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 Post subject: 1.5 or 2 way lsd?
PostPosted: Tue Jan 26, 2016 8:06 pm 
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3rd Gear
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Looking to upgrade my oem torsen lsd in my 2013 frs. Any input on of I should go with a 1.5 or 2 way? I want lock on decel so 1 way isn't in the picture. I think 1.5 way would be less hairy recovering from oversteer. Thoughts?

I found last year that my car was pretty useless coming out of turn 2 on the uphill. It would unload almost all the weight and the torsen would allow the light wheel to spin up even with lowered throttle.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Tue Jan 26, 2016 8:07 pm 
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Oh and as far as the 2 ways being much clunkier I don't care about street behavior. I want whatever works best at the limit on the track.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Tue Jan 26, 2016 11:26 pm 
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Why do you want lock on corner entry?

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Tue Jan 26, 2016 11:46 pm 
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Good question... From the reading I've been doing most are suggesting 1.5 way instead of 1 way for circuit grip use.

Thinking on the principle of how the LSD works though, I would think lock on decel would actually promote understeer, or a resistance to turning in the very least, compared with a 1 way...

I'm definitely under informed on the subject, so perhaps to rephrase the thread title, which clutch based LSD would you suggest for track use?


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Jan 27, 2016 12:37 am 
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A locked diff on decel will give you some issues with turn in, and bigger issues with understeer as you get back to throttle, you can of course setup the car to work in this configuration, and drive to accommodate, but its much easier to have it open, or very little lock off throttle.

Torsen diffs in RWD cars for track use, in my experience, are not very good. A clutch type is prefered, so you are going in the right direction to move away from the torsen.

With a clutch type, there are many many variables, I would research what others have good experience with.

We have 2 cars with clutch type diffs, and one with a spool which we are converting to a locker over the winter. The spool is 100% lock all the time, it is not great, essentially you are always sliding the rear of the car, if it is hooked up, its understeering. The locker we are going to is 100% open off throttle, and 100% locked on throttle, a bit brutal, but they are effective in big HP, big slick racecars. This car had a torsen when we first got it to AMP and it sucked, then it broke.

The 2 clutch diffs we have a are quite different from each other, different ramp angles, different pre-load, # of discs, but both are quite open off throttle, and both work REALLY well putting down power, very smooth, very easy to modulate the throttle at the apex, etc.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Jan 27, 2016 7:37 pm 
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Thanks for the insight Paul.

Can you speak to any of the pluses for the slight lock on decel? I am finding the overwhelming majority of people using the FRS/BRZ for lapping choose 1.5 way for lapping. 1 way seems to be the differential of choice for auto cross with these cars.

The decel locking rate is much lower on a 1.5 way. See the chart attached for the Cusco RS. It looks like ~ 35% decel lock vs. accel.

Image

I find a lot of folks are praising the rear end stability you get from the decel resistance, but I can't put my finger on why that would be the case.

Have a look at my exit from 2. You can see even on what ended up being my quickest lap, with a concerted effort to not overdrive the car on the corner exit, I still have to dial in some countersteer to keep things in check. I am new to track driving, so this is quite possibly just my poor driving skills, but I found the torsen pretty useless in that spot; each and every lap.

https://www.youtube.com/watch?v=Q4cl0w2-IPg

The Cusco RS can be setup for 1 way, 1.5 way and 2 way, with the parts included. The OS Giken (while supposedly a better diff) is not easily changed without buying extra cam plates.

I really want to make sure I'm making the right decision here.

From what I'm finding online, pros of 1 way are easier to drive properties, and better turn in. Pros of 1.5 way are better stability on braking, but at the cost of turn in, especially if you're overdriving.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Thu Jan 28, 2016 12:21 am 
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I don't think some lock on decel is bad at all, the diff in our GT3 car is about 20% locked on entry. High percentages of lock, or fully locked is for sure not an ideal way to go, trust me, I have struggled to change how I drive to work with the spool in our gt1 car all year.

