Why you need a LSD if you like cornering!

[ZDan]

Originally Posted by CSG Mike

I was having a discussion with a former S2k Challenge board member, and he brought up that Billy was trying to tell all the S2k owners that a clutch type diff was something that should be done very early in the stages of modding around 5 years ago
I'm starting to think he was on to something...

No way that ALL S2000 or FR-S/BRZ would benefit. I would bet that fewer than 1% of *all* drivers and probably fewer than 10% of the drivers who track them would actually benefit.

If you're running Hoosiers or slicks with aero that gives rear downforce at speed, I can see how you might need a stiff clutch-type diff to power out of lower-speed corners. For the vast majority of people who drive these cars "spiritedly", and for a solid majority of those who mod and track them, probably unnecessary.

When my S2k is retired from street duty and becomes a track whore, the diff is going to be the LAST thing I mod, if ever. If I never get inside wheelspin, I'll never change the diff.

[ZDan]

Originally Posted by Element Tuning

I'm not at all saying there aren't different ways to make the Torsen work well on the FRS and I do have track records and a national championship with the FRS to back that up. Making it work on a track day car and breaking unlimted track records however are two different things.

Exactly. How many of this audience are in the former category and how many in the latter?
If a well-developed nationally competitive track car *might* benefit, that does NOT mean that most of the cars on these forums that are tracked will benefit.

We are running professional racing slicks that are 325" wide,

8255mm :O

have ridiculous grip, and with aero exceeding 700 lbs at 120 mph. The spring rates and front roll stifness required to keep a mac strut front end planted is huge. The rear multilink gains negative camber unlike the front so a softer rear with more independence can work really well. We focus on using the front to drive more weight to the rear to help "dig" it in with 400+ hp.
With how our car is set up, I'm very happy with the torsen

If you're happy with the Torsen with that setup, how much do you think someone who's tracking on street/track suspension with no aero on NT01/R888 level tires NEEDS an aftermarket clutch-type diff?!

but I know at some point I may be forced to increase the rear spring rate to deal with the aero weight that I'll give up too much mechanical grip or I'll be forced to avoid curbing which could hurt lap times.

But of course you'll wait and see, right?

Now when I was running stock power, slicks, and coilovers, ditching the rear bar netted me 2 seconds at VIR as I was able to drive out of the turns much, much earlier. While there are other ways to help this nothing costs less than disconnecting the end links and giving it a try. Lap times do not lie!

And I gained 1.5 seconds at New Hampshire Motor Speedway (south oval config) disconnecting the rear bar in my CLUTCH diff equipped 240Z after I'd made a couple of mods that increased front grip and corrected rear toe (stock was ~1/4" toe-in, :P )

Totally agree that disconnecting a link is a great way to easily change handling balance. That you gained 2 seconds disconnecting yours doesn't necessarily mean the stock Torsen sucks, just that your suspension setup was off.

Yes, a tight clutch-type diff will require very different suspension setup than a Torsen, but that's because a tight clutch-type induces understeer which you then have to *correct* with the suspension setup.
A lightly-preloaded clutch type or a Torsen doesn't induce as much understeer and allows a more "natural" suspension setup.

I've driven Z's with very tight clutch-types, and I greatly preferred the handling characteristics of mine with its ~20 lb-ft breakaway stock Z31 turbo diff. Never a problem putting 250ish rwhp down on Hoosers, even with stiffer rear wheel rates and the S30's higher rear roll center (further loads outside/unloads inside rear under hard cornering).
FWIW, I didn't disconnect the rear bar due to inside rear wheelspin, it was because someone commented that I was going around the South Oval turn at about a 10 degree slip angle! I reasoned that that could *not* be the fastest way around...

[Element Tuning]

[QUOTE=ZDan;1890605] Haven't tracked an FR-S/BRZ yet,.........[/QUOTE=ZDan;1890605]

Just want to make sure everyone knows that your strong opinions are based on zero FRS/BRZ track setup knowledge. I'm not saying you don't have valuable information to add about other platforms and how they "might" be similar to this car.

Now Mike and I do have practical setup knowledge that will help most enthusiasts and I have knowledge that can help the 1% that are going for track records.

Thanks,
Phil Grabow

[ZDan]

[quote=Element Tuning;1891063]

Originally Posted by ZDan

Haven't tracked an FR-S/BRZ yet,.........[/QUOTE=ZDan;1890605]
Just want to make sure everyone knows that your strong opinions are based on zero FRS/BRZ track setup knowledge. I'm not saying you don't have valuable information to add about other platforms and how they "might" be similar to this car.

Absolutely! Should put that disclaimer at the bottom of every post of mine.

Now Mike and I do have practical setup knowledge that will help most enthusiasts and I have knowledge that can help the 1% that are going for track records.

Acknowledged! You guys are a great asset to the FRS/BRZ tracking community to be sure.

My experience with the Z was that many who tracked them were entirely too eager to either weld the diff (eww...) or shim the 300ZX turbo clutch type diff up to 90+ lb-ft for track work, which IMO did nothing at all for the handling of the car and wasn't at all necessary to put the power down anywhere.

For sure car setup and driving style will be big players on whether or not a tight clutch diff is called for.

To tell the truth, I had ordered the shims/belleville springs for the R200 clutch-type in the Datsun to bump it up to the Nismo-spec 45 lb-ft, but I never installed them because I never got inside wheelspin, even over 15+ years of tracking it with evolving suspension development. And I never tried to set the suspension to overcome any shortcomings in the diff.

In my experience with the Torsens in my S2k and RX-7, I have found them to behave very similarly to the light-preload clutch-type I had in the Z.

