What is this noise? Brake 'lsd'?
 

I've heard this noise at a couple of events but this is the best one that got captured on video. I'm running my 2017 Brz with Traction Control 'OFF' which I thought disables the brake lsd thing? So what do you think it is? It can be heard at: ~:35 and ~:45

[ame="https://www.youtube.com/watch?v=Ao3HYMnGQhk"]July 9th Alaska SCCA Autocross C-Street 2017 Subaru BRZ - YouTube[/ame]

Read the owners manual.
http://www.ft86club.com/forums/showthread.php?t=8212
2017's are slightly different.
And search for "pedal dance"
Traction control and stability control are two different things.

I have and it says here that in a manual car all systems should be off
https://view.joomag.com/subaru-brz-m...028204?page=11

But I'm not sure they are...

How exactly did you turn it "off" ?
And did you search "pedal dance" as previously mentioned?

CSG says the pedal dance is still required on the '17+ models, however I have no idea what the "problem" is based on the video and your description.

It "sounds" like you've just overdriven the car into the corner and it's skipping along the pavement potentially exacerbated by throttle and steering inputs. No car setting will change the laws of physics that you've tried to violate. (well, ok you might be able to tune it out with some fancy dampers, but it's much cheaper to drive the car the way that keeps it happy)

fwiw ABS never shuts off if you're feeling the brake pedal pulse

There was no 'problem' persay, I just heard a high pitch mechanical noise coming from the back tire. The car wasn't skipping across the pavement, but I was making those Michelin pss work. That run I finally hit the line I was wanting and resulted in besting the 2 other CS miatas and the 2 Z06s :)

well dang... I really thought I could avoid the pedal dance non-sense by going with a 2017 model... I guess we will see next month if I feel/hear any differences at the next event.

Now that's something I can listen for.

I hear it too, what brake pads are you running?

If it is the brakes activating (which would make sense for 'auto-LSD' to be working hard there) the pedal dance should cure it. Presuming you're doing the full 3s press to turn off the TC already. (based on the description in the OP you have read the manual for your car and are differentiating between the modes)

Supposedly the slip light will flash when the car engages auto-LSD mode, if you can get a camera over your shoulder, on the driver window or on your helmet that could tell you right away if that's what's happening.

Marketing has pulled the wool over the eyes of new sports car buyers for a long time, at least this doesn't render the car undriveable.

And it could always be some other odd noise, these aren't bimmers after all with several hundred lbs worth of sound deadening.

Read through the whole pedal dance thread, there are some foibles and I certainly struggled with adapting to it.

Thanks, I'm running the factory brembo pads. At the next event I'll do the pedal dance and see if the noise is still there.

I was doing the 3-sec hold and thought everything was off. The day before we ran the cars in a downpour and the car let me loose control the put it in a spin, so a fair bit of the system is disabled.

I guess it really boils down to two concerns for me. 1) Did Subaru lie and the Brake LSD on or 2) is something loose that shouldn't be.

Either I', missing something or your mixing up terminology.

WTF is a "Brake/Auto LSD"?

AFAIK all are cars have is a basic Torsen unit.
100% mechanical

Am I missing something?

http://www.ft86club.com/forums/showthread.php?t=25494

Toyota's traction control will still apply the brakes on the inside wheel if it has lifted as part of an "auto-LSD" function, there's more written about it elsewhere but the above is the effects and how to 'beat' them if you feel the need to.

TC "off" really is mostly off, it won't save you unless it thinks there is something wrong with the car, rear wheels leaving the ground is apparently part of that equation.

This has a great explanation: https://practicalmotoring.com.au/car...baru-brz-work/

Why would one want Brake LSD off?

Does the pedal dance turn it off?

@strat61caster and @Sleeples
Thank you for the info.

Very smart idea if you ask me.
Only big problem with the torsen being a lifted wheel making it an open diff.
And if that is the case, yes, why turn it off.

@Sleepless @x808drifter

Per the CSG thread mentioned like 6 times already some feel that the EBD system prevents trail braking and weight transfer and the sudden application of brakes midcorner creates unexpected behaviour. (I haven't really felt that, trail braking for me)

I honestly don't know if that's what op is hearing but I think it's worth experimenting with. Knowing if the slip light is flashing will determine if the car is doing something without having a test.

That was a good read, I read it before I got my car but rereading leads me to believe that it may be the EBD I'm hearing not the brake lsd... I'm gonna have to wait 2 weeks to test my hypothesis.

I’m pretty sure that EBD is not the same as Brake LSD. Pedal Dance definitely gets ride of EBD; main reason I have the 86 Nanny from Beastronix. I’ve not seen anything regarding Pedal Dance and Brake LSD. EBD is active under braking. Brake LSD is active under acceleration.

Ebd only happens when you use the brakes, it's not spontaneous, if you're using the brakes midcorner than that may be your high pitched noise.

idk just parroting the thread that pedal dance turns off the auto lsd, maybe not the case anymore for the '17+ I'm not quick enough or good enough to notice when auto lsd kicks in.

It's my understanding that while they are independent systems they both get turned off via pedal dance. I never meant to imply they were the same.

I don't see any mention of Auto LSD or Brake LSD in the Pedal Dance thread. Is there a reference about it somewhere else?

You're right, there's no explicit link in that thread except the description of lifting a wheel which is consistent with the description of what "auto-lsd" purports to accomplish:

http://www.ft86club.com/forums/showp...89&postcount=1

Mentioned here as well:
http://www.ft86club.com/forums/showp...02&postcount=7


Guess I just drew my own conclusions (that could be false), the "auto-LSD" feature didn't really come to light as an explanation until a year or two after this initial "research" and it's rare for anyone to go back and update a technical post years later.

When the car is being pushed to the limits, the VSC ECU can think the inside rear wheel is spinning under certain conditions, and applies brakes to assist the Torsen.

Imagine having brakes suddenly being applied to one corner of the car at 125+. I've experienced it, and can replicate it at will. Pedal dancing eliminates this behavior. So does a mechanical LSD (like Cusco or OS Giken).

Normally, it's pretty seamless, particularly at lower speeds. When it happens at triple digit speeds... code brown may result. I've seen some cars fly off at T8 of WSIR (very bumpy 120+ corner) because of the E-diff function. The corner itself is only about 0.65G lateral, but the bumps can let a wheel spin, and then it gets scary.

Nothing wrong with using the pedal dance!