I've been considering the fact that my transaxle doesn't come with a torsen diff (dissappointing). My initial plan was/is to use the ABS
rings to run traction control but that's sub-optimal. IT struck me that I could use an ESP module on some tiny secondary brakes (or even the
primary brakes I guess) to force the open diff free-spinning wheel to transfer torque and match the other wheel speed +- some offset.
Has anyone given this a try. Clearly it would require reverse engineering the ESP unit electronics/signals and would only be needed on one axle.
Safety yada yada yes I know, and I'm not being flippant, I'm just aware of the risk/likelyhood and fairly good with electronics 
Sorry I've read this three times and you've lost me.
Are you trying to create traction control by locking either side rather than transferring power to either side?
thats the kind of thing that would work on an off roader - but on a racer wouldn't it just slow you down?
Yep, grab the wheel with lost traction (so it doesn't affect vehicle speed negatively) and slowing it increasing torque to the other side (which
would normally get none as the other is spinning freely). Won't slow the vehicle at all, it'll push both tyres to their slip limit (if
controlled correctly). Essentially it will just need to work akin to ABS - only any wheel spinning too fast (requiring a reference speed - front wheel
maybe) get's its brakes applied, forcing it to get back in line with road speed while the other gets more torque until it slips. Could have some
issues with oscillation I guess, I've not planned that far ahead.
The biggest issue I see is getting that reference speed right, if you ahve that you can then tailor both wheel slipping to the ideal amount. I think
it's fairly standard launch control on some cars these days.
[Edited on 1/12/11 by coyoteboy]
Isn't that what the call torque vectoring? Or is it similar to brake steer that the mp4-12c mac uses ? Im Sure getting it work properly would take some serious electronics.
quote:
Isn't that what the call torque vectoring? Or is it similar to brake steer that the mp4-12c mac uses ? Im Sure getting it work properly would take some serious electronics.
It's all gobble-de-gook to me, but good luck.
Couldn't consider doing myself, but it sounds plausible.
As i say, it's do-able and when I find a usable ESP/ABS unit cheaply I just need to reverse engineer it to sus out how it works from an
electro-hydraulic point of view. From that point I reckon I can fairly easily follow a simple control strategy to maintain a constant maximum wheel
speed differential aross the back axle and hand the front-rear control over to the ECU (pull advance/spark cut). And of course ignore anything that
happens under braking.
I'm sure I'll come across something that'll cause an issue but for now I'm just looking to see if anyone else has done it
"DIY" style, as it's always easier to push forward from someone elses progress.
[Edited on 1/12/11 by coyoteboy]
Could we have some pics of how your cars progressing,
now that you are re inveting the wheel
Steve
Not really reinventing the wheel is it, it's called "hacking" 
And yes, hit the www button at the bottom of my posts.
Glad to see the eternal pessimist has returned I don't know what the chip is on your shoulder, but I'm not playing the game for it.
[Edited on 1/12/11 by coyoteboy]
Pretty sure BMW use that technique for their Stability Management.
If you're overly harsh on it, you'll end up cooking your rear brakes (and then you have the new issue of a very fast rear on the entry of
corners)
Yes, massive brake wear is a concern, but since it's used in OEM's I guess that's really just a case of getting the control parameters
correct and not being so damn right foot heavy I'll look into the BMWs, see if I can find out. The Saab ESP units sell for ~100 quid on
fleabay - bit much for current funds after engine and box purchases and with xmas round the corner, but maybe in the new year. I'd like to get
the scope/bus sniffer on a working car while it was activated but I don't have a car with it or the nuts to package all that into a car while
someone else drives like a nut job
[Edited on 1/12/11 by coyoteboy]
Oh, sorry, my mistake !!
and from your pics, you are building WHAT ??
A garage full of push bikes, and some weights, and an engine in bits
mmm, looks like your build plan, has a problem
I've not finished planning the build. As mentioned in the past this is a self-design/build, something organic that will evolve as I investigate
each area in turn and then finally come together - not a kit, not something laid out to begin with with all plans fixed in stone. I have the basics,
I have a plan in my head and the rest is in my mind floating around while I consider the options. I know my powerplant, my drivetrain, from there
I'm moving on to suspension - not that any of that bothers you, you just wish to take a stab, I know. As for the engine, yes there's an
engine in bits while I strip it and check it's condition, get a few things replaced/repaired/coated.