I just find it hard to believe that for the 99% an aftermarket clutch-type is warranted. For the 1%, maybe, but then again you yourself said you've been happy with the Torsen! With 400+hp, 325 *slicks*, and downforce!

For sure, no one should just think buying a clutch-type will *for sure* be an improvement. I would strongly recommend that anyone buying a customizable aftermarket clutch type make sure what they really want/need. There are a TON of options, including initial breakaway preload and different clamping rates for accel/decel.

Anyone who wants to look at the pretty staggering array of options for a cool aftermarket clutch-type, have a look at this:
http://www.cuscousainc.com/downloads..._lsd_guide.pdf

It is very cool to have a gazillion options (I would try the Hybrid, or maybe the ProAdjust with a low initial torque setting), but how many are going to even get close to optimizing them all for their specific setup and usage? Again, the 1% can take advantage of this, but the vast majority of casual track-day warriors aren't likely to be able to.

[CSG Mike]

Originally Posted by Element Tuning

Same thing with the STi. A clutch type diff is a game changer on that car. If you don't do it at first, you can kiss all your suspension tuning goodbye.

Funny you say that... front/rear LSDs went in the WRX we're building before anything else... even before an initial alignment...

[CSG Mike]

Originally Posted by ZDan

No way that ALL S2000 or FR-S/BRZ would benefit. I would bet that fewer than 1% of *all* drivers and probably fewer than 10% of the drivers who track them would actually benefit.

If you're running Hoosiers or slicks with aero that gives rear downforce at speed, I can see how you might need a stiff clutch-type diff to power out of lower-speed corners. For the vast majority of people who drive these cars "spiritedly", and for a solid majority of those who mod and track them, probably unnecessary.

When my S2k is retired from street duty and becomes a track whore, the diff is going to be the LAST thing I mod, if ever. If I never get inside wheelspin, I'll never change the diff.

Once you drive a S2k/BRZ with a clutch type LSD that's properly tuned, I'm willing to bet you'd change your mind.

If you're in Socal, I'll arrange for it to happen.

Originally Posted by ZDan

Anyone who wants to look at the pretty staggering array of options for a cool aftermarket clutch-type, have a look at this:
http://www.cuscousainc.com/downloads..._lsd_guide.pdf

It is very cool to have a gazillion options (I would try the Hybrid, or maybe the ProAdjust with a low initial torque setting), but how many are going to even get close to optimizing them all for their specific setup and usage? Again, the 1% can take advantage of this, but the vast majority of casual track-day warriors aren't likely to be able to.

That's why we test what settings work first, before we recommend it

[solidONE]

Originally Posted by Element Tuning

Well given the FRS/BRZ does not have a solid rear axle and is not front wheel drive, we are just out of luck!

I'm not at all saying there aren't different ways to make the Torsen work well on the FRS and I do have track records and a national championship with the FRS to back that up. Making it work on a track day car and breaking unlimted track records however are two different things. We are running professional racing slicks that are 325" wide, have ridiculous grip, and with aero exceeding 700 lbs at 120 mph. The spring rates and front roll stifness required to keep a mac strut front end planted is huge. The rear multilink gains negative camber unlike the front so a softer rear with more independence can work really well. We focus on using the front to drive more weight to the rear to help "dig" it in with 400+ hp.

With how our car is set up, I'm very happy with the torsen but I know at some point I may be forced to increase the rear spring rate to deal with the aero weight that I'll give up too much mechanical grip or I'll be forced to avoid curbing which could hurt lap times.

Now when I was running stock power, slicks, and coilovers, ditching the rear bar netted me 2 seconds at VIR as I was able to drive out of the turns much, much earlier. While there are other ways to help this nothing costs less than disconnecting the end links and giving it a try. Lap times do not lie!

Heh... Front roll stiffness is "moot" and clutch LSD is "necessity" and BBK does not enhance braking performance... Or so I've heard.

Carry on, gentlemen. Just trolling by.

[Captain Snooze]

Originally Posted by ZDan

Anyone who wants to look at the pretty staggering array of options for a cool aftermarket clutch-type, have a look at this:
http://www.cuscousainc.com/downloads..._lsd_guide.pdf

Holy mang!! Way too much choice!!

Originally Posted by ZDan

For sure, no one should just think buying a clutch-type will *for sure* be an improvement.

*deletes aftermarket diff from shopping list*

Edit
Still deciding upon shopping list delete.

[acro]

Personally i think the Stock LSD is good but even i with limited track experience i have gotten the inside wheel spinning at some points on track. If i could put down more power on corner exit im sure i would be faster. So if i was serious about track times this would be a definite consideration.

[Fizz]

Originally Posted by Captain Snooze

Still deciding upon shopping list delete

Add box cutter to your shopping list. You need to cut your bumpstops they're way too long.

[Captain Snooze]

Originally Posted by acro

So if i was serious about track times this would be a definite consideration.

Argggghhhhh!!!!

[acro]

Explain the arrghhhh. As a newbie to trackdays I'm trying to maximize what I have now. Learn the car to its fullest, lap times (in and of themselves) aren't a priority.

Basically I'm trying to upgrade the driver first (that's me btw) before the car

[wparsons]

Originally Posted by acro

Explain the arrghhhh. As a newbie to trackdays I'm trying to maximize what I have now. Learn the car to its fullest, lap times (in and of themselves) aren't a priority.

Basically I'm trying to upgrade the driver first (that's me btw) before the car

Until the car is holding you back, just work on improving your skills. Driver mods are the most affordable and also most effective.

[acro]

Agreed. That's the plan. The major thing I have done so far are pads and fluid as I exceeded the limits of the stock setup fairly early.