[urq] Locking diff actuators - some history of options

Fri Feb 12 14:46:58 PST 2010

Thats exactly right... in version 1.0, when you hit the diff lock button 
the solenoid engaged, but I found that with an adequate flogging they 
would eventually come undone.  Version 2.0 had a timer circuit in it, 
that kept pulsing the solenoid a few times a second to keep it engaged, 
and it worked perfectly.
Bob

qshipq at aol.com wrote:
>  Hmm...  I spent dozens of hours on 'better' locker designs about 5.-6 years ago.  At that time I emailed D'Amato on the idea of using solenoids, before I went to the electro-pneumatic route with the stock vacuum actuators.  The problem I confirmed with D'Amato with solenoids is they need to be re-hit at given intervals, the vacuum actuators always hold (and with extreme prejudice I might add), which meant to me, the electro-pneumatics are the best avenue.   Aux push-on push-off switches for the boxes can be mounted anywhere, and there is also a single ground hit (blue white speed sensor wire in stock app) that can be used to disable both diff locks at any time. The problem I was having with the vacuum actuators at Steamboat altitude and at track events, is that sustained boost tends to reduce the vacuum reserve in the actuator locking system.  At the time, I also designed a system using a cruise control pump and electric vacuum switch, but found that the cruise control motor can only generate about 17in of vacuum, whereas a properly designed vacuum resevoir  (read: big reserve) system to the IM, can hold a consistent 25inHg or more.  I also double up the ck valve to the vacuum resevoir system which increased the overall vacuum reserve total by another inch or so of Hg.
>
> Also to note that all <84 urq's use a center diff return spring under the boot for the center diff rod into the transmission.  84> quattros did not use this spring, and I have removed them from several 83 cars without any issues.  However, keeping the spring will create a problem if using a solenoid or vacuum actuators, in that the 'return to unlocked' spring tension is pretty significant.  
>
> The best part of the electro-pneumatic setup is using the graphic and the rear diff switch (91>94 audi q rear).  The switch triangle will light when activated, and go out when deactivated, but the graphic LED's will only light/go out when the diff is 'actually' locked or unlocked.  Very nice for racing or competition ice/rallycross driving.
>
> WRT Andrews question on Center diff locked on tarmac tracks = All the time!  The rear can also be used (see Jeff Goggins and my posts in the archives), but it is a different driving style, and it chews tires.  In designing the 5ktq racecar I service, I locked the center by welding, and used a torsen rear.  Randy Probst drove it at Brainerd in 03, and commented on how well it handled as we outran the Beddor SQ in all but the straights.  I'll admit I like locker center/torsen rear for tarmac, but like the locking rear better for rallycross, ice or low cf conditions.
>
> HTH and my .02
>
> Scott J
> 84 Urq
> 83 Urq ice track car
> Eventmaster
> USAudiclub Gruppe-q Steamboat Ice Driving Experience 2010
> www.USAudiclub.com
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> -----Original Message-----
> From: John Cody Forbes <cody at 5000tq.com>
> To: larichard at plguide.com; laraa at sympatico.ca; vittorio at mybares.com; qshipq at aol.com
> Cc: urq at audifans.com; quattro at audifans.com
> Sent: Fri, Feb 12, 2010 3:58 pm
> Subject: Re: [urq] Tire pressure for ice racing ?
>
>
> I've seen (Mark Besso and Bob D'amato on a 4kq rally/hillclimb car) electric door actuators from a junkyard used as diff lock solenoids. They put buttons on the steering wheel so the diffs could be unlocked quickly and easily without taking your hands off the wheel. Seems like the way to go to me! 
>  
> -Cody Forbes 
>  
> -------------------------------------------------- 
> From: <qshipq at aol.com> 
> Sent: Friday, February 12, 2010 3:20 PM 
> To: <larichard at plguide.com>; <laraa at sympatico.ca>; <vittorio at mybares.com> 
> Cc: <urq at audifans.com>; <quattro at audifans.com> 
> Subject: Re: [urq] Tire pressure for ice racing ? 
>  
>   
>> L-A 
>> If you are looking to 'win' a competition, then the rear diff should be > locked, as coming out of a turn apex it will give you more traction.  I > won FTD in the 42 car SCCA Ice Rallycross at Steamboat in 97 using this > technique on a borrowed 5ktq with Blizzacks (somewhere in the archives I > did a turn by turn breakdown).  Basically, if you have a tight turn, just > before the turn unlock the rear diff, and blip the throttle (unlocks rear > diff), then at the apex, lock the rear again, and repeat.  Center always > locked. 
