someone please write a dissertation on LSD's, Quaife, ZF, torsen, lockers, phantom's.. Options

[campbellcj]

There have been a bunch of detailed differential threads on the Pelican (racing) board in the past few months.

http://forums.pelicanparts.com/showthread....5&highlight=lsd

http://forums.pelicanparts.com/showthread....8&highlight=lsd

http://forums.pelicanparts.com/showthread....7&highlight=lsd

http://forums.pelicanparts.com/showthread....4&highlight=lsd

http://forums.pelicanparts.com/showthread....6&highlight=lsd

http://forums.pelicanparts.com/showthread....5&highlight=lsd

http://forums.pelicanparts.com/showthread....4&highlight=lsd

etc....

There was a very good (but not flawless) overview in the POC Velocity magazine a few years ago.

http://www.guardtransmission.com/velocity.htm

(I believe the full magazine issue is also still on the POC website in PDF format).

[KenH]

Arron - not sure I can answer all, or any of your questions, but I can give you my impressions driving with an LSD.

I added an 80% ZF LSD to my 914-4 set-up for the track, but running stock motor & tranny.

The main thing I noticed the car felt far more stable and under control. Situations that would have be "Oh Shit" were only "oops". The LSD increased my confidence in the car and therefor I could, and did, drive it faster.

Depending on the situation the LSD helps keep the back-end under control, sometimes by adding throtle sometimes by backing off, depends on the situation.

Some say there is a minimum engine power you should have before the LSD makes any difference and this may be so when powering out of turns, but the there is no question in my mind the LSD makes my 100hp car better.

I know this is not nut & bolt secific info but I would certainlly hate be without the my LSD.

Ken

[brant]

QUOTE (pek771 @ Mar 4 2006, 10:47 PM)

It seems the useful combinations we would consider are the open, Quaife type, ZF type and the Phantom Grip. The lockers are impractical, and the track cars would just run a welded rear. I know there is a difference between the Quaife and the ZF, because I hear the autox guys rave about the Quaife, and the track guys say they suck.

Quaife and ZF work VERY differently.

and I would also argue that the paul guard brand of GT (also a clutch pack) works very differntly in real world application than a ZF, so add one more to the list.

The GT and ZF are both Clutch packs, but the GT allows different ratio's of ramp up/slip on both Accel and Decel, where as the ZF only allows one ratio period. So in real world applications they are very different when used. (although using the same technology to get there)

[brant]

One more thing..
in a conversation with Paul Guard directly he admitted to me that the standard 911 rule of thumb does not necessarily apply to a mid engined car like the 914.

Its a commonly held belief that the clutch type is better on a track and the Torque Biasing type is better in autox.

However, in low horsepower cars my race GURU did testing and found that despite this commonly held belief they were picking up significant time on track using the same car with the Torque Biasing style.

As you can imagine, this left me confused.
I spoke with Paul Guard about it and he confirmed that there is a difference in application between a 911 and 914 and that the Torque biasing could be better on track in a 914 under some conditions (like low level of HP)

so I'm on the waitlist like JP

The TB does not have clutches and works differently.. very differntly than a ZF style

here is the ATB propaganda:
---------------------------------------------------------------------
The Quaife torque biasing differential enables your car to accelerate quicker and corner faster. How?

By getting the power to the ground!

The Quaife Differential powers both drive wheels under nearly all conditions, instead of just one. With an ordinary open differential, standard on most cars, a lot of precious power is wasted during wheelspin under acceleration. This happens because the open differential shifts power to the wheel with less grip (along the path of least resistance). The Quaife, however, does just the opposite. It senses which wheel has the better grip, and biases the power to that wheel. It does this smoothly and constantly, and without ever completely removing power from the other wheel.

In drag-race style, straight-line acceleration runs, this results in a close to ideal 50/50 power split to both drive wheels, resulting in essentially twice the grip of an ordinary differential (they don't call open diffs "peglegs" for nothing).

In cornering, while accelerating out of a turn, the Quaife biases power to the outside wheel, reducing inside-wheel spin. This allows the driver to begin accelerating earlier, exiting the corner at a higher speed.

The Quaife also controls loss of traction when the front wheels are on slippery surfaces such as ice and snow or mud, providing the appropriate biased traction needed to overcome these adverse conditions. The Quaife Differential provides constant and infinitely variable drive. Power is transferred automatically without the use of normal friction pads or plates seen in other limited-slip designs.

The Quaife's unique design offers maximum traction, improves handling and steering, and puts the power where it is needed most. A definite advantage whether on the track or on the street.

The Quaife is extremely strong and durable and since the Quaife is gear operated, it has no plates or clutches that can wear out and need costly replacement.

The Quaife is great for street driving or racing. Racers don't have to put up with locking mechanisms or spools that created unwanted understeer under power, or in the case of front-drive cars, even tear the steering wheel out of their hands when cornering. Because it behaves like an open differential during ordinary driving, street drivers will have trouble telling it's there until pushing the car's limits.

The Quaife has been proven in everything from SCCA Rally to Formula 1. It provides autocrossers with such an advantage, it has become "required" equipment for a winning effort.

[kdfoust]

I've made my descision for my big track car (944S2). It's getting a Porsche OEM (ZF type) LSD. In fact it's being installed end of next week. I won't get to shake 'er down on the track until the first part of April but I've got pretty high hopes.

My goal for next week's LSD install is twofold:
1) Better hookup on corner exit (with a trade-off in understeer expected).
2) Better initial turn in (like trailing braking).

My experience with the open diff on that car has been that a very delicate pedalling act was needed to keep it hooked up coming out of corners. It was actually quite enjoyable to do and really fun and quick when I'd get it right with the loud pedal. A little wrong and I'd have over heated back tires and a oversteering beast in one lap.

I talked with Paul @ Guard about my application and I decided that the Guard version of the LSD wasn't worth another $1300 to me (I'd picked up a used LSD for $400 and spent $100 in parts to refurbish it) in that car. The only disadvantage I see between the Guard and this particular version of the OEM LSD is that Guard and Porsche went to asymetrical angles on the thrust rings which can then be setup for different amounts of lock on accel and decel. That sounds appealing but not appealing enough for the difference in cost.

The interesting thing about this LSD install is that the car has been well sorted for about a year and the times on the track are well defined. I'll know what it's worth to me timewise after I re-learn how to drive the car... (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

Good luck,
Kevin

PS - Later this year the 3.2-914 will get an LSD as well. What type: I don't know yet.
(IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)