AC525

How much?

jas_r_1

In simple terms (because I don't know what this is) what will this add to the car performance wise? Why not just stick to a remap?

mmitev

In even simpler terms, watch this:

You can remap your car to 1,000 bhp, but the power will be going nowhere as your wheels will just spin.
An LSD simply puts your bhp on the road (what the open diff fails to do, particularly in wet/slippery conditions).

mmitev

I would be interested.
With a nice juicy discount and shipping to Europe (or pick-up from Quaife directly), that is.

jm545i

YMMV, but there's lots written about this. Depending on what engine you have you may or may not find this a cost-effective upgrade. Those with higher-powered engines often have a hard time exploiting all of that power because very often the torque of the engine will overpower the available grip of the rear tires. Many times that will happen when going around a turn, but sometimes as well in a straight line (v-8s are able to light up the rear tires in first gear from a roll, at least mine is - particularly in cool weather). When that happens, one of three things happen, (i) the DTC system will attempt to control the resulting wheelspin by clamping individual rear brakes, or (ii) if that doesn't work, engine power will be cut dramatically, or (iii) you'll smoke one of the rear tires, which makes a lot of sound and fury, but doesn't result in very much forward motion.

A LSD, and in this case a torque-sensing LSD, acts mechanically to eliminate wheelspin, assisting the DTC system (in most cases eliminating its need to intervene), and reducing the likelihood that the traction control system will actually have to cut engine power. There are advantages and disadvantages to the Quaife system versus clutch-type LSDs (with the biggest disadvantage being that if one wheel completely loses traction, it reverts to being an open differential), but in my opinion its advantages overwhelm any disadvantages, particularly because the DTC basically solves its primary disadvantage by providing resistance to a free-spinning wheel, preventing the open-diff scenario.

Note that mechanical LSDs were available from the factory on a lot of BMWs until a few years ago, and now are only available from the factory on M-cars (though they are very fancy clutch-types with hydraulics, etc., to control the amount of lock). Note that M-cars also have traction control systems, so it's not as if these things aren't designed to work together, or that the LSDs don't add something.

The other handling benefit they provide is that they make the car feel more alive, particularly in situations where you might be able to create some power oversteer. Rather than just have you just lose the inside rear wheel in spin/tire smoke when getting on the power coming out of a turn, you can more easily get the rear to step out a bit under power. Not that I'm advocating that of course.

They are also great in snow. My older BMW with a clutch-type LSD was great in the winter. You could just get the wheels spinning the car could get up almost any hill, while most lesser cars were spinning only one wheel and getting nowhere, my rear-end would lock up and both wheels would work to create forward motion. The car would take a set with the rear end to the left or the right depending on the crown of the road, and would just tractor its way up.

mmitev

JM, can you elaborate a bit on the "one wheel completely loses traction" scenario? I have read lots of opinions on the Quaife LSD, but this is something new to me.

Does this happen only when the wheel suddenly and completely loses traction, i.e. when you have parked the car with one wheel on really smooth ice?

Because under real-life driving circumstances one wheel will only gradually lose traction and the LSD will prevent it from continuing to do so (by taking torque off it).

And in the first case, does the DSC help at all if you are still at the same spot with one wheel on ice?

jm545i

It will be a very rare occurrence indeed where the Quaife reverts to what you have now, which is a completely open differential. In normal spirited driving, 99.999% of the time it will be a great plus. It's very very rare for a wheel to have zero traction - it would usually have to be off the ground. That said, the way the thing works is to divert torque to the wheel with better traction based on a multiple of the 'lesser-tractioned' wheel. If the weaker wheel is off the ground, zero torque is zero torque. Keep in mind that as clutch type LSD's wear (and the preload decreases), they too will basically turn into open diffs with one wheel off the ground, so don't fret it.

There are quite a few folks around here who have Quaifes installed, and I have only heard rave reviews. The DTC function is said to work seamlessly with the Quaife, and the Quaife can only be a traction benefit, even on ice.

AlexFW

Absolutely: there is an entry, in the FSW_PSW, to tell the car you have the LSD.
So yes, the car was prepared for LSD.

And after 3.5 yrs with the Quaife installed, I confirm no problem with the DSC/DTC.

jjsigpi

+1 and god it makes coming out of turns so much more fun !!!

HP Autowerks

We are in Santa Barbara, CA. The price is $1450 with free shipping to the 48 States(up to $35 value) and free stub axle seals(a $39 value).



If we can get 5 people together we can order a batch of these units. Then we can do $1305 with free shipping and stub axles. We can save each person an additional $145 on top of the free stub axle seals and shipping.