LSD, Worth the money? Options

[machina]

An open diff is best in a low hp car. The only losses are at the wheel/'pavement interface, which should be controllable with the driver's right foot. This is especially true for DE. At an AX you may feel otherwise.
A LSD or TB diff will have internal friction losses and consequently will heat up the gearbox.

what do you consider low horsepower? less than 200?

[Joe Bob]

I'm putting one in my V8 box....

[IronHillRestorations]

If you want a competitive autocross car, then you need some sort of LSD, either kind will do and depending on who you talk to one better than the other.

The difference is inside tire spin. If you are getting all you can out of the car, and you are spinning the inside tire on tight turns, then you can probably benefit from a LSD. If not, then wait until your driving skill exceeds the performance of your car.

If you are rebuilding a transmission for a performance/competition application, you are wasting money if you don't pop for a LSD. C'mon what's another $2k???

A LSD will help improve traction, but it will also change the way the car handles. As an 'ol red neck hot rodder told me "a posi rear end will make it hook up". Detroit used to call a limited slip diff "posi-traction".

[brant]

Chris F.

what do you run for a diff ?

brant

[ChrisFoley]

what do you run for a diff?

Open.
I currently have about 125RWHP and haven't found any need for a change yet.
I have a factory lsd and plan to build another box around it to go with my next engine that I hope will have more like 155+RWHP. Other 914 guys I know in FP are running fully locked. There aren't too many corners where I race that the limited slip will benefit me, and I'm not sure the benefits will outweigh the liabilities.

what do you consider low horsepower? less than 200?

Up to 150 anyway.

[KenH]

REMEMBER -If one of the rear wheels loses contact with the ground, as in a really tight A/X turn, the Torque-bias diff STOPS working and the wheel spins. The ZF will continue to supply power to the wheel on the ground.

The ZF will work in ALL conditions - the Torque-Bias works in limited conditions.

I think the choice is clear.

Ken

[Joe Bob]

True...just another reason to run withOUT a rear anti-sway bar on tight AX courses.

[brant]

REMEMBER -If one of the rear wheels loses contact with the ground, as in a really tight A/X turn, the Torque-bias diff STOPS working and the wheel spins. The ZF will continue to supply power to the wheel on the ground.

The ZF will work in ALL conditions - the Torque-Bias works in limited conditions.

I think the choice is clear.

Ken

I thought the choice was clear in the past also...
but now I don't know if it is that clear anymore...

I'm told that at 160hp (flywheel)
I will get better times with a quaffe than a clutch/zf lsd...

so ultimately the fastest time is what I'm after.

(and I picked up 2 seconds with a locker versus open using the same pair of tires in my old 130hp-flywheel motor)

I've been told that the break is around 200-250 hp.
the 914 race shop here locally, builds their 250hp machines with 915's and ZF's, but recommended the TB to me with a 901.

I'm not arguing, just looking for lots of input.
brant

[groot]

I, too, am researching the options.

I've run lots of Quaife torque biasing differentials on fwd cars on the track and auto-x. I have had wheelspin on tight corners, but that's on a front driver. If your lifting the inside rear on a 914, I think there's some suspension adjustments that can be made to reduce that.

I'm leaning towards a Quaife because of corner entry. I don't like the thought what the ZF does to the corner entry balance of the car.

Also, I used to run my mild 2.0L 914 (certainly no more than 110 horsepower) on street tires with an open diff at auto-x's. Huge wheelspin due to the low end torque of the engine. Now, having said that I've run the same engine and trans with race tires and haven't spun the tires on the race track yet.

[nebreitling]

what class is your car going to be in?

i THINK that running LSD will put you into Bp in PCA. it will earn you another 30 points in the new point system.

neither of which are bad per se (it's a stock engine class anyway), just make sure you look before you leap!

