon_cool.gif

Z

[Christian Amersbach]

Hi!
i could tell you what changing the position would do to the handling of the car. But than you wouldn't learn anything and you wouldn't understand why it works... but thats the goal in FSAE. isn't it?
So i would recommend you first to understand exactly how the drexler works (using google and the book recommandations here in the forum, you will find plenty of literature about it ; thats how did it ;-) )
with that knowledge and some understanding of vehicle dynamics and your suspension layout you can figure out how changes to the differential would affect handling of the car....

if you have a good simulation model of your car, of course you can calculate your "optimum" setting..
if not: test it ;-)

Cheers

[Kirk Feldkamp]

I've always like this page for a quick/simple picture of what the ramps do:
http://www.intothered.dk/simracing/differential.html

As to what that means for your vehicle handling, well, you're going to have to figure it for yourself. Think of your diff setup as one of your primary setup parameters. If you tune the car one way, and then decide to change the diff ramps... expect to rework your tuning.

-Kirk

[onemaniac]

Originally posted by Adam P:
Recently the team acquired a drexler lsd. As many of you may know the drexler lsd for fsae has different acceleration and decceleration ramp angles that dictate different lock up percentages. We have only run the car with the diff set in the stock position. Does anybody know what changing the position would do to the handling of the car? Is there anyway to calculate the changes that need to be made? Or is the only way to got out testing?

Before you play with the diff you certainly need to understand your tires. Do you have tire data?
You can probably achieve some improvements (improvements meaning faster lap times for the designated driver) through trial and error in testing but where is the fun of learning?

[Adam P]

thanks guys. i had tire data but seeing how goodyear is not suppling tire anymore all our tire data is useless. Those links posted where very helpful.

[billywight]

It should be noted that a diff never "sends" torque anywhere no matter what kind of diff it is (unless perhaps it has some sort of internal motor or something). A limited slip diff simply reacts the torque imbalance between the two wheels, it's just a matter of how that reaction happens (generally friction related). Also, you don't need to have tyre data to understand the basics of tuning a diff, do some reading about the basics, then just go out there and try it!