I can't see any of the standard OTS salsbury type diffs for the FRS being bad.

Meant to ask, are you having issues with the Torsen?

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Thu Jan 28, 2016 12:35 am 
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Our diff is set up with 30/90 ramps and a small amount of static preload. I guess that would technically make it a 1 way diff. Only place I'e ever dealt with the 1, 1.5 and 2 way terminology is with Japanese cars and Gran Turismo, most all the German stuff is usually dealing in degrees of ramp angle. That said, I do like a small amount of preload but the more open the better on entry and mid turn for me. I also want something that locks up fairly quickly and aggressively on accell.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Thu Jan 28, 2016 9:15 am 
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We are running the same setup as Steve but I thought this would be considered a 1.5 way because it is not 0/90. I could be wrong with the terminology, not sure. I think a little lock under decel is good to help keep the car straight under hard braking especially on a bumpy track when the rear of the car is so unloaded.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Thu Jan 28, 2016 10:33 am 
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I think most of us run 1.5 way diffs by definition, a locker is a 1 way at 0/100.

In my mind anything under say 30% lock on decel is pretty close to open, not sure there would be much feeling in those low % numbers in a street based car.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Thu Jan 28, 2016 12:52 pm 
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Yes the 1.5 way is considerably less lock on decel. I think I might try the cusco rs and do some testing with it setup on 1.5 vs 1 way. If I find any understeer at 1.5 configuration I could try removing all decel lock and see how it treats me.

Thanks for the input everyone much appreciated.

Oh and Paul, there's nothing wrong with my torsen other than the fact it doesn't perform very well, most notably in 2nd gear turn 2.

Mike


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Sat Feb 06, 2016 5:10 pm 
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Paul, what didn't you like about the performance of Torsens? I know they aren't as reliable as lockers and spools on high power and slick cars but why not on street based RWD cars?

Mike, any chance you were lifting or significantly unloading the inside rear wheel? Most Torsen diffs don't have a preload so it won't transfer much power if the inside wheel has no traction. I have actually switched from a clutch LSD to a Torsen and it worked wonders coming out of turn 2. Night and day difference. My car is much more softly sprung in the rear and has a solid axle so it's less likely to unload one wheel as much as yours. I think I read that the T2R torsen has a preload or can be ordered with a preload spring that allows it to work even if one wheel is completely lifted but it will probably has a much higher TBR and will understeer more on power compared to stock.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Sat Feb 06, 2016 10:22 pm 
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theramseye wrote:
Paul, what didn't you like about the performance of Torsens? I know they aren't as reliable as lockers and spools on high power and slick cars but why not on street based RWD cars?



I have never found that they work that well, especially on IRS RWD cars. I have driven a few of them and they all had the same issues, too much inside wheel spin, especially if you involve curbs.
I think with a REALLY stiff setup you might get one to work ok, but then you compromise other things. they may work better at bigger, smoother tracks as well.
We destroyed one in our pro stock car in one day of testing, unknown as to why, it was working, then complete failure.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Feb 10, 2016 11:02 am 
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My old bmw has a 30% clutch type lsd that also shortened my final drive ratio. User friendly on the street and added a few seconds to my lap time.

My old 911 also has a (much nicer) clutch based lsd. I have it setup for a more street friendly 40/60, meaning it locks up more on deceleration (60%) than acceleration (40%). With a rear engined car this helps keep the rear behind you on trail braking, and you need less lock on corner exit given these cars have so much rear grip under power anyway. So a lsd in a 911 is biased reverse to what a traditional rwd, front engine car would have.

I could set it to 50/80... But that is only advised for dedicated race cars.
Image

And the whole 1 way, 1.5, two way, 40/60, 30%... It is all a bit of hand waving, or at least an oversimplification of how these things work.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Feb 17, 2016 2:37 pm 
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theramseye wrote:
Paul, what didn't you like about the performance of Torsens? I know they aren't as reliable as lockers and spools on high power and slick cars but why not on street based RWD cars?

