Electronic Limited Slip?

[JeffD]

ok, So obviously this is going to be a very technical, long term project.
Basically All i believe i need to do is retrieve an ABS unit from an Alero I have that has traction control capabilities, install it into the beretta along with the front spindle and bearings, run new brake lines (which i need anyway) from the ABS unit out to the wheels and hijack the control part of the abs unit with a computer of some time. My hope is to gain Electronic limited slip abilities and something similar to a line lock for the the rear end. I know it may seem overkill to do all this, but I want to hear some feedback. plus I dont want to replace my trans with one that is compatible with the limited slips that are available.

[ErichZ26]

That system is integrated with the PCM and controls fuel and spark as well.

[Barry]

I was thinking the same thing a few years ago. Just never went anywhere with it. Your probably better off building a controller from scratch. The algorithm is simple, but integrating it might be a bitch.

While this will help with wheels spin it also wastes power any time it's correcting slip up front, but I'm sure you know that. The positives probably outweigh the negatives

[JeffD]

@erichz26, your thinking of traction control. this will be more like an independent system that only corrects wheel slip and doesn't try to manage torque. I am not going to use the same controller that the alero has, I am thinking of a 32bit Arduino style controller to manage the 2 front wheel channels in place of the original controller. I'll have to gut the original controller so I can use the sealed case and just hijack the internal solenoids.

@Barry, I dont see how it will be wasting power. it more or less redirects power lost from wheel slip to the side with the better traction. to me that is always a gain. originally I was trying to find out if the original abs unit could be reflashed with different instructions, but I abandoned that idea for the simplicity of creating my own controller that is easily programmable.

[3X00-Modified]

FYI info I pulled from a BMW forum... you are techincally talking about a E-LSD aka Traction control...

I'll start by correcting your assumptions:

- Yes, a mechanical LSD is a WORLD of difference from an open diff with traction control. There is a reason why virtually every performance/racing car has one.

- The "E-LSD" IS traction control. That's exactly what it is; nothing more. Calling it an "E-LSD" is BMW marketing nonsense.

- Traction Control and Electronic Stability Control have nothing to do with whether or not the car has an open diff. A mechanical LSD will supplement those programs, but does not replace them. On most cars, the TC/ESC are standard "off-the-shelf" programs made by Bosch and are the same on cars with and without a mechanical LSD.

- The "E-LSD" (call it traction control because that's what it is) brakes the slipping wheel in pulses, resulting in an ON-OFF-ON-OFF power application, sending the vehicle into a bucking motion. You are correct, during the time that the slipping wheel is being braked, power is sent to the outside wheel; but again, it's in an ON-OFF-ON-OFF manner. A mechanical LSD DOES NOT send power to one wheel at one specific ratio; it sends power at a variable ratio that depends totally on the instantaneous grip available to both rear tires. No mechanical LSD splits power at a specific set ratio.... they all vary based on the instantaneous grip available.

- "If the electronic LSD clamps down on the inside wheels rotor in hard jitters, it would be pretty efficient." - NO, it wouldn't. It would be very inefficient. This is why, again, virtually EVERY racing car on the planet has a mechanical LSD. A mechanical LSD acts instantaneously and constantly. An E-LSD reacts to the loss of grip that already happened. On a track, that = time lost.

On to your questions:

1) No. BMW's "E-LSD" allows a massive amount of inside rear wheel spin. I'll post pics later tonight.

2) No. The E-LSD has a very low threshold where it simply stops engaging and allows all-out wheelspin.

3) Every traction control system I've tracked has been massively inefficient and in no way a substitute for a proper mechanical LSD.

Hope that helps clear things up...

