OS Giken Diff Review
02-01-2016, 02:24 PM
#1
OS Giken Diff Review
The Car
My car is an S2000 CR prepared for SCCA STR autocross class. It has coilovers, offset balljoints, an adjustable rear sway bar, 17x9s all around, 255 EHP tires(sometimes 245), and some basic bolt-ons for power. I've been developing my car with another STR S2000 driver (well, he does all the R&D as well as a good bit of the wrenching and I just try to learn as much as possible in the process). Our cars have the same shocks, spring rates, sway bars, and alignment. The biggest difference from a handling perspective was the clutch-type LSD he had in his car vs the stock torsen in mine.
The Driver
I'm a mid-pack driver. I've done one NT and one prosolo and finished 5th of 12 and 6th of 12. I feel like my experience and skill level is in line with most of the others in the R&C forum who are looking to get faster and learn to develop their car. My codriver is on that upper level with one NT win and several second place finishes in NTs and Prosolos. I'm typically .5s - 1s slower than him on low speed courses and 1-2+ slower on high speed courses.
During development I noticed that my friend’s car always felt more stable than mine, even when we put the same set of wheels and tires on both cars and ran the same course. With everything else being the same, I attributed it to the differential. Also worth noting, I was always slower than my friend by the most significant margins when we were driving my car with the torsen. When we drove both cars on the same course with the same wheels and tires, his fastest time was in my car with more power and a torsen while my fastest time was in his car with less power and a clutch-type diff. Before I had thought that a clutch-type differential was more for the top level guys driving for all the marbles but my observations suggest they’re more for the guys in my shoes--not so much to inflate times, but also as a learning tool.
Coincidentally, when I started shopping for a diff Speed Freaks was just starting an OS Giken group buy. I’ve had great experiences with Speed Freaks in the past--getting parts to my doorstep faster than any other vendors I’ve worked with, overnighting brake pads to me at the track, and calling me before shipping when my orders didn’t look right--so I said sign me up.
The Installation:
I picked up a used complete diff and carrier from an '07 with around 30k on it as well as a pair of new output shaft bearings and new OEM diff mounts from Majestic Honda. My friend disassembled it and marked everything for reassembly.
Checked the backlash.
The ring gear attached to the OS Giken.
Checking the wear pattern after assembling.
Swapping the diff carrier out was a breeze with two people. I already had the exhaust off for other maintenance and we popped the upper balljoints off the rear knuckles to get clearance on the halfshafts. It took us the length of the Panthers Seahawks playoff game to complete the swap, with a little break during halftime to see the highlights and first drive of the second half. The only thing that really caught me off guard is the service manual I had only listed the torque specs for the AP1 input flange. After a quick look on s2ki I saw the AP2 is 36ft-lbs.
My Initial Impressions:
I've run one event so far with the differential. The big difference in the car is the added stability. There are a few crucial benefits you get with the added stability. Obviously it’s great for when you’re pushing the limits of the car. It also gives you the confidence to ignore your survival instincts that are telling you that you’re going to fast and need to slow down. Last but not least, the added stability allows you to push the limits of the car and still have consistent results in your times--helping you analyze what about your driving is working and what isn’t.
In the past I've been pretty good about pitching the car into a corner with trailbraking but most of the time when I get the rotation I need to get through the corner, I need to counter steer past 12 o'clock to keep the car in check on exit and end up scrubbing speed. Now with the OS Giken, as long as you keep your foot in the gas the diff will progressively lock, making the car want to go straight. Now I can pitch the car into the corner and recover on exit without a big correction and without scrubbing any speed. Evidence of this behavior can be seen here where I give the corner workers a little scare. Here my reaction was based on the way the car used to handle. When the back end starts coming around, I overreact with my correction and the car just goes the direction I point it.
http://www.youtube.com/watch?v=A-YA0sKWxgc
I ended up with the smallest gap between my codriver and I that I've ever had, .2s. In the past I felt like I would dedicate about 60% of my focus on car control and the remaining went to driving the line. Now it's like I'm dedicating 20% of my focus to car control and the rest split between the line and carrying entry speed. It really felt like my technique improved more on that day than any other so far. Here's my best run from that day.
http://www.youtube.com/watch?v=Gd7KVXSb-uU
My car is an S2000 CR prepared for SCCA STR autocross class. It has coilovers, offset balljoints, an adjustable rear sway bar, 17x9s all around, 255 EHP tires(sometimes 245), and some basic bolt-ons for power. I've been developing my car with another STR S2000 driver (well, he does all the R&D as well as a good bit of the wrenching and I just try to learn as much as possible in the process). Our cars have the same shocks, spring rates, sway bars, and alignment. The biggest difference from a handling perspective was the clutch-type LSD he had in his car vs the stock torsen in mine.