(IMG:style_emoticons/default/beerchug.gif)

[ppickerell]

Class? not sure...car will have:
new shocks koni yellows
new springs
rebuilt 2.0 with stock FI using "better grade" of parts IE ceramic lifters and fancy headstuds
replace fuel lines
rebuilt tranny
shift conversion
ssi's
bursch
probably will upgrade tires, but no flares planned as of yet

So whatever class this puts me in for the SF bay area ax scene. I would like to run 5-10 events next summer and would like to be competitive! Interesting that there is a 50/50 split of opinions on this. I am having the work done by a shop I trust, and their recommendation is the $2000 route but they wisely caution me to "do the research". I have the $2000 budgeted, but is the more expensive option better for my intended use?

[bob91403]

I can see there would be an advantage to a LSD in deceleration situations where the traction might vary between the right and left wheel. ie- a patch of oil, running one wheel into the dirt. But, don't you always accelerate through a turn? If the quaife is on only during acceleration, and the LSD is on all the time, under what situation does this difference apply?

[nebreitling]

Class? not sure...car will have:
new shocks koni yellows
new springs
rebuilt 2.0 with stock FI using "better grade" of parts IE ceramic lifters and fancy headstuds
replace fuel lines
rebuilt tranny
shift conversion
ssi's
bursch
probably will upgrade tires, but no flares planned as of yet

what spring rates?

stick to 140 rear springs, add a 19mm bar, add sticky tires, and you'll be in Bi.

getting more aggressive suspension than that will put you in Bp with me, trekkor (scratch that -- he's doing the /6), darren, howard yao and others. you can also have a header in Bp (most of us do). again, LSD might put you in Bp, so do check. i don't know who in Bp has LSD. i don't, but i'd sure like it!

either class is fun and usually has at least 3 cars. Bp has had like 5+ the last couple AX's.

budget for tires, alignment, and corner balance before you put down money on LSD. you can be competitive without LSD -- you'll get your ass kicked without tires.

[ppickerell]

Nathan,
The motor and tranny are out now, so it's decision time. I will go with one style or another. There does not seem to be any concensus, so I will probably go with my shop's recommendation.

[nine14cats]

Hi Pat,

I went through the same thing as you are last winter. I decided on a Paul Guard ZF style LSD with 80% lock. If you're serious about taking it on dual purpose on the car (lotsa auto-x and some DE/Time Trials) I think you will like the LSD. I really enjoyed driving the car after I got used to it.

Keep in mind that I had a 2.7 liter 6 with ~230HP, so I could lite up the back pretty easily. But I also found that having the LSD not only helped me in Auto-x, but really helped at the track, I could feel the car not as wiggly when on the brakes hard after a fast section. I'm sure it's all preference, and I've never driven a TB type, but I prefer the LSD to an Open diff. It takes you a few runs at the auto-x to get used to the understeer of an LSD, but you adapt pretty quick and then you can feel the difference.

Just my $0.02!

And if in the back of your mind you're going to put more poop in the motor (150hp+) you'll really like it!

Bill P.

[rick 918-S]

I heard a rumor at the FFC that some of the 914's delivered to the midwest and some of the snow covered parts of the country had factory LSD installed. Is this true and if so What years was this offered?

[ppickerell]

WOW cool man, I can see trails, LSD it is.

[Aaron Cox]

check the classifieds. someone has a line on quaiffe's

[Toast]

I guess I am still a newbie teener owner. What is this LSD?
Where can I finds some?
How much does it cost?
How much do I need?
How fast will it work?

Um.... I think I got confused about what I was asking about. (IMG:style_emoticons/default/unsure.gif)

Let me start over........
What is this LSD?
(IMG:style_emoticons/default/smoke.gif)

[Joe Bob]

Limited slip differential.....LSD. Like a "locker' rear end on a 'murican car.....makes BOTH drive wheels spin at the same time. Equal power and more balls out of a turn.

Kinda like a two handed booby grag..... (IMG:style_emoticons/default/rolleyes.gif)