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Project DC2 Integra- Getting More Grip With OS Giken and Better Response With Centerforce

by Mike Kojima

 

With our DC2 Integra rocking a state of the art suspension, it was time to get our drivetrain in order for our anticipated track use and increased power. To get the power to the ground, we needed a limited slip differential, and we selected what we feel is the best FWD limited slip on the market- the OS Giken 1-way differential.

A limited slip differential is a differential that applies power to both front wheels, even when one tries to spin. A conventional differential will apply all the power to the spinning wheel which is the opposite of what you want to happen. So when coming out of corners or during drag launches, a limited slip differential is a huge advantage. It is also an advantage in braking as well, but more on that later. 

We had previously installed a Centerforce lightweight steel flywheel and Dual Friction Clutch. We decided to improve response further and install a lighter Centerforce aluminum flywheel at the same time while we had the tranny out. 

 

The OS Giken limited slip differential is what is called a Salisbury type differential. This means it uses clutches to help prevent the tire that has less traction from spinning freely. It also uses a wedging action from the pinion cross shafts to put additional pressure on the differential clutch packs if one wheel starts to spin. This increases the locking of the clutches right when you need it the most.

For an in-depth look inside the OS Giken diff and tips on how to set it up and tune it, check out this previous article we did on the subject.

The OS Giken diff for the DC2 Integra is a 1-way differential. This means that the diff locks under drive loading conditions and freewheels with no load on it. For an FWD or the front of an AWD car, this is desirable because it allows the diff to not resist independent rotating under freewheeling and braking. It also reduces the propensity of a solidly locked diff to cause understeer, especially under turn in. 

Well, this is not exactly true. The OS Giken diff has some resistance to the wheels freely spinning independently with no load. This is due to the initial breakaway preload applied to the clutches and a slightly rounded shape on the cross shaft cam that causes some wedging action when freewheeling and under braking. 

Having some resistance to independent rotation is desirable because it reduces the chances of inside wheel lock up when trail braking or late braking and keeps the low traction wheel from locking up when encountering split traction surfaces under braking. This helps stability under braking without a lot of contribution to understeer. 

Another advantage to the OS Giken LSD is that it is the most tuneable differential on the market. The diff can be adjusted for initial lock-up torque, locking torque slope, total amount of lock and how much lock is applied on acceleration and deceleration. This is accomplished with changes to the differentials pressure ring springs, cross shaft cam shape, amount of clutches active and pressure ring cam track shape.

Our Integra diff was set up from the factory for a mild lock on decel, a more aggressive lock on power with a smooth ramp up to maximum lock. This is optimized for an FWD car. OS Giken diffs have grooved clutch plates for good lubrication flow through the clutch plate stacks for long life. This makes for a smooth acting differential, important for a FWD car.

 

So how does the OS Giken diff work? Let's look at the insides. First, we removed the case side that the ring gear bolts to. The ring gear takes engine torque and spins the entire diff case.

The first thing we remove is the cone spring. The cone spring is a conically-shaped plate that gets squished flat when the diff case is bolted together. The springiness of the cone spring preloads the differential clutches and controls the initial breakaway torque. This is the minimal amount of lock that the diff has at all times.  

There are three different cone springs that OS Giken makes to set three different levels of initial breakaway torque as a tuning factor.  For instance, a drift car would want maximum initial lock and thus would use the stiffest cone spring. The front of an AWD car or a FWD car would use the softest cone spring to have the least initial lock to avoid understeer on turn in. 

 

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Comments
jeffreyball610
jeffreyball610link
Wednesday, February 14, 2018 8:15 AM
I know some clutch type LSDs require special fluids. Is there any hard set rule on what fluid (or additive) and which LSD? Or is this more of a manufacturer spec kind of thing?
Mike Kojima
Mike Kojimalink
Wednesday, February 14, 2018 10:11 AM
Most LSD manufactures have there own lube. I tend to use whats good for the transmission and use something like Redline friction modifier if the diff chatters. I have found that OS Giken diffs are generally pretty quiet.
Bradl3y76
Bradl3y76link
Thursday, February 15, 2018 1:37 PM
I've looked for a front did like this for a 2017 WRX, does anybody know of one? I looked through giken's website and didn't see anything.
Mike Kojima
Mike Kojimalink
Thursday, February 15, 2018 1:46 PM
I would try calling them
MattAtPlaton
MattAtPlatonlink
Thursday, February 15, 2018 3:47 PM
Great article! Did you have to replace the pilot bearing fork with a new one? That was something that failed on my GS-R.
Mike Kojima
Mike Kojimalink
Thursday, February 15, 2018 5:13 PM
no, the old one was ok.
brian6speed
brian6speedlink
Saturday, February 17, 2018 10:49 AM
Hey Mike, I have 2003 Acura CL comes with factory lsd. I believe it is a Mfactory 1-way helical. I use my car for autocross and track. Only aftermarket lsd I've seen is Cusco RS. Would you recommend that over factory? 1-way I'm assuming for fwd?
feluke
felukelink
Sunday, February 18, 2018 3:41 AM
"When one wheel starts to spin faster than the other, the side gears put a torque on the spider gears which transfers the torque to the cross shafts. The cross shafts cams then spread the pressure rings apart which puts more clamping force on the clutch packs[...]"

First part is all wrong, locking have nothing to do with wheel slip, quite the opposite. It should be: "When torque is applied to the insides of diff through ring gear, pressure rings are spread apart because they encounter resistance from cross shaft cams which are connected to wheels through spider and ring gears. That spreading action increase clamping load on clutch packs, increasing the amount of lock that the differential has."
In short the more traction and torque the more clamping force the diff have.

At last i would like to point out that you should put Loctite inside hole, not on the bolt when bolting flywheel.
ThisGuy
ThisGuylink
Monday, February 19, 2018 4:04 PM
@Feluke, You both are right and wrong. Mike is missing a few words but has the principle correct. You are missing one major thing that is required for a clutch diff to work, traction/road resistance. Which once you add it you will get right back to what Mike is saying. Mike saying "when one starts to spin faster.." is in the right direction just a little misleading.

The diff cannot lock without traction. If you free spin a diff, since there is no load on the spider gear/cross shaft, the diff will not add any additional breakaway torque other than what is in the clutch preload. As soon as you add load, to even one side of the diff is when the cross shaft will wedge on the hub and start to add additional force on the clutch packs. This will then try to lock the front wheels. What you need to take into consideration is what is more, traction on the inside wheel over total clutch load or if the clutch load is greater than the available traction. If traction is greater than the diff breakaway, the diff will differentiate(desirable). If the dynamic breakaway torque is greater than traction you will get wheel slip(undesirable). You will see this when looking at wheel speed data. with the steering wheel turned and off or part throttle you will see wheel speed differential, as soon as your diff settings come into effect you will see wheel lock up(to the diff) and front wheel speeds will equalize even though the steering wheel is still turned. When and where this happens will really determine how much your diff is hurting or helping you.

@Mike, I have practiced more decel ramp than a 1 way(maybe 60:40 or 70:30), less clutch preload/initial breakaway torque and a really slow/delayed lock timing. I have found a lot better drive ability due to the low initial preload. The added decel allows for a good wedge to help rotation. This is similar to what you are trying to achieve with more preload and zero lock/ramp angle. Once mid corner and part throttle comes you will have a lighter diff preload to help the target wheel slip differential mid corner. Once to exit you will have the delayed lock timing and still a good lock. Too much lock too early and once locked you are loosing traction on the inside wheel since it is spinning faster than road speed. Then you just hope you don't over power the outside wheel and start to push.
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