[Diy_efi] Jetronic - RFI

[Lee M. Lemoine]

Well, i'm sure there are other threads for this however, this will help you
a little:

http://auto.howstuffworks.com/anti-lock-brake.htm

http://auto.howstuffworks.com/master-brake.htm

I'm not trying to dumb anything down, its jsut a real decent explanation of
how this stuff works.

Also, before trying to implement ABS, you'll have to have the same size and
diameter tires front and rear -- or have appropriately ratio'ed reluctor
rings front and rear...   I know GM's ABS system on the '91-94 cavaliers
very well.  It's 4000 pulses per mile resolution...   Different cars came
with different resolutions...  My front outer CV axles have notches in them,
with a sensor to pick up each tooth.  In the rear theres simply teeth on the
inside of the wheel hub, and a small sensor that protrudes just below the
wheel cylinder, to sense the notches on the back of the wheel hub.

All ABS pumps are electronically operated, as to operate during and after a
collison, as long as the electrical system is intact.  They typically draw
10-30 amps...

And a reluctor ring is a round disc with impermeated magnetic strips...  or
(similar) setup, for the purpose of position detection.  The simplest
example would be to look on allpar.com for a Dodge 2.2 / 2.5 liter
distributor cap's hall effect sensor.

This is used in a lot of places in cars, such as Vehicle Speed Sensors(VSS),
Wheel Speed Sensor (WSS) Crank Position Sensor (CrPS) Cam Position Sensor
(CaPS)  -- look any of those up online ;)

-- Lee


On 3/5/06, Ian Molton <spyro at f2s.com> wrote:
>
> WSCowell at aol.com wrote:
> > In a message dated 04/03/2006 10:22:47 GMT Standard Time, spyro at f2s.com
> > writes:
> >
> >
> >     whats involved in retrofitting ABS to a vehicle ? Does anyone make
> kits?
> >
> > Hoo boy, where shall we start?
>
> Thats never a good sign :-)
>
> > Modify the wheel hubs to carry suitable reluctor rings, modify hub
> > carriers to hold sensors, modify the hydraulic pipework from the master
> > cylinder so as to include the pump piping, accumulator and valve block,
> > design & fit bracket for hydraulic pump for the high pressure lines,
>
> Ok, so it was probably obvious I know nothing about practical ABS
> implementations from my post (nevermind that we're straying far from efi
> here...). Suggestions for a place to read up on this would be most
> welcome...
>
> The theory is, AIUI, keep the wheels from locking up by pulsing the
> brake when lockup is detected. So, needing wheel sensors was obvious...
>
> whats a reluctor ring?
>
> I'd guessed already that pipework would need rto be re-done, but Im not
> familiar with how its done.
>
> I know ABS systems must 'fail safe' so clearly theres some kind of
> allowance for that in the valve block.
>
> My car currently has a 2-way split crossed front/rear setup with a
> balancing block in it and a vacuum assisted master cylinder.
>
> I assume any ABS pump would typically be run off the fanbelt or a
> seperate line from the crank pulley.
>
> What does the valve block and such *do* in an ABS setup (beyond the
> obvious). well, I guess I want to know more *how* it does it...
>
> This is all a bit hypothetical right now because a) it'd need
> certification from the authorities here, and also affect my insurance,
> and b) I need to find some discs for the back end long before this is
> worth the bother.
>
> are ABS computers often standalone devices ?
>
> > In short it's do-able, but definitely not trivial!  :-)
> > I think if you have to ask that particular question, don't attempt the
> > job, because of the danger involved in implementing a project that you
> > don't understand from top to bottom.
>
> Oh, dont worry, Im not dumb enough to tinker with the braking system
> without the effort to fully understand it.
>
> My dad once used his lathe to trim the discs on his fiat, not realising
> that the fiat system depended on a minimum wear not being exceeded,
> which resulted in the pad over-extending and jamming - you only need one
> graphic example of why not to do something like that ;-)
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--
Sincerely,

Lee M. Lemoine
http://www.turbochargedsoul.com/
'06 Subaru Legacy GT Limited - 250/250 AWD 5EAT
'93 Chevy Cavalier Z24 Convertible - 300/330 FWD 5MT (Mclaren Turbo!)
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