[JeffD]

I tried not to refer to it as traction control for the sake of differentiation between a E-lsd (wheel slip control w/o torque management) and traction control (Wheel slip control with torque management and brake intervention.)
I believe there is a mistake in assuming that the limited slip diff causes no wheel slip. the name implies this power loss, although momentary, there is still a loss.
the e-lsd is in the same boat, it is a pulsed spike in hydraulic pressure to the slipping wheel's brake to direct more power to the wheel with greater traction until no longer needed. there needs to be slip in order to correct it.
I don't see to much of a difference.
obviously, as seen above BMW, uses e-lsd's. many companies do, If I am not mistaken, Toyota doesn't have any real LSD's, but the one that I think of that has used it extensively is Jeep on their wranglers and other's that are not full-on off-road machines with lockers. These vehicles effectively use e-lsd to mimic lsd's in slippery situations and are pretty decent considering it's just brakes engaging.

My point is that depending on the way the system is designed it can be greatly effective or mildly useful.
The set-up I am building is going to be aggressive in managing wheel slip, and because It is not the stock controller I can also change when I want it and when I don't.

What are your thoughts 3x00 modified? I don't plan on drag racing it, I need it for acceleration out of corners.

[Barry]

Theres no doubt that it could work. I think the biggest challenge is making it operate quickly enough to make it feel smooth.

[3X00-Modified]

I agree with Barry... for a system like that to work as noted your already slipping before it engages and it will have an on/off feel to it... where as a true internal diff LSD its using the applied torque from the engine to lock the spider gears in place and limit slip in a consistent manner before it happens.

The way I see it is your going to spend alot of money on this and many will look at it as a traction control system which may bump you into a different class or not able to compete in some autox events... I would look into the rules a bit more on that. Also with a LSD option available for the diff on these cars I don't see the purpose of going through all this trouble, unless you've already proved that to not be effective.

[JeffD]

as far as money goes I won't have more than $400 invested. I already have the parts car ($300) I needed it for the somewhat low mileage 3400 anyhow. I want to do the front brake conversion anyway, so chalk up the spindles and bearings (has two new ones in it.) and calipers. The controller I want to use is less than $40 and the transistors and misc electronics probably another $20.
so I am not too concerned about that since $300 of it got me very far ahead on other projects i wanted anyway.

The SPID label on my car is gone so I am still trying to decipher what trans I have, most lsd's I have seen have been for the muncie in the GTZ, mine is either the Getrag or the Isuzu. it's a 1987 built 88. so if you know which trans this would be let me know. obviously a LSD will be better, but if none is available this is my only option.

[3X00-Modified]

Talk to Jeff at Engineered Performance he builds LSD's for the Getrag's and thats the trans you have. I just worked on an 88 5-speed GT and he has an EP LSD. Its a fully custom clutch type LSD with the ability to rebuild it. Yes your looking at either $499 to $599 depending on if he is offering a winter sale still, but its a reliable option.

http://www.engineered.net/

Tell him Jon from CT sent you his way.

[ErichZ26]

@erichz26, your thinking of traction control. this will be more like an independent system that only corrects wheel slip and doesn't try to manage torque. I am not going to use the same controller that the alero has, I am thinking of a 32bit Arduino style controller to manage the 2 front wheel channels in place of the original controller. I'll have to gut the original controller so I can use the sealed case and just hijack the internal solenoids.

I am thinking of that.

I was not aware the Alero had this system. Did the Grand Am GT get it too? I don't think mine has that.

[JeffD]

Thanks 3x00, but for that money, ill have to start saving my pennies till the next winter sale... the car is a hobby right now, I am going to start gutting the Parts Alero and set the stuff aside I need.
I am still going to play around with this idea since the cost is pretty low and I know I can use the controller for other purposes if this doesn't work out.

[JeffD]

Erichz26, I know the Alero has traction control, and that is all I need. Basically I need an abs unit with the proper valving and motor to build pressure and apply it independently per wheel, without brake pedal input. the control will be from an arduino controller, i.e. a completely programmable microprocessor with digital and analog inputs and outputs.

[JeffD]

I need some info on the front wheel speed sensors on the 2002 alero. I cant find anyone who has the tooth count on the reluctor wheel inside the front hub. the model number I found for it is the AC delco FW153. Not that I expect this info to be common knowledge but we have a good number of members that would not surprise me if they knew the count.

[JeffD]

I had a bearing from an olds 88 with abs, found that it had 47 teeth. still no idea what an alero has though, Different part number on bearings...