I've used OS Giken in my s2000 and NSX, one of the best options for street/trackday JDM cars. There are a lot of different specs, not sure which is offered for Porsche. went with the Quaiffe on the 996tt, more DD orientated.

 

Hello,
You are right that it's not about the brand and about the type, however, I'd just like to make a couple points of correction here. The OS Giken is not a gear driven (torque biasing differential). It is a true clutch type LSD. But you are correct that any TBD (either a Quaiffe or ours) will not put any power to the ground if you hop a wheel.

I also don't think it's wholly accurate to say that clutches are less reliable. Clutches have a service life. Depending on application the service life of those clutches is going to have a huge range. For a street car that sees the occasional track day, that service life will be tens of thousands of miles. Same thing for something like One Lap where they do a bunch of little short events. In those situations, I would expect ANY brand of LSD to last you 40-50,000 miles before it needs to be rebuilt.

But go run your car in a 6 hour, 12 hour or 24 hour event and that service life is substantially reduced, as it is on every other component on the car as well. It's pretty common for the top race teams to fully strip and rebuild any LSD after every race of those lengths. However, a PCA racer doing 1 hour enduros can often get a season or two out of an LSD between rebuilds. Like an engine, once you get into real racing it becomes more about hours of service than miles.

The last thing I'll just mention is that a TBD does not offer any lock up on deceleration. That's a feature that is only offered on a true clutch type LSD. This is why more road racers use clutch type LSD's. That lock up makes for faster lap times.

On the other side of the coin, that lack of lock up, and the fact that the TBD allows greater speed differentials between the two wheels from side to side is why many auto-crosser go with the TBD. It's that coupled with the fact the TBD doesn't dial in any understeer on tight turns that it's generally favoured.

Sorry for the hijack, but just saw a few points I wanted to clarify. With respect to the install of your Carbonetics LSD all you really should need is fresh bearings and the proper shims to adjust the ring gear. It should only take a few hours for the shop to get it in and get it right.

 

Open diffs don't lock at all. That is what is on the 996 Turbo. All you do is spin one wheel uncontrollably. When I tried RWD at Barber I would leave clouds of smoke coming over the hill at turn 4 (about 100 mph blind overhill right hand turn).

The difference is that some diffs will lock both wheels if one loses traction. I thought the Quaife was, or maybe they used to be.


Peter, thanks for the clarification on the Giken dif. I got all the kinds mixed up so disregard my last post.

 

Are the GT LSD and the OS Giken direct competitors? IE --do they essentially do the same job? In a racing situation? In a high performance road car?

 

Thanks Peter, great post.

Congrats on your preparation and Fantastic result!!!
So much for 4wd advantage in the wet.

Mate on this board has just bought a 997 GT2 and will find this info very interesting.

I didn't know there was such a price difference..

Do you think that the OSGiken or similar diff would help improve handling in a 996tt?

 

I'd appreciate any feedback on your experience, since my purpose is also for mostly DD.

 

Extremely technical article(couldn't possibly read the whole thing)...amazing effort...but maybe of more relevance to engineers than end users who are more interested in how they perform.

 

Hi Matt, thanks for clarifying. In 996tt apllications, can you expand on the benefit for road use/road racing of locking up on deceleration.

 

A couple things you guys should know about me and our business, since I'm the new guy here. First off, I will never bash the competitor's product. It's just not how we do business. Secondly, if I don't know, I won't pretend to know. I'll just tell you that I don't or I'll go find the answer for you.

That said, my answer to the question is that they fancy themselves a direct competitor to us. However, I can't claim to have enough direct experience with their product to give you an honest answer. Reading their published literature and website I'm not even 100% sure what their locking percentages are. Furthermore, I haven't talked to enough people who have been running their differentials long enough or hard enough to give me an idea.

Everyone who is running their differentials seems to have good things to say about the performance of the unit. But that's also usually someone who is upgrading from an open differential. I suspect they would say the same thing about ours or a Quaiffe after running an open diff. Furthermore, I still haven't seen anyone speak up who has run it in a serious endurance event or through a hard season of racing.

