5% to front wheels permanently. 40% max to front wheels in extreme situations. Straight from Porsche. So no point debating this fact.

 

Landjet, firstly you need to decide on your aims and objectives. LSD for a street turbo and an occasional track car is pointless that’s why Porsche didn't fit it. PSM is there to do the job. If you have lightened turbo with serious bhp then LSD might make some sense. But then you should also make it rwd to benefit fully. Honestly, unless you are building a dedicated track rwd turbo with serious bhp it is a waste of time. I have driven a crank 500bhp LSD equipped turbo on the track (dry - superb grip) and LSD was non-detectable to me. So spend your money elsewhere.

 

Landjet, as you can see, there will be two different schools of thought for every purpose. Not only will people have different opinions on various upgrades (there is no question an LSD is an upgrade over an open diff), but people will also see different results. I would say that for anyone other than a championship winning amateur or pro driver, you would not be able to get much out of an LSD on the track. The LSD will provide some additional traction in slick street and track conditions (notably rain). I really like the LSD, but like terminator said, I could not tell the difference combined with AWD other than some additional understeer (I resorted to running with the front sway disconnected completely). Your driving style and track selection will have a lot to do with that as well.
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However if you do decide to go with one, the OS Giken unit is a great unit and reasonably priced, I love mine. The 996 TT is EXCELLENT at putting power down in AWD form, don't forget that. I will say that if you have a hardcore track car and can really tune in quite a bit of oversteer with AWD, that combined with an LSD could be a serious beast on the track. But I'm talking serious track car here. Even most advanced and instructor level DE drivers wouldn't see much difference in a street driven Turbo on track.

Keep in mind that the new AWD systems use braking by the inside front wheel (I forget the technical name for it) to induce oversteer and then use the LSD + AWD to power the car out of turns, and even these cars still have some power understeer. That is ultimately a very good combination. PSM does it to an extent, but with PSM on, the power is being cut when you need more of it, and with PSM off, it's purely a safety measure.

 

It is achieved by the difference in rolling circumference front and rear. On standard sizes the front rolling circumference is slightly less than the rear, hence the small amount of torque that is always transferred to the front axle.

 

With some many strong opinions on the subject, I am really surprised not a single one of the posters in this thread has address the benefit an LSD offers under braking. Up to half, or more of the time gained on track with the use on an LSD in the 911 chassis will come from the lock up under braking. The ability to break later and deeper with more rear end stability is not something to be overlooked in this discussion.

People can argue until they are blue in the face about whether or not the LSD helps or improves upon the corner exit traction and power to the ground that is aided by having AWD on this car, but the lock up under braking is an indisputible gain that the LSD introduces.

And just for clarity, this is not something the guys running a TBD will experience. Only a true LSD with clutches will offer this benefit and anyone running a TBD in their car is missing out on this benefit of an LSD.

 

whats the though on Quaife products ?

 

How does the braking stability system that the 996tt has compare to the stabilizing effect of your guards lsd? My car is mostly a street car which is why I went torsen, never found much instability under braking (pre lsd) and our local track is pretty bumpy.


Would be included in the non clutch torsen style catagory, have a look at the wavetrac over the quaife as it is basically an improved version.



Gez

That would make sense, i have never driven on the stock sizes as I bought the car with rim that had no tires. I put on very close (basically exact) size tire f/r (diameter).

Really looking forward to tracking the car, i have some lap data from last year looking forward to improvements especially in the slower tighter turns.

 

Lots of misinformation in this post.

The 996 has a pretty primitive PSM by today's standards. From what I've seen The factory PSM does not do any torque vectoring or LSD function via braking under power. When it's turned off it's off unless you hit the brakes then it turns on. When activated, it cuts out the throttle and brakes individual corners to bring the car back in line.

The viscous coupling AWD system does not send a lot of torque up front despite Porsche's claims of "5-40%". You will be be hard pressed to see the AWD spin all four tires in the snow let alone the tarmac. The idea of a 4 wheel burnout in a 996 is just fantasy.

This video is very typical of many 996turbo in the snow videos. The wife is impressed, but the front tires do 0 spinning.

http://www.youtube.com/watch?v=zy7cMZe1JAk

Even more proof
http://www.youtube.com/watch?v=ETG1x...eature=related

 

It's hard for me to speak on that, I added a getty wing about the same time as the LSD, I know the 63 inch wing is helping some in the braking zone too so it's hard to tell how much is one or the other.

 

Ari, with all due respect there are a TON of people here, me included that have spun all four wheels at the drag strip. The TT most certainly can put power up up there. Wheel hop on all four wheels is easy to do with a good launch. Are you trying to say no power is going to the front wheels at all and our cars are rwd?

If you are you certainly have not driven the car in both configurations in track. It is also well known that you can burn up the front diff and several cars have had front diff failures most likely from being on the wrong kind of dynos as it has not always been so well known how to dyno the car, and even still all the people with turbos dont have this knowledge

 

I would love to see video of all 4 wheels spinning on a 996TT. I am not questioning your knowledge on the 996TT but I have never seen a 996TT or 996 C4 spinning the front tires even in snow. That isn't to say it doesn't happen, but it seems odd that the two videos of 996TTs in the snow above show only the rear tires spinning.

 

this is not the best, but the front wheels are definitely working in this video, but there is snow, so no dry pavement to answer your question.

http://www.youtube.com/watch?v=_ZwHN...1&feature=fvwp

 

I would imagine most people could feel the difference considering all of the rave reviews of RWD conversions and all the extra turn in ability. Not only that, I'm sure there are enough people that have put their car on a non mechanically linked awd dyno and watched the front wheels sporadically try and turn the drums. I know I've seen that. I know the actual output is paltry, no argument there.

But are you guys trying to say that the 996 TT is not actually AWD. That is a bit far fetched to say the least.

 

My car was RWD on and off for about a year total (not full conversion, but front drive shaft removed). I'm not saying that Porsche didn't actually make an AWD car, but maintain that the 996 specifically is primarily RWD with a minor boost to the front wheels when the rears slip. I challenge you to show me a definitive video of the front wheels spinning (especially in the dry).

This video may show a small amount of slip (see the really small circle skidmark) on the inside front wheel at about :28 seconds in. I maintain that it took a LOT of rear spin to get that tiny amount of spin on an inside front wheel (with most of the weight on the outer wheel). If you notice at the beginning of the video, that small circular skid mark is already there so no real proof that it's even from the Porsche...

http://www.youtube.com/watch?v=Q84jf...eature=related

 

I agree, but I think that the TT is always putting a small amount of power to the front wheels slip or not. I don't have any vids, but my car felt distinctly different at the drag strip in AWD vs RWD when wheel spin (or hop) occurred. Could it have been the vibrations from the back of the car make it feel like the whole car was bouncing around since the front diff was still connected? Possible, but that's what it felt like to me. But there is no doubt in my mind that on a healthy AWD Turbo, there is power going to the front wheels at all times. Anyone who's put one on a Dyno Dynamics that's not linked should be able to confirm that. Unfortunately, I don't video my dyno runs, but you can search my post from early 2007 and others that state the same, the car will sporadically turns the drums on the dyno. A few people have made the runs anyways and burned up the diff, but I can't remember if more power went to the front the faster the car went or not.


Now back on topic, how does this affect an LSD? Is anyone doubting that a AWD Turbo has more grip than a RWD one with no LSD? I think it's almost unanimous that anyone who has tried both knows the AWD Turbo has significantly more grip. The only way that is possible is with power going to the front wheels. The driving experience is too different to say otherwise. How much power and when? Who knows, but there is some power there, and it creates enough grip without making the car a plow tool.