Need advice: FD Torsen or aftermarket Clutch type diff
 

I have a 89 RX-7 Turbo II with the stock viscous limited slip differential. I've come across a deal for the FD torsen differential, which should slip into the pumpkin of my turbo II without any problems. However, I have also been considering a 1.5 way clutch type diff, like a Kaaz. Based on your experiences, which would be the better choice for autox and/or road racing? I posted on a local Auto x forum, and the majority seem to prefer the clutch types. Because of that, I'm slightly leaning towards the clutch type right now. If I do get it, what would be a good brand to get? The 3 that seem to be most prevalent are cusco, kaaz, and mazdaspeed.

I've heard good things about both, so it's difficult for me to make my decision. If it helps, I run in BSP. Thanks. :)

cusco by far better than kaaz, yes have driven both,

by order

1.ATS
2.Cusco
3.kaaz

Go with the Torsen, especially if you're a beginner.
The Torsen has the more linear lock-up characteristics.

Keep the clutch-types for drifting. :)


-Ted

Why not a s4 t2 lsd? They're cheap, rebuildable, capable of handling lots of power and do not have the clunking the kaaz guys complain about. The torsen is easier to drive in tight corners, but is a weak link for a high hp car.

because a s4 is a clutch-type LSD.

It really does depend on how much power you are looking to put out. For a modest amount of power, the Torsen is the way to go. In auto-x, if you're not careful with the clutch-type, (huge generalization coming up) you'll get a nice amount of understeer, followed by power-on oversteer in the tight corners.

Yeah, reduced turn in is the one thing that I'm afraid of. However, can't the clutch plates be adjusted to lock a little less, resulting in easier turn in?

As of right now, my power is staying stock. My class does allow for open exhausts and fun stuff like that though. However, my car is built for the sole purpose of track/autocross and is generally only goign to be driven to and from events. I have driven it maybe 10 miles since my last event 2 weeks ago.

Yeah, it's hard to make the decision :p

stock power, go with the torsen.

You can adjust the clutch plates if you want to rip out your diff everytime. I prefer the smoothness of the torsen.

As with any clutch-type LSD, it wears out.
Torsens do not if you don't blow it up.
Normally, you should not be killing a Torsen unless you're drag racing.


-Ted

go with a clutch type for roadracing.

you do realize the clutch-type's take away from your turn-in, which is not what you want for road racing, right?

Stick with the torsen.

The 2 fastest autocross RX7's in the nation run KAAZ 1.5 clutch type LSD. If you are generating larger cornering forces with larger wheels and tires, you will tend to lift the inside rear tire briefly and the torsen will spin. If you end up getting the KAAZ, set it to the 66% locking. Turn in is as good as the torsen on our car. Add a little friction modifier to get rid of the bad clunking.

true, i forgot about the fact that in autox, it's very easy to lift wheels in the tight sections......

Torsen's don't work at all if one wheel loses traction completely (i.e. lifts off the ground)

On the circuit though, there aren't many corners that force you to three wheel your car, now, are there?

The curbing can do it, if the car is stiffly sprung.

-bill

So you would still recommend a clutch-type diff vs. a torsen diff?

Well, I think it depends on the car, the suspension, the power, the driver, etc. Many of the ITS people seem to prefer the clutch-type. I imagine that they are willing to trade off a little of their turn-in for the ability to better put down power coming out of the turn. But I also know of several people who run torsens because they are fairly easy to source (from Miata's) and are pretty bomb-proof at the lower power levels.

But what do I know, I currently run an open diff. :D Not an ideal solution, but I look at the positive side: if I get the line correct through Oak Tree turn at VIR the car lets me know by spinning the inside rear tire coming off the curbing!! ;)

-b

Yeah, a load of autox people all seem to prefer the clutch type diff to the torsen. The torsen works fine for what it is, but if I step up to stickier tires (which will be necessary if I want to be competitive) then the clutch type will work better if the tires lift off.

I'm still of the opinion that on a road course, the torsen would be ideal, since there's no way you should (competitvely speaking) three-wheel every corner on the track.

Unless you have a VW rabbit I doubt you will ever lift a tire...

Get the Torsen... when your driving skills increase.... then look into other options.

Andy McKee (AMRX7) has won multiple national SCCA autox events with a Torsen for many years. He finally stepped up to a Kazz after breaking a couple Torsens (he thinks there may have been some shifting in the diff housing as he simply swapped in used ones and they broke immediately... after running his stock Torsen for years). He makes much much more power than your little T2 and has 315/17's up front and 335/17's out back.

indycars and champcars run torsens. And i have used one in my roadrace rx7 since 1997. many wins and championships. zero failures witha 430 hp motor. I do run a cooler with a pump which is mandatory for roadracing with this diff.

wouter