My wholesale customers who are selling both our product and the Giken product are telling me that they are putting their "recreational" customers in the Giken. They are selling them to guys doing DE's in their street cars or running track days with their mates. When it's a purpose built racecar they are tending to stick with our product because it's a known entity with a proven track record. Also, when it's a high powered turbo car that could break something, they err on the side of safe and put in our GT2 chromoly differential because they know it won't crack. Factory GT3 diff. housings are cracking. They don't know if the Giken will hold up. So again, they play it safe.

Only time will tell where the Giken will fall out. 2 years ago the Kaaz was the latest greatest new thing to hit the market and a bunch of them got sold and put into cars. Some people like them. Some people broke them. I can't tell you where the Giken is going to end up in a year. People are going to have to buy them, run them, and tell us about them for us to know what's really up with them. Guys with powerful cars are going to need to buy them and see if they can break them. It's too early for me to give you an honest opinion of how good of a product it really is. My gutt tells me it's better than the Kaaz. Is it as good as ours? I don't know, yet. I'd be lying if I told you anything else.

 

Definitely have learned something about LSD's on this thread. I don't understand why an LSD would be designed to not provide power when a wheel lifts off, that is exactly why you get an LSD. So in other words the Quaife will not provide power in that situation that blows.

 

Especially on these high powered cars that can hit unreal speeds on long straightaways, having the car stable under braking is essential. If you go read on some of the GT3 forums where guys are burning up the factory LSD plates in a couple of track sessions, you'll see their complaints about how the manners of the car change substantially when the LSD wears out and starts to act like an open diff. The tail gets loose and wags. For the higher speed cars it's really scary to have your **** end all over the place at 100mph under full braking.The LSD settles it down. It keeps the back end from wanting to walk.

 

Thanks, that makes sense.

In relation to " For the higher speed cars it's really scary to have your **** end all over the place at 100mph under full braking" ....or when it happens at over 200 mph flat out.....

 

Um, yeah. I was just thinking about the guys who come down from 160 or 180mph and are actually entering the turn close to 100mph. I'm lucky if I get my WRX up to 125mph on our local tracks, and dog knows my little 914 2.0l has rarely peaked past 105mph. You guys go scary fast in your cars...

 

***Only time will tell where the Giken will fall out. 2 years ago the Kaaz was the latest greatest new thing to hit the market and a bunch of them got sold and put into cars. Some people like them. Some people broke them. I can't tell you where the Giken is going to end up in a year. People are going to have to buy them, run them, and tell us about them for us to know what's really up with them. Guys with powerful cars are going to need to buy them and see if they can break them. It's too early for me to give you an honest opinion of how good of a product it really is. My gutt tells me it's better than the Kaaz. Is it as good as ours? I don't know, yet. I'd be lying if I told you anything else.
__________________
Matt Monson
Guard Transmission LLC
303-530-1094***

Matt,

That is the reason I am posting my experience's with the OSgiken. I am probably 1 of the earliest users. True my GT2 is not a racecar but it turns sub 2:00 @ VIR and a 2:18.7 on Michelin PS2's @ Sebring. Weighing 3375#'s with driver. I admit that if I hadn't had experience in my T3 S2000 with the OSgiken it would have been much harder to install in the GT2 instead of 1 of your GT units. I guess somebody has to be the Test Dummy.

Peter

 

Hello Peter,
I've seen your posts and will be watching you. And just for the record, I in no way betlittle your achievments at One Lap when I talk about it being a different usage within a range of applications. While it's a different kind of event, it's clearly still "real" racing in my book. In fact, we're involved with a car that will be out there next year. I'll look for you and try to say hi.

Also, if you decide to regear your car down the road let us know. While we're best known for out LSD's we do make gears as well. Steve at Rennsport Systems is a dealer and can help you run charts and analyze what might make an already fast car even faster.