So I'm thinking of swapping out the stock torsen differential on my FD for a clutch type LSD (Either KAAZ, OS GIKEN, CUSCO). Do any of you road racers have any experience with any of the aforementioned? What set up do you recommend? The 2-way, 1.5 way, 1 way?? How does this change the handling characteristic of the car on a road course?

 

Grassroots motorsports tested a Torsen vs. a Kazz vs. a OS Giken and the OS Giken was fastest in an S2000 around a road course.

 

A fellow racer told me the os giken gave him 1 second a lap improvement in lap times. He was able to get on the gas sooner with less wheelspin.

 

Thanks guys. But does anyone on this forum who has first hand experience?

 

What's the downside to the OS Giken? Noise or streetability?

 

Compared to what? The torsen?

 

Cost? I Believe they are around 1.2K. Other than that they are just a plate-type LSD with a ****-ton of plates (23 or so?)

 

Did he use a 1.5 way or a 2 way?

 

I prefer the KAZZ not to noisy on the steets.

 

Is that to say the OS Giken is noisy?

 

it shouldn't be, but that all depends on what fluid you run and how it's shimmed. I'll be breaking in my kaaz 2 way shortly. I had an ATS diff in my old car that made a ton of noise, but i think that was by design.

 

I have an OS Giken 1.5way in my FD. I have to say it was one of the better mods I made for the track, topped only by the Stoptech BBK. The rear-end is extremely predictable flying into corners and powering out of them. Even with the rear sliding out a bit, you can keep your foot in the power controlling it and steering the car.

I also drive my car on the street a lot. The only noise you ever hear from the diff is on the highway. On deceleration at high speed, the diff whines a little bit. Also, if your making a 90" turn and you try accelerate quickly making that turn, the diff locks and the inside tire jerks. If you accelerate normally or even light acceleration, it does not happen. It's only when you try to accelerate aggressively through the turn.

One major thing I did notice about the OS Giken diff is that it doesn't overheat the diff oil as much as the stock one does. After merely one track day on the stock diff, my Red Line 75-140 oil would turn black, and smell like ***. After multiple track days on the OS Giken, it would still be yellow and clear. It saves me some money since I only have to change the oil 2-3 times per season.

For the record, a 2-way diff is for drifting. Since I tune cars, I get to drive a lot of differently modified FD's. I drove a JDM one with a 2-way LSD and man was that car tail happy in corners lol. I could start a drift with just a blip of a the throttle. Almost felt like a game lol.

thewird

 

Hey Pete, give me a call when you get a chance- Arlington eh?

I've been researching the various LSD options this past year and I've decided on the Giken unit. I haven't installed it yet and it looks like I'll be the second 993 guy to run it. The standard for the P-car crowd is the Guard GT diff and I would probably have gone this route if it wasn't 50% more since it's basically a more robust version of the Porsche Motorsport diff- IMO Porsche knows what they're doing in motorsports. Of course, that's my own opinion.

The Guard differential has always had a similar design the Porsche Motorsport differential, that being a plate type ramping differential. It made it's mark with the ability to custom choose between two different ramp angles within the same differential. Usually 40/60 and 80/80 but certainly a couple of other options as well. It also features 4, 6 or 8 plates internally, that is 2, 3, or 4 plates per side. It also features a more aggressive friction composition to that of the Porsche Motorsport diff.

Here is the rub. The Guard differential has on average a 65 to 85 lbs. breakaway preload. This has shown to cause a couple of issues. The first being that as you enter into a tight turn your car has to overcome this preload in the process of turning in. So what right? That should not make much of a difference. Well actually it does. The more preload there is the harder it will be to get the car to turn, but this is not usually much of a problem as you get used to the differential, and modify your driving to compensate. What is a problem is the material that is removed from the plates inside the differential ever time this happens.

The Porsche Motorsport differential utilizes carbon as the primary friction material in their differentials, the Guard diff does not. They use a moly blend, which is then plasma sprayed onto the plates to cause a friction material. This material is highly coarse and reacts in a way to not only lock the differential, which is good, but also remove metal from the opposing plates, which is bad. This combination of friction material and removed metal goes where? Through out the gearbox, very bad. It especially goes directly into the input and pinion bearings, where it begins to cause problems inside of them as well. This isn't an issue for you RX7 guys, but you'd probably want to change the diff fluid more often.

So how is the OS Giken different? The ramps themselves are counter springs that help you pull the ramps back to neutral when there is no force applied to them. It essentially reduces the breakaway to a very minimal amount, it basically opens the differential up, releasing the plates, so that you do not get unneeded lockup, and as a result unneeded wear. The friction material is again carbon, but due to the amount of plates which is more then double the Guard or the PMS, as well as the way the differential works, they do not suffer from premature wear. Nor do they require the rear of the car to overcome excessive lockup in order to turn the rear end- this is all in theory, time will tell.

Guard Differential, $2,400 to $2,800 give or take.
OS Giken Differential $1,790.00 for the 993

The OS Giken is essentially, a negative preload diff. Used in Indycar in the 90's. They are effective in battling the yaw damping characteristics of a traditional, or positive preload diff. More preload, more heat, more yaw damping but does kill off initial turn-in.

One thing that appears to be excessive is the friction surface count -- there are a lot of them, 32 it appears. That is a lot of heat generation. One aspect of this number of plates is the steep ramp angles one would need to use as a result. More plates, the steeper the ramp angles. It seems like a lot of lock up for a rear engined car, but I'll give it a shot anything has to be better than having an open diff! When I get it installed I may install a temp probe.

Here is what I think I've learned:
1) Carbon friction material is the least abrasive, provides for the longest transmission life at the expense of the diff itself. "Motorsports" plates provide much longer diff life at the expense of added wear to the rest of the transmission as the plates shed abrasive material.
2) There is no “right” answer as to how aggressive lockup is applied.
a. Drag cars want immediate 100% lockup
b. Drift car want immediate 100% lockup
c. Street car wants a very loose diff with low preload to accommodate sharper turns
d. Road race wants something in between, driving style, car setup would dictate how quickly lock comes on and let’s go. I’m guessing a 993 with low horsepower and rear engine would be on the slower end of the scale. A FD RX7 would want to be higher end of the scale. Also, I think the extra plates would be helpful for you guys with 400 plus wheel HP.

 

^thanks^
that was very informative for a me, a wannabe beginner road racer. lol

 

Thanks for the info. Overall, do you think that this was an improvement over the stock torsen unit? Also, do you have any data with respect to your lap times? I want the fastest lap times possible out of my car so I think I would be going with a 1.5 way...

 

Any one with any opinions on the Quaife vs. the OS Giken differentials?

 

The Quaife requires machining of the diff housing.

 

Not for the FB. Anyway, I decided to go with the OS Giken.