The Driver
I'm a mid-pack driver. I've done one NT and one prosolo and finished 5th of 12 and 6th of 12. I feel like my experience and skill level is in line with most of the others in the R&C forum who are looking to get faster and learn to develop their car. My codriver is on that upper level with one NT win and several second place finishes in NTs and Prosolos. I'm typically .5s - 1s slower than him on low speed courses and 1-2+ slower on high speed courses.
During development I noticed that my friend’s car always felt more stable than mine, even when we put the same set of wheels and tires on both cars and ran the same course. With everything else being the same, I attributed it to the differential. Also worth noting, I was always slower than my friend by the most significant margins when we were driving my car with the torsen. When we drove both cars on the same course with the same wheels and tires, his fastest time was in my car with more power and a torsen while my fastest time was in his car with less power and a clutch-type diff. Before I had thought that a clutch-type differential was more for the top level guys driving for all the marbles but my observations suggest they’re more for the guys in my shoes--not so much to inflate times, but also as a learning tool.
Coincidentally, when I started shopping for a diff Speed Freaks was just starting an OS Giken group buy. I’ve had great experiences with Speed Freaks in the past--getting parts to my doorstep faster than any other vendors I’ve worked with, overnighting brake pads to me at the track, and calling me before shipping when my orders didn’t look right--so I said sign me up.
The Installation:
I picked up a used complete diff and carrier from an '07 with around 30k on it as well as a pair of new output shaft bearings and new OEM diff mounts from Majestic Honda. My friend disassembled it and marked everything for reassembly.
Checked the backlash.
The ring gear attached to the OS Giken.
Checking the wear pattern after assembling.
Swapping the diff carrier out was a breeze with two people. I already had the exhaust off for other maintenance and we popped the upper balljoints off the rear knuckles to get clearance on the halfshafts. It took us the length of the Panthers Seahawks playoff game to complete the swap, with a little break during halftime to see the highlights and first drive of the second half. The only thing that really caught me off guard is the service manual I had only listed the torque specs for the AP1 input flange. After a quick look on s2ki I saw the AP2 is 36ft-lbs.
My Initial Impressions:
I've run one event so far with the differential. The big difference in the car is the added stability. There are a few crucial benefits you get with the added stability. Obviously it’s great for when you’re pushing the limits of the car. It also gives you the confidence to ignore your survival instincts that are telling you that you’re going to fast and need to slow down. Last but not least, the added stability allows you to push the limits of the car and still have consistent results in your times--helping you analyze what about your driving is working and what isn’t.
In the past I've been pretty good about pitching the car into a corner with trailbraking but most of the time when I get the rotation I need to get through the corner, I need to counter steer past 12 o'clock to keep the car in check on exit and end up scrubbing speed. Now with the OS Giken, as long as you keep your foot in the gas the diff will progressively lock, making the car want to go straight. Now I can pitch the car into the corner and recover on exit without a big correction and without scrubbing any speed. Evidence of this behavior can be seen here where I give the corner workers a little scare. Here my reaction was based on the way the car used to handle. When the back end starts coming around, I overreact with my correction and the car just goes the direction I point it.
http://www.youtube.com/watch?v=A-YA0sKWxgc
I ended up with the smallest gap between my codriver and I that I've ever had, .2s. In the past I felt like I would dedicate about 60% of my focus on car control and the remaining went to driving the line. Now it's like I'm dedicating 20% of my focus to car control and the rest split between the line and carrying entry speed. It really felt like my technique improved more on that day than any other so far. Here's my best run from that day.
http://www.youtube.com/watch?v=Gd7KVXSb-uU
02-01-2016, 03:36 PM
#3
It sounds obvious but it's easy to forget that the fastest guy is usually the guy who has the throttle down the most time over the course. The ability (or confidence) to put the hammer down as much as possible means a lot.