I wasn't aware I had to follow your project planning schedules in order to do things that work, sorry. Jesus, get over yourself you moron. Anyone
mentions doing anything different or isnt building something from a kit in 6 months and you think you have license to claim they're doomed to
failure and incapable. Good sign of the insecure as it happens. Maybe you need to grow up a little before making comments.
Damn, I started to play the game You know I don't like making enemies on forums, but some peope do just come across as asshats, even when
they're really nice in real life. I hope you are, for your sake. And yet again you've managed to turn an interesting informative thread into
one about you and your schedules/belief - well done. Now please leave, it was going well without you.
[Edited on 1/12/11 by coyoteboy]
I like the sound of what youre trying to achieve. Do you have a degree in electronics as it may come in handy (not dissing). The setup might take a while but its interesting
Yep, I've got the required quals to do that side of it no problem (and bring too much of it home at night!) - I'm hoping that if I can do a bit of hacking around I might be able to make a cheaper (if slightly less effective) solution to the torsen equiv. For my box you're looking at £1k for the diff and no technical challenge, so I guess lumping in an esp module and a few months tinkering might create something usable a bit cheaper. It should be really transferrable to any open-diff RWD car, could easily make it open source in case people want to tinker.
what transaxle is it?
it may not come with a LSD in standard form, but does anyone like quaife or tran-x make one?
personally (and i don't know how much you've looked into it, so you might have already covered it) i'd be looking into a quaife atb, or
even a plate lsd from tran-x, if there is one. i'd be surprised if there isn't one tbh. i'm guessing its a audi transaxle or something?
only other ones i can think of easily available is porsche...
i think the electronics to make a reliable and useful system will be very difficult to get right. as said brake wear would be worth thinking about,
don't think it'll slow you down much, but i don't know, it wouldn't be my plan
i see from your photos its an audi 4.2 V8, i assume you're using the same transaxle, quaife have an ATB diff listed for the audi A6, with a 4.2
engine
http://www.quaife.co.uk/shop/search/results/taxonomy%3A824%2C621%2C50%2C67
any good?
ok, not cheap, but you know... 
[Edited on 2/12/11 by blakep82]
There's a few diff options available for the audi transaxle (01E) but as I say, you're looking around £1K for them and of course a full box
stripdown (which hasn't long been done by the previous owner) which is (currently) outside of my planned expenses.
The electronics are really not an issue, I'm more than aware of the problems involved in creating vehicle electronics and all the protection and
environmental/noise issues related to it. I have built a fair few in car systems (and been bitten by a few of the bugs!) so that side of it I'm
fairly comfy with achieving, it's the elec/hydro interface item I've no experience with hence the request for any similar work done. I know
electronics are not everyone's cup of tea, especially not on cars of a very simple format, but while I was challenging myself to something
mechanically taxing I felt the project was lacking in electronic challenge and since this can be done as a side-project and the car run without it
seemed like an interesting add-on (or way of locking wheels and spinning lol)
my bmw has something like this sort of trying to mimic an lsd and to be honest it sucks its very unpredictable sometimes it wont react quick enough
and lets it slid sometimes it corrects it and it bogs the car down and most of the time it slips then catches it and you start understeering
although its more complicated than your thinking of doing as it compairs all the wheels speeds along with the steering angle to work out if it thinks
its sliding or not
personaly i would look at getting a proper diff as when i want to play it ets turned off and just use the open diff
well, 2 very different options, 1 easier but expensive, the other cheaper but more complicated i'd say. its a difficult choice i think
personally.
will be an interesting project! will it be more of a mod, as in build the car, get it legal (if needed) and add it later? or is this a main
consideration from the start?
i'll be getting an LSD for mine when i can afford it and the car's done (or as near as...)
