by "Bryan doesn't drive a 1M" (bryantakespictures)
Published 04/13/2017 at 10:11
by "Bryan doesn't drive a 1M" (bryantakespictures)
Published 04/13/2017 at 10:11
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STARS: 4
My wife works as a pharmacist and instantly started laughing when she saw the “C.DIFF” button in my car. For those of us who aren’t in the medical field:
http://www.webmd.com/digestive-disorders/clostridium-difficile-colitis#1
So... I guess I should select “-”? I definitely want less of that.
Edit: My wife was laughing at the tone-deafness of Subaru naming their control C.DIFF, not at the infection itself, if that wasn’t clear.
"TheTurbochargedSquirrel" (thatsquirrel)
04/13/2017 at 10:14, STARS: 10
I think the STI is more concerning than the c.diff.
"Rico" (ricorich)
04/13/2017 at 10:17, STARS: 0
Can someone Explain like I’m 5 when are you supposed to use that toggle and what does the + and - represent?
"ToyotaFamily" (robbav35)
04/13/2017 at 10:21, STARS: 0
Haha she’s not the first to notice. I think Road and Track made the same comment a while back.
"bob and john" (bobandjohn)
04/13/2017 at 10:22, STARS: 1
faster or slower lock up of the center diff.
faster lock up: harder to turn on grippy surfaces, but better to slide with on gravel and stuff.
slower: easier to turn on grippy stuff, but when a wheel loses grip, its going to spin the one wheel more, rather then sending power to the other, grippy wheels.
the toggle is so you can set your setting and leave it ONE setting and the car is predictable, where as if you leave it in intelligent, its going to change automatically as you drfive.
"HammerheadFistpunch" (hammerheadfistpunch)
04/13/2017 at 10:25, STARS: 1
Plus is more 4wd and minus is more awd
"theuserformerlyknownasaluminumfoil" (theuserformerlyknownasaluminumfoil)
04/13/2017 at 10:27, STARS: 0
This. I wonder if she giggled at STi as well
"t0ast" (t0ast217)
04/13/2017 at 10:29, STARS: 1
I believe it adjusts the amount of locking force in the center differential. More lock = 50/50 front/rear power distribution, less lock = rear-biased power distribution. Manual lets you choose how much from 6(?) levels and the car will just run consistently with that setting. Auto lets the car handle that setting but can still be set to Auto+ or Auto- if the driver wants to bias it one way or the other.
"Bryan doesn't drive a 1M" (bryantakespictures)
04/13/2017 at 10:35, STARS: 1
True, there is that too. This car is riddled with disease.
"71MGBGT Likes Subarus of Unusual Colors" (adamprotter)
04/13/2017 at 10:38, STARS: 1
It sounds really gimmicky, but it’s actually really fun in practice. You can also fully lock the center dif in manual mode and that helped my car quite a bit when there was a lot of snow on the ground.
"Rico" (ricorich)
04/13/2017 at 10:45, STARS: 0
Is the gist of it:
Lots of snow/loose gravel = +
Normal street driving = -
Is there any time on normal street driving that you should add a little +? Like when hitting a backroad?
"Rico" (ricorich)
04/13/2017 at 10:46, STARS: 0
When you say it’s going to spin the one wheel more do you mean to compensate for the lack of grip?
"bob and john" (bobandjohn)
04/13/2017 at 10:48, STARS: 1
so when its loose, that one wheel that has no grip is going to spin more as the diff isnt locking up.
"Rico" (ricorich)
04/13/2017 at 10:52, STARS: 0
I don’t think it sounds gimmicky at all. I’ve never driven a WRX or STI before so I am curious about what those toggles do. What are some situations in which you + or - the toggle? I know you said for snow you fully locked it but besides that?
"Rico" (ricorich)
04/13/2017 at 10:55, STARS: 0
See my only experience with AWD systems are usually the opposite - they send power to the wheels with grip but I’ve never driven one with a center differential or the ability to adjust what it’s doing.
"Rico" (ricorich)
04/13/2017 at 11:00, STARS: 0
Wait so can you drive it strictly in rear-biased mode? Or does that put unnecessary strain on the differential when you are on normal street surfaces?
"bob and john" (bobandjohn)
04/13/2017 at 11:03, STARS: 1
its NOT supposed to do that. thats what happens when you have an OPEN dif.
however, you cant be driving around with it locked all the time. you need to turn.
the AWD in these cars lets you adjust how much wheel slip it allows before it will start to lock up, as in some conditions, you may want more or less lock up (eg: pavement? less lock. gravel/ ice? more lock)
+ = faster lock up, less slip.
- = less lock up, more slip.
"Rico" (ricorich)
04/13/2017 at 11:04, STARS: 0
Sad to admit as an auto enthusiast I know zilch about Subaru’s AWD system in the STI/WRX
"Rico" (ricorich)
04/13/2017 at 11:07, STARS: 0
Yeah my C300 used 4Matic which used open differentials. That’s pretty interesting though. Since you can adjust it up and down a few levels is there any reason to leave it a little more locked or a little less locked when driving around some curvy backroads?
