Limited slip diffs

[eimc]

<_< Iam looking into a Audi cp. - ITB car The only issue is it has a open diff. Any openions on this particular car(1986 Audi Cp.) ? Thanks Paul

[RSTPerformance]

Paul... we have been fairly successful with our development of the audi coupes... contact me with a PM and we can chat...

as for limited slip, it is the same as a porche 944...

as for compedability... we win with them, with some of the toughest compeditors in the country IMO!!!

Raymond

where are you located? and are you purchasing a built car or building your own?

[eimc]

Raymond PM&#39;d you Paul

[Bildon]

Is that Andy&#39;s old GT3 GTI?

Also, you guys need to stop running the Torsen diffs. The clutch types are cheap now and much more effective.

[JamesB]

I guess my question about the clutch type is how often do they need to be serviced or rebuilt? Torsen is pretty much maintinence free. then again due to budget I will be running a welded diff for some time to come. Oddly, once you get used to what it wants to do in corners its not that bad except in the paddock.

[eimc]

Is that Andy&#39;s old GT3 GTI?

Also, you guys need to stop running the Torsen diffs. The clutch types are cheap now and much more effective.
[/b]
Yes it&#39;s Andrew Kings old car. We purchased it about 14 months ago. Did a few changes(cylinder head mods etc) and ran it in PHA (pa hillclimb assoc. ) for a complete season. Please tell me the difference in how a clutch type diffs handles compared to a Torsion diff. The car has a peloquin now. Thanks Paul

[ryotko]

Please tell me the difference in how a clutch type diffs handles compared to a Torsion diff. The car has a peloquin now. Thanks Paul
[/b]

Hey Paul,

Slow night at work here.

I am no expert by any means but I think the big difference is with a TBD (like the Peloquin) if you put a wheel into the loose stuff or get it off the ground you&#39;re back to a one wheel wonder and don&#39;t put any torque to the road. I think it&#39;s something to do with x% of 0 torque = 0 torque. I think there&#39;s also different kinds of clutch type diffs. Some lock up only while accelerating and some lock up during acceleration and deceleration. How this effects handling I don&#39;t know.

I&#39;m sure Bill S. will chime in here and explain things better.

Now for my question. Can anyone explain the effects various types of diffs (LSD, welded, open) have on handling and driving style? Due to my budget my only option at this point is welding up a spare that I have but I hate to do something that I&#39;ll hate later.

Thanks,
Bob

[JOESELLSVW]

Hey Bob, How are you? If you&#39;re looking for a gearbox for your (my!) car I still do have the box that I had BSI build for that car. It has the 4:32 ring and pinion and a Quaife, freshly rebuilt. The total receipt from BSI was $2060! I&#39;ll sell it for $1000. since it&#39;s not legal in the A3 GTI. It has never been used! I hope to make it out to a few events this year... I think that Otto&#39;s will be sponsoring the Pagoda and Dureya hillclimbs. PhillySCCA will be doing more events at Warminster also. Joe

[ryotko]

Hey Bob, How are you? If you&#39;re looking for a gearbox for your (my!) car I still do have the box that I had BSI build for that car. It has the 4:32 ring and pinion and a Quaife, freshly rebuilt. The total receipt from BSI was $2060! I&#39;ll sell it for $1000. since it&#39;s not legal in the A3 GTI. It has never been used! I hope to make it out to a few events this year... I think that Otto&#39;s will be sponsoring the Pagoda and Dureya hillclimbs. PhillySCCA will be doing more events at Warminster also. Joe
[/b]

Are you trying to double the value of my (your) car or something? That&#39;s very tempting. With a 4.32 I might actually use 5th gear on the hill. Let me see what I can scrape up. No promises but I&#39;ll be in touch. I hope you do make it out to Reading this year, it&#39;s so close. It would be great to see you. I&#39;m moving within 1/2 mile of the Warminster site this spring/summer so I plan to make a few events. I have no excuse, I can hear the cars from my new back yard.

How&#39;s the baby?

-Bob

Sorry for the hijack Paul....

[eimc]

Yo Bob not to change the subject buttttttt... What does the "warn O% " at the bottom of location mean? Also forgot to tell you I now have a silver enclosed 20 ft trailer for this year. Have to go wife is calling. Paul

[racer_tim]

Driving styles do differ with a locked diff vs a LSD or open. With a locker, you need to be on the loud pedal in order for it to turn. Remember, the inside tire is traveling the shortest distance, or it has the most "friction"

Also, making slow 90 degree turns around the paddock is also very challenging.

I had my tranny freshened up and the diff locked for $600 back in 1993. Haven&#39;t done anything except change the RedLine MTL each year, but that&#39;s it. It has 5+ years on it and no additional wear.

I also change the hubs/bearings and 1/2 shafts each year and have only had 1 CV joint failure.

[shwah]

I am in the process of building a box with a locker now.

I am going this route due to - lower $$, power always available at either wheel, friends that have had very good experiences running them.

Anything should be better than the open diff I have now.

