Why you need a LSD if you like cornering!

[CSG Mike]

Originally Posted by ZDan

Same-day back-to-back testing, same car, same driver(s)?

The S2000 should have a lot more to gain with a "better" limited slip, and of the two racing clutch-types tested in the GRM article, one was 0.4 seconds quicker and the other was .04 seconds quicker vs. the factory Torsen. Gokart course, 40 second laps, but arguably the benefits of a better limited slip should be exaggerated vs. most tracks.

Same day, same session, spec cars that are otherwise identical, same drivers.

Specifically, Emilio of 949 racing. He is an OS Giken dealer, but the testing was actually performed to confirm that a clutch LSD does improve performance.

Why was the testing performed? Because it settled the debate on whether to ban aftermarket LSDs for the Supermiata series. It was banned because if it was allowed, it is mandatory to be competitive. Thus, with all aftermarket diffs being banned in the series, everyone runs an OEM Torsen.

[CSG Mike]

Originally Posted by Ubersuber

My interest is in how such modifications would affect use as a street car, given that even track junkies will be streeting this car 99% of the time.

My interest also is in stimulating discussion about what is really going on when the lsd is installed and whether it is the diff, the driver or other modifications that are responsible for the claimed lower lap times.

As you know, the "correct" answer to the percieved problem depends on what you want out of your BRZ/FRS.

Preload too high? You get LSD engagement at parking lot speed turns. You correct it by properly setting preload appropriate to the tires you run.

Now, if you're hardcore enough to be running slicks at the track, and set the LSD for that, then you're probably going to be willing to deal with the ratcheting.

[CSG Mike]

Originally Posted by Sleepless

So, which LSDs are people installing in the FT86? What are your practical results, observations, critiques

We've had a mixture of OSG and Cusco units go into the car. The net result is the same, and even the units themselves are nearly identical.

We've played with a lot of different settings on server different cars (and different platforms), and I can say that a badly tuned LSD can get REALLY annoying on the street. However, even an off-the-shelf LSD will make the car be substantially more behaved when cornering hard (both entry and exit; effect is lesser mid-corner unless you're at the level where you can consistently throttle steer)

We consider it essential enough that a pair of LSDs (front and rear) were the first mechanical modifications that went in our 2015 WRX; the STI already comes with a front rear, and center LSD. Now if we could somehow get a center LSD into the WRX...

[Element Tuning]

Even factory STi diffs can wratchet so it's not really "unacceptable" in a performance car. My Cusco in my race car is only bad with a near full lock turn so that's like backing out of your driveway or parking lot situations.

I'm sure one day I'll have one and sooner than later if a sponsor tosses one my way

[CSG Mike]

One thing I'd like to point out, is the exotics. Everyone is constantly pointing out that exotics often have a Torsen (older) or electronic differential (newer), when they're obviously a very high performance car. There's a few reasons for that.

Exotics, while being high performance, are still luxury cars. Your average owner expects to only hear the engine. As such, they make the differential unintrusive, and brake pads quiet (street pads). They also have the budget to use things like electronic differentials, instead of a mechanical.

[wparsons]

Originally Posted by CSG Mike

Exotics, while being high performance, are still luxury cars. Your average owner expects to only hear the engine. As such, they make the differential unintrusive, and brake pads quiet (street pads). They also have the budget to use things like electronic differentials, instead of a mechanical.

A lot of exotics have also done away with sway bars but that doesn't mean we should all go remove ours right now.

[gramicci101]

Originally Posted by CSG Mike

Now if we could somehow get a center LSD into the WRX...

Is the DCCD in an STi a separate removable unit like the rear diff LSD is? Or is it woven into the inner workings of the transmission? If it's removable, do you think it would fit in the WRX transmission? If it's not... transmission swap? 6 speeds must be better because they have 1 more speed, right?

[CSG Mike]

Originally Posted by wparsons

A lot of exotics have also done away with sway bars but that doesn't mean we should all go remove ours right now.

Precisely!

[CSG Mike]

Originally Posted by gramicci101

Is the DCCD in an STi a separate removable unit like the rear diff LSD is? Or is it woven into the inner workings of the transmission? If it's removable, do you think it would fit in the WRX transmission? If it's not... transmission swap? 6 speeds must be better because they have 1 more speed, right?

I'm actually not sure, since I know the effects, but haven't examined it mechanically.

It'll be swappable once the STI transitions to the FA20DIT...

Also, 2015 WRX is a 6 speed with taller gearing than the STI in all gears....

[gramicci101]

Originally Posted by CSG Mike

I'm actually not sure, since I know the effects, but haven't examined it mechanically.

It'll be swappable once the STI transitions to the FA20DIT...

It's probably built into the transmission itself, to save weight and size.

Originally Posted by CSG Mike

Also, 2015 WRX is a 6 speed with taller gearing than the STI in all gears....

Is it? Huh. I ought to go lie to the dealer and take one for a test drive. I won't buy one though; not having a turbo was actually one of the selling points for the BRZ when I was shopping.

[acro]

Originally Posted by Ubersuber

Well, in most cars putting that level of torque down you would not expect much wheelspin let alone "power" oversteer. The key to this question even needing an lsd to answer lies in understanding how Subaru/Toyota even got here in the first place. It was designed in and for better handling it needs to be designed out.

Others may differ with me on this but the evidence is clear that Subaru/Toyota deliberately designed the FRS to be tail happy, the GT86 slightly less so and the BRZ even less so. The BRZ is still more tail happy than is ideal which is one reason for all these suspension mod threads.

I don't see these cars as tail happy and I have a gt86. I see them as balanced. Buts maybe that's just me.

[CSG Mike]

Originally Posted by gramicci101

It's probably built into the transmission itself, to save weight and size.



Is it? Huh. I ought to go lie to the dealer and take one for a test drive. I won't buy one though; not having a turbo was actually one of the selling points for the BRZ when I was shopping.

Even better! The 6 speed is expensive, but nearly a bolt-on for a WRX. IIRC, it's just a transmission though. Time to log into that 10+ year old nasioc account...

[gramicci101]

Originally Posted by CSG Mike

Even better! The 6 speed is expensive, but nearly a bolt-on for a WRX. IIRC, it's just a transmission though. Time to log into that 10+ year old nasioc account...

The DCCD is a separate unit. Check this out.
http://forums.nasioc.com/forums/show....php?t=2384890

Here's a shot of the internals.

Would it fit? Not a clue. It's an interesting idea though.

[Element Tuning]

The STi 6 speeds are totally different and way stronger than the 6 speed used in the new wrx or the frs/brz. The DCCD center diffs cannot be installed in a WRX, BRZ, or Legacy 6 speed. They also vary depending on the year STi trans as they are conversion diffs (different front vs rear final drive in some models).

We are breaking 3rd and 4th gears in the 700 hp range (under race conditions) but that's pretty good for a factory transmission