Johnny's review of the
OS Giken Twin Disc race clutch and the front and rear Super Lock Limited Slip Differentials that are utilized on the Subaru Impreza Race Car.
We put our newly VEX Performance built, OS Giken sponsored, open class Subaru rally car on our dirt test track for the first time on March 16th 2010.
Knowing I was to give feedback I was prepared to bring my "A" game when it came to schmancy writing words, and observations from a drivers perspective. But all that I could say after even the first lap was.... wow, unbelievable, awesome, unreal, wow.... etc etc etc etc. Which probably wouldn't really be that helpful. So I will try to calm my crazy excitement and put this in phrases far more understandable. The best place to start, as with any spec race car, is understanding the purpose of our race car build!
We have built an open class Subaru that will compete in the 2010 Western Canadian Rally Championship and the Canadian Rally Championship in 2011 and beyond. We needed a build that would suit the classing and rules of the Canadian Association of Rally Sport (Cars) and be competitive in its top open class. We started with a GC8 Impreza chasis stripped it bare, and began seam welding and caging the car. This provided a rigid and safe chassis as our foundation. We added GD (04 Sti) subframes for a wide, strong stance, and began adding Sti and race components to the car. The car will run roughly 300hp and 300 torque to the wheels, and weighs the minimum 2500lbs required by the Cars rulebook. In addition to Pro Rally, I will be driving the car at rally cross, time attack, and autoslalom events. Because of this, we wanted to keep the competitiveness of the other styles of racing in mind while planning.
When we started talking to OS Giken about using their clutch and prototype Subaru front and rear Super-Lock LSD's our team's head Tech was very excited. He was beaming about it for days! After receiving the components we were all amazed at the quality of design and manufacturing, and the install was a perfect fit.
Now, after 40 minutes on our test track, let's talk clutch. The quality was immediately apparent. The friction point is so gentle that it's more street-able and easy to drive than a stock OEM clutch, yet when you run up the revs and launch the power is immediately yet smoothly applied to the ground. I have driven many different clutches in many different cars and in many different situations. Daily driving, track, dirt, snow, etc, in cars from a Neon to a Porsche, and I have never found one so easy to drive. I have also had many different performance clutches, and most resemble a light switch. Power on, or off, not very comfortable, and usually have a steep learning curve especially with heel-toe downshift in order to drive smooth and not upset the weight transfer of the car. The OS Giken twin disc race clutch was so comfortable even when double-clutching, that I took to it right away like a "Trekkie" talking smack about Star Wars. Here are my main points this clutch is worth every penny from a drivers perspective.
#1 In order to be fast you must be smooth.
#2 You need a clutch that can hold strong power and torque.
#3 Lighter flywheels make your car more responsive in the throttle
#4 The more relaxed and less you have to work the better you will drive, especially after a long day of racing!
#5 rebuildable clutches save you $$$which means you can enter more events and get better as a driver.
#6 You will abuse your clutch, and you want one that can take it.
#7 Chicks are impressed when you say "yeah... I only buy the best for the things I love" as you point to your ride.
The OS Giken clutch delivers on all these points.
Let's talk traction. What is the number one mod you can do to your car, and what should everyone do first? OK it sounds like I am going to say LSD but... I am going with tires. Why tires? Because they are the only part of your car that touches the road, and traction is everything in not just racing and performance driving, but in handling and safety on the road; not to mention mending bones, which has nothing to do with tires, I digress. With traction you can control your lateral G's when cornering, your braking and of course acceleration and all the ways those 3 go together. Now, let's talk about the best way to control the traction that you have available to you through your tires. Everyone will go straight to suspension here, and they should, however differential setup doesn't get talked about enough in my opinion. So let's talk diff's.
Remember this "all limited slip differentials are NOT created equal!" After the initial time on the track in dirt conditions with our OS Giken Super lock LSD's installed in the front and rear of the Subaru, I know this to be true. My amazement at the control I had over the car literally left me speechless, well sort of. All I could yell was amazing, unreal, unbelievable, wow, amidst the laughing in sheer joy. The best way I can put it is this: In rally, I find that I need to change from corner to corner using both understeer and oversteer slides depending on available traction and all the varying elements on a stage. With STOCK suspension, sway bars etc., the car became as easy to handle as the clutch was to drive. This is before we add the upgraded suspension, sways etc., and start to tune the suspension. To be a little more descriptive as a driver I was able to control the car very comfortably on corner setup, entry and exit by using mainly the throttle. At every turn, tight hairpins, and fast flowing turns the OS Giken diff's afforded me an incredible measure of control. I was seriously knocked off my feet like nothing I had felt in a car before. I started to change my driving style and my lines, experimenting with early, neutral and late apex, extreme oversteer driving and understeer to traction styles on a variety of corners and the outcome was always comfortable, consistent, predictable, and smooth. Even when I threw the nose of the car into a hard left with intense positive camber on the road the back end still rotated exactly how I wanted it to under acceleration. Because of this I am even more excited for the new car this season, and I am now a firm believer that these products are well worth every penny spent, and I will joyfully recommend them to anyone that wants their car to be competitive, fun, comfortable, smooth and consistent.
I look forward to honing this fantastic Subaru platform with the stability that the OS Giken products afford us. And I wholeheartedly recommend these products as essential to any build, with great tires and suspension, even before adding power!