sprintamx

Since there are no stupid questions . . . How do you tell if a lsd is still properly/optimally functioning?

jrgordonsenior

Do you hsve one in your 99'? They're quite rare and a good LSD to begin with, much better with Guard's replacement clutches which aren't very expensive.

The easiest test is to simply jack up one side of the car leaving the other rear wheel firmly planted on the ground. With the trans in neutral and the parking brake off try to rotate the lifted rear wheel by hand at first. If it rotates you either don't have a LSD or it's clutches are worn out.

If it doesn't rotate then remove the wheel and put a torque wrench on the axel nut and try to rotate the lifted wheel. Start at 20lbs, 30lbs, then 40 lbs, etc. until it breaks free. That breaking point will tell you the condition and ramping preload of the LSD. Please report back with your findings....

pete95zhn

Engine weight as per DIN 70020 A in kg (lbs), Manual transmission ( According to the WSM )

190* (418.86*) -- 3.4l
274.0* (595.2*) -- GT3 mkI
260* (572.7*) -- turbo

* including double-mass flywheel

sprintamx

Thanks JR. A VIN check confirmed a factory lsd. But, at 118,000+ miles, and who knows how many track days other than mine, I do begin to wonder.

Since I need to do a brake bleed between sessions, I'll do the check within the next few days and report back.

GTgears

sprintmax,
Not to take this thing too far off the original track, but you might consider heading over to Maryland instead of Philly for your set up needs. What I mean is schedule an appointment with Mike at TPC in Jessup. I'll give you an example.

Last fall he spent a day at VIR with a car (a Cayman but it doesn't matter) that was what we in the business call an "internet" car. It was loaded with all the usual coilover and sway bars and end links and strut bars, etc. etc that are very popular on these forums. On paper the car should have been fast. In one half day at the track, with corner weighting and lapping, Mike found something like 10 seconds a lap on retuning the guy's setup. I cannot emphasize strongly enough how important it is to have a professional who knows these chassis doing the suspension set up for you.

As for the whole LSD conversation? Results don't lie. People can say that their factory LSD isn't worn out or that an LSD won't make much difference. All I know is I have rebuilt BRAND NEW 2010 GT3 RS LSDs and the customers found 2 seconds or more a lap before and after. Maybe the LSD did work the way Porsche intended it to, but if it did, they didn't intend it to be much of an LSD at all...

sprintamx

I'll look into TPC. Thanks for the info.

Ahmet

Not hard to believe at all, lots of goodies don't necessarily make a car fast or fast-er, particularly w/out proper set up, which is not easy to come by.
Porsche's LSD is intended to be very weak in order to allow the electronics to brake (or accelerate as the case may be) an individual wheel independently of others. For a track application, perhaps a good LSD would make a big difference on a C2, I've just yet to witness that. Remember that more track oriented/advanced ABS systems (BOSCH 5.7?) can help keep the rear wheel rotation speeds close under deceleration as well.

Aaron, I only put that car on track a handful of times on street rubber before selling it to you, I doubt it's seen any other track use before that. I'd be interested in hearing about the breakaway torque none the less.

jrgordonsenior

The Bosch ABS unit will definitely let you brake harder without going into the ABS mode, but I've never heard that it balances wheel rotation speeds. I'll ask a GA 997 racer/friend. Also, that unit costs $10k for the part compared to Guard's LSD at roughly 25% of that cost. His disc replacements for the factory LSD are even less at about $750.
Here's video of my car at Cal Speedway a few weeks back at a NASA race. The camera car is actually a pro-truck and although I out-qualiified him, he along with half the field, pass me on the start in my low HP 996. After the start fast forward to the 4:40 mark and I come back into the pic. If you follow us around you can see my car breaking at 155mph off the banking lap after lap. We go around like this for 5 or 6 laps until he spins but it gives a good view of the stability of my rear end under hard braking. It hardly moves especially when I trail break into a corner....

FWIW, the white #23 993 RSR is Chris Cervelli's old car....

http://www.youtube.com/user/american.../3/q-HXJi1JasM

GTgears

JR is right. If you are DEing the car, I wouldn't term an LSD essential. But if you want to win the kinds of titles that JR and Jay Matus are winning with their 996's then it's a required piece of equipment.

ohdavey6286

How much of a difference do you guys with street cars notice from taking out 200lbs or so? I find my 996 a little to docile for my taste and was thinking about changing it up a little bit.

jrgordonsenior

200lbs is huge. How do plan on removing that much weight from a street car?

ohdavey6286

Spare tire & tools, lightweight front seats, delete backs, muffler bypass, lightweight flywheel, lightweight wheels & Tires, and whatever Else I could take out that is bearable. Shouldnt the bypass, rear seats, and spare tire & tools take off ~100lbs alone?

jrgordonsenior

Maybe since the mufflers are really heavy pigs. Even so, where's the other 100 coming from? I'm not trying to persuade you from trying, but I think you're optimistic unless you go to lighter body panels or strip the interior.....

GTgears

I know changing the wheels can save some substantial weight. In that process, how many of you guys went an inch smaller at the same time? Not only would that be a drop in weight, specifically rotational weight, but the smaller rolling diameter also makes for a shorter effective final drive, which would help acceleration even more.

quickxotica

Don't forget to syphon out the washer fluid. If your car has xenons, it's 1.5 gals... that's about 12 lbs right there. Four floor mats = 5 lbs. Bose or aftermarket stereos are notoriously heavy (mine was 73lbs total). Removed! Rear seatbacks, belts & pads = another 22lbs.

Of course, if you fill up the gas tank you negate all that.

Drive around with a near-empty tank and all the above removed... see if you can appreciate the difference. If this is just a street car, and you can't appreciate the difference behind the wheel, then don't worry about it anymore.