LSD Questions

[Phippy]

Hello,

I have been researching information in regards to a mechanical LSD. I seem to be getting conflicting information and its starting to becime very confusing!

I am wanting to install a mechanical LSD in my fiesta. My research led me to believe a mechanical LSD is better then a clutch based LSD.

My understanding was, an LSD would not only assist in acceleration, but would help in icy conditions, as i expierence in northern Alberta.

However, i was told that, an LSD would greatly have a negative effect in cornering in cold and icy weather. This goes against my research.

So im turning to you all to help me with this. Im feeling like maybe i dont know what i read or i dont understand how this works. And now im very confused.

 

[foodtruck]

> I am wanting to install a mechanical LSD in my fiesta. My research led me to believe a mechanical LSD is better then a clutch based LSD.

Clutch based LSD is also mechanical, you probably mean torque biasing one based on helical gears? The reason torque biasing is preferred for our cars (MFactory, Quaife, Wavetrac) is because there's no wearable clutches inside and so you don't have to go through pain of taking out the transmission again to replace them once they wear out. The catch is torque biasing stops working when one of the wheels completely loses traction. One exception is Wavetrac that has some clutch material in addition to helical gears (and I think MFactory was making something like that as well?), but the differential will continue working even if that material wears off.

> My understanding was, an LSD would not only assist in acceleration, but would help in icy conditions, as i expierence in northern Alberta.

It will assist in accelerating in icy conditions. What other kind of improvement were you looking for? I would say outside of purely accelerating, the biggest advantage in icy conditions are studded tires.

> However, i was told that, an LSD would greatly have a negative effect in cornering in cold and icy weather. This goes against my research.

I ... haven't heard that one before. Maybe someone else can chime in. I have Quaife installed and I haven't experienced any negative effects like that.

 

[atlantaM3]

the 'negative' effects are largely related to RWD drive cars that have overly aggressive decel config in their diff - it can cause them to not want to turn as easily. This is where you see '1.5 diff', and such comments, where the accel and decel profiles of the diff are dfferent.

 

[Phippy]

> I am wanting to install a mechanical LSD in my fiesta. My research led me to believe a mechanical LSD is better then a clutch based LSD.

Clutch based LSD is also mechanical, you probably mean torque biasing one based on helical gears? The reason torque biasing is preferred for our cars (MFactory, Quaife, Wavetrac) is because there's no wearable clutches inside and so you don't have to go through pain of taking out the transmission again to replace them once they wear out. The catch is torque biasing stops working when one of the wheels completely loses traction. One exception is Wavetrac that has some clutch material in addition to helical gears (and I think MFactory was making something like that as well?), but the differential will continue working even if that material wears off.

> My understanding was, an LSD would not only assist in acceleration, but would help in icy conditions, as i expierence in northern Alberta.

It will assist in accelerating in icy conditions. What other kind of improvement were you looking for? I would say outside of purely accelerating, the biggest advantage in icy conditions are studded tires.

> However, i was told that, an LSD would greatly have a negative effect in cornering in cold and icy weather. This goes against my research.

I ... haven't heard that one before. Maybe someone else can chime in. I have Quaife installed and I haven't experienced any negative effects like that.

So re reading the conversation, the person i was talking to said an LSD would generate understeer in long cornering. Again. Exactly the opposit of what i thought the LSD was supposed to do.


Thank you for all your info so far its been VERY helpful. Im aware studded tires are the way to go and i do have them. But the guy i was talking to seemed to believe it was going to hinder me vs assist me.

So let me restart!

My fiesta has the following:
After market intercooler
Cobb access tuner
Cat-back exhaust
All motor mounts replaced
Front suspension work (i dont know WHAT exactly)
Short throw shift kit

I bought this car with all these mods. Im looking to improve handling now that power has been upped. This is what started me down the path of an LSD. The car itself is my daily drive. I would like to have a few track days in the summer for fun, but thats all.

So im trying to figure out the pros and cons of installing an LSD. Talking to my buddy about it is what lead to all my confusion.

Does this help?

 

[atlantaM3]

Torque sensing lsd will def help it power out of corners. Have one in , a quaife, my focus rs, can feel it pulling the car through the corner under power, keeping rhe intended line as long as you manage the throttle properly.

 

[foodtruck]

> LSD would generate understeer in long cornering.