Mike, any chance you were lifting or significantly unloading the inside rear wheel? Most Torsen diffs don't have a preload so it won't transfer much power if the inside wheel has no traction. I have actually switched from a clutch LSD to a Torsen and it worked wonders coming out of turn 2. Night and day difference. My car is much more softly sprung in the rear and has a solid axle so it's less likely to unload one wheel as much as yours. I think I read that the T2R torsen has a preload or can be ordered with a preload spring that allows it to work even if one wheel is completely lifted but it will probably has a much higher TBR and will understeer more on power compared to stock.


I think that was the issue that I was significantly unloading the inside rear wheel.

I think I need to re-evaluate how I take T2. What I was doing wasn't working for me. My OEM torsen works great for straight line stuff, but if you've got the car leaning significantly it seems to love to spin up the light corner.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Feb 17, 2016 3:09 pm 
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Mike Hiscott wrote:
theramseye wrote:
but if you've got the car leaning significantly it seems to love to spin up the light corner.


S2000 has a torsen and I always had the same problem. lifting the rear inside wheel and not being able to put power down. Softening the rear anti roll bar is all it took to eliminate it. I didn't have an adjustable rear bar, so I just took it off. I had to soften the front anti roll bar stiffness and driving style a bit to deal without it. the car is a bit slower in transitions and will roll more, but no traction problems at all.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Feb 17, 2016 6:31 pm 
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The car does have kwv3 coilsovers. I wonder if some adjustment to the rebound and dampening settings would provide any relief.

I love the fact the car is a bit tail happy. I'm running stock antiroll bars front and rear. It would be interesting to disconnect the rear bar for a session, but I'm thinking I'd be less able to rotate the car with trail braking that way.


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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Tue Mar 08, 2016 1:06 pm 
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Late to the game here. I run a Torsen in the truck. Admittedly it's a pretty non-standard 'race car' but I find it works well in auto-x. I've never had an issue with it not locking up, even with the inside rear tire off the ground. I have the T2 version though, maybe it has a different torque bias than the other versions. I run without a rear swaybar as well but only because it's extremely tail-happy otherwise.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Sun Mar 13, 2016 10:30 pm 
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Paul Machan wrote:
theramseye wrote:
Paul, what didn't you like about the performance of Torsens? I know they aren't as reliable as lockers and spools on high power and slick cars but why not on street based RWD cars?



I have never found that they work that well, especially on IRS RWD cars. I have driven a few of them and they all had the same issues, too much inside wheel spin, especially if you involve curbs.
I think with a REALLY stiff setup you might get one to work ok, but then you compromise other things. they may work better at bigger, smoother tracks as well.
We destroyed one in our pro stock car in one day of testing, unknown as to why, it was working, then complete failure.


Oh okay. I hear a lot of Mustang guys don't like them either for 1/4 mile runs with radials or slicks. Probably because they work by binding so a lot of torque + a lot of traction means a lot of stress. I'd imagine that the main disadvantage to a SRA is an advantage in a torsen - when one wheel goes up, it pushes the other down and there's no camber gain. Wouldn't a softer rear bar or softer rebound on a two way adjustable help as opposed to going stiffer? or a little bit more travel if the wheel is lifting clean off.

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Wed Mar 16, 2016 7:48 am 
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This guy has a 1.5 available.

http://www.ft86club.com/forums/showthread.php?t=102895

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 Post subject: Re: 1.5 or 2 way lsd?
PostPosted: Fri Apr 01, 2016 5:00 pm 
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OS Giken, nice. Looks like it went in a heartbeat though.

I'm still on the fence on the OS Giken/Cusco, but I'm focusing on getting the car built back up for the '16 season before pulling the trigger.


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