Can't seem to locate an answer through search.

Does anyone know if the LNF's BLD is electronically disabled by the factory if your car is equipped with the LSD; or if the BLD is simply override by the action of the LSD before it kicks in.

Thanks ahead.

 

BL what?

 

lol i bet only 2-3 ppl on here will be able to help ya on that one

 

It's still there I believe, Im pretty sure its just part of the traction control system.

 

BLD: Brake Limited Differential

It is active ONLY when the TCS is off. Do you mean it is active even if you have the LSD?

 

The only time i know it is on is when traction control is off so it will help you from burning out so much on take off.

 

I could be mistaken, but as far as I know this is just the way GM traction control works, limited slip differential or not, it limits tire spin independently fron wheel to wheel if ignition timing/fuel adjustments arent enough to moderate wheel spin. Ive never heard it called BLD or seen it referred to as such in any GM publications. I think that is actually Nissan terminology........

 

GM mentioned this Brake Lock Differential system in the tech presentation: https://www.cobaltss.net/forums/08-10-ss-turbocharged-general-discussion-152/cobalt-ss-tc-technical-presentation-%5Bpdf%5D-can-stickied-139348/

I think it is a system that when the TCS is off, the BLD will indenpendently use the ABS to slow the wheel that is losing traction to prevent it from spinning and force the torque to the other wheel in an open diff, hence the term brake lock differential. My question is if I also have the LSD, how do I know if the BLD if it is not disabled in a car with LSD; will kick in before the LSD had a chance to work which in turn render the LSD useless.

 

If you PM me your VIN I can look up the ABS calibrations on your car and a non LSD car, if they are the same.....theres your answer.

 

If he isn't online I can get you mine

 

I thought their plain-Jane TCS just killed throttle when it detected one drive wheel moving faster than the other. I know that's what it did in my Grand Am, but of course that car is 10 years old now.

 

PM'd

 

Thanks steddy, I already with his VIN(hes got G85) and the VIN from another 09 non-G85 car that the operating system and all calibration are exactly the same on the '09 TCs regardless of whether it has LSD or not.

I got your VIN, and tried searching through about 300 files to find an 08 without G85 and couldnt, so I cant say for certain whether or not the 08s have a different calibration if they have G85 or not. If anyone has a non-G85 '08 TC , PM me your VIN and we can end this debate

2008 and 2009 use different ABS systems.

 

Sounds like us 08 are going to have a helluva time finding parts eventually

 

Thanks Maven.

So there is no difference in ABS calibration with or without LSD? So would that mean that the BLD is actually less sensitive than the LSD?

 

I made a comment about this in a thread I posted after the GMPD tech presentation was released. They note in the presentation that the brake limited differential (i.e. electronic limited slip through brake modulation via the ABS system) is active "...any time TCS is not (“TCS OFF”, “Comp Mode”, “ESC Off”)".

That would mean if you started the car and didn't change the stability/traction mode and were in normal, full-on mode the brake limited differential/electronic LSD isn't even active no matter if you have the mechanical limited slip or not. You'd need to switch to one of the other modes for it to become available. I'd say more likely it's not that it isn't active, but when the traction control (ETC) is also active it tries to kill all wheel spin on both wheels (usually via ABS, spark, fuel and/or the electronic throttle on most systems). ETC won't allow the lighter ABS brake modulation on just one wheel in order to send torque to the other wheel through the open diff.

In other words, the ETC system is too heavy handed and tries to stop all spinning, which consequently slows the car down vice the brake limited differential function that just needs a tiny bit of brake pressure to do its job. You apparently can't have both at the same time with the current ABS hardware/software. The electronic limited slip feature is more than likely implemented via that ABS controller and if you have the mechanical limited slip differential option you shouldn't have unequal wheel spin to start with so the electronic version wouldn't need to go active (but is still there).


There would be one exception I could see where the electronic feature could complement and be beneficial to having only a mechanical LSD. We have a Quaife/Torsen-style helical gear LSD that is a torque biasing diff. In order for it to "bias" or send torque to the wheel with the most traction there has to be some traction on the driven wheels. If you had a car with one of these types of diffs and were on a surface such as solid ice you could end up in a scenario where there wouldn't be enough traction to bias the engine power to both wheels and you'd end up just spinning one wheel even with the LSD. The work-around would normally be to gently tap and hold the brakes while trying to accelerate. That would provide enough resistance so the LSD can send torque to both wheels (whether your tires would be able to do anything on solid ice is another matter, but at least they'd both be spinning).

Having the electronic "brake limiting differential" would essentially do the same thing for you, automatically, since if both wheels were on a near zero traction surface and one started to spin it would apply the brakes to that spinning wheel which would in turn create resistance the mechanical helical gear LSD needs to work.

 

Nah, 08 ABS system is same as 07

 

You know what, that actually kind of make sense. Cause I know from reading the R&T's "A Time for Turbos" where their test car didn't have an LSD and they were complaining about the usually open diff wheel spin when rushing the throttle out of the corners. So there is a limit to the BLD system of how much wheel spin it can control.

It sounded to me that the BLD can ONLY reduce so much wheel spin until the power applied overcomes the system. With the LSD in place, the LSD can simply pick up where the BLD left off and begin to bounce the torque around for maximum traction.