Wayslow
Wayslow Dork
8/2/22 10:08 a.m.

I'm  sure someone on here has already done this. I have an autoslalom car with an open diff.  A limited slip version doesn't exist. Could I use sensor rings and an ABS pump to make a home brew electronic traction control system? Can anyone point me in the right direction?

GameboyRMH
GameboyRMH MegaDork
8/2/22 10:50 a.m.

If anyone's done that there's a good chance they're on here, but I wouldn't be so sure it's been done before laugh

Turns out it has been done at least once:

https://digikogu.taltech.ee/en/Download/3fc6839e-1fcc-4510-b6c4-e3bc7624aed6

Jesse Ransom
Jesse Ransom UltimaDork
8/2/22 10:56 a.m.

I only just heard last week for the first time about using junkyard bits for standalone ABS (HP Academy has a video up about using a BMW unit in a Land Cruiser). And I think the DIY grade EFI stuff probably does traction control by power modulation, not brake application.

It's hard to imagine that anything from adapting another diff to swapping another drivetrain wouldn't be simpler than building something to modulate the ABS hardware after recognizing the onset of inside wheel slip.

It could also be a lot of fun, of course.

Cactus
Cactus HalfDork
8/2/22 10:59 a.m.

If you put enough electricity into your spider gears you can limit your slip to whatever the tires will provide.

therieldeal
therieldeal Reader
8/2/22 11:31 a.m.

What is the application?

I would generally never recommend one of these as they aren't particularly effective... but it's better than nothing, and much easier/cheaper than trying to engineer your own traction control system. https://phantomgrip.com/

Robbie (Forum Supporter)
Robbie (Forum Supporter) MegaDork
8/2/22 1:21 p.m.

I have thought about this a lot and I would love to do it. I think you need more than an ABS pump though, as ABS is meant to 'release' or push against driver applied brake pressure, you need mechanicals that can apply brake pressure when the driver is not applying. So you might need something from a donor car that has more advanced traction or yaw control, etc. 

Also, some people run manual "fiddle" brakes, which seems like way too much work for me as a driver but apparently it can be done. Think of basically a lever that has one brake master on each side, and when you fiddle it left that applies the left rear brake caliper, when you fiddle it right that applies the right. 

ProDarwin
ProDarwin MegaDork
8/2/22 3:19 p.m.

Isn't this way several manufacturers do in place of a LSD, and they suck?

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
8/2/22 3:30 p.m.
ProDarwin said:

Isn't this way several manufacturers do in place of a LSD, and they suck?

In my personal experience with every VW/Honda we have owned, yes.

trucke
trucke SuperDork
8/2/22 3:52 p.m.
therieldeal said:

What is the application?

I would generally never recommend one of these as they aren't particularly effective... but it's better than nothing, and much easier/cheaper than trying to engineer your own traction control system. https://phantomgrip.com/

I would shy away from Phantomgrip.  A friend of mine (& GRM) makes a version of the PhantomGrip (original design)  If you want it to work, you need to have the gears machined for parallel, perpendicular, and the proper surface finish.  Along with the right material for the plates.  I have a custom one that works great!  Would not touch a Phantomgrip.   

A work of art!

GameboyRMH
GameboyRMH MegaDork
8/2/22 3:57 p.m.
ProDarwin said:

Isn't this way several manufacturers do in place of a LSD, and they suck?

This is a common setup used by OEMs in place of an LSD, and they're...not as good as a real LSD but they're not necessarily bad. Did some offroading in my dad's X-trail and whenever it lifted a wheel in the air, you'd hear some banging noises as the brakes grabbed on the airborne wheel and it would jolt forward with each one. Worlds better than an open diff for offroading. On pavement, all they seem to do is prevent runaway one-wheel-peeling and make your brake pads disappear.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
8/2/22 3:59 p.m.

In reply to Robbie (Forum Supporter) :

The pump part of an ABS unit applies pressure, so yes it already exists.  The rest is just valves.

z31maniac
z31maniac MegaDork
8/2/22 4:55 p.m.

