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Old 09-13-2011, 04:04 PM   #1
Storm
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Although I've been using the same couple Subaru R160 LSD's for many years now, I'm making enough torque that the design is pretty much at it's limits. I've overstuffed the preload washers by a hair over 1mm per side and changed the clutchpacks when they would loosen up and start to slip. This is a fairly costly and time intensive process for a budget DIY guy like myself. Here's the guts of the "old skool" Subaru LSD I'm using:

Note, just 4 plates per side....


4 spiders, and 2 way design.


What I'm running into now, is that I have plenty of preload. It's up to nearly 150lb/ft from the scant 60 lb/ft that it was in stock form. My locking force just seems to be lacking. With my car on slicks now, and making much more power than stock, It's painfully spinning the inside wheel(s) more than ever before, and I'm not really lifting them off the ground. The more I read about pressure ring ramp angles, I am curious if changing the angles on the accelleration side of the pressure ring openings to 60* will provide the extra lockup I'm looking for.

Loosely assembled spiders and pressure rings:


If I've been reading correctly, changing the angles to 60* will exert more mechanical leverage against the rings and provide more lockup force between the axles. I don't mind leaving the decelleration side alone, as the off throttle traits are just fine to me, and I'm quite used to how it reacts.

If any of the diff gurus smarter than me can offer some insight as to whether I'm on the right track, it would be most helpful.

Questions I'm looking at right now are:

Will changing the ramp angles actually provide for more lockup force?
Will I have to change the angle on the cross shafts to match the pressure rings?
Will the "longer" openings result in catastrophe?

None of this stuff is sufficiently covered in the gospel sticky threads....so I'm asking here, and will post results.

Jay Storm
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Old 09-14-2011, 09:36 AM   #2
FuJi K
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it will help. I want to mod my R180 like this too.
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Old 09-14-2011, 02:35 PM   #3
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Contact Rallispec maybe as they were among the first to bring this to light though without much fanfare.
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Old 09-14-2011, 04:59 PM   #4
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I've been meaning to call Rallispec, specifically to get some measurements on the R180 rebuild parts. I have a funny feeling those discs are too similar looking to be coincidental....

FWIW....I think I can call myself a liar now..... for as I was browsing pics from the Solo nationals taken by Perry Bennet, I found this shot of me. There's no bump here, and I'm more than rolling back into the gas at this point.

Yes, the front diff is a helical, so 0x0=0....yay me!
phuque......now what am I supposed to work on?

Jay
ps....non-turbo EJ25
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Old 04-12-2012, 04:47 AM   #5
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this 2 way rear LSD came from a type RA 95?
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Old 04-12-2012, 11:55 AM   #6
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LucaWRX: No, it came from a 1989 XT Turbo...

As somewhat of an update, I removed this diff to test with a welded "spool". I encountered the same wheelspin, further proving that I must be unloading the front inside by enough to overpower the helical LSD. I have made changes to the front suspension geometry and chassis stiffness to eliminate flex and lift "in theory". To be tested as soon as the motor is back together.

Changing these ramp angles is certainly on the list of things to do. I will update when complete.


Jay
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Old 04-12-2012, 01:17 PM   #7
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What you have discovered is that there is no such thing as a helical LSD. It's an oxymoron that Quaife has been promoting for a number of years now as part of their marketing spin. Torsen-gleason gear driven diffs do not have a limit to the amount of wheelspin they will allow. They behave as if they are open at the limit. Lift a wheel and have zero resistance and you have no lock.
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Old 04-12-2012, 02:18 PM   #8
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Changing the ramp angle will help. That's what the bmw guys do and it seems to work well for them.
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Old 04-13-2012, 12:18 AM   #9
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Read noob!!!! That's why I wrote 0x0=0
What I discovered was that my angry non-turbo EJ25 is lifting the inside front enough to be a problem. This has NEVER been a problem prior to this motor going in!

I am still curious is I will have to case harden the freshly machined ramps and if I should also machine the cross to match the angles.

Jay
Quote:
Originally Posted by Matt Monson View Post
What you have discovered is that there is no such thing as a helical LSD. It's an oxymoron that Quaife has been promoting for a number of years now as part of their marketing spin. Torsen-gleason gear driven diffs do not have a limit to the amount of wheelspin they will allow. They behave as if they are open at the limit. Lift a wheel and have zero resistance and you have no lock.
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Old 04-13-2012, 01:36 AM   #10
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time to upgrade center diff!
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Old 04-13-2012, 10:01 AM   #11
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Quote:
Originally Posted by FuJi K View Post
time to upgrade center diff!
That pic was taken with the DCCD set in auto, at about 20% aggressiveness. The rear bias was increased to try and get the f***er to rotate more.

Jay
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Old 04-13-2012, 03:49 PM   #12
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Quote:
Originally Posted by Storm View Post
Read noob!!!! That's why I wrote 0x0=0
What I discovered was that my angry non-turbo EJ25 is lifting the inside front enough to be a problem. This has NEVER been a problem prior to this motor going in!

Jay
You call me a noob, but you are the one who still continues to promote the misnomer of a TBD LSD. Stop calling it an LSD and I'll stop hassling you.
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Old 04-13-2012, 10:45 PM   #13
Storm
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Quote:
Originally Posted by Matt Monson View Post
You call me a noob, but you are the one who still continues to promote the misnomer of a TBD LSD. Stop calling it an LSD and I'll stop hassling you.
gotcha, though we both know that if I labeled it a TBD from the start, we'd have seen a dozen replies as to WTF a TBD is. "TBD? Do you mean like an LSD?"
lol

Jay
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Old 04-17-2012, 07:39 AM   #14
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You can buy an STI upgraded ramp angle ring set from japanparts.com but they only list them available for R180 diff centers, contact them and see if there is one for the R160 diff.
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Old 04-17-2012, 09:28 PM   #15
Storm
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Thanks for the tip! I will look into this!!!

Jay
Quote:
Originally Posted by STIV6 View Post
You can buy an STI upgraded ramp angle ring set from japanparts.com but they only list them available for R180 diff centers, contact them and see if there is one for the R160 diff.
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