Not that this addresses the "hard questions", but I'm guessing the Porsche 911 can get away with an open front diff because that is a rear-heavy car, so they probably direct most of the torque to the rear wheels most of the time anyways to keep the RWD feel, whereas our Evos are carrying 60 percent of the weight on the front axle and 50 percent of the torque.

 

In order for our evo8 to do well with a LSD in the front we would have to re-adjust the rear suspension accordingly. New sway bar would help, maybe different alignment specs, and so on. Anyone that beleives that a simple installation of an LSD on the Evo will create a handling monster is wrong. The car is already a handling monster, among the best in the world. I would almost guarantee some nasty understeer with that upgrade. Anyhow, I go along with Distantea. He seems very well knowledged on the topic. I personally owned a TYpe-r that came with a torsen type lsd that worked wonders on the roadcourse, but the key word here is Type-r. It was tuned from the factory to work with the Lsd, therefore canceling out most of the understeer.

 

Correct, same goes with skyline GTR, it has an open front diff but ATTESA ETS (pro) pretty much distribute the power to the rear wheels most of the time unless all wheel traction is needed.

 

Of course if one just install a LSD without tuning it properly it will understeer depending on the amount of power that is apply. There are settings to LSD (I don't know too much about tuning them) so I am not going to comment on it.

 

The Evo understeers quite severely on a racetrack. A front LSD would provide better traction = more grip at the front. How could this possibly cause more understeer? Sometimes I just don't understand you guys.
Cheers,

 

i had a Quaife diff in my eclipse GST and it made a world of difference with FWD. if there is a quaife available for the EVO, i'll be sure to get one. the Quaife can put down a 50/50 split in power and puts power to the wheels with the most grip. in my GST coming out of turns, all of the power would be transferred to the outside wheel which in turn would whip the car out of turns. it was awesome

 

Adjustable LSDs require tweaking, it’s not as easy as install and no understeer. Like I said, I don’t know much about tweaking them so I’ll just hush up.

 

I rest my case.
Cheers,

 

If you have a front LSD that just locks the tires at 50/50, it is possible for a front LSD on an AWD car to cause the car to understeer more.

Here is my reasoning. In a corner, the outside front tire gets the most grip. I've even seen some cars lift the front inside tire. You do not want that outside tire to lose traction because you are giving the car extra throttle. An open diff will allow that tire to grip and will not apply as much power to it as it will apply power to the inside front tire (with less grip).

An LSD that just locks the tires at 50/50 (like the center diff in the Evo) would cause both tires to spin at the same rate. And if you overpower that outside front tire, you will understeer.

Of course, different things will happen at different points in the corner.

 

Fascinating thread.....but I don't agree with this last point.
The reason you get understeer in the corner to begin with is that the inside front tire is unloaded in a turn has little traction, but in an open diff, still gets 50 % of the power....once it loses traction it starts to spin and actually pushes the car opposite of the direction you are turning (def. of understeer). Someone else explained that this is the classic problem with open diff.
The wheel that loses grip 1st spins 1st and then gets more and more power causing runaway spin.

An LSD will prevent the front inside tire from spinning (faster than the outside tire) and so stop this from happening........your theory is based on the notion of overpowering the outside front tire. How? With an open differential this will virtually never happen. The outside front has 90% of the load and traction, long before you overpower it.....the unloaded inside front tire has given up and begun to spin. Someone said: there's a reason Mitsu left out the front LSD on the US Evo. Sure there is......money. There's also a reason every other Evo sold in Japan and elsewhere has the front LSD. It's not because it causes the car to understeer....that's for sure.

 

That was my point. With an open differential, the outside front tire doesn't get much power, so the inside front tire spins. But the outside front tire is the one that is doing 90% of the steering. If you give it more power by using an LSD, it will also start to spin, and there goes your steering.

 

If you can get both front wheels to loose traction with excessive power then you need to work on other areas like suspension and tires not diffs. But first you still need to get both of them the most traction possible with means and LSD.

PS: When both front wheels loose traction it is easier to control than one with all the traction and the other with none. Just think if this happens to the rear of the car (rear wheel drive) it will be a nice drift. That is why you can’t drift without LSD.

 

You can definitely get both front tires to lose traction with excessive power if you are in a turn, which is what we are talking about.

An LSD doesn't give the most traction to each tire. It gives balanced torque to each tire, depending on traction. And that may or may not be what you want. Balanced torque could just send your inside front tire spinning with an LSD, whereas with an open front diff, it would not spin.

 

Only the cheaper LSD like phantom grip will "give balanced torque to each tire" (50/50 split). LSD like KAASA and Cusco maintain traction to both wheels with the maximum amount of power with out breaking lose, and if it does break loose it will distribute power to the 2 wheels accordingly. It changes torque distribution, it is not a constant 50/50 split.

 

A front LSD in general will help with understeer. The wrong setup with a front LSD can actually cause massive oversteer on a FWD car, just as the wrong setup with a front LSD can cause massive understeer as well.

It comes down to chasis design and what changes were made to accomodate the LSD. Some cars it is possible to just throw in an LSD ***** nilly and get the desired effect. Other cars have bigger problems than powered wheelspin though and an LSD will do nothing for it.

I think the US Evo is setup fairly conservative for handling and I think its the open front diff that gets them that safety margin. Unfortunately at this point I'm reaching deep within my *** because I've never compaired two Evo VIIIs side by side on an autocross course to know what throwing in the LSD does for it at the extreme handling ends.

But a car I did drive side by side was the WRX. A WRX straight off the showroom floor understeers like a pig. You have to left foot brake to get it into the swing of things. I drove a D stock WRX and had a good time that day. But then for the fun runs I drove a street prepared WRX with a front quaife and was blown away. His only mods were the LSD, exhaust and unichip... it took very well to the LSD and I couldn't believe how much faster it was around the course. Made my S4 feel like a three legged pig covered in burlap.

I can't stress enough though that proper driving techniques can make or break any car. No LSD can save you *** from going into a corner too fast. Even 1973 Porsche 911s will understeer then.

And the way your limited slip works greatly depends on what kind you get. My mazdaspeed has a cheaper torque sensing conical ring but its very effective for the setup. The STi has a SureTrac electronic cone type, which is virtually an open diff until the electronics interveine... power transfer, torque split, response... it all varies from manufacter and type of LSD. I want a Quaife racing diff... I heard they can increase length up to 3", get me a lower mortgage rate and help me make money from home...

Ok I'm getting too much spam today.