I've had the privilege (or bad luck, depending on how you look at it) of trying different differentials on my FN2, thought, I'd share my impressions.
Started with the OEM open diff to a Quaife, which then broke to be replaced with a JDM LSD, and replaced again with an OS Giken 1.1-Way.
Would be interested to see what other people are doing with their gearbox as well. Car is running about 192wHp with KW coilovers and a variety of street tires as well as semi slicks.
OEM Open Diff
Anyway, the FN2 gearbox has same ratios as FD2R (i.e. 5.1 Final Drive)
But comes with an open differential from factory (at least the pre-2009 model)
Not much to say about open diff really, what a PoS. Understeer was the name of the game, can't put any sort of power down unless the wheel was straight. If I throttle too early in the corner, I just ended up washing wide.
OEM Torsen Diff
Day to day, I don't actually notice the diff, it's smooth and quiet. But most of you guys would know that considering they came like that standard on the DC5R! On track the difference is quiet obvious, you don't have to put the power down so late in the corner. Though you gain traction, it doesn't seem to help the car turn much. I still have to sensitively feather the throttle here and there, it’s still quite easy to overwork the diff, especially on really tight turns where most of the cars weight shifts to the outside.
Quaife Torsen Diff
A bit more of the same really, the difference that I can feel on track is, the Quaife has a slight "tuck-in" affect. Where if you apply throttle, the front end will turn better. Great advantage over the OEM diff as it allowed me to start applying throttle before the apex of the corner. I was quite happy with it till it broke! Was doing a 6000rpm launch at the drag strip with 235 semi slicks, and the side gears failed, sending shrapnel all over the gearbox. Lucky it didn't damage anything. I've never heard of a Quaife failing so I’m assuming I just got a weak one.
OS Giken Limited Slip Diff
I pondered long and hard what to replace the Quaife with wasn't sure if I wanted to go plate type for fear of maintenance requirements and noise. My mechanic insisted I go plate type for the traction and strength. But I’ve ridden on a few FWDs with Kaaz LSD and it was clunky ass! But then I tried my Wuism's DC5R with an ATS/Carbonetics Carbon LSD and it was silent and smooth, so plate type doesn't have to be noisy at all. The thing that put me off the ATS LSD was it recommended you change the gearbox oil every 5000Km and it was very picky on what oil you can use. I wasn't up for spending $150 on gearbox oil every 5000km, so I kept looking.
Then I got this email from OS Giken USA
I was sold on the idea, and sure enough, as promised I have a Silent LSD!
I put some 75w90 Motul Gear FF Type II in; the diff would only clunk on cold start, when its up to temperature it’s absolutely silent.
At the circuit, the traction difference is like night and day! Absolutely phenomenal, front grip, anytime, anywhere. My limit of traction is now defined by suspension and tire setup. I have absolute confidence in front end grip. Being a 1.1-Way, the LSD doesn’t hamper turn in, and the moment I apply some throttle, it would pull me towards the apex, once I’m on the exit, it’s usually a no brainer foot flat to the floor. Loving it
Started with the OEM open diff to a Quaife, which then broke to be replaced with a JDM LSD, and replaced again with an OS Giken 1.1-Way.
Would be interested to see what other people are doing with their gearbox as well. Car is running about 192wHp with KW coilovers and a variety of street tires as well as semi slicks.
OEM Open Diff
Anyway, the FN2 gearbox has same ratios as FD2R (i.e. 5.1 Final Drive)
But comes with an open differential from factory (at least the pre-2009 model)
Not much to say about open diff really, what a PoS. Understeer was the name of the game, can't put any sort of power down unless the wheel was straight. If I throttle too early in the corner, I just ended up washing wide.
OEM Torsen Diff
Day to day, I don't actually notice the diff, it's smooth and quiet. But most of you guys would know that considering they came like that standard on the DC5R! On track the difference is quiet obvious, you don't have to put the power down so late in the corner. Though you gain traction, it doesn't seem to help the car turn much. I still have to sensitively feather the throttle here and there, it’s still quite easy to overwork the diff, especially on really tight turns where most of the cars weight shifts to the outside.
Quaife Torsen Diff
A bit more of the same really, the difference that I can feel on track is, the Quaife has a slight "tuck-in" affect. Where if you apply throttle, the front end will turn better. Great advantage over the OEM diff as it allowed me to start applying throttle before the apex of the corner. I was quite happy with it till it broke! Was doing a 6000rpm launch at the drag strip with 235 semi slicks, and the side gears failed, sending shrapnel all over the gearbox. Lucky it didn't damage anything. I've never heard of a Quaife failing so I’m assuming I just got a weak one.
