If you get the Cusco RS and it's making a bit of harsh noises, throw some friction modifier in there, it quiets down quite a bit.

 

so i broke in my LSD at buttonwillow mid-december. wow, what a difference over a VLSD at the track! corner exit speeds are much higher and the rear end is very predictable.

after the first 750 miles (to and from buttonwillow, and about 130 track miles), i changed the oil. i have probably never smelled anything more putrid in my life! the description of the oil is the same as others - dark, purplish/gray; a great departure from the golden color of new oil.

i used amsoil 80W-90, and have replaced it with the same. i will drive it around for a month and maybe change it again to 75W-110 before the next track day (end of this month or beginning of the next). in the manual, cusco recommends either 80W-90 or 80W-110. i think for track days, since it is a clutch type, you should go with the 110. it does see a lot of friction, constantly.

 

Can anything be done to improve the performance of the factory LSD?Will changing fluid help?Can the unit be blueprinted or rebuilt to improve it's performance?

 

The VLSD has inherent drawbacks. Changing the diff fluid to a synthetic will help with durability, but won't provide better performance. If you take your car to the racetrack for extended periods of time, even synthetic fluid will begin to shear and breakdown.

 

You can put the finned cover on it to dispurse more heat. It is a Nissan part so it's not a class violation. The NISMO diff cover is the best option besides the synthetic fluid choice.

 

You cannot change the fluid inside the VLSD unit itself. The suggestions above help with keeping the VLSD unit as cool as possible but that only helps a little bit.

You can pull the VLSD out of the car, drain the internal fluid, and refill it with epoxy. But you didn't hear that from me.

 

Interesting...how long will this work before it blows up under heavy HPDE runs?

 

Has anyone actually tried this?

 

Not on the 350Z that I know of. Its been done on lower powered FWD cars running in a "stock" racing class. Its a racing only cheater modification and probably lasts a weekend.

 

Actually, it would take you out of B Stock in autocross. Other forms of motorsports are not quite as "literal" about the idea of "stock" -- and there are even people who think that even allowing non-OEM replacement parts is stretching the idea of stock.

Emphasis on "cheater." You might win with that "modification" but it wouldn't take a whole lot of work to figure out that "modification."

My solution -- tame the front end. Put a slightly stiffer bar on the front and you don't get as much body roll. Less body roll = both rear tires on the ground.

 

My solution -- tame the front end. Put a slightly stiffer bar on the front and you don't get as much body roll. Less body roll = both rear tires on the ground.[/QUOTE]
I've already gone with the stiffer bar,now I'm going with less negative camber in the rear.I figure that getting more of the 295/30s in contact with the pavement can't hurt.

 

What rear camber do run on track days?

 

Here's an interesting article about LSD's:
http://www.guardtransmission.com/velocity.htm

Sorry it's mostly geared towards rear engined Porsches, but I found the article very interesting, and it confirms how little I understand about how these units affect handling.

FYI, I went from the OE viscous unit to the Cusco RS set at 1.5 way and 80% locking. I think Porsche would call this a 80/40 LSD setting (80% locking under acceleration/40% locking under deceleration), which seems to be vastly different than what they spec their track/race cars with (45/65, 50/80, and 80/80).

A couple things I noticed when I upgraded to the Cusco unit:

1. More consistent lockup on exit, especially noticeable on sharper turns.
2. More understeer on throttle application. I'm trying to find a way to reduce the amount of understeer with alignment/sway bar adj/different springs/track width as I'm already running a square tire setup.
3. Very stable off throttle and under braking. In fact, the car no longer responds to throttle steer. I'm also considering changing my driving style a bit to take advantage of the cars resistance to off-throttle spinning like braking further into turns.

 

Good read, thanks for sharing.
Once you get the suspension dialed in, post up your specs and settings! I'm sure your lap times will improve quite a bit.

 

Power on understeer means you need to increase grip in front.

 

Especially if you are running same tire size all around.

Try to increase the amount of negative camber you are running up front as well, if you have not done that already. -2.5 degrees might be a good starting place.

 

Last time I heard he was running OTS Koni Yellow's with Tom Motorsports coilovers 500/500.

 

Thanks for posting, especially your owner comments about having the Cusco RS. I've been considering that LSD.

 

I suggest you take yours apart 3 times like I did to change settings

One thing that helped me realize the effects of a limited slip was driving on track in the rain. I really felt the on-throttle understeer with the limited traction of the front tires.

Perhaps the 45/65 numbers the article (that I haven't read) refer to are ramp angles. BMW's commonly use ramp angles of 30/90 to tame understeer. It's a different feel than our lsd's in that it takes much more torque to get to full lockup. Different ramp angles are the equivalant to a 1 / 1.5 / 2 way as the japanese lsd's. I'm sure different platforms work better with different ramp angles and breakaway settings.

 

nice info, thanks for the post