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The diff is complicated. The main principle is to get the power to the ground most effectively but how we use the diff to do this depends on all the details about the car. Weight, layout, tires, down force, all impact how we set it up.

Generally Speaking

INT tightens up the diff making the car less willing to rotate the higher the setting

The accell tightens up the diff on acceleration

The decell tightens up the diff on deceleration.

I'll give my 2 fav examples of set up.

A light car with high down force and high grip tires has low power. In this case we go for a lose diff, close to open because the car has more grip than it has power to overcome that grip. The tighter the diff the more diff induced under steer will become a problem.

But if we add more power to the scenario, the car can overpower its grip easily, so we tighten up the diff, the more powerful car can use the throttle to overcome diff induced under steer.

Then to complicate things further we tune our diff with our springs and roll bars

example
High spring low roll bars will go tight on the diff where if we reduce springs and increase roll bars we loosen up the diff. The high springs and low roll bars has a heavy inside tire where the tuned softer springs and stiffer roll bars will have a lighter inside tire. It's is a kicker that many don't seem to get..... Its NOT all about the outside tires, we tune to use ALL 4 TIRES Grip as best we can, not just the outside tires..... The weight of the inside tire in combination with the car specs will effect how much power we can put through the tires...

Its one of those things that depends on every other detail on the car. The thing that always remains the same is we use diff to put power down most effectively, how we do it just depends on so many things..

When it comes to tuning its like a giant intertwined jigsaw puzzle. Everything is working together. There are no quick steps to tuning, that's partially why no tuning guides posted are useful. To many look at tuning completely wrong going for a universal method to tweak one setting at a time until set them moving on to the next setting.. That's NOT how to tune in a game or real life.. Tuning is closer to engineering than "mechanic" work. Mechanics turn wrenches, I know Ive been turning wrenches on cars for years, every garage has somebody who can turn wrenches, tuning cars takes MORE than a mechanic, it takes more than just knowing how to work on cars... Mechanics, Engineering, and Physics are all things one needs to be familiar with when tuning, No you don't need to be a Physicist, Engineer or even a Mechanic to tune cars, but you damn sure do need to have a working understanding of mechanics, engineering and physics..

I have a Mechanics Background, and was fortunate to ride my uncles coat tails growing up helping him work on his cars, but I still had to learn about engineering and physics. Physics governs speed, so to get fast, one needs to get familiar with the physics at play..

Heureka, of course 4 wheels grip and the use of that grip. I have thought ( one again ) thigs too complicated and forgot basics.

Thank You for bringing me back to the KISS principle ( Keep It Simple Stupid ) - it helps understanding and headache.

Jounijkk

Love that expression, I use it often.

On a side note we did diff testing on around page 50, might shed some light on diff inter workings.

Then there is this old ass video that has been shown all over the place, even my teacher in auto mechanics school showed it when we started the differential module.



No joke its from 1937

BUT when we have real horsepower we have a problem of bleeding power through the inside tire slipping, the outside tire only able to put down as much power as the tire with the least grip, if 1 tire is spinning all power to the tire with grip is lost, nothing accelerates the car. Its called power flow, the power flow always takes the path of least resistance. When the tires have equal grip they resist spinning equally so power is distributed equally, when one tires grip is lost the power flows through the spinning wheel as the wheel with grip has resistance.

This one gives some explanations on the different types and essential use of a "Limited Slip" Differential

I found this video that I believe may help a lot on the Subject.



It explain HOW and WHY the diff does what it does in the corner NOT just when one tire slips as this can occur on the straights, this should give some insight into what the diff is doing before a wheel slips.

Also the STOCK Diff in the GT6 version of the FR-S, BRZ and FT-86 can be used to see how PoDi is Simulating the Diff in the game.. Note the HIGH settings. Also note its a 1 way diff with no deceleration lock.


The 8-6 family is a great set of cars for learning on. I also like the Miata with a factory LSD for similar reasons. I think the Miata should be the first car then the 8-6 family as the step up. I think getting these cars tuned with high grip at low pp can be very rewarding learning experience for all new tuners.

This is a Spec Build Sheet for that Miata

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Spec Uses the Factory LSD, no tuning, BUT the fixed LSD will force the Tuner to adapt the suspension to make best use of the factory diff under the circumstances... You would be surprised just how much fun these cars are to drive and race online.

@jounijkk, sinister give you good Kickstart for LSD tuning, inside spoiler there is one approach, tried to keep it simple.

