Best type of LSD for track use
 

I'm starting to think about putting an aftermarket LSD in my FRS after last year's track days. I use the car for grip driving on roadcourse/time attack as well as some autox.

Currently I'm using the oem torsen diff, and I have found the car to not be very planted on corner exit. Particularly when weight is uneven on the rear axle.

I had done some research on this prior to now and many folks seem to suggest a 1.5 way (say a cusco or os giken) would be great for track use. I wonder, though, if a 1 way may be better. Wouldn't a 1.5 way promote a bit of understeer on corner entry due to the push of it effectively providing rear lock on the entry?

I'd love to hear some input on this from guys who have used both in track environments.

Mike

"People on Ludes should not drive"

When we ran an open diff we were experiencing understeer in some long sweeper corners from middle to exit.

After installing a Cusco 1.5 the car still had the same understeer in the sweeper but exit speeds for other corners increased.

We loosened the preload on the diff to allow the inner rear wheel to "freewheel" a bit more and solved the problem easily.

With a diff it's one more component to fiddle with set-up adjustments. Compared to an open diff, where grip issues need to be fixed using suspension and tire pressures.

We have no experience with a 1-way.

Good luck

Only if you enter the corner with an unbalanced car (aka you're rushing the entry and the car isn't settled).

For autox, you want a 1 way. For a road course, you want a 1.5 way.

You'll need to decide if AutoX or Road course is more important to you; if you're unsure, a 1 way is "easier" to drive.

The stock is a 1.5 way in behavior.

Also, I'm pretty sure I'm the *ONLY* person on this board who has experience with more than one brand of aftermarket LSD for this platform. I can probably answer all of your questions, as long as they're specific.

Sounds like a suspension tuning and/or tire pressure issue to me. If you aren't lifting the inside rear wheel off the ground, then the stock Torsen should be fine.

This is probably a rat hole, but why did you put an open diff in the car?

Whats with the caps? I'm on here, experience with multiple brands.

OP, sounds like upgrading to a clutch type is will do what your looking for. As for picking what brand and settings thats up to you. OS Giken are very highly regarded but the price isn't for everyone. Kaaz, Cusco, MFactory are a little friendlier on price. I have been experimenting with an OEM MK3 Supra clutch type LSD for a few months now, lots of fun and real cheap.

My Supra LSD is sort of a 2 way in that it doesn't differentiate between accel and decel. I don't AutoX but I would say there would be some front end push if I did. The flip side of that is an increase of stability under braking in a faster, larger turn scenerio. This I enjoy. I had to make some little finesse adjustments in my driving style to suit the LSD but now I've got a feel for it and I'm super happy.

If I was shopping again for a LSD it would be a 1.5 for my uses. It's also possible to have a LSD that can be adjusted from 1.5 to 2 or 1.0 to 1.5. Sure you have to remove it to make the adjustment but at least you can make the change without purchasing all over again.

You don't have to lift the wheel to turn the Torsen into an open diff, only apply enough torque to lose traction (spin) with one wheel.

I actually teach a variation of a controlled single rear wheel traction loss to induce faster yaw rates under specific circumstances on track.

Thanks for the input Mike.

I likely do more auto slalom than lapping, but I take the track more seriously, and do slalom more for fun.

I have had no issues with the car understeering with the stock differential. It's more that I found I couldn't get on the power exiting turns as early as I figure I should be able to.

Here's a video of the track I run at. You can see at T2 (tight left uphill) I struggle to put much power down without unstabilizing the rear.

[ame="https://www.youtube.com/watch?v=Q4cl0w2-IPg"]1:21:69 at Atlantic Motorsports Park - YouTube[/ame]

The car has all whiteline products available for it, kw v3 coilovers, and ~ -3/-3 fr/rr camber. I currently run zero toe as I do DD the car in the summer, but I am open to mucking with some toe out to stabilize the car a bit on braking.

The car does make over the stock power. Around 280 wheel or so. That could climb to around 300 wheel next year.

From a lot of the reading I've done, many have suggested the 1.5 way for track use. When I brought this up on a local pro solo forum, an experienced driver suggested I would be better off with a 1 way due to the push/understeer I would realize with a 1.5way. I'm not sure what to think as I don't really know of a clear set of pros/cons of both.

I was leaning towards the OS Giken til now, but the Cusco RS seems to get a good rep, and would allow me to try both 1 way and 1.5 way and see what I prefer.

What measurable differences am I likely to see between the 1 and 1.5? Is there a significant benefit to 1.5 way in having a small amount of lockup on decel that I should consider? I see braking stability mentioned alot, but I'd love to hear your take on it, having used both.

Last point - I like to drive like a bit of a hooligan in closed course environments, and enjoy the ability to control oversteer and force slides when I want to. By no means am I constantly drifting around like a mad man, but I wouldn't want to make the car into an understeer machine in order to shave a few tenths at the track. I like having a tail happy car, and enjoy playing with the limits of grip.

Any insight or suggestions would be much appreciated.

Mike

Thanks for the input mrk1. Your build is badass by the way. I love seeing updates to your thread.

The point about going with a differential that allows multiple configurations is a good one. The Cusco allows this. I wouldn't have that flexibility with the OS Giken.

I think the 1.5 way is a great starting point, but the downsides to the lock on decel that I'm reading about are making me nervous of that option. I definitely don't want to be stuck with an option I don't enjoy driving.

I'd really like some more insight on the benefits of the 1.5 vs 1 in terms of braking stability.

I normally don't condone the acts of being under the influence while driving especially while on the track.

It seems to me your rear is a bit unsettled, which is where the rear oversteer manifests in that tight corner. The LSD would definitely help there, but you'll still need to modulate the throttle, even with the LSD; you'll just be able to put down a bit more power, a little earlier.

CSG has both the Cusco RS and the OSG in stock at the moment.

The rear was definitely loose. Bear in mind this was on 215 width RE11a. I will be running 245 width RE71r this summer on a 17x9 tc105n. Last year I was on the stock wheels.

Shoot me a PM on the pricing of those units if you don't mind. I'm struggling on the Canadian dollar exchange atm. Still trying to decide whether to commit now and take the 45 percent currency hit, or hope things improve and the price of oil stabilizes and ride it out til the CAD comes out of the toilet lol.

Mike - Can you give any insight into what benefits I would see with the 1.5 way on braking stability vs 1 way? How are the OS Gikens setup from the factory? I know you can custom order them for different configs, as they can't be changed between 1/1.5/2 like the Cusco. Have you tried both diffs back to back?

:lol:

At least someone else caught it.
Surprised no-one pointed out where my quote was from (dates me)