As I'm sorting the handling of my own car and building my meager skills, I'm getting more comfortable with the rotation induced by the stock diff and how I can apex a tad earlier and use the diff to get the car to yaw a bit and complete the direction change while under full throttle. But there's also corners where that behavior saps confidence because the car might already feel loose and I'm afraid getting on the gas will just make it rotate too much. I'm guessing more confidence to be able to handle whatever the car does when you get on the gas is probably faster, even if it's pretty fun to exit the corner with a pinch of rear slip angle. If matting the gas can be the solution to the car rotating too much, that's probably a pretty consistent and quick way to exit a corner.
As I'm sorting the handling of my own car and building my meager skills, I'm getting more comfortable with the rotation induced by the stock diff and how I can apex a tad earlier and use the diff to get the car to yaw a bit and complete the direction change while under full throttle. But there's also corners where that behavior saps confidence because the car might already feel loose and I'm afraid getting on the gas will just make it rotate too much. I'm guessing more confidence to be able to handle whatever the car does when you get on the gas is probably faster, even if it's pretty fun to exit the corner with a pinch of rear slip angle. If matting the gas can be the solution to the car rotating too much, that's probably a pretty consistent and quick way to exit a corner.
02-01-2016, 04:16 PM
#4
Thanks, man.
To add on to your point, the fastest guy is usually the guy who has the throttle down with the steering wheel straight the most. I don't see any way someone with skill as limited as mine is going to be able to hold full throttle and no wheel angle as long with a torsen as they can with a clutch-type when driving at the limit.
You can still drive the car with a decent amount of rear slip angle but now you get the car straight by feeding in throttle instead of shuffling the wheel. It's almost like cheating.
It sounds obvious but it's easy to forget that the fastest guy is usually the guy who has the throttle down the most time over the course. The ability (or confidence) to put the hammer down as much as possible means a lot.
As I'm sorting the handling of my own car and building my meager skills, I'm getting more comfortable with the rotation induced by the stock diff and how I can apex a tad earlier and use the diff to get the car to yaw a bit and complete the direction change while under full throttle. But there's also corners where that behavior saps confidence because the car might already feel loose and I'm afraid getting on the gas will just make it rotate too much. I'm guessing more confidence to be able to handle whatever the car does when you get on the gas is probably faster, even if it's pretty fun to exit the corner with a pinch of rear slip angle. If matting the gas can be the solution to the car rotating too much, that's probably a pretty consistent and quick way to exit a corner.
As I'm sorting the handling of my own car and building my meager skills, I'm getting more comfortable with the rotation induced by the stock diff and how I can apex a tad earlier and use the diff to get the car to yaw a bit and complete the direction change while under full throttle. But there's also corners where that behavior saps confidence because the car might already feel loose and I'm afraid getting on the gas will just make it rotate too much. I'm guessing more confidence to be able to handle whatever the car does when you get on the gas is probably faster, even if it's pretty fun to exit the corner with a pinch of rear slip angle. If matting the gas can be the solution to the car rotating too much, that's probably a pretty consistent and quick way to exit a corner.
You can still drive the car with a decent amount of rear slip angle but now you get the car straight by feeding in throttle instead of shuffling the wheel. It's almost like cheating.
02-01-2016, 06:52 PM
#7
Due to the precision manufacturing, high-grade materials, and unique design, a break-in period nor rebuild is required for OS Giken LSD’s. OS LSD is purposefully over-engineered to offer the best performing, most durable clutch-type LSD available.
Thanks. I definitely recommend trying it--especially if you can drive the same course back to back with and without.
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02-03-2016, 10:30 AM
#8
Former Sponsor
Thank you for posting such a thorough review! I have noticed the same increase in stability as you describe but possibly to a lesser extent since I chose to spec mine a little differently than the standard unit. The clutch pack type LSD really seems to help smooth out the the breakaway characteristics of the S2000 and as a result I think many people will find it easier to pickup the throttle sooner and reach closer to the limits with the added confidence as you describe.
-Matt M.
-Matt M.
02-03-2016, 02:12 PM
#9
Registered User
