I still think the Quaife LSD is the best mod I have ever done to my Z.

Here is some "cut and paste" from other threads I have posted in regarding the Quaife....

 

Is it true there is no 1.5 way or 2 way? Those terms do not apply to the Quaife?

 

Quaife doesn't release too many details on their LSD's, and I have never heard or used the 1.5 or 2 way terms with respect to any Quaife LSD.

Quaife basically says "We made the application we are selling you for your car. Trust us."

Had it not been recommended by a few different people I trusted, I probably wouldn't have rolled the dice with a product that comes with so few details.

 

how was the ride in the BMW compared to your car. Curious how a race car handles the track

 

I have one, works great.
I've written about it before so you'll find info on the forum.

 

That's right. It's not a clutch-type differential with different ramp profiles to affect engagement characteristics, it uses helical (worm) gears to transmit torque between the case and side gears.

Will

 

Quaifes are different compared to other LSDs. They require a softer rear suspension setup because if you lift an inside rear wheel the diff goes open. Some people are reluctant to make the suspension adjustments and have a poor opinion of the Quaife. I was one of those people when I raced a 240Z. I siwtched from a CLSD to the Quaife and just hated the thing.

I ended up talking with Craig Taylor at Taylor Race Engineering for long time and decided to do some wholesale changes to the suspension on my 240Z. I moved roll stiffness forward, changed the spring bias from rear to front, and reduced rear camber.

The car was a little slower on corner entry but I could pick up the throttle a couple heartbeats before the corner apex and the throttle was mashed to the floor just past the apex. My lap times everywhere improved by 5% and the car just launched out of the corners, which got scary sometimes. Other cars would sometimes beat me to the inside of the corner at turn in but I would just rocket into their rear bumper coming out of the corner.

 

Good info..... Thanks.

 

Check with Mike B (SinCity350Z)

He was running one for awhile, but with major TT power, and I think it broke apart on him.

If you are running NA, and use the car a lot on the street, the Quaife is something to seriously consider. The clutch type LSD units work very well, but are "bad boys" on the street which requires you to adjust your driving technique to avoid scaring old ladies in supermarket parking lots and passengers in your car.

 

FYI... Quaife's come with a lifetime warranty and they cover racing. Blow it up, they send you a new one. 'Course, if you blow something up in your race car, why would you re-install a new one?

 

FYI2... the easiest way to blow up a Quaife is to lift an inside rear wheel under power and then bring it back down hard (curb hopping) while putting a lot of torque through the unit. The units themselves are very strong and we ran them behind GTS-R Vipers running in ALMS during the early part of this century.

 

nice writeup

 

Just an update on the suspension tuning adjustments made during the past several events. Adjustments were made sequentially.

1 Added neg camber to front. It is set to -3.0 front(from -2.7) and -2.2 rear. Temperature measurements were taken by Yokohama reps on a CCW track configuration. I was running 275/35/18 RA1's at 37psi hot front and rear, and the temps taken with a probe thermometer indicated I could use a little more air pressure and more negative camber for both front and rear passenger-side tires while the driver-side tires needed a bit more pressure and less neg camber. Somehow, adding more neg camber to a multilink type suspension does not seem right, which indicates that there may be excess body roll. Reduction of understeer was barely noticeable.

2. Removed the 5mm spacer in the rear. 5mm doesn't sound like much, but it made the rear wheel look more tucked in (yuck). However, handling balance seemed to improve as I felt more rotation when throttle lifting. Yet, I was not content, and was seeking more front-end grip.

3. Lowered the front end 1/8" while leaving the rear unchanged. This change made a bigger difference than steps 1 and 2. The car is feeling much better! And, I've realized that the balance of the car must have been much worse than I thought before making these adjustments.

4. Set my front Hotchkis sway bar to full stiff (up from med stiffness). Now this adjustment really surprised me. I was expecting more understeer, but I ended up getting more front-end bite and grip. This was a big eye opener for me. I am much happier with the balance of this car now. Both front and rear tire are losing grip nearly at the same time while on maintenance throttle though a 180 degree flat sweeper. So, what I think I was dealing with was too much body roll necessitating more negative camber to chase the problem down.

Conclusions: Much better balance. But, I believe I need stiffer springs to resist body roll, which would lead to shock revalve, and possibly re-alignment for less camber followed by re-adjustment of tire pressures and sway bars. I guess that's what's in store for '09.

 

Good Info ! Thanks for sharing.

 

Exactly.

Way back when I road raced a Contour SVT in a stock class. By adding a huge front anti-roll bar (38mm) in front, the car picked up a couple seconds per lap. That's counter intuitive (especially for a FWD car) but reducing roll camber loss the front tires stayed more perpendicular to the pavement and tire temps improved.

 

I'm also contemplating looking for a stiffer front bar. I'm using the 1st version of the 35mm hollow Hotchkis front bar (3 holes). Hotchkis Tuning claims that the stiffest setting is 63% greater than stock. However, their newer 4-hole bar is also hollow and 35mm, and they claim the 3rd and 4th stiffest settings are 82% and 129% stiffer than stock. I'm wondering whether Hotchkis either botched up their calcs or the new bars have thicker walls (1/16" thicker would make a huge difference).

 

I'm sure you know this, but just in case...

A big anti-roll bar is a band-aid for too soft springs. If the rules allow, you're much better off installing stiffer springs then going with a big bar. Combine stiffer springs with shocks that have low speed compression/rebound valving and adjustment and you can run very small bars.

 

I wouldn't call it a band-aid by any means. Why is a big bar a bad thing? A bar adds spring rate when cornering while not affecting spring rates when braking or straight-line accelerating. Softer springs generally yield more grip anyway (keeping effective contact patch, tire temps, and camber in check) and the 350 can use as much rear grip as possible.

A lot of racecars utilize the softest rates they can get away with, many of which use very large bladed swaybars...



0.02

 

Sometimes, I need a reminder from a more level head

 

Its not a "bad" thing, its just not better then stiffer springs. The main reason is that any anti-roll bar reduces the independence of an independent suspension. What happens on one side of the car now starts affecting the other side which is why big bars DO affect braking and acceleration. In the Contour SVT example I cited above, the car became more darty under braking when I added the big front bar.

Anytime you transfer load from one side of a tire pair to the other you reduce the total tractive force of that pair of tires. Big anti-roll bar cars tend to pick-up inside wheels in corners and in extreme examples they bicycle (the Larssons' DSP 325is at the Nationals in 2006 is a perfect example).

I don't know what other racers on this board are doing and I'm sure a big bar, small spring setup can turn fast laps - if one fast lap is your goal then pretty much any setup can be man-handled to a fast lap by a good driver. On my own 350Z I'm running big bars with stock springs, but that's only because of how NASA does its point mod system.

Myself and most of the racers and engineers I've worked with (when the rules allow) do their best to reduce the size of the anti-roll bars using track width, spring rates, and low speed compression/rebound damping. There are better ways to control lateral load transfer then anti-roll bars.

EDIT: In the context of this discussion, I'm assuming we're talking about standard bent bar anti-roll bars. More exotic single acting anti-roll bars and Z bars are a different discussion.