[FM2] Differential Settings - What to YOU use and why do you use it?

[bimmerlovere39]

I've noticed you tend to use WAY higher diff settings than I prefer.  Wondering if you wanted to talk about the method of your madness?  (Or mine for that fact?  lol)

Fender posted this in another thread, and it got me thinking: what are the advantages of my high diff settings?  Of his low diff settings?  In short: why do we use what we use?


First off, I recommend at least this article to make sure there's a common level of basic differential knowledge.
http://auto.howstuffworks.com/differential.htm

[bimmerlovere39]

Alrighty!  Not to the meat and potatos.  I like potatos.  Yum... potatos...

Anyway, back to the topic at hand, potat-erm, differentials.  As fndr noted, I do tend to use high accel and decel settings.  I have gone very high, as far as 100/100 on an A-Class Cobra 

I've got more to write, but I need sleep lol.  more to come tomorrow with a little luck

[fndrbndr]

I like potatoes, too. 

That said, this explains the loss of some power in turns.  I had suspected based on intuition that the differential robbed a little power at times.  I'm guessing this is why the tiny terrors lose power going up the shortcut at road atlanta short?

[BarbecuePete]

Im more of a meat man... Flame grilled to perfection on a BBQ.. lol
Although I do have a soft spot for potatoes too..

For rear wheel drive, Im tending towards a higher Decel at the moment as it seems to keep the car more stable under braking, accel settings im still not to sure about, lower seems to feel better and allows to get on the power mid turn without the rear wheels spinning...

For Front wheel drive, No Decel but a again a low (about 25) Accel setting, I've not tried many variations on FWD, I think I even picked up this setting from Ske's Universal FWD tune...

I'd be interested to know how that 100/100 diff performs Bimmer?

I thought that a really tight limited Slip diff like that was more useful for drifting as it keeps both wheels spinning at the same speed and makes the car easier to control in the drift rather than having the inside wheel start to spin more as the car slides and the weight transfers over...

[fndrbndr]

I keep my diff settings in the 35/25 (accel/decel) range for RWD, about 25/0 for FWD.  I've also noticed that with my typical tunes, a higher diff setting means that I have a wider turn radius at a given speed, but I'm not sure what causes that.

[bimmerlovere39]

Didn't get a chance for a nice write-up.

A higher rear differential setting keeps the rear wheels a closer speeds than a lower setting.  Coming into a turn, the decel setting locks the wheels together, which makes the car resist turning.  Depending on other settings, this car cause an infuriating corner-entry push, or is can work miracles to stabilize a car that is twitchy under braking.  On corner exit, a higher accel setting will cause the two wheels to spin at similar rates.  This forces more power to the outside wheel. (High-powered, open differential cars are notorious for performing one wheel burnouts, where the inside wheel loses traction, and then all the power goes to that wheel, as it is the path of least resistance.  While smoke looks good, this is obviously not the fastest way out of a turn.  It is also inherently less cool than powered sliding, hence the popularity of LSD among the drift crowd.)  For a road racer, a high LSD lock % will allow more power to be put down, at the expense of overall traction.  A car with a low LSD setting should be easier to drive than a car with a high LSD setting. (There are 2 main reasons that most modern cars use open differentials: 1) They're cheaper, and 2) they don't cause oversteer.)

Now, what LSD settings are best is dependent on a number of factors, including torque, corner radius, tire slip angle, suspension settings, and personal preference. 

I'll write more later, but I need to hit the hay - first day of school tomorrow 

[fndrbndr]

Good luck with that.  I go down Thursday, and have orientation Monday. 

On topic, I tried my Hemi Cuda for the current challenge with the old FDog calc, which includes a 50/40 diff setting.  It puts more power down, but does it less effectively, than my typical settings.  This may be the result of my ham-fisted throttle control, but for me a relatively open setting is faster, possibly just because it fits my driving style, but also because it allows me to hit the throttle earlier.

[JG4tr]

I too use fairly open settings for both accel and decel, generally under 30 and occasionally as low as the single digits depending on the car, its available power and it's tune.

The low decel allows me to get a tight turn in for slow-corner entry. This I adjust to get a balance of turning ease / stability that I want.

The accel, I adjust so that at full throttle, the car wants to over-rotate the turn. Example: For turns preceeding long straights, I set up for a deep entry/ late apex, 'diamonding' the corner. I get back to the throttle well before the apex and then use this diff-induced rotation to keep the car pointed out through the exit. With this style, if it looks like I'm going wide on exit, I can actually apply more throttle and get more rotation to keep it on track, instead of letting off the throttle or braking.

If the car has too much rotation to control effectively, I back off the accel. If I can't get enough rotation and the car starts to push, I add accel. I don't want to ever lose time by having to get out of the throttle on exit so, I'd much rather 'feather' a diff-induced oversteer...

[fndrbndr]

Interesting approach.  I prefer to be able to lift to tighten my radius, but this likely comes from driving FF cars and riding bikes IRL.  In both cases, more speed means a wider turn radius, at least with me at the controls.  I guess it just feels more comfortable for me, and I can set up the car so that my natural inclination is the correct one, so I do. 

I've added air to the front tires and let a little out of the rear to try to get ready for autocrossing my sebring, but that's another topic for another time. hehe.

[Drift2XL]

I use a 40 acc / 30 dec diff.

I too like the nose to tuck in off throttle. And while I have pretty good throttle control, I do find myself getting over eager sometimes and the realitively high accel helps plant the tires going through, say the second chicane section at Mugello.

I have tried lower settings and have had the "hook" shoot me off there a few times.

The hook is where the inside tire spins slightly and the outside grips turning the car. If I hit some turns right, I can get the hook to work for me. But my lack of consistancy doesn't allow for it most times.

Its gotten to where that is my default setting. I can't seem to drive anything else, unless the car needs something else due to drivetrain (MR, RR).

[fndrbndr]

25/35 here...similar concept, though arrived at a little more by accident, I suspect.  It turns out, though, that a lot of what I was just calling throttle oversteer may just be the "hook" effect you're speaking of.

[Fit4aking]

Here's my default.  Not very scientific how I came to it but over the life of Forza I've found that this is a good place to start.

Accel - 35
Decel - 55

I like the traction that I get from an open accel diff as well as the off throttle oversteer I get from the higher valued decel.  It means that I almost always have to have some type of throttle input, even if its very slight.  If I can't get a car to rotate using suspension settings I'll up the decel value so it loosens the rear off throttle.  I then judge corner exit wheelspin using the accel setting.  Generally I end up decreasing accel and increasing decel as needed.

[Spiny Anteater]

I'm in the low decel setting camp myself. Typical values are 40/25 for an RWD, dropping to 35/20 or 30/20 for the high power cars. As others have mentioned, I prefer the low decel setting for that extra little bit of instability you get under braking which assists with turn-in (I use ABS so that might help there a bit).

The low accel setting I find useful for me when I'm accelerating out of corners as I tend to roll on the power as I roll off the steering. If I have a high accel setting, the car tends to want to step out at the back when I do this, so a lower setting is faster for me, even if I might be losing some speed to the relatively open diff.

Moving away from RWD, I tend to run around a 30/0 for the FWDs as I find that allows the front inside wheel to spin up under over-heavy acceleration and help pull the car around the corner in the event of over-eagerness on the throttle rather than spearing off into the outside barrier.

With 4WD's I tend to run similar front settings to the FWDs, but the rear diff is usually around 80/50 to help get the back end to step out a bit and counteract the 4WD understeer - a torque split of 70/30 to the rear helps a bit with that too.