You could use some real life specs on starting point of LSD tuning base, but then you have to feel what's happening on tires and understand why it's happening, then you're again on sinister path, understanding and more understanding

LSD

Initial = constant lock amount(preload), affecting during coasting, between Accel and Decel happens often during long turns also, you just coast keeping gas on position what doesn't increase or decrease speed, braking side and acceleration side values easily affecting simultaneously

Acceleration = amount what it will lock more above initial during acceleration, initial+acceleration= total locking

Braking = amount what it locks when there is reducing speed on tires, turning means reducing speed on inner tire, braking(engine and brakes) means reducing both tires speed, both cases are activating this, amount is initial+braking= total locking

Easy ABC principals for RWD LSD tuning:
A) Search highest Initial value what keeps car steerability on Apex and thru cornering, coasting light chicans(flying thru with mild steering). = No Understeer or Oversteer. (testing_value/5/5 during this)
B) Search highest Acceleration value what allows you push most out during accelerations out from corner, and also in corner. (tested_A_initial/testing_value/5 during this)
C) Search highest Declaration value what keeps rear planted during corner entry and inside corner, also be sure at test that value to be working on highspeed corners when throttle is sailing between accel/coasting/decel. (tested_A_initial/tested_B_Acceleration/testing_value during this)

After you have high Init founded, mostly that will be between 5-20%, exceptions can be found, but mostly there, rule of thumb, higher with higher power and wider wheel rail. Then put some approx 60% lock for acceleration and 40% declaration, so ie if car handles well with 10% Initial then put 50% accel and 30% to decel (totals that 60-40% lock with 10% preload) and start searching balance of that lock, should it be higher decel to avoid huge locking changes on wheels or how it overall handles to understand what you need (or handle) more or less.


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Coasting corner 1 and 2, coasting 5 and 6, coasting 10 and 11 are good for initial steerability search.
Corners/turns from 2 to 5 and from 7 to 10 are good for base initial search on high speed.

Corners 1 exit, 6 exit, 11 exit are good for searching base acceleration value.

Entering corner 1, entering 5, entering 10 are good for base declaration search.

Turn 12 is best to check are all working well together.


@sinister, will do some Miata soon on those specs, just want to test what it will become.

Edit: grabbed some education plus just for fun LSD videos on one playlist LSD collection: You must login or register to view this content.

This has been a very good day. I have increase my knowledge about tuning and I really must thank You Sinist3r and Odefinn. I've been watching Your videos, try to understand what I have read and I must say I know much more about tuning than yesterday.

Now I understand preload and accel, but I'm still in the moon when we are talking about deceleration. I really don't understand what are the benefits to aim high amount of deceleration lock. If I'm thinking right, high amount of deceleration lock is weakening the cars ability to turn in ( understeer ). For me is the biggest poison if the car doesn't follow my eyes to the apex and to the exit point. Maybe I can use this deceleration lock to control cars ability to turn in.

Biggest mistake I have done is that I haven't focus enough for the grip of inner tyre.

Next I go to the track and try to feel the cars reaction of lsd deceleration and mots important, the settings which improve the grip of inner tyre. I must also go to shopping and buy that Miata. Sinist3r, which track and what is Your time ( my target time for tuning )?

Jounijkk

Poor mans abs lol

It can add stability while braking, an overly loose car on entry can be twitchy requiring corrections, deccel lock can help keep her going straight while getting on the brakes. Too much and she will understeer on turn in.

@Jounijkk @sinister, poor mans ABS is pretty valid naming for brakeside lock, Jouni brake lock reduces one wheel locking during braking, with open differential engine brake goes on tire with least traction, effecting like e-braking one wheel on rear during braking. That's not wanted, nor inside corner too, limiting slip during engine brake can be done on GT6 two ways, declaration lock and brake bias to more rear, combining both to get best results. This is reason why some locks are not easy for other driver than lock/BB maker.
Also to be noted is difference between accel and decel locks, if you modulate gas pedal during cornering and switch between accel/coasting/decel locks thus comes in big role, bigger the difference is so bigger is change to loose traction during gas pedal position changes, locking is not happening smoothly so radical changes on locking percentages lock either inside or outside wheel or both, depends which way change is happening and where car body mass is laying during change.

Edit: you have to remember also your suspension setup plays huge role how much LSD brake lock can be used or be needed. This includes toe and camber.
Edit 2: example if you lower ride height of car it makes body roll less, what also means less needed resistance against it from springs, so you could run bit softer springs with it and maybe get more traction to wheels because of bit softer suspension. There is also other side of coin when lowering ride height, it might bottom some corner during body roll, and if that happens you'll loose traction, so here were are again searching best balance where body has enough space to roll freely.
If you reduce body roll by adding more ARB, you have to remember at adding more ARB stiffness makes right and left side suspension more clued together(ARB joins suspension sides together, what happens on left will happen also on right, more ARB and more transferring happenings from side to side), bit like multiplying your spring and damper stiffness, so adding more ARB might need reducing stiffness on those to keep overall balance/softness on stable condition.

Great post OdeFinn, glad to have you active in the thread

Lol yeah "poor mans abs" was a true joke, as in I'm joking but at same time its true lolololol more so back in the day as everything these days comes with ABS now, even the grocery getters.