More brakes stuff..
Background:
E36's came with 3-line ABS (early) and 4-line ABS (late).
The 3 line system has a single line to the rear (ie both brake calipers are dealt with together) whereas the 4-line treats and modulates each brake separately. This was done in part to improve performance, and also to allow the use of what is now often referred to as "E-Diff" instead of a mechanical LSD
This brakes the wheel which is slipping, transferring drive torque to the wheel with grip
The early 3-line system copes quite well with sticky tyres, brake balance adjustment, etc., as its basically looking at wheel speeds only
The later system looks at acceleration values, etc and so can have a complete meltdown with plausibility issues! One of the worst things from a track perspective is in the event of a spin - the wheel speed sensors and the accelerometers can have a right wobbly, and try to stabilise the car rather than stop it, Basically if you spin and slam the brakes on you don't really get the desired effect of locking all 4 wheels and slowing the car down, rather a pulsing of brakes on individual corners trying to stop the spin and straighten the car out! Apparently it can be a proper trouser-messer!
My initial thoughts were to ditch the 4-line system, and go to the 3-line system which can be upgraded to "Group N" software by Wayne Schofield - this software works brilliantly with slick tyres and is worth significant time on-track. Basically ABS WON'T stop your wheels from "slipping", only locking, and the slip ratio (ie the ratio of speed of wheel rotation rolling (ie ground speed) : braking) for normal tyres is usually set somewhere around 5-8%. This is optimum for a road tyre.. On a slick this is more like 15-20%, so even with the older 3 line system there's braking to be had if you're on track day or slick tyres..
After a bit more research, I found a lot of the guys in the US are now dropping the 3-line system and going to the newer 4-line system from the e46 m3. This is a considerably more powerful system (computer power) and has a lot more clever stuff going on, which gets around the short comings of the older 4-line system. It has the ability to cope with (mechanical) brake balance adjustments, can cope with bias adjustment on the fly and can manage the torque steer effect to give considerably higher braking power than the older system - for example, if there's braking power to be had from one corner on the front, it can apply more pressure on that line and ramp up pressure on the opposite rear corner to prevent the left/right brake imbalance from steering the car! All very neat stuff..
This system also has an up to date CAN interface which allows you to pull out data such as brake line pressures (front / rear) wheel speeds, steer angle, etc., etc. which is all useful stuff too
There are also other features when its fitted to a BMW with all the right bits, like self-wiping brakes (based on windscreen wiper sensor, the abs will dry the discs every 20 or 30 sec so they're ready to go), electronic differential, if you jump off the accelerator quickly, it will pre-empt a braking operation and close the gap between pads and discs, etc.. All really neat stuff, but not relevant to me
The final kicker is the pump and ECU hardware forms the basis of the Bosch Motorsport ABS System (as used in 911 Cup / RSR's, BMW factory race cars, etc, even now) and for a price can be re-programmed to give you most of the same functionality of this system. I think the only thing you can't get is the "on the fly" adjustment of ABS intervention (ie how agressive the ABS is) via a dial on the steering wheel. I'm sure this could be reverse engineered, but really its willy-waving stuff unless you're actually competing at the level of the Z4GT or the 911 RSR's (which I'm not!)
Anyway..
The pump:
You need a specific pump part number to be able to run the above firmware upgrades and things - I managed to find one pretty quickly, and they're not very expensive. I think I paid about £50 delivered. This is ECM and pump combined, so quite cheap even compared with the old 3 and 4 line system hardware (which is a separate ECU / Pump)
There are other pumps you can use, this is the one I ended up with which gives the best bang for buck (a CSL pump gives a little more benefit out of the box, but at the expense of extra expense! and rarity
)
The 813 bit is the number you're looking for..
There are a couple of other pump part numbers which can not be reprogrammed, so its important to get the right one up front to allow for upgrades down the line if required
There are a lot of guys in the US who have made many posts about how to wire stand-alone ABS - because the system is a safety system it will run on its own with very few inputs, however to get full functionality you need to do some messin'!
Some of the guys in the US will turn the car on, clear fault codes using a laptop, and then start the engine to make things work 100% (things such as Steer Angle sensor, the CAN Data transmission, etc) - the ABS pump has communication with the engine ECM in the M3 to manage traction control aswell, and if its not there (ie the ABS pump doesn't see it) it has a wobbly and shuts all this extra stuff down! It will run as ABS, but none of the other good stuff works. I don't have the money for an S54 engine in my track car unfortunately, hence I'd be in the same boat with these issues. If you don't want the CAN data it’s not an issue, but it seems like a waste if you have the data available and could use it..
Fortunately there's a clever guy in Milton Keynes (Demlotcrew - he's on youtube and some of the BMW forums), who is really REALLY clever! He's created a small plugin module which effectively mimics an S54 engine to the ABS pump, so the fault codes don't appear or need clearing - as far as the ABS pump is concerned it’s in an M3 and all is well
The only thing you have to do is plug it in, and re-program your ABS pump to a specific VIN number to match the module and you're away!
