I have a bit of a conundrum, I have a 4.1 Torsen II diff and a 4.1 Tochigi Fuji Super on hand. I've done some research and it seems the TFS has some preload on the torsen, but at it's core is still a torsen unit? It's for a track only Exocet is there a better/worse option for installing my shiny new gears on ?
Honestly, if you can swing it, the OS Giken is the guy to get. Torsens are nice for being unobtrusive, and are a damn sight better than the viscous LSDs, but they still go open if you lift a tire. Not sure if that's as big an issue on the Exocet as a stock body Miata. Btw, the 3.63 gears with the 6-speed is the cat's pajamas. I'm running that combo in my car
Tochigi Fuji Super is a much cooler name so I'd go with that one.
Don't the TFS diffs have a habit of spitting parts out? I'd stick to the Torsen.
In reply to NickD :
Yeah - I've heard that, but haven't had too many issues with my car/power levels (<200hp). I'm running it with the 5 speed for now, though I have the 6 speed and short shifter - for the tracks I'm at I'm trying to avoid that 5th gear shift - with the Exocet keeping lock up at bay is really hard without having to worry about the extra downshift. I'm keeping the 13" wheel to avoid having to deal with 0 offset wheels (additional load on bearings, etc) - I have a theory that 13" wheel (20.5" high) + 3.63 gears at this power level is going to be near perfect, but hey - who knows?
In reply to EvanB :
That's reasonable.
In reply to cmcgregor :
Well I have nothing first hand, but from what I heard it wasn't a major issue? I suppose more likely because it does have additional parts, but I'm also not running big power.
EvanB said:Tochigi Fuji Super is a much cooler name so I'd go with that one.
Plus it looks cool written on the side of the car. The hard part is writing it backwards on the other side of the car.
Neither one is great for track use. You need a clutch type LSD for that. The ToFu diff will break the tangs off the cone clutches in street use, while the Torsen will likely not break anything. There may be a way to get a bit more limited slip from the Torsen, but I am unsure how.
I'd stick with the Torsen for it's reliability. I would wager Torsens last much longer than the TF, which looks like a metal-on metal single puck pseudo clutch LSD.
Also, is this a street car, or track car? Because without FI, I'd spring for the 4.10
In reply to gencollon :
The car is rotrex supercharged, the 4.1 w/ the wheels I'm running is fairly annoying at Road Atlanta (front straight needs a 5th gear shift) and NCM . @ Baber it's fine, but I think the longer diff will help. See the above graphs for the gear spacing.
I do know a clutch diff is probably better, but I seriously doubt it's the weak point (that's the driver). I'm looking for reliability mainly.
I would venture a guess that the regular Torsen is going to be the most reliable. With the low weight and realllly low tire weight it might even be more reliable than in a stock miata (under same use) in spite of having a bit more torque going across it.
That's what I figured, dropped off the torsen unit and R&P to be installed, fingers crossed it goes well.
ChasH said:Neither one is great for track use. You need a clutch type LSD for that. The ToFu diff will break the tangs off the cone clutches in street use, while the Torsen will likely not break anything. There may be a way to get a bit more limited slip from the Torsen, but I am unsure how.
A Torsen is great for track use IF you're not lifting drive wheels off the track. A torsen/wavetrac or 1-way clutch type are the best diffs for track use IMO (next to individual wheel-motors, which aren't a diff 
)
In reply to GameboyRMH :
I've seen RWD cars lift the front wheel, but is it a common problem for track miata's to lift their rear wheel? Everyone on this thread seems to be indicating this is a common problem? Apparently I need to be driving way harder. I guess I could see on some curbs... Or are we generally referring to autoX? I don't care too much about autoX. I don't run a rear sway bar either, so maybe that's playing a role.
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