Everything I've read says our cars need 1/8 toe out for autox and 0 for road course. Assuming everything else is working normally, of course.

 

been thinking about this a little lately - i'm starting to think for USDM evos, a 1-way rear diff may be more appropriate over a 1.5 way, for any given situation - is there any reason USDM evos would want partial locking of the rear on decel?

 

 

essentially i think for corner exit, 1.5-way, corner entry, 1-way for better rotation? i have a 1.5-way, i think on decel/turn-in the car's too pushy

 

Corner exit you should be on the gas, so there wouldn't be a difference between a 1 and 1.5. The 1.5 in most cases will make the car more pushy but I wouldn't move to a 1 way if you're doing track stuff for the same reason track guys don't remove sway bars and autox guys do, high speed stability.

 

not to be argumentative, I like these technical discussions:

There can be a difference under accel depending on the ramp angles for all clutch type diffs - i.e., the 141FG uses an aggressive 55 degree ramp angle, vs it's 141F which I believe is a 45 degree, though they are both 1-way diffs.

That said, if we're talking about high speed stability, and for a given 1-way and 1.5-way that have the same cam angle, what we are referring to is the high speed braking stability, correct? Since under accel they would be the same. So for high-speed braking, the 1-way is going to be open, and the 1.5-way is going to weakly attempt to lock the rear wheels together. While I agree that will lead to more stable braking, how much is needed in sacrifice for corner entry is my question. Right now, I feel I have too much binding in my rear diff.

 

My last comment would be assuming that they're using the same ramp angles + have the same amount of clutches etc.

A 1.5 in most cases isn't exactly a weak lock up under decel. No one runs a 2 way for track driving because going full lock under decel would make the car twitchy and hard to control properly. The ramps rates between accel and decel do not have to be equal with a 1.5 way and they can be set to lock harder on decel if for some reason that was desired.

Yes, high speed braking/decel where you come off the throttle. I don't see there being a sacrifice in corner entry, if you're understeering then tune that out with the suspension. What makes you feel the there's too much decel lockup?

 

just a feeling with how the car turns. my set up is pretty darn "loose" i'd say - ohlins 8/10, tanabe fsb w/ cusco brackets set on "soft", WL 24mm on full stiff, 265s all around, various WL bushings for suspension geometry. it's a street car, so it's not gonna be much more extreme than that. then i've got ER's ACD tune, and the cusco 1.5way. the more i think about it, the more a 1-way is the right way to go for the evo. with all it's EBD and diffs working, i don't see it losing much stability under high speed braking, compared to say a rwd car

 

I had John at TRE do a 1.5 way for me. 100% track car and couldn't have been happier.
At the limit a light mid corner lift would help the rear come around. Also enhanced the ability to throttle steer the car around long high speed sweepers.
And made driving it loosy goosy like a rally car far and away better.
Evo's don't like to turn. If you can get the rear to help you'll go faster.

Shoe

 

i'm also interested in trying the OSG 1.5-way - the negative preload springs sound interesting to me, curious what the best place to pick up one of these diffs would be?

 

Any updates on this?

 

yea, my ****ing axle won't go back into the diff. i've tried everything, i'm 95% it's the axle snap ring on the passenger's side (driver's side is inexplicably much smaller, and goes in with the force you would expect). i've stood against the wall with both hands on the axle pushing it in, no go. i'm hunting sources for a smaller snap ring. i think it needs ~26mm, this one is 28mm. I spoke with my friends who regularly work on cars and did this the last time the diff was out. they said getting the axle in was the hardest thing they've EVER done on a car. so, yea. I can get the driver's side in with ease now, and not the passenger's side. i ordered from Mitsu, and it's the same oversized ****. The pn seems to have been superceded and it is likely that the new part is larger. I'm contacting a number of places to see what they've got.

 

Sort of relevant to the rear diff... How is it possibly I missed out on this beauty of an aftermarket piece?
https://www.maperformance.com/produc...SABEgLPyvD_BwE

It's $100 cheaper then the Buschur competitor and aluminum. Eliminates 13 pounds from the rear end.

 

Where have you been? I've been semiactively keeping an eye out for a used one. Maybe I'll just buy new. It's just been low on the priority list for me.