Thinking about it you may not need a reference from the front. Think of it this way :- The diff is to allow the wheels to turn at different speeds when cornering. The greatest difference is when the car is turning the smallest radius it can. This gives you a relative maximum. If the relative speed difference of the wheels exceeds this, the fast one must be spinning.
There may already be some code available like this for the Megasquirt, is that not how it does traction control i.e the crank cannot possiby
accelerate at that rate if there is any load on it and then backs off the ignition timing.
Also if your looking to do it all electronically rather than delving in the the electro/hydraulic interface, I'm sure I've seen electronic
rear calipers or handbrake calipers for new VW's or something similar on eBay
I'm pretty sure this idea of braking the spinning wheel on an axel is how my mates S3 manages on snow otherwise with 2 open diff's and the
way it transfers power you'd very easily get stuck!.
VAUXHALL OPEL OMEGA BOSCH ABS PUMP ECU 0 273 004 207 | eBay
VAUXHALL OMEGA ABS UNIT PUMP ECU 0 273 004 207 DY 94-03 | eBay
[Edited on 2/12/11 by stevebubs]
I will have the option for electronic disabling of course, but I suspect if it's done right (which will be no mean feat) it would operate just
like an LSD. There could be two stages of operation - one to just keep the wheels within a certain ratio and one with the squirt traction control
included to limit both-slipping conditions, but the latter removes more of the fun but might be helpful with new drivers to it.
quote:
will be an interesting project! will it be more of a mod, as in build the car, get it legal (if needed) and add it later? or is this a main consideration from the start? i'll be getting an LSD for mine when i can afford it and the car's done (or as near as...)
quote:
Thinking about it you may not need a reference from the front. Think of it this way :- The diff is to allow the wheels to turn at different speeds when cornering. The greatest difference is when the car is turning the smallest radius it can. This gives you a relative maximum. If the relative speed difference of the wheels exceeds this, the fast one must be spinning.
quote:
There may already be some code available like this for the Megasquirt, is that not how it does traction control i.e the crank cannot possiby accelerate at that rate if there is any load on it and then backs off the ignition timing.
quote:
Also if your looking to do it all electronically rather than delving in the the electro/hydraulic interface, I'm sure I've seen electronic rear calipers or handbrake calipers for new VW's or something similar on eBay
Stevehubs- thanks for the links, they're looking rather cheap.
I was thinking this over - I'm not sure I'd need an ESP pump arrangement - ABS units include pumps to re-pressurise the wheel-side of the
circuit after the pedal side has been severed with the valve, otherwise the ABS would cause the pedal to travel to the floor as the ABS action
progressed. A two valve system may indeed work in this case - one valve to isolate the pedal input and the other to oscillate between the pump circuit
and the release circuit. Time to dig out some manuals and see if I can find an ABS pump expert!
[Edited on 2/12/11 by coyoteboy]
I played around with this idea for ages but gave up and bought a quaiffe unit. Problem was finding a pump with enough capacity to actuate the
brakes.
Cheers
Sounds good and is akin to what many oems are doing now as the electronic option si cheaper and easier to fit than a proper diff.
Beware electric calipers, they're not yet mature enough IMO and have some horriffic failure stories, not the mention their frankly insane
relacement cost (£500 ish!)
Following with interest and looking forward to seeing how you get on!
quote:
I played around with this idea for ages but gave up and bought a quaiffe unit. Problem was finding a pump with enough capacity to actuate the brakes. Cheers
Range rovers have had this for years, all the way back to very late classic models with air suspension, I had an LSE but it was pretty crude, slightly
better on P38 I had as it clicked in a little more smoothly.
It felt like ABS was rattling the pedal when forcing the car through mud or towing a trailer across a grassy field, I would not want to use it when a
car is on its limit, lightly to throw you off the road IMHO, best left as an agricutural tool.
