kaws03

Hello everyone!

The winter is coming, and it would be so nice to have anything, but an open diff.
Easiest option (except for welding, but it's my daily, so no), is a diff from an Aristo with T1 Torsen. Torsen was an option, so it's pretty hard and pricey to get one, and still, it has a gearing of 3,769 instead of our (GS430) stock 3,266. Top speed will drop dramatically (like 220 instead of 250 kmh), and that matters, since I live in Germany.
It is also possible to put the gearing from my diff, but that has to be done profesionaly. So the diff should be sent somewhere, blown-up car has to stay somewhere, yadayada, it all will cost more, then I payed for my entire GS.
Pretty much same applies for aftermarket LSD options.

That made me think about an "eLSD". A.k.a. "Auto LSD", a.k.a. braking the loose wheel.
We already have everything needed- ABS sensors to read wheels speed, solenoids to apply brake individually, so it's worth a shot.

The idea is to read ABS wires, and hijack actuator solenoid wires to control them with a custom control unit.
Resistors can be added to emulate solenoids, so that VSC Module does not freak out.
It all will happen in VSC Off mode only, to keep daily driving as safe and intact as possible.
Another issue- even with VSC Off- it still tries to stabilise a car when it is really sideways. At this times (when it sees pulses from stock VSC ECU)- unit can "let go" and let the stock unit do it's thing directly.
Anyway- the most important thing is to initiate the turn with both wheels spinning. After that, when we're sideways- it's much less crucial (imho)

So, finally, to the questions I have for those who are familiar with a whole VSC operation.
Here is a piece of schematic, that we're interested in.




There are 8 ABS solenoids like "SFLH" (2 for each wheel), S = Solenoid, F = Front. L = Left, H = Hold / R = Reduce. Pretty intuitive, but not 4 more, which are

STR = Solenoid TRacktion?
SA1 = SRCF = SMCF = have no idea
SA2 = SRCR = SREA = ?
SA3 = SRMF = SREC = ?

Here is a hydraulic schema from a 2005 Tacoma, which, I am sure, is pretty close.



From my understanding STR introduces the pressure to ABS solenoids to let them apply brake pressure.
So I need to open STR + SRLR/SRLH.

What also important- is a PWM signal characteristics. Frequency should be low enough to move solenoid, but high enough to not overheat it.
My plan is to read stock PWM's with an oscilloscope during active tests via Techstream, but if someone has any info already- would be super nice if you can share some.

Any input is highly appreciated!
Thanks

firelizard

iTrader: (1)

This sounds like what the factory traction control and VSC already do.

kaws03

Pretty sure they don't
Happens very often, that under slippery conditions the back is going absolute nuts (like 5k rpm at 10 kmh), while car still doing an absolutely normal turn.
Which tells me- one of the wheels is still in a perfect contact
That's with VSC Off. VSC On does not let you anything, basically

Scigheras

I unfortunately do not know much about the details of the factory traction control but very cool that you want to do this!
Interested in what you will achieve.

I can think of two ways you might be able to find the answers to your questions:
There are probably aftermarket standalone ECUs out there which are capable of driving the factory ABS system. You could look for info on how one of those is wired into the factory system.
Look at every factory service/repair and info manual you can get your hands on, often there is quite some detailed descriptions in there about how stuff works.

These cars are quite closely related to other toyota's of the same era, you might find relevant info when looking at jza80 for example.
I already found this, no idea if it can help you https://www.supraforums.com/attachme...em-pdf.282693/

kaws03

That is extremely helpful, thank you so much! I kinda figured that 4 additional solenoids switch abs solenoids from being pressurised by either master cylinder, or a pump, but this doc even has timings for their operation
Super cool!

Though this message made me doubt my judgements.

The thing is- there is no single confirmation that our car does emulate LSD. But I guess there are some about our generation IS.
2WD Tacoma does state it on the dash, by "AUTO LSD" light, but that could purely be a "show-off thing" in a truck world.
At the same time- I have much less problems with less grippy tyres. Could be that brake forces it produce are just not enough for good summer tires even on wet
Could also be pure power and wheel inertia thing. I also have never heard solenoids clicking going straight.

So the next step would be to connect the logging device to read all the important signals, and that could also confirm everything for sure.
If we see pulses to the solenoids on a rapid straight acceleration- case would be closed, haha