He's also able to provide pre-made harnesses which are full motorsport specification, however my car layout is different to the norm (pump position, different chassis, etc) and so I brought all the parts from him and made my own to suit (why did i do that?!.. JEEEEEZ I hate wiring!)
That said, he can make harnesses for anything, so if any of you are interested in an ABS system for your race or track cars get in touch with him (or me and I can pass on his details) - he REALLY knows his stuff
Anyway.. Under the guidance and support of "Demlotcrew" I set about building a stand-alone wiring harness for the ABS. I couldn't really justify buying meters and meters of 20 different coloured wires, so decided to be careful and use one colour per "system" in the car - this makes troubleshooting a bit tricky, but provided its built right to start with it shouldn't be too bad..
Purple wires = ABS
I measured where things were in the car, and once I had one cable going to each location, I turned the garage into spidermans bedroom running all the other wires from connector to connector!
All of the wires in..
I then covered everything in the braided wire covering stuff and shrink-wrapped the ends - I used glue lined heat shrink so it shouldn't move, and also prevents any fraying, etc..
1/2 finished harness on the living room floor..
And installed in the car
The layout is as follows..
ABS Pump - passenger footwell
3-axis Accelerometer / 3-axis rotation sensor - front edge of passenger seat. This is installed as far out from the centre line of the car (left/right) as possible, but as close to the centreline of the car as possible (front/rear) and at floor level
Fuse box and S54 Emulator - "glovebox" area
Pressure sensors - end of brake master cylinders - these need to be as close to the m/c as possible, on the m3 they're IN the master cylinder (ie 2x ports per outlet)
Data connections – driver’s doorway for easy connection
Other / switches - centre console area
Wheel speed sensors - one per wheel
Ground speed - diff speed sensor.. This isn't required for ABS, but I ran the wire with the ABS harness and straight into the Pi dashboard for speed reading
I now have two OBD2 ports on the car - one is for the engine (which is the older K-Line set-up) and one for the ABS - I have created extensions effectively so both of these ports will be in the drivers door-way of the car (probably mounted to the cage on a little bracket or panel somewhere - this still needs figuring out)
The entire data stream from the ABS pump is available in the door way (CAN Hi / Low and also the TX for coding, fault finding, etc.)
Lines for CAN Hi / Low are also routed to the middle of the car where the data logger lives, providing wheel speeds, brake line pressures, steering angle readings, etc.
Hoping this will be a useful tool for learning
Unfortunately the engine isn't a CAN enabled system, so I have additional sensor wires from the engine bay area to the datalogger which are analogue or digital inputs to the datalogger - I have RPM, Throttle Position, Coolant Temp, Oil Pressure
I also have some spare sensor slots which can be used for whatever else - I will wait and see what I find value in once I get going, but I think maybe clutch is a good one (to look at "coasting")
I also have some digital inputs - I'm only using one right now, for a "log" switch. This starts logging and also turns the go-pro on (via wifi) to record
Just as a little aside - the datalogger I purchased is from Autosport Labs in the US. They design/manufacture the RaceCapture series of data loggers, from the basic "OBD2 Plug" type logger, through to the RaceCapture Pro Mk2 (which superceded the Mk1). These units are really well made, and expandable. They offer a HUGE level of data logging capability, and compatibility with a lot of sensors, cars, data systems, dashboards, etc. at a very sensible price! They also have the ability to do funky things like control fans based on coolant temp, warning lights based on oil pressure, etc. or even go-pro's
They also have a telemetry module which uses a data sim card (currently 3.5G not 4G) to offer real time car to pit telemetry which is pretty impressive in a package costing under $500! (it was even more impressive when I brought mine as the exchange rate was.. ...shall we say, favourable! )
The system also has "Lua Coding" capability, allowing people to write their own code to do specific things (for example my logging switch, and the coding to read the BMW ABS Can bus). There is a free app to analyse the data, plus this can be used as a digital dashboard through a mobile phone or tablet. All in all a really nice system!
Mine is mounted as close to the cars COG as possible, on the transmission tunnel
I put a couple of holes in the trans tunnel, and pulled in some thread inserts..
Then mounted it directly to the car with a couple of SS Bolts
Its hard to see in the pictures, but its kind of under the handbrake - it doesn't get in the way when you're operating the handbrake at all, but it is also kind of well protected by the brake from above.. Once its all done and dusted I will probably make a small cover to go over the wiring terminals either side to protect them a bit more, but for now it should be fine
Thats probably enough for one post - I got a bit carried away, and a bit off track from ABS where it started!! Promise the next post will be more interesting and less wordy!
Either that or the MAF is TOAST! Or that's just how the cams are at idle. another job on the massive "to do when everything else is finished.." list 