OS Giken Limited Slip Diff
I pondered long and hard what to replace the Quaife with wasn't sure if I wanted to go plate type for fear of maintenance requirements and noise. My mechanic insisted I go plate type for the traction and strength. But I’ve ridden on a few FWDs with Kaaz LSD and it was clunky ass! But then I tried my Wuism's DC5R with an ATS/Carbonetics Carbon LSD and it was silent and smooth, so plate type doesn't have to be noisy at all. The thing that put me off the ATS LSD was it recommended you change the gearbox oil every 5000Km and it was very picky on what oil you can use. I wasn't up for spending $150 on gearbox oil every 5000km, so I kept looking.
Then I got this email from OS Giken USA
For our OS Super Lock LSDs we recommend
Using full synthetic fluid (GL-5 or higher)
With a grade of at least 75w140. In Japan,
we use our OS Giken 250R (80W250) oil and will
soon make it available here in the US.
Lighter oil will not hurt the differential,
but you may get some occasional noise.
As long as it is full synthetic, you will be fine.
We recommend that you change your fluid after the
first 3000 miles or first track day after installing
an OS Giken LSD to ensure any foreign particles are
flushed. From that point, however, we recommend you change
fluid as per the normal OE maintenance schedule.
We have had vehicles in Japan using the OS 250R oil go
up to 150k km without and oil change and not harm the
Differential. However, we do not recommend it.
As far as mechanical maintenance, we have not had a differential
failure nor rebuild of any production OS Giken unit in almost 9yrs!
From Website:
OS Giken now proudly introduce our OS Super Lock LSD after 3 years of research and development. This limited-slip differential is derived from our experience of automotive drive train engineering since the 1980's.
It has unique and epoch making-making technologies with adjustable lock timing adjuster. Incredibly durable and reliable, as only the best materials are used for this LSD, regardless of the production cost. Gears are all hot forged, which improves the precision of the product. It also enables us to miniturize each gear, thus providing more space for friction plates. US patent pending bevel gear-in-pressure ring mechanism also allows more friction plates. Increased number of friction plates improves the locking force of the LSD, as it generates less heat, resulting in higher durability even in the toughest racetrack environment.
The higher locking force prevents a weaver action of the vehicle at the drag strip while its bevel gear-in-pressure mechanism allows easier drive feel, close to an OEM diff, during ordinary operations such as parking the car. This mechanism brought another favourable characteristic: it reduces the impact when the power load is applied, preventing the sudden traction change during cornering, or a sudden "pop", making it easier to trace the line. It also produces less mechanical clicking noises.
Using full synthetic fluid (GL-5 or higher)
With a grade of at least 75w140. In Japan,
we use our OS Giken 250R (80W250) oil and will
soon make it available here in the US.
Lighter oil will not hurt the differential,
but you may get some occasional noise.
As long as it is full synthetic, you will be fine.
We recommend that you change your fluid after the
first 3000 miles or first track day after installing
an OS Giken LSD to ensure any foreign particles are
flushed. From that point, however, we recommend you change
fluid as per the normal OE maintenance schedule.
We have had vehicles in Japan using the OS 250R oil go
up to 150k km without and oil change and not harm the
Differential. However, we do not recommend it.
As far as mechanical maintenance, we have not had a differential
failure nor rebuild of any production OS Giken unit in almost 9yrs!
From Website:
OS Giken now proudly introduce our OS Super Lock LSD after 3 years of research and development. This limited-slip differential is derived from our experience of automotive drive train engineering since the 1980's.
It has unique and epoch making-making technologies with adjustable lock timing adjuster. Incredibly durable and reliable, as only the best materials are used for this LSD, regardless of the production cost. Gears are all hot forged, which improves the precision of the product. It also enables us to miniturize each gear, thus providing more space for friction plates. US patent pending bevel gear-in-pressure ring mechanism also allows more friction plates. Increased number of friction plates improves the locking force of the LSD, as it generates less heat, resulting in higher durability even in the toughest racetrack environment.
The higher locking force prevents a weaver action of the vehicle at the drag strip while its bevel gear-in-pressure mechanism allows easier drive feel, close to an OEM diff, during ordinary operations such as parking the car. This mechanism brought another favourable characteristic: it reduces the impact when the power load is applied, preventing the sudden traction change during cornering, or a sudden "pop", making it easier to trace the line. It also produces less mechanical clicking noises.
I put some 75w90 Motul Gear FF Type II in; the diff would only clunk on cold start, when its up to temperature it’s absolutely silent.
At the circuit, the traction difference is like night and day! Absolutely phenomenal, front grip, anytime, anywhere. My limit of traction is now defined by suspension and tire setup. I have absolute confidence in front end grip. Being a 1.1-Way, the LSD doesn’t hamper turn in, and the moment I apply some throttle, it would pull me towards the apex, once I’m on the exit, it’s usually a no brainer foot flat to the floor. Loving it
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