Until I realized you were looking for an "E-diff" and not an "electronically controlled LSD" I was going to suggest pulling one out of the 1LE Camaro's and figuring out the can bus and such. 

84FSP
84FSP UberDork
8/2/22 5:05 p.m.

I had ok luck with a phantom grip due to low cost.  A better verison of it would be fine from my perspective.  They do wear out over time but such is life.

kb58
kb58 SuperDork
8/2/22 5:20 p.m.

It comes down to the purpose. Is it to build one as part of a fun "can I make this work" project, or is there a car sitting there in need of LSD? Budget? Development time? Very different answers.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
8/2/22 5:23 p.m.

I do not see how the phantom grip type diffs even help... they are all preload and no torque based reaction.  A clutch pack diff, even the scrody Positrac/Traction Lok type that use the side and spider gears as the ramps, will apply the clutches more tightly the more torque is applied.  This way the diff locks up when under load but eases off when not needed so much.

A PG type diff will either have to be essentially locked all the time, or not very useful.

It should be noted that all bevel gear diffs have some level of slip limiting already thanks to the thrust loads.  As NSU discovered when they made a cogged wheel type diff that put no side loads on anything...  

Jesse Ransom
Jesse Ransom UltimaDork
8/2/22 7:12 p.m.

In reply to Pete. (l33t FS) :

Certain values of "help?" I'm assuming preload basically gives us the ability to choose, in theory, an amount of improved drive grip and degraded levels of civility, turn-in, etc that can be adjusted along a fairly linear graph from "open diff" to "spool."

That doesn't necessarily suggest that a happy medium exists, that it gets anywhere near "ideal," or that it's worthwhile, just that the continuum may contain benefits.

SkinnyG (Forum Supporter)
SkinnyG (Forum Supporter) PowerDork
8/2/22 9:46 p.m.
Cactus said:

If you put enough electricity into your spider gears you can limit your slip to whatever the tires will provide.

This made me giggle all day.

Thank you!

Wayslow
Wayslow Dork
8/2/22 10:46 p.m.

In reply to kb58 :

This is for my Lotus Europa that has a VW Passat drivetrain. This is the longitudinal 1.8T drivetrain that we swapped directly from the front of the Passat into the rear of the Europa. 
 It works very well except for the one wheel peel at launch and out of corners. Quaife made a LSD for this transaxle but it's pricey. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
8/2/22 10:54 p.m.

In reply to Wayslow :

There is a clutch pack diff available for the 01E transmission from a company in Italy, not sure if they make one for the 01A.  But if you find yourself breaking the 01A based transmission, there is at least a step up.

(I am pretty sure that 034 Motorsport used a Boxster transmission in their mid engined Golf, that would be your source, assuming that the Boxster is "dual pattern".  034 used a V6 which is a different bolt pattern from the 4 but most/all Audi versions of the trans were dual pattern)

kb58
kb58 SuperDork
8/2/22 11:20 p.m.

Yeah if it's for a VW tranny, I think you should be in good shape to find a real LSD, as I know VWs are modified quite often overseas, so they must be out there. Real LSDs are not cheap, figure around $800-$1400, and it's been a while since I bought one. Your car sounds like a nice project, btw :)

Honsch
Honsch Reader
8/3/22 1:30 a.m.

Quaife has a diff that can work in an 012 transmission from the B5 Passat, we have one in our VW Fox race car.

In order to make it work you have to machine out the diff cover for the correct larger bearing, or source a rare and expensive diff cover from Europe.

Paul_VR6 (Forum Supporter)
Paul_VR6 (Forum Supporter) SuperDork
8/3/22 8:18 a.m.

Peloquin has a lot of options for diffs as well for vw/audi, and is my go-to.

therieldeal
therieldeal Reader
8/3/22 10:34 a.m.

I don't speak VW-ese, but MFactory also has a number of VW/Audi diffs.  Perhaps one of them can be made to work.  http://www.teammfactory.com/catalog/mfactory/helical-lsd

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