Let's talk about limited slip differentials
10-30-2010, 11:56 AM
#42
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I mention the sway bar because there is a really tight banked hairpin at my local track that was causing me to lift the inside rear tire. I would just spin that tire on corner exit. Pulling the rear sway bar solved it for me. I assume it helped increase droop travel and let the inside tire get some grip. Worked for me on that particular corner. I think some of the spec drivers found the same thing. May have zero relation to what Sav is seeing. YMMV
http://forum.miata.net/vb/showthread...=362012&page=3
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10-30-2010, 03:33 PM
#43
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I was searching for a diff after driving Johnwag's car with a Cusco. However since putting the AST dampers in I don't feel the need to buy a diff. I was getting on the gas just as soon as I did in John's 130whp car with no-more inside wheel spin when sucking-up the curbs.
"The Elise was always designed from the outset to work without an LSD. We have recently started to offer an LSD as an option on the Toyota engined cars, primarily in response to market demand from the Autocross enthusists in the USA, who need one to be competitive when accelerating away at full throttle from very slow, tight corners in first or second gear.
In this type of competition they do not tend to run high speed (100mph +) corners and therefore the increase in understeer on this type of corner which you get with an LSD is of little negative consequence to them and they therefore are better off with an LSD.
In our experience an Elise or Exige equipped with an LSD is at a disadvantage to one without an LSD on a typical European race track. On top of that the LSD bluntens the steering feel and respsonse of the car which we don't like.
If you want an LSD then by all means fit one, but please understand that there are negative as well as positive effects. In the instance you describe, instead of spinning the inside wheel as you accelerate away at full throttle (which can be easily fixed by modulating the throttle! Very Happy ) a car with a 2:1 LSD like the obne we supply will provide twice the torque to the outside wheel as it does to the inside one. This will increase the slip angle of the outside wheel and the car will tend to oversteer heavily on corner exit, requiring a reduction in throttle if you are not to spin.... It isn't much quicker, honest.
The optional diff we supply is a Torsen unit, the aftermarket unit supplied by Motorsport is a plate diff, with a similar 2:1 bias and no preload so in terms of action it mimics the Torsen closely."
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10-30-2010, 04:21 PM
#44
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Maybe you have an advantage you haven't fully explored yet. This discussion is about Lotus'. Perhaps it's applicable, perhaps not?:
"The Elise was always designed from the outset to work without an LSD. We have recently started to offer an LSD as an option on the Toyota engined cars, primarily in response to market demand from the Autocross enthusists in the USA, who need one to be competitive when accelerating away at full throttle from very slow, tight corners in first or second gear.
In this type of competition they do not tend to run high speed (100mph +) corners and therefore the increase in understeer on this type of corner which you get with an LSD is of little negative consequence to them and they therefore are better off with an LSD.
In our experience an Elise or Exige equipped with an LSD is at a disadvantage to one without an LSD on a typical European race track. On top of that the LSD bluntens the steering feel and respsonse of the car which we don't like.
If you want an LSD then by all means fit one, but please understand that there are negative as well as positive effects. In the instance you describe, instead of spinning the inside wheel as you accelerate away at full throttle (which can be easily fixed by modulating the throttle! Very Happy ) a car with a 2:1 LSD like the obne we supply will provide twice the torque to the outside wheel as it does to the inside one. This will increase the slip angle of the outside wheel and the car will tend to oversteer heavily on corner exit, requiring a reduction in throttle if you are not to spin.... It isn't much quicker, honest.
The optional diff we supply is a Torsen unit, the aftermarket unit supplied by Motorsport is a plate diff, with a similar 2:1 bias and no preload so in terms of action it mimics the Torsen closely."
"The Elise was always designed from the outset to work without an LSD. We have recently started to offer an LSD as an option on the Toyota engined cars, primarily in response to market demand from the Autocross enthusists in the USA, who need one to be competitive when accelerating away at full throttle from very slow, tight corners in first or second gear.
In this type of competition they do not tend to run high speed (100mph +) corners and therefore the increase in understeer on this type of corner which you get with an LSD is of little negative consequence to them and they therefore are better off with an LSD.
In our experience an Elise or Exige equipped with an LSD is at a disadvantage to one without an LSD on a typical European race track. On top of that the LSD bluntens the steering feel and respsonse of the car which we don't like.
If you want an LSD then by all means fit one, but please understand that there are negative as well as positive effects. In the instance you describe, instead of spinning the inside wheel as you accelerate away at full throttle (which can be easily fixed by modulating the throttle! Very Happy ) a car with a 2:1 LSD like the obne we supply will provide twice the torque to the outside wheel as it does to the inside one. This will increase the slip angle of the outside wheel and the car will tend to oversteer heavily on corner exit, requiring a reduction in throttle if you are not to spin.... It isn't much quicker, honest.
The optional diff we supply is a Torsen unit, the aftermarket unit supplied by Motorsport is a plate diff, with a similar 2:1 bias and no preload so in terms of action it mimics the Torsen closely."
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10-30-2010, 09:31 PM
#45
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Is a preloaded torsen possible? Is it possible to squeeze a small self-contained viscous or clutch unit inside the torsen and attach it at the center of the output gears? How much room is in there? It wouldn't have to provide for the full strength of limited slip, it would only be preloading the torsen unit. If it put 50 ft-lbs of preload on the torsen, then the torsen would treat a wheel in the air as having (0+wheel inertia+50 ft-lbs) of torque, and would use that to apply torque to the grounded wheel.
Also to note, you won't have to service a Torsen, unlike a clutch pack. (No clutch plates to wear).
I would say Torsen style for the street, clutch for the track.
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10-30-2010, 09:46 PM
#46
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The Torsen T2R is preloaded
http://www.torsen.com/products/T-2R.htm
By combining the patented Equvex gearing from the Torsen T-2 with a coil spring pre-load and/or friction enhancing plates, the Torsen T-2R can remain locked, providing torque to both wheels, under low torque inputs. The addition of the friction plates allows the Torque Bias Ratio (TBR) to be tailored to differential design needs.
http://www.torsen.com/products/T-2R.htm
By combining the patented Equvex gearing from the Torsen T-2 with a coil spring pre-load and/or friction enhancing plates, the Torsen T-2R can remain locked, providing torque to both wheels, under low torque inputs. The addition of the friction plates allows the Torque Bias Ratio (TBR) to be tailored to differential design needs.
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10-31-2010, 05:00 AM
#47
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No, there is no room inside a torsen. We use one on the FSAE car because of the very tight turns we have.
Also to note, you won't have to service a Torsen, unlike a clutch pack. (No clutch plates to wear).
I would say Torsen style for the street, clutch for the track.
Also to note, you won't have to service a Torsen, unlike a clutch pack. (No clutch plates to wear).
I would say Torsen style for the street, clutch for the track.
bullshit the torsen doesnt need service. it wears as much as anything else, even more, with the proper amount of power applied to it
OSG for street and track : its better at everything, period
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10-31-2010, 11:51 AM
#48
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True the torsen does have wear parts, they look something like the conical springs in a clutch type but are much smaller and there is one for each of the helical gears.
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10-31-2010, 01:42 PM
#50
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Has anyone here tried the S2K diff swap in there miata? I thought about it but couldn't find the stub shafts that you need out of the S2K cheap enough so I just went the RX7 route. Those Honda dont let parts go cheap.
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10-31-2010, 04:41 PM
#51
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I would say that the giken unit is properly set up too. no point in arguing, osgiken diff= best diff for our miatas :P Please find someone that has tested one, that disagrees .
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