Limited slip diffs in FWD cars

[miata#37]

It's silly season....

I was going through the Ford Racing parts catalog and pondering some upgrades for my daily driver: a 2005 Focus ZX3. I was looking at their SVT suspension kit for phase one and noticed that they have a Torsen differential available as well. The price on it didn't seem too far out of line and I've found myself considering it for phase 2 of the project.

My question is for those of you who have either driven FWD cars with Torsen style diffs or, better yet, those who have installed them in cars that previously had open diffs. How did the Torsen affect the handling of the car? Did it still turn in as sharply? How was the balance affected? Did torque steer become an issue? Did you need to make other changes to the cars suspension settings to compensate for any of these effects? How did it affect the drivability of the car in snowy or icy conditions?

Thanks

[SmokingTires]

When did the great chris become new to cars? :p

Torque-steer is a biproduct of an open diff. It's when one wheel "gains traction" so the other ones spins faster, creating a pull to one side. A limited slip would reduce that.

I haven't driven a FWD car with a torsen, but I imagine turn in isn't affected horribly unless your on the throttle.

[MNbiker]

Torque-steer is a biproduct of an open diff. It's when one wheel "gains traction" so the other ones spins faster, creating a pull to one side......
Not exactly......:rolleyes:

Here's a simple explanation of torque steer from NissanPerformanceMag:
http://www.nissanperformancemag.com/september03/ask_sarah/

Here's a more detailed explanation from Dave Coleman:
http://www.themininut.com/torquesteer.asp

[pinhead]

I used to autocross my Integra GSR, and at the time I owned it, I also autocrossed my friend's Integra Type R several times. So it's not a 1-to-1 comparison, but close. Basically, the Type-R felt the same as the GSR, only with more traction.

I also autocrossed my friend's insane street mod civic (I got in it, and he said, just shift after the needle on the tach is past all of the numbers) with a kazz lsd, which I think uses a clutch pack. It was effective, but that one seemed to dumb down the turn in a little bit. For an autocross car, the extra traction is TOTALLY worth it, though.

I say do it :D

[SUV-ETR]

A Torsen/Quaife-style "torque biasing" differential (which means it is NOT actually a limited-slip device, FWIW) is immensely helpful on an autocross in a FWD car. The inside wheel will actually pull the car into the turn, which I guess you *could* call torque steer...but it isn't the same. The only downside are that they rely on some small amount of traction on both wheels, so it will actually behave like an open diff if you get one wheel totally off the ground. This is really only a problem on cars with bad suspension or *lots* of power. If you are doing off-road racing or drag racing, they also tend to be a tiny bit less bullet-proof than clutch-type LSDs, but it is a non-issue on any street/autocross car.

On FWD cars, clutch-type diffs tend to induce understeer on corner entry (unless you have a pure 1-way shim stack installed). They also cause more understeer on corner exit as well, since it is a true LSD and locks the axles, which doesn't allow the wheels to rotate at different speeds. FWD cars can't rotate through throttle application like RWD cars, so it just induces more understeer. Thus, they don't tend to work as well for autocross in FWD cars...

Neal
(Quaife)

[miata#37]

Thanks guys! No, I'm not new to cars or torsen style LSD's. I was just curious about this specific application.

[Shrep]

I've driven 03 SRTs (open diff) and mine's an 04 (LSD). To me, LSD makes a HUGE difference. I can be flying around a corner in an 03, mash the pedal and plow the front tires...if I do that in my 04, the front grabs and tucks me in.

[weidnerpaul]

I've driven 03 SRTs (open diff) and mine's an 04 (LSD). To me, LSD makes a HUGE difference. I can be flying around a corner in an 03, mash the pedal and plow the front tires...if I do that in my 04, the front grabs and tucks me in.

Does it put chocolates on your pillow too?

[GodSquadMandrake]

What about a shim kit "LSD" where it just basically locks the differential? Does that cause understeer? I bought one and I am scared now :o

[washburn]

I think Neals description above is pretty close, but the "rest of the story" is that this can be overcome by a combination of driving style and setup. (Phil can tell you about mt old Neon setup back in the day...and that didn't have a LSD) I don't think that shim kit will change things enough that your going to have to mess around too much with the V Dub. Will be fun trying it out though!

[phile]

(Phil can tell you about my old Neon setup back in the day...and that didn't have a LSD)

You mean about how you spun it in a slalom while teaching me how to drive it?