[eimc]

Hey Bob, How are you? If you&#39;re looking for a gearbox for your (my!) car I still do have the box that I had BSI build for that car. It has the 4:32 ring and pinion and a Quaife, freshly rebuilt. The total receipt from BSI was $2060! I&#39;ll sell it for $1000. since it&#39;s not legal in the A3 GTI. It has never been used! I hope to make it out to a few events this year... I think that Otto&#39;s will be sponsoring the Pagoda and Dureya hillclimbs. PhillySCCA will be doing more events at Warminster also. Joe
[/b]
If Bob doesn&#39;t take your trans I will . Is a 4:32 a good ratio for hills? I currently have a 4:64. Thanks Paul

[racer_tim]

Paul, if you really want to increase your R&P number, go down to a 13" rim and run the 20x8x13 or the 20x9.5x13 slick. The overall tire diameter reduction running your 4.32 will act like a 4.6x

I have a stock close ratio GTI box with the 3.94 in it. In IT trim, running the 205x55x14 tires, I never used 5th gear. When I converted it over to GP and now run the 13" slicks, I only use 3-4-5 at all 3 tracks that I run.

My 3.94 with a 13" rim and a 20" overall diameter slick makes it act like a 4.30 or so. I haven&#39;t done any numbers to prove this, but that&#39;s what it feels like.

[ryotko]

If Bob doesn&#39;t take your trans I will . Is a 4:32 a good ratio for hills? I currently have a 4:64. Thanks Paul
[/b]

Wow Paul. Jumping right in there are ya? I left Joe a message this morning, so maybe I&#39;ll pick up a second or two this year.

Now I have to find out what happened to my wife and who this is that is taking her place and letting me spend money. :&#39;)

-Bob

And I have no idea what that "warn" thing is next to my name. Maybe the Admin. is an old girlfirends dad or something.

[Al Seim]

FWIW, I did quite a bit of research on the fwd LSD options and here were my "findings" (based on talking and reading, not testing):

Locked - light and maintenance free (unless welds break), gives odd handling which some like and some detest. Spool is lightest and most reliable version of this.

Torque-biased clutch type (like the Bildon unit) - excellent handling and excellent torque transfer, almost certainly best choice for a powerful car. Re handling, should decrease power understeer vs open, similar otherwise. (By torque biased, I mean that a cam pushes the clutches tighter under power than under overrun) Should last a long time and can be rebuilt.

Pure gear-type torque sensing "Torsen" type (Quaife and Peloquin) - excellent handling and good torque transfer, with the limitation that no load on light wheel (think mud, wet grass or lifted) may result in no drive at all. Re handling, should decrease power understeer vs open, similar otherwise. Should last forever.

Mark Coffin has driven both the clutch and gear type units, and if I understood him correctly, saw little to no handling difference between them.

Kirk Knestis did the research and bought a Bildon clutch type and is, I think, happy. I did the research and bought a Peloquin (from Bildon) and have yet to install it, so we&#39;ll see (hopefully soon). My car is an HP Scirocco and will have only ~120bhp, that influenced my choice, as well as a fascination with the Torsen units and the fact that the Peloquin is US made, by a small business.

All that said, I think that Bill S. is on the money in that the clutch type is probably best for the widest range of track-only applications.

Hope that provides some insight,

Al Seim
Race Technology USA
(Formerly Action Digital Inc.)

[racer14itc]

As Al noted, I&#39;ve driven a variety of limited slip and torque sensing diffs but I haven&#39;t driven a locked diff (welded).

Currently I have three gearboxes with three different diffs: Quaife, Clutch type (VW Motorsports), and cam & pawl diff (Gemini).

The Quaife requires the MOST smoothness in driving style and throttle application. As long as you understand the limitations of the Quaife (uloading the inside tire will result in some wheel spin) it will work well. Very little to no maintenance, allows trail braking into corners, excellent turn in. It requires a slightly later apex in corners to be fast. It is heavy so there is more of a "flywheel" effect, especially in lower hp cars.

The VW Motorsports limited slip is lighter than a Quaife, will not slip AS MUCH under power but still will slip if you exceed the bias ratio of the diff (which is dependent on the clutch friction surfaces, ramp angles, etc.). It does require maintenance and the parts are becoming more difficult to find. It unlocks on corner entry, helping turn in and facilitating trail braking. You can be a bit more agressive off-line with the power (when trying an inside pass for example). Good luck finding a VWMS limited slip for older gearboxes.

The Gemini type of diff is a cam & pawl design which is simpler than the clutch pack type but is self destroying by design. It is light and effective but will require more frequent maintenance. When fresh it is probably the fastest of the three designs but will continue to deteriorate over time.

The reason the torque biasing diffs are so popular are because of their reliability, little to no maintenance and they are huge improvement over an open diff. They (in theory) should be a lot easier on the drivetrain components of a FWD car (CV joints, gears, etc.) than a welded diff. The limited slips are probably faster (at least that&#39;s what I&#39;ve consistently found although the improvement is small but in racing tenths are important).

If you&#39;re building a locked diff and race a VW, I&#39;d recommend you go to bildon&#39;s website and buy the spool instead of welding your diff. It&#39;s lighter, and you don&#39;t have to worry about welds breaking or flaking off and ruining your gears/transmission.

MC