Ciotti

Thanks for that picture y8s, that helps a lot.

Anyone have a recommendation for which stacking/initial locking setup will work best in an autocross setting? %100 vs %66 vs %33

circuitmstr74

iTrader: (1)

anyone have an answer to this guys question above?

Leafy

iTrader: (1)

How much power? what tires? what surface? different surfaces? will it ever rain? I dont know if the KAAZ is as touchy as the OSG, but on a CSP car a setting that was perfect for our local site in the dry was a pushy over locking mess at lincoln, and what worked at lincoln was a one wheel peel machine locally. If it really is an auto-x car, the real answer isnt OSG or KAAZ, its torsen. The torsen my only ever be 90% of a perfectly setup OSG, but getting a perfectly setup OSG for every possible combination of surface, temp, wetness, etc is impossible and a torsen is better the a mediocre setup OSG.

y8s

iTrader: (8)

I haven't had the KAAZ on an autox course (or maybe I have, but I forgot because it was ages ago), but my gut says 100% is too much and will end up causing understeer problems at power-on-corner-exit. At 100% you really can feel the car change yaw angles just by wiggling the gas pedal. And not in a good way if you're trying to go fast anywhere before the end of the turn.

mx5-kiwi

What sort of power levels are you guys running?

At 240hp at the wheels and 9" wheels with nitto's I am not getting much of any wheels spin anywhere with my 3.9 torsen.....

I presume you guys are at signifcantly higher power and torque levels?

circuitmstr74

iTrader: (1)

My car is a nasa PT/TT road race car. Around 2200lb and 150hp. Hoosier a6 and sm6 depending...I currently have a kaaz and have been using it in the default 100% lockup configuration. It is driveable, I have set a couple track records with it but it does engage rather harshly. I'm not sure why this would make the car push, it makes my car step out in the back. I would rather it be more progressive.
So I was thinking of trying restacking the plates to the 66% setting but am unsure if that will feel too soft or produce in lift? Has anyone used that setting for a road race car

Leafy

iTrader: (1)

100% lockup ( or even 80% or 60%) can make the car push if you dont have enough torque to spin both wheels in the current gear. If its locking harshly enough to shock the tires and cause them to loose grip, you need to work on the ramps most likely, changing the pre-load and/or total lockup can mitigate it at the expense of the rest of the lsd's performance but the problem there lies in the ramps/cams.

circuitmstr74

iTrader: (1)

Well I have never ever experienced a push and it use one of te stickiest tires available. Exactly the opposite

Leafy

iTrader: (1)

But something in the setup of the diff is making the engagement too harsh which is shocking the tires. Remember tires are hyperelastic, which means that not only the force that is applied matters but the rate that the applied force changes. So going from 10% of max grip to 70% of max grip in a fraction of a second can still overwhelm the tires. /oversimplifiedexplination

jpreston

iTrader: (4)

It sounds like changing the ramp angle on the accel side would be the best fix for you, but that's expensive and rearranging plates is cheap. Going to the 66% setting shouldn't be too far and should be a change in the right direction, but might cause a little wheelspin. I think most BMW stock diffs (also Salisbury type, like Kaaz and OSG) are 25% locking. They don't feel OSG good, but every one I've driven on track has felt reeeally good for a factory diff. Seems like most of the BMW race guys mod them for 40-80% lockup for track use. I'm not sure how their ramp angles compare to OSG/Kaaz, though...

Don't forget that, with this style of diff, lockup is based on torque input- throttle position and RPM. The variable lockup on these diffs is just another variable that you can use to control the car, which means it's also another way for imperfect driving to make the car handle like ****. I'm currently having similar complaints about my OSG and have been thinking about swapping a couple plates around. It does almost everything perfectly, but if I'm a little too early/harsh when rolling into the throttle out of a sweeper, the rear end gets squirmy. It's not scary and I can drive around it, but it takes a lot more concentration and hurts confidence a little, and is probably costing me a small amount of time since I'm having to wait a little longer before going full throttle.

On that note, does anyone have any input on tuning an OSG for track use and how many plates I should switch? Assuming the miata OSG has 12 discs per side, I'm thinking I'll start with deactivating 2 discs per side. I think that should give 83% lockup?

circuitmstr74

iTrader: (1)

Here is a video from my last time out:

pay attention at 2:56, 3:15, 4:32, and 4:40 and you will see what I am describing.

y8s

iTrader: (8)

100% lockup may be a very different experience on 9" race tires. Having more front traction may be all the difference.

circuitmstr74

iTrader: (1)

I welcome any input to how my car is behaving and how I could make it better

zossy1

iTrader: (4)

Thread rez...

My car came with a Kaaz. Car is 2100lbs or so, around 170whp (non Turbo). It has done a couple of years of racing so the Kaaz is well and truly broken in. The car is circuit raced.

I love it - very progressive, very predictable. I have run a variety of tyres, from NT01s to Dunlop slicks (similar in durometer to Hoosiers). It works well with all of them. It is set at 33%. I have tried 100% which drove a lot like a welded diff mid-corner and on exit, inducing power-on understeer which necessitated firming up the rear to keep the inside rear off the ground. It was not as fast for me at 100%. Have not tried 66% but might try that in the future.

Would love to try an OSG equipped car for comparison.

circuitmstr74

iTrader: (1)

I did end up swapping out my kaaz for an off the shelf OSgiken. It is noticeably smoother. No real input other than that. I had made a bunch of other huge changes to the car at the same time so... idk. Im focused on tuning other areas of the car first.