>>
>> In my old 83 urq, I rigged up two late style electropneumatic rear diff > switches to run the center and rear diffs.  The key is to have as much > reserve vacuum (I added a vw eggcrate style vacuum accumulator tank) as > possible, so that the diffs can lock and unlock when under boost. 
>>
>> All that said, for Steamboat, I just lock the rear all the time.  The > trick there is to come up hot to all tight turns in a straight line, brake > hard, then take the turn slow.  Or, if wanting to dance, you can just > leave the rear locked, and go at it, like you can see me driving the track > mars-urq in front of fellow urq lister Nate E in a 90q 
>> http://www.youtube.com/watch?v=KfxjwHWuTzA 
>>
>> With a lot of sheer ice, the rear diff locked will always yield better > control IMO/E.  If the cones are tight, it's not as easy, but good > directional placement can be had by just a quick dump of the clutch (quick > in/out to disengage the driveline, helps oversteer). 
>>
>> WRT 3000rpm, the technique I use is to keep the engine at 3000> all the > time.  If there is a snow hook-up section, I'll run close to redline, > which once traction is gained, keeps the car spooled up enough to not bog. > I used this same technique in a 90q20v at the 6900ft track, which worked > just as well. 
>>
>>
>> IMO/E 2 the Rsi and the WS50/60 are transparent in tractive ability (newer > the better) for dedicated ice tires.  IMU, the Hakka Rsi is discontinued > in favor of the Hakka R.  The Hakka R takes a step down in sheer ice for a > step up in mixed ice/snow and ultimate snow traction.  BTW, just before > Steamboat this year, we tied the center diff locked all the time, and I > ran a new line from the IM to a ck valve to the diff knob, using the > climate control vacuum canister as an accumulator, and the knob then only > operated the rear diff.  Worked immediately and without fail for 4 days. 
>>
>> HTH and my .02 
>>
>> Scott J 
>> 84 Urq 
>> 83 urq ice track car 
>>
>>
>> -----Original Message----- 
>> From: Louis-Alain Richard <larichard at plguide.com> 
>> To: qshipq at aol.com; laraa at sympatico.ca; vittorio at mybares.com 
>> Cc: urq at audifans.com; quattro at audifans.com 
>> Sent: Fri, Feb 12, 2010 12:32 pm 
>> Subject: RE: [urq] Tire pressure for ice racing ? 
>>
>>
>> Scott, why "good luck " ? You think I'll need some ? :-) 
>>
>>
>>
>> Never popped a tire, but I never ran lower than 26 yet. I'll bring the two > sets 
>>
>> next time, just in case I pop a tire. These are difficult to replace on > the rim 
>>
>> when temps are around 0F and there is no air supply close... Brady can 
>>
>> confirm... 
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>> About the rear diff, when locked it makes the rear end very nervous under > power 
>>
>> but as you say, tight corners are a nightmare if you missed your approach. > She 
>>
>> just goes straight. And with that stock engine, 7:1 compression ratio, > there is 
>>
>> NO torque below 3000 rpm. I must play with the revs and the clutch to make > the 
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>> rear end slip in some slow corners. 
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>> So no one think that the Michelin will be any good ? 
>>
>>
>>
>> Louis-Alain 
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>> -----Message d'origine----- 
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>>
>> At Steamboat Springs Ice track with the urq, we run between 24 and 26psi > with 
>>
>> WS50 Blizzacks.  For the urq on ice, the best pressure will be lower, > generally 
>>
>> 24-28psi.  I run to the low end of that using innertubes, but it really > depends 
>>
>> on the tire size, a 205 on a fuch 15x7 will tend to pop it's bead when 
>>
>> encoutering a snow patch at 25psi (btdt), but a 205 on a 6in rim or a 215 > on a 7 
>>
>> should be fine. 
>>
>>
>>
>> The studded/bolted/spiked  tire will always have the advantage on an Ice > track. 
>>
>> At Steamboat, none of these are allowed, but usually in Ice racing > competition, 
>>
>> non-studded ice tires are in a separate competition category.  I also > suggest 
>>
>> that you run the center locked always.  I also run the rear locked, but > can be a 
>>
>> handful in a tight competition course. 
>>
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>>
>> HTH and good luck 
>>
>>
>>
>> Scott J 
>>
>> 84 Urq 
>>
>> 83 Urq ice track car 
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