Hey guys,
I am sending in my OS Giken LSD for service and I want to change the % of lock. This is a 28 plate clutch style Superlock LSD.
I spoke with OS Giken about it and they said their diffs are designed for 100% as the ramp angle is very progressive. I think the 100% is a bit much. I do feel it progressively lock but at full throttle its a handful in a tight corner. It also does not do well in the rain. Its VERY bad in the rain. At Autobahn Country Club (already a very slick track in the rain) in the rain if I am anything but perfectly straight and I hit the throttle the back end comes around and I have to catch it QUICK.
The car is an 07 350Z. Its about 3300 lbs and has about 300 HP to the wheels. So not a high powered car.
A couple of questions I have:
1. Will reducing the lock make the breakaway less aggressive? Does it slow it down? I know stock BMWs come with something like 40% and their rear ends have a pretty slow breakaway. I know I am comparing two different cars with two different suspension systems here.
2. I know drifters like to run 100% as they say its more controllable but I also hear that a higher percent of lock makes the car less controllable. I am trying to wade through the information and its not leading anywhere. I am getting two different parties saying opposite ends of the spectrum are more controllable. Can anyone expand upon this for me?
I appreciate any help and any replies. Thanks.
So at 100% is that just expressing maximum locking force, or does the diff actually become a spool?
For track use you generally want just enough lockup to keep one-wheel-peeling in check. Reducing the lock will make breakaway less aggressive and reduce the car's tendency to resist rotation while accelerating. So instead of the whole rear end suddenly breaking loose you should get some wheelspin on the inside wheel first which will cause a more progressive loss of traction.
In reply to red_stapler :
It locks into a spool at maximum throttle
In reply to GameboyRMH :
This is what I thought. I am thinking 60-80% would do me good. Just trying to see if anyone has any experience with different lock percentages so I can kind of get an idea of where I want to be
I'm not a race engineer but I feel like this answer is going to be very specific to the chassis and a little bit to the driver. Probably hard to say without some testing?
I am not a diff expert and didn't sleep in *any* hotels last night, so a whole shaker of salt may be needed to go with these observations which are worth what you're paying, to just pile the trite caveats all over each other...
It sounds like a lot of your concerns are for tuning something other than total lock percentage. The rain comment in particular makes me think that your concerns is more preload or ramp rate, because it's misbehaving under conditions that aren't the max acceleration force; the wet ground would start bleeding torque before you got there no matter whether you're matting the throttle. There's also a possibility for driving style inputs here; it kinda sounds like you're tiptoeing until you "hit" the throttle, but that's me reading a lot into some text where you weren't particularly trying to describe what you're doing, so I could be in left field.
Is there a transition in tight corners where it pushes due to increasing lockup and then snaps? Remember that a locking diff wants to go in a straight line until the tires are too busy to enforce that... Any chance there's interaction like extra steering angle to deal with the push which needs to come out as power is applied and the straightening force declines?
Have you asked OS Giken for guidance based on your specific "I don't like the way it behaves under these conditions" feedback?
I am also curious about how much drift wisdom transfers; you're talking about folks who are expecting and initiating a big slide in every corner. You're trying to go quickly and if the car decides to slide you want it to do it gently. Good time to bookend with a reiteration that I'm a long way from expert...
ShinnyGroove (Forum Supporter) said:
I'm not a race engineer but I feel like this answer is going to be very specific to the chassis and a little bit to the driver. Probably hard to say without some testing?
OS Giken has a in house tech support that can help. At least they did with my ACR. We left it at 100% and it was fantastic on the track. Street less so as you would expect.