"bob and john" (bobandjohn)
04/13/2017 at 11:12, STARS: 1
less lock means it will be easier to turn. the axles arent tied together as much, and its a more natural feel for the car to turn in.
more lock means they wheels will slip less under power.
it depends on the road conditions and the road itself (lots of tight turns, long sweepers) that kinda deal.
"Rico" (ricorich)
04/13/2017 at 11:15, STARS: 0
Awesome, thanks for the info. As I mentioned to HFP I’m sad to admit it but I know nothing about Subaru’s AWD system even though most auto enthusiasts do.
"HammerheadFistpunch" (hammerheadfistpunch)
04/13/2017 at 11:16, STARS: 1
I would say its more a tuning thing than a terrain thing. More Colostridium Difficile trades stability for agility. i.e. on the rough stuff you can fine tune the “tightness” of the car. + means more stability and less tendency to rotate with more chance of recovery. - means more agility at the expense of stability. Its not night and day though, its subtle. I also would not use it on the street.
"bob and john" (bobandjohn)
04/13/2017 at 11:16, STARS: 1
everyone has to start somewhere man.
"Neil drives a beetle and a fancy beetle" (1500sand535)
04/13/2017 at 11:19, STARS: 2
I once was behind an STI in traffic and said something to my wife of, “what I wouldn’t do for an STI.” And I grew up at a time when it was called STD but my wife is more in the know and laughed her ass off at me and said something like “what the hell!”
"71MGBGT Likes Subarus of Unusual Colors" (adamprotter)
04/13/2017 at 11:21, STARS: 2
So what I’ve found is that the - lets it have a little more rear bias and makes it feel a little bit more fun on a spirited drive. The + gives me better traction in bad conditions like rain or snow. I basically used a parking lot as a skid pad during the first snow and the rear swung out way more in - and stayed planted in +.
"RiceRocketeer Extraordinaire" (ricerocketeer2)
04/13/2017 at 11:35, STARS: 0
My wife is a nurse and that apparently that stuff is no joke if you work in a hospital.
"Bryan doesn't drive a 1M" (bryantakespictures)
04/13/2017 at 11:40, STARS: 0
Yeah, that’s what it sounds like.
"If only EssExTee could be so grossly incandescent" (essextee)
04/13/2017 at 12:03, STARS: 0
I lost my great grandmother to c diff last summer :(
"Bryan doesn't drive a 1M" (bryantakespictures)
04/13/2017 at 12:09, STARS: 0
Sorry to hear that. My wife said it’s a really big problem in hospitals.
"If only EssExTee could be so grossly incandescent" (essextee)
04/13/2017 at 12:13, STARS: 0
Nursing homes too. All it takes is for one orderly to forget to wash their hands and you get an outbreak. And when you’re 98, a small infection can go downhill really fast.
"Bryan doesn't drive a 1M" (bryantakespictures)
04/13/2017 at 12:15, STARS: 0
People have explained this pretty well, but I think Subaru should have labeled the switch with up and down arrows or even front/back labels to make it clearer. Yes, what it does is lock the center differential more or less, but what the driver is thinking about is front or rear wheels. I had to look this up to be sure of what +/- meant even though I knew in general what their center differential control allowed.
"t0ast" (t0ast217)
04/13/2017 at 13:18, STARS: 0
The TL;DR is that rear-biased is actually the “default” behavior of the differential, and a significant wear difference is unlikely regardless of setting. More in-depth info below, though in the interest of full disclosure, my knowledge is based purely in casual research. I have a Subaru, but not one with the trick center differential.
Generally speaking, a center limited-slip differential (regardless of setting or type) doesn’t have to do a whole lot of work under normal driving conditions until there is a certain amount of difference between the front and rear wheels (like speed or traction). If you think about driving around town, the front and rear wheels are almost always rotating at or near the same speed and have the same amount of grip. Even if you encounter some low-grip surfaces, the difference (and corresponding differential stress) is pretty short-lived once you get up to cruising speed or get away from that surface. Subaru also strongly recommends against mismatched tires because it could lead to a consistent difference and force the differential to work harder and/or more frequently.
Back to the Subaru unit in particular, from what I’ve read so far, the main center differential internals are an asymmetrical set of gears biased towards rear by default, like 35/65 or 41/59 (depending on year). It’s also probably worth noting here that the front/rear ratio is how much of the available engine “effort” goes into moving each pair of wheels rather than the difference in wheel speeds. Anyway, barring abusive driving conditions, you probably don’t have to worry about those gears wearing out if the maintenance routine is followed, sort of like the gears in a transmission.
The C.Diff +/- adjustment part of the differential uses an electronically controlled set of clutches which can change the ratio up to 50/50 by exerting some additional force to make the outputs more equal. Clutches, by nature, do slip and wear with use over time, but these come in a group with several plates to distribute forces across, and as I mentioned before, the center differential doesn’t have to do a whole lot of work under most normal circumstances. There is probably a non-zero additional amount of wear that comes with them adjusting the ratio away from the rear-biased default, but I’d wager that it’s negligible for most people if they keep up with maintenance.