Limited slip

[THier]

It has been a while, has anyone heard if one is out there anywhere?
Thanks,
Tom [?]
The rock-on smiley was at the request of my almost three year old daughter

[GLH_TC 16V]

I have got limited slip units for sale on my website. I haven't seen a PT Cruiser differential yet, but if they are the same as the Neon, then they will fit. If you are interested, you can check out the Automotive section of my website at http://connect.to/YBT. If you have any questions, please feel free to e-mail them to me.

[Punch]

isn't traction control limited slip?

Punch[:I]

[GLH_TC 16V]

No, they are completely different. Limited Slip will aid traction control but they work in completely different ways.

Traction Control stops the tires from spinning when the ECU senses traction loss. The ECU engages traction control in 1 of 2 ways. 1. apply the brakes to the spinning tires until tires stop spinning, 2. back off on engine timing, fuel and spark (and in some cases boost pressure) to reduce engine output to a level that won't spin the tires.

Limited Slip differentials are like clutches where they transfer the power from the spinning wheel to the wheel which has traction so they (ideally) move at the same rate. An LSD helps traction control because now the traction control doesn't have to "kick in" until BOTH tires are spinning. On a FWD car, usually the passenger side tires spins because there is less weight over that tire. This is one of the factors in "torque steer" as well.

I've done quite a bit of research on LSD's in my quest for FWD traction. On my race car I've eliminated all of the problems associated with FWD traction (torque steer, one wheel peel, understeering during HARD cornering). If you have any questions, please feel free to ask.

[Cal Cruzer]

I know that DC is coming out with one for the SRT but I don't know if it will fit the PT. I would love to have one though.

[Kirby]

The reason that Limited Slip Differentials (LSD) are not and probably will not be available as stock for most front wheel drive vehicles is "Torque Steer". That much power down to both wheels will almost assuredly lock the steering. Anyone with a Stage 1 kit can verify what one wheel burried in torque steer mode does. Also LSD under power does cause Understeer (it wants to go strait all the time).

If you want to go in a strait line though, LSD is the ticket, along with firmer engine mounts, good rubber, and some more substantial axles.

Just be careful which direction you have your rocket pointed when you slip into warp drive!(Unless you are Canadian ,and in that case you won't have any torque steering problems.)

[Kirby]

GLH
I don't mean to be disrespectful. I am sure that you have spent years working with FWD racing. I think that torque steer is going to be a major problem to deal with in the PT with the massive power from the Stage 1 and Stage 2 kits. Any help here is going to be monumental!!

[GLH_TC 16V]

Torque steer is caused by a number of things, drive shaft length, suspension geometry/movement, and the differential.

Torque steer by definition is lateral movement (simulated steering) caused by an imbalance of torque from the driving wheels. In a front wheel drive car with an open differential, the wheel with the most torque is also the tire with the least amount of traction. The differential will transfer the power to the wheel which isn't "stuck". If you can imagine your one of your wheels clamped to the pavement in gear, if you apply the throttle the other tire will get 100% of the power. If you have a closed differential (LSD) then the LSD acts like a clutch, transferring power to both wheels equally (ideally). If the torque is equal at both wheels, neither one of the wheels can steer the vehicle due to an imbalance of torque from the driving wheels.

As for the cornering aspect, yes you will understeer intially as both tires want to spin at the same speed. In a corner though, you want the outter tires to spin faster, and the inner tire to spin slower. The problem is, that with an open differential, the outter tires has all the traction (due to the weight transfer) and the inner tire has relatively little traction. The understeer is compounded by the fact that the open differential will transfer most of the torque/power to the inner tire because it is free. The net effect is that the inner tire will 'torque steer' you away from the apex, and we call that understeer. An LSD will 'attempt' to transfer more power to the outter wheel where it is needed and thus slow down the inner wheel in the process. The differential will still be at different speeds (that's the limited slip part of it) but much closer to the ideal of having the outter tire faster, inner tire slower. To sum up, an LSD will help you corner better because the tires speeds are 'closer' to the ideal rotating speeds than in an open differential. Yes, you still *might* understeer but not as bad as having an open differential.

The one other benefit of an LSD is that you can induce oversteer in a corner by mashing the throttle to the floor and letting the front wheels pull you out hard causing a 'swinging' motion on the rear end just like oversteering.

I hope that this explains how an LSD is beneficial in both straight line and cornering applications (it also helps in braking too). And Kirby, no disrespect taken here... I just hope that I have cleared a few things up about LSD's and why they are so great. One thing I do agree with you about is that with Stage 1 and 2 we will have to watch out for the monster that is torque steer... I believe that the LSD will be that monumental help you are looking for.

[Kirby]

Have you seen this inexpensive Phantom Grip setup? Is it worth anything?

[GLH_TC 16V]

Yes I have. It the same design that I sell and the same design that I've had in my race car for over 3 years now trouble free.

Now, I will be the first to admit that my Spider Trax or the Phantom Grip is NOT as good as the Quaife LSD. But for the price and the performance, the LSU (limited slip unit) cannot be ignored. For those on a budget, it is a great deal.

Now, I'm not trying to hock my wares on this forum, I don't know enough about the PT setup yet to offer any performance solutions other than what is already available. I am merely extolling the vitures of what an LSD will do for any FWD vehicle.