Would you notice the LSD activating when one of the wheels loses grip? And is an LSD system similiar to the ATTS system on the '97+ Prelude SH's?

 

A limited slip is just that...it prevents slip during hard launching...meaning both tires spin without losing as much traction as the one wheelers from open diffs. The ATTS system is more like the VSA on our CL...it is a yaw control with a twist. It is more driver-oriented in that it senses that a car is going into a turn and tries to keep the revs to both wheels consistent....it however, is useless on a hard launch...so, after typing all this out...I guess it's a limited slip for cornering.

 

VSA/VSC/DSC and ATTS are quite different.

The intent and function of VSA/VSC/DSC is to prevent the loss of control that comes from progressing into severe understeer/oversteer. In both the case of understeer and oversteer, engine power is reduced and judicious braking of individual wheels (do you guys now see why VSA and 4-channel ABS are interrelated?) slow the car down while ameliorating the yaw to bring the four wheels back into "grip." VSA/VSC/DSC and TRAC/traction control are all really just extensions of ABS and work through the existing brakes of the car.

Unlike the above, ATTS no control over engine power. Instead of using the existing ABS braking system, ATTS works through two dedicated hydraulic clutch packs on either side of the differential in the transaxle casing.

In contrast to the ABS-derivative systems, ATTS doesn't brake smartly to bring the car under control, but rather redirects power to the appropriate wheel to adjust yaw. The ATTS system can bias up to 80% of drive torque to one side or another. Think about how a tank turns, and you'll get the idea. This allows the inherently understeery FWD configuration to understeer less and at higher limits. Suppose you accelerate hard coming from a slow speed into a medium radius corner. Do it hard enough in a regular FWD car and it starts to plow, forcing you to either steer more (until you reach lock) or let off the throttle. But ATTS-equipped car would bias torque to the outside wheel, negating some of the understeer. It's basically torque steer harnessed and made intelligent to aid maximal-performance handling.

As I said before, VSA/VSC/DSC works via the existing ABS system. It cannot hold one wheel to redirect torque through the differential to the other wheel because between the brake and the differential, there exists the halfshaft and the floating engine mount. If somebody attempts to rig up an ATTS-like system through the existing VSA/VSC/DSC, the engine will twist on its mounts, for sure reducing the mounts' life, will not approach the transparency of ATTS, and possibly playing havoc with handling as the CG shifts around with system activity.

 

Okay after reading my own post...I did say it is like a yaw control...but more along the lines of a limited slip type...am I correct?

 

Well, yes and no.

ATTS is definitely yaw control, yet so is VSA/VSC/DSC. Here's a slightly more user-friendly interpretation I just thought up:

VSA/VSC/DSC turns on (toggle switch activity) to correct what it feels are your mistakes. It allows speed to drop and brakes the car in a certain way to correct the yaw. It's obviously useful as a safety feature, but it hinders at-the-edge-of-the-envelope high-performance in the hands of a skilled driver.

ATTS operates in the background during all turns to correct what it feels are the FWD configuration's shortcomings. It adjusts how FWD cars put power to the ground, to produce a yaw moment that counters the inherent power-on understeer. It's a performance feature that aids at-the-edge-of-the-envelope high-performance in the hands of a skilled driver. And you're right, it doesn't help at all in a straight-line launch, assuming the Prelude is modified enough so that single-wheel slip become an issue to good launch times.

LSD operates constantly, but it doesn't try to do anything whatsoever with respect to vehicle yaw. It doesn't sense nor counteract yaw. It does, however, give the driver consistent control over both sides of the drive axle, which in the hands of a skilled driver can be used to manipulate yaw better than that can be done with an open diff (but not better than ATTS, which manipulates yaw not by the brute-force, slip-both-wheels method, but by actively driving one wheel more than the other). Something that ATTS doesn't do, LSD improves the axle's ability to put power to the ground during an edge-of-tireslip (or burnout) situation, allowing him/her to get on the power sooner and harder accelerating in a straight or semi-straight (corner exit) line. Like ATTS, it's a performance feature that aids at-the-edge-of-the-envelope high-performance in the hands of a skilled driver.

ATTS is most helpful when you're railing and aren't breaking traction, like driving at 9/10ths in a FWD car. It also helps stretch the grip-driving performance envelope a little bit. LSD is most helpful when you're racing at 10/10ths and are constantly at the edge of breaking traction (and sometimes veer over that edge a little bit). VSA/VSC/DSC is most helpful when you think you're driving at 8/10ths, but are in fact are going into that corner at 11/10ths.