Regards Mark
Little bit confused Mark, as this is used now in some very high end performance machines. There's no reason at all that it should be agricultural
or likely to throw you off the road? I also had a classic rangerover LSE, but it didn't have that option I don't think. I'll look into
it. Either way, back in the 80's 90s the processing power and capability was not available that is available now, not even close. I can hook up a
DSP that can make the required measurements at 1MHz and re-calulate the required adjusments a couple of hundred thousand times a second. Back then
you'd be lucky to have electronic ignition that didn't use entirely discrete components 
Add that to the fact that it's on a 4wd system with masses of backlash, horrific driveline wind-up, soggy tyres, compliant suspension etc - no
wonder it wasn't fun. Pushing a RR is never fun
[Edited on 2/12/11 by coyoteboy]
I've been following this thread and my mechanical head keeps steering me to some sort of vacuum brake or system that puts the brakes on at rest
when there's no fluid pressure. During normal use the brakes work as they do on vacuum brakes on a lorry (did Rollers use a positive pressure
system at some point?) so to apply some brake pressure to the spinning wheel, you would be 'bleeding' pressure away from it. Not knowing too
much about electronics, I'm imagining some sort of wheel speed comparator that would be 'bleeding' pressure away from which ever wheel
was 'gaining' on the other.
I've read through my own post and it makes no sense. Sorry.... 
Anyway, you'll never build a car and it will take you too long to not build it, all your ideas are rubbish and your jumper doesn't suit
you.... Just thought I'd join in..
I have been doing a bit of work with electro-hydraulic systems recently and from what I gather you will need....
a) a pump capable of supplying the pressure you require
b) an accumulator capable of holding enough fluid to apply the brake to the pressure you require.
c) a feedback pressure sensor
d) a servo valve to isolate the brake mastercylinder
e) two servoproportional pressure control valves to supply pressure to the brake calipers
f) two servo valves to release the brake pressure back to the LP side of the system
g) your electronic stuff (I dont do that...)
You map your wheel speed differential to the feedback pressure in your computery thing and use it to supply a voltage to the servoproportional valve
to maintain the pressure required.
Then some sort of system to cut the pressure and reconnect the mastercylinder when the brakes are applied.
ITS EASY
I have just been looking at the spec for Rover 75 traction control and it works by partially using this system coupled with fuel cut as well.I should
imagine most parts are fairly standard mechanical and electrical units that are fitted to many other cars.
http://en.rover-club.net/graphics/manuals/17/r75_technical_brochure.pdf look at the traction control section.
Paul
quote:
Anyway, you'll never build a car and it will take you too long to not build it, all your ideas are rubbish and your jumper doesn't suit you.... Just thought I'd join in..
My jumper does look a bit old-man, you're right quote:
I've been following this thread and my mechanical head keeps steering me to some sort of vacuum brake or system that puts the brakes on at rest when there's no fluid pressure. During normal use the brakes work as they do on vacuum brakes on a lorry (did Rollers use a positive pressure system at some point?) so to apply some brake pressure to the spinning wheel, you would be 'bleeding' pressure away from it. Not knowing too much about electronics, I'm imagining some sort of wheel speed comparator that would be 'bleeding' pressure away from which ever wheel was 'gaining' on the other. I've read through my own post and it makes no sense. Sorry....
quote:
I have been doing a bit of work with electro-hydraulic systems recently and from what I gather you will need.... a) a pump capable of supplying the pressure you require b) an accumulator capable of holding enough fluid to apply the brake to the pressure you require. c) a feedback pressure sensor d) a servo valve to isolate the brake mastercylinder e) two servoproportional pressure control valves to supply pressure to the brake calipers f) two servo valves to release the brake pressure back to the LP side of the system g) your electronic stuff (I dont do that...) You map your wheel speed differential to the feedback pressure in your computery thing and use it to supply a voltage to the servoproportional valve to maintain the pressure required. Then some sort of system to cut the pressure and reconnect the mastercylinder when the brakes are applied. ITS EASY
quote:
I have just been looking at the spec for Rover 75 traction control and it works by partially using this system coupled with fuel cut as well.I should imagine most parts are fairly standard mechanical and electrical units that are fitted to many other cars. http://en.rover-club.net/graphics/manuals/17/r75_technical_brochure.pdf look at the traction control section. Paul