Well, in my experience, the way the diff in my car feels is that the outer wheel wants to rotate around more, which actually _reduces_ understeer. This makes sense because in a corner, the weight comes off the inside wheel and so it has less grip, which makes the differential bias more torque towards the _outer_ wheel (there's some multiplier factor in each diff and it varies somewhat, I think its around 3x?). This is great and completely different from how an open diff behaves where all the power goes into spinning the inside wheel.

> Front suspension work (i dont know WHAT exactly)

Just the front? I would take pics of front and back suspension, its hard to comment otherwise. Typically suspension "work" is done both in the front and the rear to avoid mismatched setup unless the previous owner just replaced the shocks like for like. AFAIK typically suspension is changed based on how sticky the tires are that you're running and how hard you want to corner rather. In normal conditions on public roads where you typically run something like 400-300 tw tyres and don't corner like mad, I think stock suspension is just fine. Even if you start racing the car, I would stay stock until you have a good idea of where it limits you before upgrading anything.

Otherwise seems like a pretty typical set of mods.

The only con of installing a helical biasing differential I know of is the cost of the diff and the work (and, for me, the shifting became a bit noisier, but your experience may vary). These differentials come standard or part of performance packs on many cars such as Civic SI, Corolla GR, etc etc, and even Mk8 Fiesta that we never got. I can't say I feel it working on public roads but it most certainly makes a difference on the track and autocross courses.

 

[Grsemky]

> LSD would generate understeer in long cornering.

Well, in my experience, the way the diff in my car feels is that the outer wheel wants to rotate around more, which actually _reduces_ understeer. This makes sense because in a corner, the weight comes off the inside wheel and so it has less grip, which makes the differential bias more torque towards the _outer_ wheel (there's some multiplier factor in each diff and it varies somewhat, I think its around 3x?). This is great and completely different from how an open diff behaves where all the power goes into spinning the inside wheel.

> Front suspension work (i dont know WHAT exactly)

Just the front? I would take pics of front and back suspension, its hard to comment otherwise. Typically suspension "work" is done both in the front and the rear to avoid mismatched setup unless the previous owner just replaced the shocks like for like. AFAIK typically suspension is changed based on how sticky the tires are that you're running and how hard you want to corner rather. In normal conditions on public roads where you typically run something like 400-300 tw tyres and don't corner like mad, I think stock suspension is just fine. Even if you start racing the car, I would stay stock until you have a good idea of where it limits you before upgrading anything.

Otherwise seems like a pretty typical set of mods.

The only con of installing a helical biasing differential I know of is the cost of the diff and the work (and, for me, the shifting became a bit noisier, but your experience may vary). These differentials come standard or part of performance packs on many cars such as Civic SI, Corolla GR, etc etc, and even Mk8 Fiesta that we never got. I can't say I feel it working on public roads but it most certainly makes a difference on the track and autocross courses.

Don't forget we have Torque vectoring baked into the the ABS which helps eliminate the inner wheel slip

 

[Phippy]

Don't forget we have Torque vectoring baked into the the ABS which helps eliminate the inner wheel slip

I was curious if that combined with an LSD would conflict or assist each other.

 

[Phippy]

https://www.raptorracing.ca/product...MPl9g8JfSYhqS6F2Q3Mb0sm6Nh0gISfoaAmwvEALw_wcB

This is what i was looking at.

 

[Phippy]

https://whooshmotorsports.com/produ...ted-slip-differential-lsd-2014-2017-fiesta-st

Is much more affordable however... thoughts?

 

[Grsemky]

I was curious if that combined with an LSD would conflict or assist each other.

They achieve the same goals, I assume it makes pad life/fade better if you're tracking... Though I'm sure someone with a LSD installed can let us know

 

[foodtruck]

I was curious if that combined with an LSD would conflict or assist each other.

Previously, https://www.fiestastforum.com/threads/quaife-atb-and-tvc-mystery-solved.1933/

 

[Phippy]

Previously, https://www.fiestastforum.com/threads/quaife-atb-and-tvc-mystery-solved.1933/

THANK YOU!! That is VERY informitive!

Normally i drive in alberta, but, i do spend time in BC and theres nothimg like driving hard through mountain passes. So this confirms, for me anyway, that i do want to go with an LSD.

Now i need to decide on one. I listed 2 above. Has anyone used either? Thoughts? Other recomendations?

 

[rallytaff]

Love my WaveTrak, even on the street. Getting on to fwy entrances with curves is a blast! Would not be without mine now I've got it. No maintenance required.